1Gene 2015 Nov 572: 175-83
TitleRole of long purine stretches in controlling the expression of genes associated with neurological disorders.
AbstractPurine repeat sequences present in the human genome are known to act as hotspots for mutations leading to chromosomal imbalances. It is established that large purine repeats (PRs) form stable DNA triplex structure which can inhibit gene expression. Friedreich's ataxia (FRDA), the autosomal neurodegenerative disorder is the only human disease known so far, where a large purine (GAA) repeat in the FXN gene is known to inhibit the expression of frataxin protein. We explored the hidden purine repeats (PRn with n ? 200) if any, in the human genome to find out how they are associated with neurological disorders. The results showed 28 PRs, which are mostly restricted to the intronic regions. Interestingly, the transcriptome expression analysis of PR-carrying genes (PR-genes) revealed that most of them are down-regulated in neurological disorders (autism, Alzheimer's disease, schizophrenia, epilepsy, mental retardation, Parkinson's disease, brain tumor) as compared to that in healthy controls. The altered gene expression in brain disorders can be interpreted in terms of a possible expansion of purine repeats leading to formation of very stable DNA-triplex and/or alleviation of the repair enzymes and/or other unknown cellular factors. Interactome analysis identified four PR-genes in signaling pathways whose dysregulation is correlated directly with pathogenesis: GRK5 and KLK6 in Alzheimer's disease; FGF14 in craniosynostosis, mental retardation and FLT1 in neuroferritinopathy. By virtue of being mutational hotspots and their ability to form DNA-triplex, purine repeats in genome disturb the genome integrity and interfere with the transcriptional regulation. However, validation of the disease linkage of PR-genes can be validated using knock-out techniques.
SCZ Keywordsschizophrenia
2Transl Psychiatry 2016 -1 6: e806
TitleGenetic deletion of fibroblast growth factor 14 recapitulates phenotypic alterations underlying cognitive impairment associated with schizophrenia.
AbstractCognitive processing is highly dependent on the functional integrity of gamma-amino-butyric acid (GABA) interneurons in the brain. These cells regulate excitability and synaptic plasticity of principal neurons balancing the excitatory/inhibitory tone of cortical networks. Reduced function of parvalbumin (PV) interneurons and disruption of GABAergic synapses in the cortical circuitry result in desynchronized network activity associated with cognitive impairment across many psychiatric disorders, including schizophrenia. However, the mechanisms underlying these complex phenotypes are still poorly understood. Here we show that in animal models, genetic deletion of fibroblast growth factor 14 (FGF14), a regulator of neuronal excitability and synaptic transmission, leads to loss of PV interneurons in the CA1 hippocampal region, a critical area for cognitive function. Strikingly, this cellular phenotype associates with decreased expression of glutamic acid decarboxylase 67 (GAD67) and vesicular GABA transporter (VGAT) and also coincides with disrupted CA1 inhibitory circuitry, reduced in vivo gamma frequency oscillations and impaired working memory. Bioinformatics analysis of schizophrenia transcriptomics revealed functional co-clustering of FGF14 and genes enriched within the GABAergic pathway along with correlatively decreased expression of FGF14, PVALB, GAD67 and VGAT in the disease context. These results indicate that FGF14(-/-) mice recapitulate salient molecular, cellular, functional and behavioral features associated with human cognitive impairment, and FGF14 loss of function might be associated with the biology of complex brain disorders such as schizophrenia.
SCZ Keywordsschizophrenia