| 1 | Psychiatr. Genet. 2004 Mar 14: 39-42 |
|---|---|
| PMID | 15091314 |
| Title | Polymorphisms in glutamate decarboxylase genes: analysis in schizophrenia. |
| Abstract | The decrease of glutamic acid decarboxylase (GAD) has been reported as an important neurochemical alteration of the inhibitory GABAergic interneurons in schizophrenia. To our knowledge no studies have investigated the genetic variants influencing GAD expression. To search for markers contributing to the genetic susceptibility of schizophrenia, we typed two polymorphisms by polymerase chain reaction-restriction fragment length polymorphism in both GAD1 and GAD2 genes in 112 triad families and 46 case-controls. We used the Transmission Disequilibrium Test to perform the qualitative family-based analyses and found negative results (GAD1, chi2 = 0.273, 1 degree of freedom, P = 0.60; GAD2, chi2 = 0, 1 degree of freedom, P = 1). In addition there were no associations with GAD1 and GAD2 and quantitative measures of suicide behaviour in this sample. Although our results are negative, this was the first study to investigate GAD genes in schizophrenia, and further studies of these genes, particularly with schizophrenia subtypes, may prove valuable. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 2 | Am. J. Med. Genet. B Neuropsychiatr. Genet. 2005 May 135B: 94-101 |
| PMID | 15806582 |
| Title | Mutational screening and association study of glutamate decarboxylase 1 as a candidate susceptibility gene for bipolar affective disorder and schizophrenia. |
| Abstract | Recent evidence from postmortem studies suggests that GAD1 encoding the gamma-aminobutyric acid (GABA) synthetic enzyme GAD67 is a functional candidate susceptibility gene for both bipolar affective disorder (BPAD) and schizophrenia. Previous studies suggest linkage between D2S326 near GAD1 and BPAD. We systematically screened GAD1 exons, flanking intronic sequences, and the promoter sequence for polymorphisms in 16 BPAD patients and five controls from Denmark. We identified eight single nucleotide polymorphisms (SNPs) including two in the promoter sequence. An association study of SNPs covering GAD1 was performed in a Danish sample of 82 BPAD subjects and 120 controls and in a Scottish sample of 197 individuals with schizophrenia, 200 BPAD subjects and 199 controls. Linkage disequilibrium (LD) and haplotype frequencies were estimated from genotype data from eight SNPs. Strong pairwise LD was observed among all pairs of neighboring markers. In the Danish sample, we found weak association between BPAD and two promoter SNPs spaced 1 kb apart. Furthermore, one, two, and three loci haplotype analysis showed weak association with BPAD in the Danish sample. The results from the association studies indicate that promoter variants are of importance for the Danish BPAD cases and we cannot reject the hypothesis of GAD1 as a functional candidate gene for BPAD. No association was observed between BPAD or schizophrenia and any of the investigated SNPs in the Scottish sample set. Thus the results obtained from the Scottish sample suggest that the GAD1 gene variants do not play a major role in the predisposition to schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 3 | Mol. Psychiatry 2005 May 10: 434-49 |
| PMID | 15700048 |
| Title | The neurodevelopmental model of schizophrenia: update 2005. |
| Abstract | Neurodevelopmental models of schizophrenia that identify longitudinal precursors of illness have been of great heuristic importance focusing most etiologic research over the past two decades. These models have varied considerably with respect to specificity and timing of hypothesized genetic and environmental 'hits', but have largely focused on insults to prenatal brain development. With heritability around 80%, nongenetic factors impairing development must also be part of the model, and any model must also account for the wide range of age of onset. In recent years, longitudinal brain imaging studies of both early and adult (to distinguish from late ie elderly) onset populations indicate that progressive brain changes are more dynamic than previously thought, with gray matter volume loss particularly striking in adolescence and appearing to be an exaggeration of the normal developmental pattern. This supports an extended time period of abnormal neurodevelopment in schizophrenia in addition to earlier 'lesions'. Many subtle cognitive, motor, and behavioral deviations are seen years before illness onset, and these are more prominent in early onset cases. Moreover, schizophrenia susceptibility genes and chromosomal abnormalities, particularly as examined for early onset populations (ie GAD1, 22q11DS), are associated with premorbid neurodevelopmental abnormalities. Several candidate genes for schizophrenia (eg dysbindin) are associated with lower cognitive abilities in both schizophrenic and other pediatric populations more generally. Postmortem human brain and developmental animal studies document multiple and diverse effects of developmental genes (including schizophrenia susceptibility genes), at sequential stages of brain development. These may underlie the broad array of premorbid cognitive and behavioral abnormalities seen in schizophrenia, and neurodevelopmental disorders more generally. Increased specificity for the most relevant environmental risk factors such as exposure to prenatal infection, and their interaction with susceptibility genes and/or action through phase-specific altered gene expression now both strengthen and modify the neurodevelopmental theory of schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 4 | Mol. Psychiatry 2005 May 10: 434-49 |
| PMID | 15700048 |
| Title | The neurodevelopmental model of schizophrenia: update 2005. |
| Abstract | Neurodevelopmental models of schizophrenia that identify longitudinal precursors of illness have been of great heuristic importance focusing most etiologic research over the past two decades. These models have varied considerably with respect to specificity and timing of hypothesized genetic and environmental 'hits', but have largely focused on insults to prenatal brain development. With heritability around 80%, nongenetic factors impairing development must also be part of the model, and any model must also account for the wide range of age of onset. In recent years, longitudinal brain imaging studies of both early and adult (to distinguish from late ie elderly) onset populations indicate that progressive brain changes are more dynamic than previously thought, with gray matter volume loss particularly striking in adolescence and appearing to be an exaggeration of the normal developmental pattern. This supports an extended time period of abnormal neurodevelopment in schizophrenia in addition to earlier 'lesions'. Many subtle cognitive, motor, and behavioral deviations are seen years before illness onset, and these are more prominent in early onset cases. Moreover, schizophrenia susceptibility genes and chromosomal abnormalities, particularly as examined for early onset populations (ie GAD1, 22q11DS), are associated with premorbid neurodevelopmental abnormalities. Several candidate genes for schizophrenia (eg dysbindin) are associated with lower cognitive abilities in both schizophrenic and other pediatric populations more generally. Postmortem human brain and developmental animal studies document multiple and diverse effects of developmental genes (including schizophrenia susceptibility genes), at sequential stages of brain development. These may underlie the broad array of premorbid cognitive and behavioral abnormalities seen in schizophrenia, and neurodevelopmental disorders more generally. Increased specificity for the most relevant environmental risk factors such as exposure to prenatal infection, and their interaction with susceptibility genes and/or action through phase-specific altered gene expression now both strengthen and modify the neurodevelopmental theory of schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 5 | Mol. Psychiatry 2005 Jun 10: 581-8 |
| PMID | 15505639 |
| Title | GAD1 (2q31.1), which encodes glutamic acid decarboxylase (GAD67), is associated with childhood-onset schizophrenia and cortical gray matter volume loss. |
| Abstract | Postmortem brain studies have shown deficits in the cortical gamma-aminobutyric acid (GABA) system in schizophrenic individuals. Expression studies have shown a decrease in the major GABA-synthesizing enzyme (glutamic acid decarboxylase (GAD67) mRNA levels in neurons in dorsolateral prefrontal cortex in schizophrenics relative to controls. In the present study, SNPs in and around the GAD1 gene, which encodes the protein GAD67, were tested on a rare, severely ill group of children and adolescents with childhood-onset schizophrenia (COS) (n=72), in a family-based association analysis. Compared to adult-onset samples, the COS sample has evidence for more salient familial, and perhaps genetic, risk factors for schizophrenia, as well as evidence for frontal cortical hypofunction, and greater decline in cortical gray matter volume on anatomic brain MRI scans during adolescence. We performed family-based TDT and haplotype association analyses of the clinical phenotype, as well as association analyses with endophenotypes using the QTDT program. Three adjacent SNPs in the 5' upstream region of GAD1 showed a positive pairwise association with illness in these families (P=0.022-0.057). Significant transmission distortion of 4-SNP haplotypes was also observed (P=0.003-0.008). Quantitative trait TDT analyses showed an intriguing association between several SNPs and increased rate of frontal gray matter loss. These observations, when taken together with the positive results reported recently in two independent adult-onset schizophrenia pedigree samples, suggest that the gene encoding GAD67 may be a common risk factor for schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 6 | Mol. Psychiatry 2005 Jun 10: 581-8 |
| PMID | 15505639 |
| Title | GAD1 (2q31.1), which encodes glutamic acid decarboxylase (GAD67), is associated with childhood-onset schizophrenia and cortical gray matter volume loss. |
| Abstract | Postmortem brain studies have shown deficits in the cortical gamma-aminobutyric acid (GABA) system in schizophrenic individuals. Expression studies have shown a decrease in the major GABA-synthesizing enzyme (glutamic acid decarboxylase (GAD67) mRNA levels in neurons in dorsolateral prefrontal cortex in schizophrenics relative to controls. In the present study, SNPs in and around the GAD1 gene, which encodes the protein GAD67, were tested on a rare, severely ill group of children and adolescents with childhood-onset schizophrenia (COS) (n=72), in a family-based association analysis. Compared to adult-onset samples, the COS sample has evidence for more salient familial, and perhaps genetic, risk factors for schizophrenia, as well as evidence for frontal cortical hypofunction, and greater decline in cortical gray matter volume on anatomic brain MRI scans during adolescence. We performed family-based TDT and haplotype association analyses of the clinical phenotype, as well as association analyses with endophenotypes using the QTDT program. Three adjacent SNPs in the 5' upstream region of GAD1 showed a positive pairwise association with illness in these families (P=0.022-0.057). Significant transmission distortion of 4-SNP haplotypes was also observed (P=0.003-0.008). Quantitative trait TDT analyses showed an intriguing association between several SNPs and increased rate of frontal gray matter loss. These observations, when taken together with the positive results reported recently in two independent adult-onset schizophrenia pedigree samples, suggest that the gene encoding GAD67 may be a common risk factor for schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 7 | Mol. Psychiatry 2005 Jun 10: 581-8 |
| PMID | 15505639 |
| Title | GAD1 (2q31.1), which encodes glutamic acid decarboxylase (GAD67), is associated with childhood-onset schizophrenia and cortical gray matter volume loss. |
| Abstract | Postmortem brain studies have shown deficits in the cortical gamma-aminobutyric acid (GABA) system in schizophrenic individuals. Expression studies have shown a decrease in the major GABA-synthesizing enzyme (glutamic acid decarboxylase (GAD67) mRNA levels in neurons in dorsolateral prefrontal cortex in schizophrenics relative to controls. In the present study, SNPs in and around the GAD1 gene, which encodes the protein GAD67, were tested on a rare, severely ill group of children and adolescents with childhood-onset schizophrenia (COS) (n=72), in a family-based association analysis. Compared to adult-onset samples, the COS sample has evidence for more salient familial, and perhaps genetic, risk factors for schizophrenia, as well as evidence for frontal cortical hypofunction, and greater decline in cortical gray matter volume on anatomic brain MRI scans during adolescence. We performed family-based TDT and haplotype association analyses of the clinical phenotype, as well as association analyses with endophenotypes using the QTDT program. Three adjacent SNPs in the 5' upstream region of GAD1 showed a positive pairwise association with illness in these families (P=0.022-0.057). Significant transmission distortion of 4-SNP haplotypes was also observed (P=0.003-0.008). Quantitative trait TDT analyses showed an intriguing association between several SNPs and increased rate of frontal gray matter loss. These observations, when taken together with the positive results reported recently in two independent adult-onset schizophrenia pedigree samples, suggest that the gene encoding GAD67 may be a common risk factor for schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 8 | Schizophr. Res. 2006 Jun 84: 253-71 |
| PMID | 16632332 |
| Title | Gene regulation by hypoxia and the neurodevelopmental origin of schizophrenia. |
| Abstract | Neurodevelopmental changes may underlie the brain dysfunction seen in schizophrenia. While advances have been made in our understanding of the genetics of schizophrenia, little is known about how non-genetic factors interact with genes for schizophrenia. The present analysis of genes potentially associated with schizophrenia is based on the observation that hypoxia prevails in the embryonic and fetal brain, and that interactions between neuronal genes, molecular regulators of hypoxia, such as hypoxia-inducible factor 1 (HIF-1), and intrinsic hypoxia occur in the developing brain and may create the conditions for complex changes in neurodevelopment. Consequently, we searched the literature for currently hypothesized candidate genes for susceptibility to schizophrenia that may be subject to ischemia-hypoxia regulation and/or associated with vascular expression. Genes were considered when at least two independent reports of a significant association with schizophrenia had appeared in the literature. The analysis showed that more than 50% of these genes, particularly AKT1, BDNF, CAPON, CCKAR, CHRNA7, CNR1, COMT, DNTBP1, GAD1, GRM3, IL10, MLC1, NOTCH4, NRG1, NR4A2/NURR1, PRODH, RELN, RGS4, RTN4/NOGO and TNF, are subject to regulation by hypoxia and/or are expressed in the vasculature. Future studies of genes proposed as candidates for susceptibility to schizophrenia should include their possible regulation by physiological or pathological hypoxia during development as well as their potential role in cerebral vascular function. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 9 | Brain Res Rev 2006 Sep 52: 293-304 |
| PMID | 16759710 |
| Title | Molecular and cellular mechanisms of altered GAD1/GAD67 expression in schizophrenia and related disorders. |
| Abstract | The 67 and 65 kDa isoforms of glutamic acid decarboxylase, the key enzymes for GABA biosynthesis, are expressed at altered levels in postmortem brain of subjects diagnosed with schizophrenia and related disorders, including autism and bipolar illness. The predominant finding is a decrease in GAD67 mRNA levels, affecting multiple brain regions, including prefrontal and temporal cortex. Postmortem studies, in conjunction with animal models, identified several mechanisms that contribute to the dysregulation of GAD67 in cerebral cortex. These include disordered connectivity formation during development, abnormal expression of Reelin and neural cell adhesion molecule (NCAM) glycoproteins, defects in neurotrophin signaling and alterations in dopaminergic and glutamatergic neurotransmission. These mechanisms are likely to operate in conjunction with genetic risk factors for psychosis, including sequence polymorphisms residing in the promoter of GAD1 (2q31), the gene encoding GAD67. We propose an integrative model, with multiple molecular and cellular mechanisms contributing to transcriptional dysregulation of GAD67 and cortical dysfunction in psychosis. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 10 | Schizophr. Res. 2007 Mar 91: 22-6 |
| PMID | 17303389 |
| Title | No association between the glutamate decarboxylase 67 gene (GAD1) and schizophrenia in the Japanese population. |
| Abstract | Postmortem studies regarding schizophrenia revealed altered expression of genes related to gamma-amino butyric acid neurotransmission system. One of the most consistent findings is the reduced level of 67 kDa glutamic acid decarboxylase isoform (GAD(67)). Moreover, several studies reported positive associations between the GAD(67) gene (GAD1) and schizophrenia. These reasons, motivated us to carry out replication study regarding association between GAD1 (fourteen tagging SNPs) and schizophrenia in Japanese population (562 schizophrenic patients and 470 controls). However we couldn't confirm significant association that had been previously reported. Considering size of our sample and strategy that corresponds well with the approaches used in gene-based association analysis, our conclusion is that GAD1 does not play a major role in schizophrenia in Japanese population. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 11 | Schizophr. Res. 2007 Mar 91: 22-6 |
| PMID | 17303389 |
| Title | No association between the glutamate decarboxylase 67 gene (GAD1) and schizophrenia in the Japanese population. |
| Abstract | Postmortem studies regarding schizophrenia revealed altered expression of genes related to gamma-amino butyric acid neurotransmission system. One of the most consistent findings is the reduced level of 67 kDa glutamic acid decarboxylase isoform (GAD(67)). Moreover, several studies reported positive associations between the GAD(67) gene (GAD1) and schizophrenia. These reasons, motivated us to carry out replication study regarding association between GAD1 (fourteen tagging SNPs) and schizophrenia in Japanese population (562 schizophrenic patients and 470 controls). However we couldn't confirm significant association that had been previously reported. Considering size of our sample and strategy that corresponds well with the approaches used in gene-based association analysis, our conclusion is that GAD1 does not play a major role in schizophrenia in Japanese population. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 12 | Mol. Psychiatry 2007 Sep 12: 854-69 |
| PMID | 17767149 |
| Title | Allelic variation in GAD1 (GAD67) is associated with schizophrenia and influences cortical function and gene expression. |
| Abstract | Cortical GABAergic dysfunction has been implicated as a key component of the pathophysiology of schizophrenia and decreased expression of the gamma-aminobutyric acid (GABA) synthetic enzyme glutamic acid decarboxylase 67 (GAD(67)), encoded by GAD1, is found in schizophrenic post-mortem brain. We report evidence of distorted transmission of single-nucleotide polymorphism (SNP) alleles in two independent schizophrenia family-based samples. In both samples, allelic association was dependent on the gender of the affected offspring, and in the Clinical Brain Disorders Branch/National Institute of Mental Health (CBDB/NIMH) sample it was also dependent on catechol-O-methyltransferase (COMT) Val158Met genotype. Quantitative transmission disequilibrium test analyses revealed that variation in GAD1 influenced multiple domains of cognition, including declarative memory, attention and working memory. A 5' flanking SNP affecting cognition in the families was also associated in unrelated healthy individuals with inefficient BOLD functional magnetic resonance imaging activation of dorsal prefrontal cortex (PFC) during a working memory task, a physiologic phenotype associated with schizophrenia and altered cortical inhibition. In addition, a SNP in the 5' untranslated (and predicted promoter) region that also influenced cognition was associated with decreased expression of GAD1 mRNA in the PFC of schizophrenic brain. Finally, we observed evidence of statistical epistasis between two SNPs in COMT and SNPs in GAD1, suggesting a potential biological synergism leading to increased risk. These coincident results implicate GAD1 in the etiology of schizophrenia and suggest that the mechanism involves altered cortical GABA inhibitory activity, perhaps modulated by dopaminergic function. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 13 | Mol. Psychiatry 2007 Sep 12: 854-69 |
| PMID | 17767149 |
| Title | Allelic variation in GAD1 (GAD67) is associated with schizophrenia and influences cortical function and gene expression. |
| Abstract | Cortical GABAergic dysfunction has been implicated as a key component of the pathophysiology of schizophrenia and decreased expression of the gamma-aminobutyric acid (GABA) synthetic enzyme glutamic acid decarboxylase 67 (GAD(67)), encoded by GAD1, is found in schizophrenic post-mortem brain. We report evidence of distorted transmission of single-nucleotide polymorphism (SNP) alleles in two independent schizophrenia family-based samples. In both samples, allelic association was dependent on the gender of the affected offspring, and in the Clinical Brain Disorders Branch/National Institute of Mental Health (CBDB/NIMH) sample it was also dependent on catechol-O-methyltransferase (COMT) Val158Met genotype. Quantitative transmission disequilibrium test analyses revealed that variation in GAD1 influenced multiple domains of cognition, including declarative memory, attention and working memory. A 5' flanking SNP affecting cognition in the families was also associated in unrelated healthy individuals with inefficient BOLD functional magnetic resonance imaging activation of dorsal prefrontal cortex (PFC) during a working memory task, a physiologic phenotype associated with schizophrenia and altered cortical inhibition. In addition, a SNP in the 5' untranslated (and predicted promoter) region that also influenced cognition was associated with decreased expression of GAD1 mRNA in the PFC of schizophrenic brain. Finally, we observed evidence of statistical epistasis between two SNPs in COMT and SNPs in GAD1, suggesting a potential biological synergism leading to increased risk. These coincident results implicate GAD1 in the etiology of schizophrenia and suggest that the mechanism involves altered cortical GABA inhibitory activity, perhaps modulated by dopaminergic function. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 14 | PLoS ONE 2007 -1 2: e895 |
| PMID | 17878930 |
| Title | DNA methylation in the human cerebral cortex is dynamically regulated throughout the life span and involves differentiated neurons. |
| Abstract | The role of DNA cytosine methylation, an epigenetic regulator of chromatin structure and function, during normal and pathological brain development and aging remains unclear. Here, we examined by MethyLight PCR the DNA methylation status at 50 loci, encompassing primarily 5' CpG islands of genes related to CNS growth and development, in temporal neocortex of 125 subjects ranging in age from 17 weeks of gestation to 104 years old. Two psychiatric disease cohorts--defined by chronic neurodegeneration (Alzheimer's) or lack thereof (schizophrenia)--were included. A robust and progressive rise in DNA methylation levels across the lifespan was observed for 8/50 loci (GABRA2, GAD1, HOXA1, NEUROD1, NEUROD2, PGR, STK11, SYK) typically in conjunction with declining levels of the corresponding mRNAs. Another 16 loci were defined by a sharp rise in DNA methylation levels within the first few months or years after birth. Disease-associated changes were limited to 2/50 loci in the Alzheimer's cohort, which appeared to reflect an acceleration of the age-related change in normal brain. Additionally, methylation studies on sorted nuclei provided evidence for bidirectional methylation events in cortical neurons during the transition from childhood to advanced age, as reflected by significant increases at 3, and a decrease at 1 of 10 loci. Furthermore, the DNMT3a de novo DNA methyl-transferase was expressed across all ages, including a subset of neurons residing in layers III and V of the mature cortex. Therefore, DNA methylation is dynamically regulated in the human cerebral cortex throughout the lifespan, involves differentiated neurons, and affects a substantial portion of genes predominantly by an age-related increase. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 15 | Schizophr. Res. 2007 Jul 93: 374-84 |
| PMID | 17412563 |
| Title | Systematic study of association of four GABAergic genes: glutamic acid decarboxylase 1 gene, glutamic acid decarboxylase 2 gene, GABA(B) receptor 1 gene and GABA(A) receptor subunit beta2 gene, with schizophrenia using a universal DNA microarray. |
| Abstract | Several studies have suggested the dysfunction of the GABAergic system as a risk factor in the pathogenesis of schizophrenia. In the present study, case-control association analysis was conducted in four GABAergic genes: two glutamic acid decarboxylase genes (GAD1 and GAD2), a GABA(A) receptor subunit beta2 gene (GABRB2) and a GABA(B) receptor 1 gene (GABBR1). Using a universal DNA microarray procedure we genotyped a total of 20 SNPs on the above four genes in a study involving 292 patients and 286 controls of Chinese descent. Statistically significant differences were observed in the allelic frequencies of the rs187269C/T polymorphism in the GABRB2 gene (P=0.0450, chi(2)=12.40, OR=1.65) and the -292A/C polymorphism in the GAD1 gene (P=0.0450, chi(2)=14.64 OR=1.77). In addition, using an electrophoretic mobility shift assay (EMSA), we discovered differences in the U251 nuclear protein binding to oligonucleotides representing the -292 SNP on the GAD1 gene, which suggests that the -292C allele has reduced transcription factor binding efficiency compared with the 292A allele. Using the multifactor-dimensionality reduction method (MDR), we found that the interactions among the rs187269C/T polymorphism in the GABRB2 gene, the -243A/G polymorphism in the GAD2 gene and the 27379C/T and 661C/T polymorphisms in the GAD1 gene revealed a significant association with schizophrenia (P<0.001). These findings suggest that the GABRB2 and GAD1 genes alone and the combined effects of the polymorphisms in the four GABAergic system genes may confer susceptibility to the development of schizophrenia in the Chinese population. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 16 | J. Neurosci. 2007 Oct 27: 11254-62 |
| PMID | 17942719 |
| Title | Prefrontal dysfunction in schizophrenia involves mixed-lineage leukemia 1-regulated histone methylation at GABAergic gene promoters. |
| Abstract | Alterations in GABAergic mRNA expression play a key role for prefrontal dysfunction in schizophrenia and other neurodevelopmental disease. Here, we show that histone H3-lysine 4 methylation, a chromatin mark associated with the transcriptional process, progressively increased at GAD1 and other GABAergic gene promoters (GAD2, NPY, SST) in human prefrontal cortex (PFC) from prenatal to peripubertal ages and throughout adulthood. Alterations in schizophrenia included decreased GAD1 expression and H3K4-trimethylation, predominantly in females and in conjunction with a risk haplotype at the 5' end of GAD1. Heterozygosity for a truncated, lacZ knock-in allele of mixed-lineage leukemia 1 (Mll1), a histone methyltransferase expressed in GABAergic and other cortical neurons, resulted in decreased H3K4 methylation at GABAergic gene promoters. In contrast, GAD1 H3K4 (tri)methylation and Mll1 occupancy was increased in cerebral cortex of mice after treatment with the atypical antipsychotic, clozapine. These effects were not mimicked by haloperidol or genetic ablation of dopamine D2 and D3 receptors, suggesting that blockade of D2-like signaling is not sufficient for clozapine-induced histone methylation. Therefore, chromatin remodeling mechanisms at GABAergic gene promoters, including MLL1-mediated histone methylation, operate throughout an extended period of normal human PFC development and play a role in the neurobiology of schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 17 | PLoS ONE 2007 -1 2: e809 |
| PMID | 17726539 |
| Title | GAD1 mRNA expression and DNA methylation in prefrontal cortex of subjects with schizophrenia. |
| Abstract | Dysfunction of prefrontal cortex in schizophrenia includes changes in GABAergic mRNAs, including decreased expression of GAD1, encoding the 67 kDa glutamate decarboxylase (GAD67) GABA synthesis enzyme. The underlying molecular mechanisms remain unclear. Alterations in DNA methylation as an epigenetic regulator of gene expression are thought to play a role but this hypothesis is difficult to test because no techniques are available to extract DNA from GAD1 expressing neurons efficiently from human postmortem brain. Here, we present an alternative approach that is based on immunoprecipitation of mononucleosomes with anti-methyl-histone antibodies differentiating between sites of potential gene expression as opposed to repressive or silenced chromatin. Methylation patterns of CpG dinucleotides at the GAD1 proximal promoter and intron 2 were determined for each of the two chromatin fractions separately, using a case-control design for 14 schizophrenia subjects affected by a decrease in prefrontal GAD1 mRNA levels. In controls, the methylation frequencies at CpG dinucleotides, while overall higher in repressive as compared to open chromatin, did not exceed 5% at the proximal GAD1 promoter and 30% within intron 2. Subjects with schizophrenia showed a significant, on average 8-fold deficit in repressive chromatin-associated DNA methylation at the promoter. These results suggest that chromatin remodeling mechanisms are involved in dysregulated GABAergic gene expression in schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 18 | Mol. Psychiatry 2008 Sep 13: 873-7 |
| PMID | 18195713 |
| Title | Serious obstetric complications interact with hypoxia-regulated/vascular-expression genes to influence schizophrenia risk. |
| Abstract | The etiology of schizophrenia is thought to include both epistasis and gene-environment interactions. We sought to test whether a set of schizophrenia candidate genes regulated by hypoxia or involved in vascular function in the brain (AKT1, BDNF, CAPON, CHRNA7, COMT, DTNBP1, GAD1, GRM3, NOTCH4, NRG1, PRODH, RGS4, TNF-alpha) interacted with serious obstetric complications to influence risk for schizophrenia. A family-based study of transmission disequilibrium was conducted in 116 trios. Twenty-nine probands had at least one serious obstetric complication (OC) using the McNeil-Sjostrom Scale, and many of the OCs reported were associated with the potential for fetal hypoxia. Analyses were conducted using conditional logistic regression and a likelihood ratio test (LRT) between nested models was performed to assess significance. Of the 13 genes examined, four (AKT1 (three SNPs), BDNF (two SNPs), DTNBP1 (one SNP) and GRM3 (one SNP)) showed significant evidence for gene-by-environment interaction (LRT P-values ranged from 0.011 to 0.037). Although our sample size was modest and the power to detect interactions was limited, we report significant evidence for genes involved in neurovascular function or regulated by hypoxia interacting with the presence of serious obstetric complications to increase risk for schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 19 | J Child Adolesc Psychopharmacol 2008 Feb 18: 25-9 |
| PMID | 18294085 |
| Title | GAD1 single nucleotide polymorphism is in linkage disequilibrium with a child bipolar I disorder phenotype. |
| Abstract | Pediatric bipolar I disorder (BP-I) and childhood schizophrenia (SZ) share certain symptoms (e.g., psychosis, aggression/irritability [A/I]), and the psychotic and A/I features are treated with neuroleptics in both disorders. Thus, it is of interest to examine the association of GAD1 to child BP-I because of its recently reported association to childhood SZ. Child BP-I probands were obtained by consecutive new case ascertainment, and the phenotype was defined as current DSM-IV BP-I (manic or mixed phase) with at least one of the cardinal symptoms of mania (i.e., elation and/or grandiosity) and a Children's Global Assessment Scale score < or =60 (clinical impairment). These child BP-I probands are part of a large, ongoing, longitudinal study in which the phenotype has been validated by unique symptoms, longitudinal stability, and 7-8 times greater family loading than adult BP-I probands. Genotyping was performed using a TaqMan Validated SNP Genotyping Assay, and FBAT was used for analysis. There were 48 families. The rs2241165 A allele was preferentially transmitted (FBAT chi(2) = 5.2, df = 1, p = 0.022). No interaction between this GAD1 SNP and the Val66 BDNF allele was found. These data are consistent with some shared genetic vulnerability between child BP-I and SZ, which may be related to similar treatments. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 20 | J Neural Transm (Vienna) 2008 -1 115: 513-9 |
| PMID | 18335162 |
| Title | Comprehensive analysis of polymorphisms throughout GAD1 gene: a family-based association study in schizophrenia. |
| Abstract | Studies suggest that GAD1 gene is a functional candidate susceptibility gene for schizophrenia. In order to investigate the contribution of GAD1 gene to the etiology of schizophrenia in Chinese, we carried out a family-based association study between GAD1 gene and schizophrenia in 235 Chinese Han family trios. The GAD1 gene is comprehensively analyzed using a systematic mutation scan and the following-up association studies between common SNPs and schizophrenia in both single-locus and haplotype levels. Altogether, we have found 17 variants including 10 SNPs in 5'-flanking regions, 4 SNPs and one novel in-del in intronic regions and 2 SNPs (one novel SNP) in the 3'-untranslated region (UTR). Using the transmission disequilibrium test of the 9 common SNPs out of 17 variants, Significant evidence of SNP rs3791878-G allele in 5'-flanking region of GAD1 was preferentially transmitted to both the all offsprings of the trios (P = 0.0063, respectively; odds ratio = 1.83; 95% confidence interval: 1.26-2.65) and the male offsprings the trios (P = 0.0045, respectively; odds ratio = 2.21; 95% confidence interval: 1.37-3.56). Haplotype analysis suggested that rs3762556(C)-rs3791878(G)-rs6755102(C) is the major risky haplotype preferentially transmitted in both all the trios and male-offspring trios (Global P = 0.016 and 0.012, respectively). The gender-dependent of the risk of SNP rs3791878 suggest the complexity of GAD1 gene in schizophrenia. Given that the switch from G to T in SNP rs3791878 might cause the loss of ARNT and XBP1 transcriptional factor binding sites using a bioinformatics approach, our positive findings of this SNP support the hypothesis that the abruption of GAD1 gene is important to the risk of schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 21 | Brain Struct Funct 2008 Sep 213: 255-71 |
| PMID | 18470533 |
| Title | Age-related changes in the expression of schizophrenia susceptibility genes in the human prefrontal cortex. |
| Abstract | The molecular basis of complex neuropsychiatric disorders most likely involves many genes. In recent years, specific genetic variations influencing risk for schizophrenia and other neuropsychiatric disorders have been reported. We have used custom DNA microarrays and qPCR to investigate the expression of putative schizophrenia susceptibility genes and related genes of interest in the normal human brain. Expression of 31 genes was measured in Brodmann's area 10 (BA10) in the prefrontal cortex of 72 postmortem brain samples spanning half a century of human aging (18-67 years), each without history of neuropsychiatric illness, neurological disease, or drug abuse. Examination of expression across age allowed the identification of genes whose expression patterns correlate with age, as well as genes that share common expression patterns and that possibly participate in common cellular mechanisms related to the emergence of schizophrenia in early adult life. The expression of GRM3 and RGS4 decreased across the entire age range surveyed, while that of PRODH and DARPP-32 was shown to increase with age. NRG1, ERBB3, and NGFR show expression changes during the years of greatest risk for the development of schizophrenia. Expression of FEZ1, GAD1, and RGS4 showed especially high correlation with one another, in addition to the strongest mean levels of absolute correlation with all other genes studied here. All microarray data are available at NCBI's Gene Expression Omnibus: GEO Series accession number GSE11546 (http://www.ncbi.nlm.nih.gov/geo) [corrected] |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 22 | Epigenomics 2009 Oct 1: 201-11 |
| PMID | 22122643 |
| Title | Antipsychotic subtypes can be characterized by differences in their ability to modify GABAergic promoter methylation. |
| Abstract | Recent advances in schizophrenia and bipolar disorder research suggest that a dysfunction of GABAergic neurotransmission that is operative in telencephalic structures may be an important dynamic mechanism associated with psychosis. We propose that this dysfunction is probably mediated by the hypermethylation of glutamic acid decarboxylase (GAD67), reelin and other gene promoters expressed in GABAergic neurons. A pharmacological strategy that reduces the hypermethylation of GABAergic promoters is to administer drugs (i.e., valproate [VPA]) that induce DNA demethylation by facilitating chromatin remodeling. The enhanced clinical efficacy of atypical antipsychotics when co-administered with VPA prompted us to investigate whether this increased drug efficacy is related to a modification of GABAergic promoter methylation via chromatin remodeling. Our previous and present results strongly suggest that when associated with VPA, clozapine or sulpiride, but not haloperidol or olanzapine, facilitate chromatin remodeling. This molecular remodeling may contribute to the induction of reelin (RELN) and GAD(67) (GAD1) promoter demethylation, and may reverse the downregulation of various GABAergic mRNAs and proteins detected in the telencephalon of patients with schizophrenia or bipolar disorders. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 23 | Nature 2010 Nov 468: 263-9 |
| PMID | 21068835 |
| Title | Dysfunction in GABA signalling mediates autism-like stereotypies and Rett syndrome phenotypes. |
| Abstract | Mutations in the X-linked MECP2 gene, which encodes the transcriptional regulator methyl-CpG-binding protein 2 (MeCP2), cause Rett syndrome and several neurodevelopmental disorders including cognitive disorders, autism, juvenile-onset schizophrenia and encephalopathy with early lethality. Rett syndrome is characterized by apparently normal early development followed by regression, motor abnormalities, seizures and features of autism, especially stereotyped behaviours. The mechanisms mediating these features are poorly understood. Here we show that mice lacking Mecp2 from GABA (?-aminobutyric acid)-releasing neurons recapitulate numerous Rett syndrome and autistic features, including repetitive behaviours. Loss of MeCP2 from a subset of forebrain GABAergic neurons also recapitulates many features of Rett syndrome. MeCP2-deficient GABAergic neurons show reduced inhibitory quantal size, consistent with a presynaptic reduction in glutamic acid decarboxylase 1 (GAD1) and glutamic acid decarboxylase 2 (Gad2) levels, and GABA immunoreactivity. These data demonstrate that MeCP2 is critical for normal function of GABA-releasing neurons and that subtle dysfunction of GABAergic neurons contributes to numerous neuropsychiatric phenotypes. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 24 | Neuropsychopharmacology 2010 Jul 35: 1708-17 |
| PMID | 20357758 |
| Title | Genetic modulation of GABA levels in the anterior cingulate cortex by GAD1 and COMT. |
| Abstract | Gamma-aminobutyric acid (GABA)-ergic transmission is critical for normal cortical function and is likely abnormal in a variety of neuropsychiatric disorders. We tested the in vivo effects of variations in two genes implicated in GABA function on GABA concentrations in prefrontal cortex of living subjects: glutamic acid decarboxylase 1 (GAD1), which encodes GAD67, and catechol-o-methyltransferase (COMT), which regulates synaptic dopamine in the cortex. We studied six single nucleotide polymorphisms (SNPs) in GAD1 previously associated with risk for schizophrenia or cognitive dysfunction and the val158met polymorphism in COMT in 116 healthy volunteers using proton magnetic resonance spectroscopy. Two of the GAD1 SNPs (rs1978340 (p=0.005) and rs769390 (p=0.004)) showed effects on GABA levels as did COMT val158met (p=0.04). We then tested three SNPs in GAD1 (rs1978340, rs11542313, and rs769390) for interaction with COMT val158met based on previous clinical results. In this model, rs11542313 and COMT val158met showed significant main effects (p=0.001 and 0.003, respectively) and a trend toward a significant interaction (p=0.05). Interestingly, GAD1 risk alleles for schizophrenia were associated with higher GABA/Cre, and Val-Val homozygotes had high GABA/Cre levels when on a GAD1 risk genotype background (N=6). These results support the importance of genetic variation in GAD1 and COMT in regulating prefrontal cortical GABA function. The directionality of the effects, however, is inconsistent with earlier evidence of decreased GABA activity in schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 25 | Neurosci Biobehav Rev 2010 May 34: 958-77 |
| PMID | 20060416 |
| Title | Genetic association studies of glutamate, GABA and related genes in schizophrenia and bipolar disorder: a decade of advance. |
| Abstract | schizophrenia (SZ) and bipolar disorder (BD) are debilitating neurobehavioural disorders likely influenced by genetic and non-genetic factors and which can be seen as complex disorders of synaptic neurotransmission. The glutamatergic and GABAergic neurotransmission systems have been implicated in both diseases and we have reviewed extensive literature over a decade for evidence to support the association of glutamate and GABA genes in SZ and BD. Candidate-gene based population and family association studies have implicated some ionotrophic glutamate receptor genes (GRIN1, GRIN2A, GRIN2B and GRIK3), metabotropic glutamate receptor genes (such as GRM3), the G72/G30 locus and GABAergic genes (e.g. GAD1 and GABRB2) in both illnesses to varying degrees, but further replication studies are needed to validate these results. There is at present no consensus on specific single nucleotide polymorphisms or haplotypes associated with the particular candidate gene loci in these illnesses. The genetic architecture of glutamate systems in bipolar disorder need to be better studied in view of recent data suggesting an overlap in the genetic aetiology of SZ and BD. There is a pressing need to integrate research platforms in genomics, epistatic models, proteomics, metabolomics, neuroimaging technology and translational studies in order to allow a more integrated understanding of glutamate and GABAergic signalling processes and aberrations in SZ and BD as well as their relationships with clinical presentations and treatment progress over time. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 26 | J. Neurosci. 2010 Sep 30: 13130-7 |
| PMID | 20881131 |
| Title | Maternal care and DNA methylation of a glutamic acid decarboxylase 1 promoter in rat hippocampus. |
| Abstract | Parenting and the early environment influence the risk for various psychopathologies. Studies in the rat suggest that variations in maternal care stably influence DNA methylation, gene expression, and neural function in the offspring. Maternal care affects neural development, including the GABAergic system, the function of which is linked to the pathophysiology of diseases including schizophrenia and depression. Postmortem studies of human schizophrenic brains have revealed decreased forebrain expression of glutamic acid decarboxylase 1 (GAD1) accompanied by increased methylation of a GAD1 promoter. We examined whether maternal care affects GAD1 promoter methylation in the hippocampus of adult male offspring of high and low pup licking/grooming (high-LG and low-LG) mothers. Compared with the offspring of low-LG mothers, those reared by high-LG dams showed enhanced hippocampal GAD1 mRNA expression, decreased cytosine methylation, and increased histone 3-lysine 9 acetylation (H3K9ac) of the GAD1 promoter. DNA methyltransferase 1 expression was significantly higher in the offspring of low- compared with high-LG mothers. Pup LG increases hippocampal serotonin (5-HT) and nerve growth factor-inducible factor A (NGFI-A) expression. Chromatin immunoprecipitation assays revealed enhanced NGFI-A association with and H3K9ac of the GAD1 promoter in the hippocampus of high-LG pups after a nursing bout. Treatment of hippocampal neuronal cultures with either 5-HT or an NGFI-A expression plasmid significantly increased GAD1 mRNA levels. The effect of 5-HT was blocked by a short interfering RNA targeting NGFI-A. These results suggest that maternal care influences the development of the GABA system by altering GAD1 promoter methylation levels through the maternally induced activation of NGFI-A and its association with the GAD1 promoter. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 27 | J. Neurosci. 2010 Sep 30: 13130-7 |
| PMID | 20881131 |
| Title | Maternal care and DNA methylation of a glutamic acid decarboxylase 1 promoter in rat hippocampus. |
| Abstract | Parenting and the early environment influence the risk for various psychopathologies. Studies in the rat suggest that variations in maternal care stably influence DNA methylation, gene expression, and neural function in the offspring. Maternal care affects neural development, including the GABAergic system, the function of which is linked to the pathophysiology of diseases including schizophrenia and depression. Postmortem studies of human schizophrenic brains have revealed decreased forebrain expression of glutamic acid decarboxylase 1 (GAD1) accompanied by increased methylation of a GAD1 promoter. We examined whether maternal care affects GAD1 promoter methylation in the hippocampus of adult male offspring of high and low pup licking/grooming (high-LG and low-LG) mothers. Compared with the offspring of low-LG mothers, those reared by high-LG dams showed enhanced hippocampal GAD1 mRNA expression, decreased cytosine methylation, and increased histone 3-lysine 9 acetylation (H3K9ac) of the GAD1 promoter. DNA methyltransferase 1 expression was significantly higher in the offspring of low- compared with high-LG mothers. Pup LG increases hippocampal serotonin (5-HT) and nerve growth factor-inducible factor A (NGFI-A) expression. Chromatin immunoprecipitation assays revealed enhanced NGFI-A association with and H3K9ac of the GAD1 promoter in the hippocampus of high-LG pups after a nursing bout. Treatment of hippocampal neuronal cultures with either 5-HT or an NGFI-A expression plasmid significantly increased GAD1 mRNA levels. The effect of 5-HT was blocked by a short interfering RNA targeting NGFI-A. These results suggest that maternal care influences the development of the GABA system by altering GAD1 promoter methylation levels through the maternally induced activation of NGFI-A and its association with the GAD1 promoter. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 28 | Mol. Psychiatry 2010 Oct 15: 987-95 |
| PMID | 20125089 |
| Title | Novel animal models for studying complex brain disorders: BAC-driven miRNA-mediated in vivo silencing of gene expression. |
| Abstract | In schizophrenia, glutamic acid decarboxylase 1 (GAD1) disturbances are robust, consistently observed, cell-type specific and represent a core feature of the disease. In addition, neuropeptide Y (NPY), which is a phenotypic marker of a sub-population of GAD1-containing interneurons, has shown reduced expression in the prefrontal cortex in subjects with schizophrenia, suggesting that dysfunction of the NPY+ cortical interneuronal sub-population might be a core feature of this devastating disorder. However, modeling gene expression disturbances in schizophrenia in a cell type-specific manner has been extremely challenging. To more closely mimic these molecular and cellular human post-mortem findings, we generated a transgenic mouse in which we downregulated GAD1 mRNA expression specifically in NPY+ neurons. This novel, cell type-specific in vivo system for reducing gene expression uses a bacterial artificial chromosome (BAC) containing the NPY promoter-enhancer elements, the reporter molecule (eGFP) and a modified intron containing a synthetic microRNA (miRNA) targeted to GAD1. The animals of isogenic strains are generated rapidly, providing a new tool for better understanding the molecular disturbances in the GABAergic system observed in complex neuropsychiatric disorders such as schizophrenia. In the future, because of the small size of the silencing miRNAs combined with our BAC strategy, this method may be modified to allow generation of mice with simultaneous silencing of multiple genes in the same cells with a single construct, and production of splice-variant-specific knockdown animals. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 29 | J. Neurosci. 2011 Jul 31: 11088-95 |
| PMID | 21795557 |
| Title | Expression of GABA signaling molecules KCC2, NKCC1, and GAD1 in cortical development and schizophrenia. |
| Abstract | GABA signaling molecules are critical for both human brain development and the pathophysiology of schizophrenia. We examined the expression of transcripts derived from three genes related to GABA signaling [GAD1 (GAD67 and GAD25), SLC12A2 (NKCC1), and SLC12A5 (KCC2)] in the prefrontal cortex (PFC) and hippocampal formation of a large cohort of nonpsychiatric control human brains (n = 240) across the lifespan (from fetal week 14 to 80 years) and in patients with schizophrenia (n = 30-31), using quantitative RT-PCR. We also examined whether a schizophrenia risk-associated promoter SNP in GAD1 (rs3749034) is related to expression of these transcripts. Our studies revealed that development and maturation of both the PFC and hippocampal formation are characterized by progressive switches in expression from GAD25 to GAD67 and from NKCC1 to KCC2. Previous studies have demonstrated that the former leads to GABA synthesis, and the latter leads to switching from excitatory to inhibitory neurotransmission. In the hippocampal formation, GAD25/GAD67 and NKCC1/KCC2 ratios are increased in patients with schizophrenia, reflecting a potentially immature GABA physiology. Remarkably, GAD25/GAD67 and NKCC1/KCC2 expression ratios are associated with rs3749034 genotype, with risk alleles again predicting a relatively less mature pattern. These findings suggest that abnormalities in GABA signaling critical to brain development contribute to genetic risk for schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 30 | Transl Psychiatry 2011 -1 1: e64 |
| PMID | 22832356 |
| Title | Disease- and age-related changes in histone acetylation at gene promoters in psychiatric disorders. |
| Abstract | Increasing evidence suggests that epigenetic factors have critical roles in gene regulation in neuropsychiatric disorders and in aging, both of which are typically associated with a wide range of gene expression abnormalities. Here, we have used chromatin immunoprecipitation-qPCR to measure levels of acetylated histone H3 at lysines 9/14 (ac-H3K9K14), two epigenetic marks associated with transcriptionally active chromatin, at the promoter regions of eight schizophrenia-related genes in n=82 postmortem prefrontal cortical samples from normal subjects and those with schizophrenia and bipolar disorder. We find that promoter-associated ac-H3K9K14 levels are correlated with gene expression levels, as measured by real-time qPCR for several genes, including, glutamic acid decarboxylase 1 (GAD1), 5-hydroxytryptamine receptor 2C (HTR2C), translocase of outer mitochondrial membrane 70 homolog A (TOMM70A) and protein phosphatase 1E (PPM1E). Ac-H3K9K14 levels of several of the genes tested were significantly negatively associated with age in normal subjects and those with bipolar disorder, but not in subjects with schizophrenia, whereby low levels of histone acetylation were observed in early age and throughout aging. Consistent with this observation, significant hypoacetylation of H3K9K14 was detected in young subjects with schizophrenia when compared with age-matched controls. Our results demonstrate that gene expression changes associated with psychiatric disease and aging result from epigenetic mechanisms involving histone acetylation. We further find that treatment with a histone deacetylase (HDAC) inhibitor alters the expression of several candidate genes for schizophrenia in mouse brain. These findings may have therapeutic implications for the clinical use of HDAC inhibitors in psychiatric disorders. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 31 | Neuropharmacology 2011 Jun 60: 1075-87 |
| PMID | 20869372 |
| Title | Analysis of the GAD1 promoter: trans-acting factors and DNA methylation converge on the 5' untranslated region. |
| Abstract | GAD67 corresponds to one of two enzymes that decarboxylates glutamate to produce ?-aminobutyric acid, the main inhibitory neurotransmitter in the mammalian central nervous system, hence defining the cellular phenotype of a diverse set of inhibitory interneurons of the brain. Reduced cortical GAD67 mRNA levels have consistently been reported in schizophrenia and bipolar disorder with psychosis. The human gene encoding GAD67, GAD1, is located on chromosome 2q31.1 and the transcriptional start site resides within a large CpG island that spans a region extending from upstream through the first exon. We have analyzed the GAD1 promoter using transient transfection analysis of upstream and downstream sequences in NT2 cells, a human neuroprogenitor cell line. Interestingly, results from these studies show that cis-acting regulatory elements are located downstream of the RNA start site and are in the region corresponding to the first exon. Trans-acting factors such as Pitx2 and the Dlx family of transcription factors are active in promoting downstream reporter expression even when all of the 5' flanking sequences are removed. However, those constructs that contain an internal deletion from +66 to +173 bp fail to support expression even when these factors are provided in trans. We have previously shown that the Class I histone deacetylase inhibitor MS-275 potently activates GAD1 mRNA expression in NT2 cells suggesting the possibility that the promoter is sensitive to drugs that induce chromatin remodeling. Using methyl DNA immuneprecipitation of MS-275-treated NT2 cells, we provide data showing that Class I HDAC inhibition mediated an increase in GAD1 expression and that this was accompanied by decreased GAD1 promoter methylation. Moreover, the reduced levels of GAD1 DNA methylation are highest in those regions proximal to the location of the in vitro defined cis-acting regulatory elements. Our data suggest that changes in promoter methylation associated with gene regulation are not random but overlap the locations of proximal cis-acting elements. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 32 | Pharmacogenet. Genomics 2011 Apr 21: 206-16 |
| PMID | 20859245 |
| Title | Glutamatergic gene variants impact the clinical profile of efficacy and side effects of haloperidol. |
| Abstract | The glutamatergic system may be relevant to the pathophysiology of psychosis and to the effects of antipsychotic treatments. We investigated a set of 62 SNPs located in genes coding for subunits of glutamatergic receptors (GAD1, GRIA1, GRIA3, GRIA4, GRID2, GRIK1, GRIK2, GRIK3, GRIK4, GRIN2B, GRM1 and GRM4), and the transporter of glycine (SLC6A5), as modulators of the effects of haloperidol. We studied a sample of 101 acutely ill psychotic patients. We then validated our result in two independent samples from Slovenia (n=71 and n=118) of schizophrenic patients treated with antipsychotics. We both investigated the antipsychotic effect (Positive and Negative Syndrome Scale) and motor side effect (Extrapyramidal Symptom Rating Scale) at baseline and days 3, 7, 14, 21 and 28. SLC6A5 variant (rs2298826) was found to be associated with a rapid rise of motor side effects at the beginning of the treatment (repeated measures of analysis of variance, P=0.0002), followed by a subsequent adaptation, probably dependent on haloperidol doses down titration. A specific effect was noted for dyskinetic symptoms. Haplotype analysis strengthened the relevance of SLC6A5: the C-A-C haplotype (rs1443548, rs883377, rs1945771) was found to be associated with higher Extrapyramidal symptom rating scale scores (overall P=0.01, haplotype P=0.000001). We successfully replicated this finding in the two independent samples from Slovenia. This result further stresses the relevance of the glutamatergic system in modulating the effects of haloperidol treatment, especially with regards to motor side effects. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 33 | Mol. Psychiatry 2012 Sep 17: 887-905 |
| PMID | 22584867 |
| Title | Convergent functional genomics of schizophrenia: from comprehensive understanding to genetic risk prediction. |
| Abstract | We have used a translational convergent functional genomics (CFG) approach to identify and prioritize genes involved in schizophrenia, by gene-level integration of genome-wide association study data with other genetic and gene expression studies in humans and animal models. Using this polyevidence scoring and pathway analyses, we identify top genes (DISC1, TCF4, MBP, MOBP, NCAM1, NRCAM, NDUFV2, RAB18, as well as ADCYAP1, BDNF, CNR1, COMT, DRD2, DTNBP1, GAD1, GRIA1, GRIN2B, HTR2A, NRG1, RELN, SNAP-25, TNIK), brain development, myelination, cell adhesion, glutamate receptor signaling, G-protein-coupled receptor signaling and cAMP-mediated signaling as key to pathophysiology and as targets for therapeutic intervention. Overall, the data are consistent with a model of disrupted connectivity in schizophrenia, resulting from the effects of neurodevelopmental environmental stress on a background of genetic vulnerability. In addition, we show how the top candidate genes identified by CFG can be used to generate a genetic risk prediction score (GRPS) to aid schizophrenia diagnostics, with predictive ability in independent cohorts. The GRPS also differentiates classic age of onset schizophrenia from early onset and late-onset disease. We also show, in three independent cohorts, two European American and one African American, increasing overlap, reproducibility and consistency of findings from single-nucleotide polymorphisms to genes, then genes prioritized by CFG, and ultimately at the level of biological pathways and mechanisms. Finally, we compared our top candidate genes for schizophrenia from this analysis with top candidate genes for bipolar disorder and anxiety disorders from previous CFG analyses conducted by us, as well as findings from the fields of autism and Alzheimer. Overall, our work maps the genomic and biological landscape for schizophrenia, providing leads towards a better understanding of illness, diagnostics and therapeutics. It also reveals the significant genetic overlap with other major psychiatric disorder domains, suggesting the need for improved nosology. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 34 | PLoS ONE 2012 -1 7: e33352 |
| PMID | 22457755 |
| Title | Induction of the GABA cell phenotype: an in vitro model for studying neurodevelopmental disorders. |
| Abstract | Recent studies of the hippocampus have suggested that a network of genes is associated with the regulation of the GAD?? (GAD1) expression and may play a role in ?-amino butyric acid (GABA) dysfunction in schizophrenia (SZ) and bipolar disorder (BD). To obtain a more detailed understanding of how GAD?? regulation may result in GABAergic dysfunction, we have developed an in vitro model in which GABA cells are differentiated from the hippocampal precursor cell line, HiB5. Growth factors, such as PDGF, and BDNF, regulate the GABA phenotype by inducing the expression of GAD?? and stimulating the growth of cellular processes, many with growth cones that form appositions with the cell bodies and processes of other GAD??-positive cells. These changes are associated with increased expression of acetylated tubulin, microtubule-associated protein 2 (MAP2) and the post-synaptic density protein 95 (PSD95). The addition of BDNF, together with PDGF, increases the levels of mRNA and protein for GAD??, as well as the high affinity GABA uptake protein, GAT1. These changes are associated with increased concentrations of GABA in the cytoplasm of "differentiated" HiB5 neurons. In the presence of Ca²? and K?, newly synthesized GABA is released extracellularly. When the HiB5 cells appear to be fully differentiated, they also express GAD??, parvalbumin and calbindin, and GluR subtypes as well as HDAC1, DAXX, PAX5, Runx2, associated with GAD?? regulation. Overall, these results suggest that the HiB5 cells can differentiate into functionally mature GABA neurons in the presence of gene products that are associated with GAD?? regulation in the adult hippocampus. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 35 | J. Neurosci. 2012 Apr 32: 5216-22 |
| PMID | 22496567 |
| Title | Transcript-specific associations of SLC12A5 (KCC2) in human prefrontal cortex with development, schizophrenia, and affective disorders. |
| Abstract | The neuron-specific K(+)-Cl(-) cotransporter SLC12A5, also known as KCC2, helps mediate the electrophysiological effects of GABA. The pattern of KCC2 expression during early brain development suggests that its upregulation drives the postsynaptic switch of GABA from excitation to inhibition. We previously found decreased expression of full-length KCC2 in the postmortem hippocampus of patients with schizophrenia, but not in the dorsolateral prefrontal cortex (DLPFC). Using PCR and rapid amplification of cDNA ends, we discovered several previously unrecognized alternative KCC2 transcripts in both human adult and fetal brain in addition to the previously identified full-length (NM_020708.3) and truncated (AK098371) transcripts. We measured the expression levels of four relatively abundant truncated splice variants, including three novel transcripts (?EXON6, EXON2B, and EXON6B) and one previously described transcript (AK098371), in a large human cohort of nonpsychiatric controls across the lifespan, and in patients with schizophrenia and affective disorders. In SH-SY5Y cell lines, these transcripts were translated into proteins and expressed at their predicted sizes. Expression of the EXON6B transcript is increased in the DLPFC of patients with schizophrenia (p = 0.03) but decreased in patients with major depression (p = 0.04). The expression of AK098371 is associated with a GAD1 single nucleotide polymorphism (rs3749034) that previously has been associated with GAD67 expression and risk for schizophrenia. Our data confirm the developmental regulation of KCC2 expression, and provide evidence that KCC2 transcripts are differentially expressed in schizophrenia and affective disorders. Alternate transcripts from KCC2 may participate in the abnormal GABA signaling in the DLPFC associated with schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 36 | Clin Ter 2013 -1 164: e319-24 |
| PMID | 24045531 |
| Title | [Genetics and epigenetics of schizophrenia]. |
| Abstract | schizophrenia is a severe psychiatric disorder with an estimate prevalence of 0.3-0.7%. Studies on family aggregation showed a higher incidence of disease among family members of affected people. This observation lead to formulate the hypothesis that schizophrenia could be inheritable, but twin studies have shown a concordance of disease between monozygotic twins only of 50%, indicating the concomitant role of environmental factors in the pathogenesis of schizophrenia. Researches in molecular biology field have allowed the identification of genes that confer susceptibility to schizophrenia on chromosomes 1, 2, 3, 5, 6, 8, 10, 11, 13, 14, 20 and 22. Epigenetic modifications of gene expression, that not involve the primary DNA sequence, may also predispose to schizophrenia, in particular the methylation of genes involved in neurotransmission (RELN, GAD1, MARLIN-1, and NR3B GRIA2, VGLUT1 and 2, 5HT2a, COMT and BDNF), the histone modifications and the action of non-coding RNAs. This review deals with the results of a bibliographic retrieval on PubMed, carried out, using the key words: schizophrenia, genetics, epigenetics. From the epitomized results it can be derived that schizophrenia seems to be a multifactorial disease. Environmental factors, that can cause epigenetic modifications, are important in its pathogenesis, acting on a biological inheritable vulnerability. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 37 | J Psychiatr Res 2013 Jul 47: 872-9 |
| PMID | 23566421 |
| Title | Genetic variation in GAD1 is associated with cortical thickness in the parahippocampal gyrus. |
| Abstract | Patients with schizophrenia show widespread cortical thickness reductions throughout the brain. Likewise, reduced expression of the ?-Aminobutyric acid (GABA) synthesizing enzyme glutamic acid decarboxylase (GAD1) and a single nucleotide polymorphism (SNP) rs3749034 in the corresponding gene have been associated with schizophrenia. We tested whether this SNP is associated with reduced cortical thickness, an intermediate phenotype for schizophrenia. Because of the well known interactions between the GABAergic and dopaminergic systems, we examined whether associations between GAD1 rs3749034 and cortical thickness are modulated by the catechol-O-methyltransferase (COMT) Val158Met genotype. Structural MRI and genotype data was obtained from 94 healthy subjects enrolled in the Mind Clinical Imaging Consortium study to examine the relations between GAD1 genotype and cortical thickness. Our data show a robust reduction of cortical thickness in the left parahippocampal gyrus (PHG) in G allele homozygotes of GAD1 rs3749034. When we stratified our analyses according to the COMT Val158Met genotype, cortical thickness reductions of G allele homozygotes were only found in the presence of the Val allele. Genetic risk variants of schizophrenia in the GABAergic system might interact with the dopaminergic system and impact brain structure and functioning. Our findings point to the importance of the GABAergic system in the pathogenesis of schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 38 | J. Neurosci. 2013 Jul 33: 11839-51 |
| PMID | 23864674 |
| Title | Conserved chromosome 2q31 conformations are associated with transcriptional regulation of GAD1 GABA synthesis enzyme and altered in prefrontal cortex of subjects with schizophrenia. |
| Abstract | Little is known about chromosomal loopings involving proximal promoter and distal enhancer elements regulating GABAergic gene expression, including changes in schizophrenia and other psychiatric conditions linked to altered inhibition. Here, we map in human chromosome 2q31 the 3D configuration of 200 kb of linear sequence encompassing the GAD1 GABA synthesis enzyme gene locus, and we describe a loop formation involving the GAD1 transcription start site and intergenic noncoding DNA elements facilitating reporter gene expression. The GAD1-TSS(-50kbLoop) was enriched with nucleosomes epigenetically decorated with the transcriptional mark, histone H3 trimethylated at lysine 4, and was weak or absent in skin fibroblasts and pluripotent stem cells compared with neuronal cultures differentiated from them. In the prefrontal cortex of subjects with schizophrenia, GAD1-TSS(-50kbLoop) was decreased compared with controls, in conjunction with downregulated GAD1 expression. We generated transgenic mice expressing Gad2 promoter-driven green fluorescent protein-conjugated histone H2B and confirmed that GAD1-TSS(-55kbLoop), the murine homolog to GAD1-TSS(-50kbLoop), is a chromosomal conformation specific for GABAergic neurons. In primary neuronal culture, GAD1-TSS(-55kbLoop) and GAD1 expression became upregulated when neuronal activity was increased. We conclude that 3D genome architectures, including chromosomal loopings for promoter-enhancer interactions involved in the regulation of GABAergic gene expression, are conserved between the rodent and primate brain, and subject to developmental and activity-dependent regulation, and disordered in some cases with schizophrenia. More broadly, the findings presented here draw a connection between noncoding DNA, spatial genome architecture, and neuronal plasticity in development and disease. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 39 | Cereb. Cortex 2014 May 24: 1230-46 |
| PMID | 23283688 |
| Title | Common variants in psychiatric risk genes predict brain structure at birth. |
| Abstract | Studies in adolescents and adults have demonstrated that polymorphisms in putative psychiatric risk genes are associated with differences in brain structure, but cannot address when in development these relationships arise. To determine if common genetic variants in disrupted-in-schizophrenia-1 (DISC1; rs821616 and rs6675281), catechol-O-methyltransferase (COMT; rs4680), neuregulin 1 (NRG1; rs35753505 and rs6994992), apolipoprotein E (APOE; ?3?4 vs. ?3?3), estrogen receptor alpha (ESR1; rs9340799 and rs2234693), brain-derived neurotrophic factor (BDNF; rs6265), and glutamate decarboxylase 1 (GAD1; rs2270335) are associated with individual differences in brain tissue volumes in neonates, we applied both automated region-of-interest volumetry and tensor-based morphometry to a sample of 272 neonates who had received high-resolution magnetic resonance imaging scans. ESR1 (rs9340799) predicted intracranial volume. Local variation in gray matter (GM) volume was significantly associated with polymorphisms in DISC1 (rs821616), COMT, NRG1, APOE, ESR1 (rs9340799), and BDNF. No associations were identified for DISC1 (rs6675281), ESR1 (rs2234693), or GAD1. Of note, neonates homozygous for the DISC1 (rs821616) serine allele exhibited numerous large clusters of reduced GM in the frontal lobes, and neonates homozygous for the COMT valine allele exhibited reduced GM in the temporal cortex and hippocampus, mirroring findings in adults. The results highlight the importance of prenatal brain development in mediating psychiatric risk. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 40 | Mol. Psychiatry 2014 May 19: 580-7 |
| PMID | 24322205 |
| Title | Modulation of behavioral networks by selective interneuronal inactivation. |
| Abstract | Gamma-aminobutyric acid (GABA)-ergic disturbances are hallmark features of schizophrenia and other neuropsychiatric disorders and encompass multiple interneuronal cell types. Using bacterial artificial chromosome-driven, miRNA silencing technology we generated transgenic mouse lines that suppress glutamic acid decarboxylase 1 (GAD1) in either cholecystokinin (CCK)- or neuropeptide Y (NPY)-expressing interneurons. In situ lipidomic and proteomic analyses on brain tissue sections revealed distinct, brain region-specific profiles in each transgenic line. Behavioral analyses revealed that suppression of GAD1 in CCK+ interneurons resulted in locomotor and olfactory sensory changes, whereas suppression in NPY+ interneurons affected anxiety-related behaviors and social interaction. Both transgenic mouse lines had altered sensitivity to amphetamine albeit in opposite directions. Together, these data argue that reduced GAD1 expression leads to altered molecular and behavioral profiles in a cell type-dependent manner, and that these subpopulations of interneurons are strong and opposing modulators of dopamine system function. Furthermore, our findings also support the hypothesis that neuronal networks are differentially controlled by diverse inhibitory subnetworks. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 41 | Prog Mol Biol Transl Sci 2014 -1 128: 89-101 |
| PMID | 25410542 |
| Title | Modeling the molecular epigenetic profile of psychosis in prenatally stressed mice. |
| Abstract | Based on postmortem brain studies, our overarching epigenetic hypothesis is that chronic schizophrenia (SZ) is a psychopathological condition involving dysregulation of the dynamic equilibrium among DNA methylation/demethylation network components and the expression of SZ target genes, including GABAergic and glutamatergic genes. SZ has a natural course, starting with a prodromal phase, a first episode that occurs in adolescents or in young adults, and later deterioration over the adult years. Hence, the epigenetic status at each neurodevelopmental stage of the disease cannot be studied just in postmortem brain of chronic SZ patients, but requires the use of neurodevelopmental animal models. We have directed the focus of our research toward studying the epigenetic signature of the SZ brain in the offspring of dams stressed during pregnancy (PRS mice). Adult PRS mice have behavioral deficits reminiscent of behaviors observed in psychotic patients. The adult PRS brain, like that of postmortem chronic SZ patients, is characterized by a significant increase in DNA methyltransferase 1, Tet methylcytosine dioxygenase 1 (TET1), 5-methylcytosine, and 5-hydroxymethylcytosine at SZ candidate gene promoters and a reduction in the expression of glutamatergic and GABAergic genes. In PRS mice, measurements of epigenetic biomarkers for SZ can be assessed at different stages of development with the goal of further elucidating the pathophysiology of this disease and predicting treatment responses at specific stages of the illness, with particular attention to early detection and possibly early intervention. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 42 | Neurobiol. Dis. 2014 Mar 63: 210-21 |
| PMID | 24239560 |
| Title | The role of cannabinoid 1 receptor expressing interneurons in behavior. |
| Abstract | schizophrenia is a devastating neurodevelopmental disorder that affects approximately 1% of the population. Reduced expression of the 67-kDa protein isoform of glutamic acid decarboxylase (GAD67) is a hallmark of the disease and is encoded by the GAD1 gene. In schizophrenia, GAD67 downregulation occurs in multiple interneuronal subpopulations, including the cannabinoid receptor type 1 positive (CNR1+) cells, but the functional consequences of these disturbances are not well understood. To investigate the role of the CNR1-positive GABA-ergic interneurons in behavioral and molecular processes, we employed a novel, miRNA-mediated transgenic mouse approach. We silenced the GAD1 transcript using a miRNA engineered to specifically target GAD1 mRNA under the control of Cnr1 bacterial artificial chromosome. Behavioral characterization of our transgenic mice showed elevated and persistent conditioned fear associated with an auditory cue and a significantly altered response to an amphetamine challenge. These deficits could not be attributed to sensory deficits or changes in baseline learning and memory. Furthermore, HPLC analyses revealed that Cnr1/GAD1 mice have enhanced serotonin levels, but not dopamine levels in response to amphetamine. Our findings demonstrate that dysfunction of a small subset of interneurons can have a profound effect on behavior and that the GABA-ergic, monoamine, and cannabinoid systems are functionally interconnected. The results also suggest that understanding the function of various interneuronal subclasses might be essential to develop knowledge-based treatment strategies for various mental disorders including schizophrenia and substance abuse. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 43 | Brain Res. 2014 Dec 1591: 53-62 |
| PMID | 25451092 |
| Title | Glutamate, GABA, and glutamine are synchronously upregulated in the mouse lateral septum during the postpartum period. |
| Abstract | Dramatic structural and functional remodeling occurs in the postpartum brain for the establishment of maternal care, which is essential for the growth and development of young offspring. Glutamate and GABA signaling are critically important in modulating multiple behavioral performances. Large scale signaling changes occur in the postpartum brain, but it is still not clear to what extent the neurotransmitters glutamate and GABA change and whether the ratio of glutamate/GABA remains balanced. In this study, we examined the glutamate/GABA-glutamine cycle in the lateral septum (LS) of postpartum female mice. In postpartum females (relative to virgins), tissue levels of glutamate and GABA were elevated in LS and increased mRNA was found for the respective enzymes producing glutamate and GABA, glutaminase (Gls) and glutamate decarboxylase 1 and 2 (GAD1 and Gad2). The common precursor, glutamine, was elevated as was the enzyme that produces it, glutamate-ammonia ligase (Glul). Additionally, glutamate, GABA, and glutamine were positively correlated and the glutamate/GABA ratio was almost identical in the postpartum and virgin females. Collectively, these findings indicate that glutamate and GABA signaling are increased and that the ratio of glutamate/GABA is well balanced in the maternal LS. The postpartum brain may provide a useful model system for understanding how glutamate and GABA are linked despite large signaling changes. Given that some mental health disorders, including depression and schizophrenia display dysregulated glutamate/GABA ratio, and there is increased vulnerability to mental disorders in mothers, it is possible that these postpartum disorders emerge when glutamate and GABA changes are not properly coordinated. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 44 | Transl Psychiatry 2014 -1 4: e371 |
| PMID | 24618690 |
| Title | Selective loss of parvalbumin-positive GABAergic interneurons in the cerebral cortex of maternally stressed Gad1-heterozygous mouse offspring. |
| Abstract | Exposure to maternal stress (MS) and mutations in GAD1, which encodes the ?-aminobutyric acid (GABA) synthesizing enzyme glutamate decarboxylase (GAD) 67, are both risk factors for psychiatric disorders. However, the relationship between these risk factors remains unclear. Interestingly, the critical period of MS for psychiatric disorders in offspring corresponds to the period of GABAergic neuron neurogenesis and migration in the fetal brain, that is, in the late stage of gestation. Indeed, decrement of parvalbumin (PV)-positive GABAergic interneurons in the medial prefrontal cortex (mPFC) and hippocampus (HIP) has often been observed in schizophrenia patients. In the present study, we used GAD67-green fluorescent protein (GFP) knock-in mice (that is, mice in which the GAD1 gene is heterozygously deleted; GAD67(+/GFP)) that underwent prenatal stress from embryonic day 15.0 to 17.5 and monitored PV-positive GABAergic neurons to address the interaction between GAD1 disruption and stress. Administration of 5-bromo-2-deoxyuridine revealed that neurogenesis of GFP-positive GABAergic neurons, but not cortical plate cells, was significantly diminished in fetal brains during MS. Differential expression of glucocorticoid receptors by different progenitor cell types may underlie this differential outcome. Postnatally, the density of PV-positive, but not PV-negative, GABAergic neurons was significantly decreased in the mPFC, HIP and somatosensory cortex but not in the motor cortex of GAD67(+/GFP) mice. By contrast, these findings were not observed in wild-type (GAD67(+/+)) offspring. These results suggest that prenatal stress, in addition to heterozygous deletion of GAD1, could specifically disturb the proliferation of neurons destined to be PV-positive GABAergic interneurons. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 45 | Eur Neuropsychopharmacol 2014 Feb 24: 271-89 |
| PMID | 23932495 |
| Title | Prenatal MAM administration affects histone H3 methylation in postnatal life in the rat medial prefrontal cortex. |
| Abstract | Several findings have indicated that schizophrenia may be connected with the impaired epigenetic regulation of gene transcription. The present study investigated the epigenetic modifications connected with histone H3 methylation at lysine (K)4 and K9 in the medial prefrontal cortex (mPFC) in a neurodevelopmental model of schizophrenia based on prenatal administration of methylazoxymethanol (MAM) at embryonic day 17, which impairs the sensorimotor gating process in adult but not adolescent animals. The effect of MAM was determined at different postnatal ages, pre-puberty (P15, P30 and P45) and post-puberty (P60 and P70), using western blot analyses. MAM treatment altered the levels of H3K9me2 before puberty. H3K9me2 was decreased at P15 and P45 but was increased at P30. In contrast, H3K4me3 was noticeably decreased in adult rats. Immunofluorescence experiments revealed that H3K9me2 protein levels were increased in neuronal cells at P30 and that H3K4me3 levels were decreased in astrocytes at P60 after MAM administration. Decreases in the methyltransferase ASH2L protein levels at P45, P60 and P70 were also observed, while the protein levels of the methyltransferase G9a did not change. In addition, levels of the demethylases LSD1 and JARID1c were analysed after MAM administration. LSD1 protein levels were increased at P15 but decreased at P30. JARID1c protein levels were increased in the MAM-treated animals at P60. Decreased GAD1 mRNA levels were found in adult MAM-treated animals, similar to alternation observed in schizophrenia. The present study indicates that prenatal MAM administration evokes changes in the methylation patterns of histone H3 during postnatal life. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 46 | Schizophr. Res. 2015 Sep 167: 1-3 |
| PMID | 26255083 |
| Title | The GABA system in schizophrenia: cells, molecules and microcircuitry. |
| Abstract | This is an overview of several papers that have been published in the Special Issue of schizophrenia Research entitled The GABA System in schizophrenia: Cells, Molecules and Microcircuitry. This issue presents a broad range of original reports and scholarly reviews regarding recent progress in studies of neural circuitry in corticolimbic brain regions in patients with schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 47 | Schizophr. Res. 2015 Sep 167: 35-41 |
| PMID | 25476119 |
| Title | DNA-methyltransferase1 (DNMT1) binding to CpG rich GABAergic and BDNF promoters is increased in the brain of schizophrenia and bipolar disorder patients. |
| Abstract | The down regulation of glutamic acid decarboxylase67 (GAD1), reelin (RELN), and BDNF expression in brain of schizophrenia (SZ) and bipolar (BP) disorder patients is associated with overexpression of DNA methyltransferase1 (DNMT1) and ten-eleven translocase methylcytosine dioxygenase1 (TET1). DNMT1 and TET1 belong to families of enzymes that methylate and hydroxymethylate cytosines located proximal to and within cytosine phosphodiester guanine (CpG) islands of many gene promoters, respectively. Altered promoter methylation may be one mechanism underlying the down-regulation of GABAergic and glutamatergic gene expression. However, recent reports suggest that both DNMT1 and TET1 directly bind to unmethylated CpG rich promoters through their respective Zinc Finger (ZF-CXXC) domains. We report here, that the binding of DNMT1 to GABAergic (GAD1, RELN) and glutamatergic (BDNF-IX) promoters is increased in SZ and BP disorder patients and this increase does not necessarily correlate with enrichment in promoter methylation. The increased DNMT1 binding to these promoter regions is detected in the cortex but not in the cerebellum of SZ and BP disorder patients, suggesting a brain region and neuron specific dependent mechanism. Increased binding of DNMT1 positively correlates with increased expression of DNMT1 and with increased binding of MBD2. In contrast, the binding of TET1 to RELN, GAD1 and BDNF-IX promoters failed to change. These data are consistent with the hypothesis that the down-regulation of specific GABAergic and glutamatergic genes in SZ and BP disorder patients may be mediated, at least in part, by a brain region specific and neuronal-activity dependent DNMT1 action that is likely independent of its DNA methylation activity. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 48 | JAMA Psychiatry 2015 Jun 72: 541-51 |
| PMID | 25738424 |
| Title | Circuit- and Diagnosis-Specific DNA Methylation Changes at ?-Aminobutyric Acid-Related Genes in Postmortem Human Hippocampus in Schizophrenia and Bipolar Disorder. |
| Abstract | Dysfunction related to ?-aminobutyric acid (GABA)-ergic neurotransmission in the pathophysiology of major psychosis has been well established by the work of multiple groups across several decades, including the widely replicated downregulation of GAD1. Prior gene expression and network analyses within the human hippocampus implicate a broader network of genes, termed the GAD1 regulatory network, in regulation of GAD1 expression. Several genes within this GAD1 regulatory network show diagnosis- and sector-specific expression changes within the circuitry of the hippocampus, influencing abnormal GAD1 expression in schizophrenia and bipolar disorder. To investigate the hypothesis that aberrant DNA methylation contributes to circuit- and diagnosis-specific abnormal expression of GAD1 regulatory network genes in psychotic illness. This epigenetic association study targeting GAD1 regulatory network genes was conducted between July 1, 2012, and June 30, 2014. Postmortem human hippocampus tissue samples were obtained from 8 patients with schizophrenia, 8 patients with bipolar disorder, and 8 healthy control participants matched for age, sex, postmortem interval, and other potential confounds from the Harvard Brain Tissue Resource Center, McLean Hospital, Belmont, Massachusetts. We extracted DNA from laser-microdissected stratum oriens tissue of cornu ammonis 2/3 (CA2/3) and CA1 postmortem human hippocampus, bisulfite modified it, and assessed it with the Infinium HumanMethylation450 BeadChip (Illumina, Inc). The subset of CpG loci associated with GAD1 regulatory network genes was analyzed in R version 3.1.0 software (R Foundation) using the minfi package. Findings were validated using bisulfite pyrosequencing. Methylation levels at 1308 GAD1 regulatory network-associated CpG loci were assessed both as individual sites to identify differentially methylated positions and by sharing information among colocalized probes to identify differentially methylated regions. A total of 146 differentially methylated positions with a false detection rate lower than 0.05 were identified across all 6 groups (2 circuit locations in each of 3 diagnostic categories), and 54 differentially methylated regions with P?schizophrenia and bipolar disorder. This work demonstrates diagnosis- and circuit-specific DNA methylation changes at a subset of GAD1 regulatory network genes in the human hippocampus in schizophrenia and bipolar disorder. These genes participate in chromatin regulation and cell cycle control, supporting the concept that the established GABAergic dysfunction in these disorders is related to disruption of GABAergic interneuron physiology at specific circuit locations within the human hippocampus. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 49 | Transl Psychiatry 2015 -1 5: e679 |
| PMID | 26575220 |
| Title | Deciphering H3K4me3 broad domains associated with gene-regulatory networks and conserved epigenomic landscapes in the human brain. |
| Abstract | Regulators of the histone H3-trimethyl lysine-4 (H3K4me3) mark are significantly associated with the genetic risk architecture of common neurodevelopmental disease, including schizophrenia and autism. Typical H3K4me3 is primarily localized in the form of sharp peaks, extending in neuronal chromatin on average only across 500-1500 base pairs mostly in close proximity to annotated transcription start sites. Here, through integrative computational analysis of epigenomic and transcriptomic data based on next-generation sequencing, we investigated H3K4me3 landscapes of sorted neuronal and non-neuronal nuclei in human postmortem, non-human primate and mouse prefrontal cortex (PFC), and blood. To explore whether H3K4me3 peak signals could also extend across much broader domains, we examined broadest domain cell-type-specific H3K4me3 peaks in an unbiased manner with an innovative approach on 41+12 ChIP-seq and RNA-seq data sets. In PFC neurons, broadest H3K4me3 distribution ranged from 3.9 to 12?kb, with extremely broad peaks (~10?kb or broader) related to synaptic function and GABAergic signaling (DLX1, ELFN1, GAD1, IGSF9B and LINC00966). Broadest neuronal peaks showed distinct motif signatures and were centrally positioned in prefrontal gene-regulatory Bayesian networks and sensitive to defective neurodevelopment. Approximately 120 of the broadest H3K4me3 peaks in human PFC neurons, including many genes related to glutamatergic and dopaminergic signaling, were fully conserved in chimpanzee, macaque and mouse cortical neurons. Exploration of spread and breadth of lysine methylation markings could provide novel insights into epigenetic mechanism involved in neuropsychiatric disease and neuronal genome evolution. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 50 | Epigenetics 2015 Dec 10: 1143-55 |
| PMID | 26575259 |
| Title | Maternal immune activation induces GAD1 and GAD2 promoter remodeling in the offspring prefrontal cortex. |
| Abstract | Maternal infection during pregnancy increases the risk of neurodevelopmental disorders in the offspring. In addition to its influence on other neuronal systems, this early-life environmental adversity has been shown to negatively affect cortical ?-aminobutyric acid (GABA) functions in adult life, including impaired prefrontal expression of enzymes required for GABA synthesis. The underlying molecular processes, however, remain largely unknown. In the present study, we explored whether epigenetic modifications represent a mechanism whereby maternal infection during pregnancy can induce such GABAergic impairments in the offspring. We used an established mouse model of prenatal immune challenge that is based on maternal treatment with the viral mimetic poly(I:C). We found that prenatal immune activation increased prefrontal levels of 5-methylated cytosines (5mC) and 5-hydroxymethylated cytosines (5hmC) in the promoter region of GAD1, which encodes the 67-kDa isoform of the GABA-synthesising enzyme glutamic acid decarboxylase (GAD67). The early-life challenge also increased 5mC levels at the promoter region of GAD2, which encodes the 65-kDa GAD isoform (GAD65). These effects were accompanied by elevated GAD1 and GAD2 promoter binding of methyl CpG-binding protein 2 (MeCP2) and by reduced GAD67 and GAD65 mRNA expression. Moreover, the epigenetic modifications at the GAD1 promoter correlated with prenatal infection-induced impairments in working memory and social interaction. Our study thus highlights that hypermethylation of GAD1 and GAD2 promoters may be an important molecular mechanism linking prenatal infection to presynaptic GABAergic impairments and associated behavioral and cognitive abnormalities in the offspring. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 51 | Schizophr Res Cogn 2015 Jun 2: 56-63 |
| PMID | 26346124 |
| Title | Hierarchical Classes Analysis (HICLAS): A novel data reduction method to examine associations between biallelic SNPs and perceptual organization phenotypes in schizophrenia. |
| Abstract | The power of SNP association studies to detect valid relationships with clinical phenotypes in schizophrenia is largely limited by the number of SNPs selected and non-specificity of phenotypes. To address this, we first assessed performance on two visual perceptual organization tasks designed to avoid many generalized deficit confounds, Kanizsa shape perception and contour integration, in a schizophrenia patient sample. Then, to reduce the total number of candidate SNPs analyzed in association with perceptual organization phenotypes, we employed a two-stage strategy: first a priori SNPs from three candidate genes were selected (GAD1, NRG1 and DTNBP1); then a Hierarchical Classes Analysis (HICLAS) was performed to reduce the total number of SNPs, based on statistically related SNP clusters. HICLAS reduced the total number of candidate SNPs for subsequent phenotype association analyses from 6 to 3. MANCOVAs indicated that rs10503929 and rs1978340 were associated with the Kanizsa shape perception filling in metric but not the global shape detection metric. rs10503929 was also associated with altered contour integration performance. SNPs not selected by the HICLAS model were unrelated to perceptual phenotype indices. While the contribution of candidate SNPs to perceptual impairments requires further clarification, this study reports the first application of HICLAS as a hypothesis-independent mathematical method for SNP data reduction. HICLAS may be useful for future larger scale genotype-phenotype association studies. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 52 | Mol. Psychiatry 2015 Dec 20: 1499-507 |
| PMID | 25623945 |
| Title | Inhibition of parvalbumin-expressing interneurons results in complex behavioral changes. |
| Abstract | Reduced expression of the GAD1 gene-encoded 67-kDa protein isoform of glutamic acid decarboxylase (GAD67) is a hallmark of schizophrenia. GAD67 downregulation occurs in multiple interneuronal sub-populations, including the parvalbumin-positive (PVALB+) cells. To investigate the role of the PV-positive GABAergic interneurons in behavioral and molecular processes, we knocked down the GAD1 transcript using a microRNA engineered to target specifically GAD1 mRNA under the control of Pvalb bacterial artificial chromosome. Verification of construct expression was performed by immunohistochemistry. Follow-up electrophysiological studies revealed a significant reduction in ?-aminobutyric acid (GABA) release probability without alterations in postsynaptic membrane properties or changes in glutamatergic release probability in the prefrontal cortex pyramidal neurons. Behavioral characterization of our transgenic (Tg) mice uncovered that the Pvalb/GAD1 Tg mice have pronounced sensorimotor gating deficits, increased novelty-seeking and reduced fear extinction. Furthermore, NMDA (N-methyl-d-aspartate) receptor antagonism by ketamine had an opposing dose-dependent effect, suggesting that the differential dosage of ketamine might have divergent effects on behavioral processes. All behavioral studies were validated using a second cohort of animals. Our results suggest that reduction of GABAergic transmission from PVALB+ interneurons primarily impacts behavioral domains related to fear and novelty seeking and that these alterations might be related to the behavioral phenotype observed in schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 53 | Schizophr. Res. 2015 Sep 167: 28-34 |
| PMID | 25458568 |
| Title | Transcriptional regulation of GAD1 GABA synthesis gene in the prefrontal cortex of subjects with schizophrenia. |
| Abstract | Expression of GAD1 GABA synthesis enzyme is highly regulated by neuronal activity and reaches mature levels in the prefrontal cortex not before adolescence. A significant portion of cases diagnosed with schizophrenia show deficits in GAD1 RNA and protein levels in multiple areas of adult cerebral cortex, possibly reflecting molecular or cellular defects in subtypes of GABAergic interneurons essential for network synchronization and cognition. Here, we review 20years of progress towards a better understanding of disease-related regulation of GAD1 gene expression. For example, deficits in cortical GAD1 RNA in some cases of schizophrenia are associated with changes in the epigenetic architecture of the promoter, affecting DNA methylation patterns and nucleosomal histone modifications. These localized chromatin defects at the 5' end of GAD1 are superimposed by disordered locus-specific chromosomal conformations, including weakening of long-range promoter-enhancer loopings and physical disconnection of GAD1 core promoter sequences from cis-regulatory elements positioned 50 kilobases further upstream. Studies on the 3-dimensional architecture of the GAD1 locus in neurons, including developmentally regulated higher order chromatin compromised by the disease process, together with exploration of locus-specific epigenetic interventions in animal models, could pave the way for future treatments of psychosis and schizophrenia. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 54 | Transl Psychiatry 2016 -1 6: e711 |
| PMID | 26756904 |
| Title | Behavioral and molecular neuroepigenetic alterations in prenatally stressed mice: relevance for the study of chromatin remodeling properties of antipsychotic drugs. |
| Abstract | We have recently reported that mice born from dams stressed during pregnancy (PRS mice), in adulthood, have behavioral deficits reminiscent of behaviors observed in schizophrenia (SZ) and bipolar (BP) disorder patients. Furthermore, we have shown that the frontal cortex (FC) and hippocampus of adult PRS mice, like that of postmortem chronic SZ patients, are characterized by increases in DNA-methyltransferase 1 (DNMT1), ten-eleven methylcytosine dioxygenase 1 (TET1) and exhibit an enrichment of 5-methylcytosine (5MC) and 5-hydroxymethylcytosine (5HMC) at neocortical GABAergic and glutamatergic gene promoters. Here, we show that the behavioral deficits and the increased 5MC and 5HMC at glutamic acid decarboxylase 67 (GAD1), reelin (Reln) and brain-derived neurotrophic factor (Bdnf) promoters and the reduced expression of the messenger RNAs (mRNAs) and proteins corresponding to these genes in FC of adult PRS mice is reversed by treatment with clozapine (5 mg kg(-1) twice a day for 5 days) but not by haloperidol (1 mg kg(-1) twice a day for 5 days). Interestingly, clozapine had no effect on either the behavior, promoter methylation or the expression of these mRNAs and proteins when administered to offspring of nonstressed pregnant mice. Clozapine, but not haloperidol, reduced the elevated levels of DNMT1 and TET1, as well as the elevated levels of DNMT1 binding to GAD1, Reln and Bdnf promoters in PRS mice suggesting that clozapine, unlike haloperidol, may limit DNA methylation by interfering with DNA methylation dynamics. We conclude that the PRS mouse model may be useful preclinically in screening for the potential efficacy of antipsychotic drugs acting on altered epigenetic mechanisms. Furthermore, PRS mice may be invaluable for understanding the etiopathogenesis of SZ and BP disorder and for predicting treatment responses at early stages of the illness allowing for early detection and remedial intervention. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 55 | Transl Psychiatry 2016 -1 6: e723 |
| PMID | 26812044 |
| Title | Toward dissecting the etiology of schizophrenia: HDAC1 and DAXX regulate GAD67 expression in an in vitro hippocampal GABA neuron model. |
| Abstract | schizophrenia (SZ) is associated with GABA neuron dysfunction in the hippocampus, particularly the stratum oriens of sector CA3/2. A gene expression profile analysis of human postmortem hippocampal tissue followed by a network association analysis had shown a number of genes differentially regulated in SZ, including the epigenetic factors HDAC1 and DAXX. To characterize the contribution of these factors to the developmental perturbation hypothesized to underlie SZ, lentiviral vectors carrying short hairpin RNA interference (shRNAi) for HDAC1 and DAXX were used. In the hippocampal GABA neuron culture model, HiB5, transduction with HDAC1 shRNAi showed a 40% inhibition of HDAC1 mRNA and a 60% inhibition of HDAC1 protein. GAD67, a enzyme associated with GABA synthesis, was increased twofold (mRNA); the protein showed a 35% increase. The expression of DAXX, a co-repressor of HDAC1, was not influenced by HDAC1 inhibition. Transduction of HiB5 cells with DAXX shRNAi resulted in a 30% inhibition of DAXX mRNA that translated into a 90% inhibition of DAXX protein. GAD1 mRNA was upregulated fourfold, while its protein increased by ~30%. HDAC1 expression was not altered by inhibition of DAXX. However, a physical interaction between HDAC1 and DAXX was demonstrated by co-immunoprecipitation. Inhibition of HDAC1 or DAXX increased expression of egr-1, transcription factor that had previously been shown to regulate the GAD67 promoter. Our in vitro results point to a key role of both HDAC1 and DAXX in the regulation of GAD67 in GABAergic HiB5 cells, strongly suggesting that these epigenetic/transcription factors contribute to mechanisms underlying GABA cell dysfunction in SZ. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 56 | PLoS ONE 2016 -1 11: e0148558 |
| PMID | 26848839 |
| Title | GAD2 Alternative Transcripts in the Human Prefrontal Cortex, and in Schizophrenia and Affective Disorders. |
| Abstract | Genetic variation and early adverse environmental events work together to increase risk for schizophrenia. ?-aminobutyric acid (GABA), the major inhibitory neurotransmitter in adult mammalian brain, plays a major role in normal brain development, and has been strongly implicated in the pathobiology of schizophrenia. GABA synthesis is controlled by two glutamic acid decarboxylase (GAD) genes, GAD1 and GAD2, both of which produce a number of alternative transcripts. Genetic variants in the GAD1 gene are associated with increased risk for schizophrenia, and reduced expression of its major transcript in the human dorsolateral prefrontal cortex (DLPFC). No consistent changes in GAD2 expression have been found in brains from patients with schizophrenia. In this work, with the use of RNA sequencing and PCR technologies, we confirmed and tracked the expression of an alternative truncated transcript of GAD2 (ENST00000428517) in human control DLPFC homogenates across lifespan besides the well-known full length transcript of GAD2. In addition, using quantitative RT-PCR, expression of GAD2 full length and truncated transcripts were measured in the DLPFC of patients with schizophrenia, bipolar disorder and major depression. The expression of GAD2 full length transcript is decreased in the DLPFC of schizophrenia and bipolar disorder patients, while GAD2 truncated transcript is increased in bipolar disorder patients but decreased in schizophrenia patients. Moreover, the patients with schizophrenia with completed suicide or positive nicotine exposure showed significantly higher expression of GAD2 full length transcript. Alternative transcripts of GAD2 may be important in the growth and development of GABA-synthesizing neurons as well as abnormal GABA signaling in the DLPFC of patients with schizophrenia and affective disorders. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |
| 57 | Neuropsychopharmacology 2016 Jan -1: -1 |
| PMID | 26822489 |
| Title | Prefrontal White Matter Structure Mediates the Influence of GAD1 on Working Memory. |
| Abstract | The glutamic acid decarboxylase 1 (GAD1) gene is a major determinant of ?-aminobutyric acid (GABA), the most abundant inhibitory neurotransmitter modulating local neuronal circuitry. GABAergic dysfunction and expression of GAD1 have been implicated in the pathophysiology of schizophrenia, and in working memory impairment. We examined the influence of the functional GAD1 rs3749034 variant on white matter fractional anisotropy (FA), cortical thickness, and working memory performance in schizophrenia patients and healthy controls (N=197). Using transcranial magnetic stimulation with electroencephalography (TMS-EEG), we subsequently examined the effect of rs3749034 on long-interval cortical inhibition (LICI) in the dorsolateral prefrontal cortex (DLPFC) in schizophrenia patients and healthy controls (N=66). We found that the rs3749034 T-allele carrier risk group had lower voxel-wise FA in the prefrontal cortex region (PFWE-corrected<0.05) but not cortical thickness. Mixed-model regression revealed a significant effect on attentional processing and working memory across four performance measures (F1,182=11.5, P=8 × 10(-4)). FA in the prefrontal cortex was associated with digit-span performance. Voxel-wise mediation analysis revealed that the effect GAD1 on poorer digit-span performance statistically predicted the lower white matter FA (PFWE-corrected<0.05). In exploratory analysis, we found a prominent GAD1 genotype-by-diagnosis interaction on DLPFC LICI (F1,56=14.3, P=4.1 × 10(-4)). Our findings converge on variation in GAD1 gene predicting a susceptibility mechanism that affects white matter FA, GABAergic inhibitory neurotransmission in the DLPFC, and working memory performance. Furthermore, via voxel mediation of FA and TMS-EEG intervention, we provide evidence for a potentially causal mechanism through which aberrant DLPFC GABA signaling may contribute to working memory dysfunction.Neuropsychopharmacology advance online publication, 24 February 2016; doi:10.1038/npp.2016.14. |
| SCZ Keywords | schizophrenia, schizophrenic, schizophrenics |