1Biol. Psychiatry 2010 Jul 68: 25-32
TitleAltered cortical CDC42 signaling pathways in schizophrenia: implications for dendritic spine deficits.
AbstractSpine density on the basilar dendrites of pyramidal neurons is lower in layer 3, but not in layers 5 and 6, in the dorsolateral prefrontal cortex (DLPFC) of subjects with schizophrenia. The expression of CDC42 (cell division cycle 42), a RhoGTPase that regulates the outgrowth of the actin cytoskeleton and promotes spine formation, is also lower in schizophrenia; however, CDC42 mRNA is lower across layers 3-6, suggesting that other lamina-specific molecular alterations are critical for the spine deficits in the illness. The CDC42 effector proteins 3 and 4 (CDC42EP3, CDC42EP4) are preferentially expressed in DLPFC layers 2 and 3, and CDC42EP3 appears to assemble septin filaments in spine necks. Therefore, alterations in CDC42EP3 could contribute to the lamina-specific spine deficits in schizophrenia.
We measured transcript levels of CDC42, CDC42EP3, CDC42EP4; their interacting proteins (septins [SEPT2, 3, 5, 6, 7, 8, and 11], anillin), and other spine-specific proteins (spinophilin, PSD-95, and synaptopodin) in the DLPFC from 31 subjects with schizophrenia and matched normal comparison subjects.
The expression of CDC42EP3 mRNA was significantly increased by 19.7%, and SEPT7 mRNA was significantly decreased by 6.9% in subjects with schizophrenia. Cortical levels of CDC42EP3 and SEPT7 mRNAs were not altered in monkeys chronically exposed to antipsychotic medications.
Activated CDC42 is thought to disrupt septin filaments transiently in spine necks, allowing the molecular translocations required for synaptic potentiation. Thus, altered CDC42 signaling via CDC42EP3 may perturb synaptic plasticity and contribute to the spine deficits observed in layer 3 pyramidal neurons in schizophrenia.
SCZ Keywordsschizophrenia
2Biol. Psychiatry 2015 Dec 78: 775-85
TitleAltered expression of CDC42 signaling pathway components in cortical layer 3 pyramidal cells in schizophrenia.
AbstractCognitive dysfunction in schizophrenia is associated with a lower density of dendritic spines on deep layer 3 pyramidal cells in the dorsolateral prefrontal cortex (DLPFC). These alterations appear to reflect dysregulation of the actin cytoskeleton required for spine formation and maintenance. Consistent with this idea, altered expression of genes in the cell division cycle 42 (CDC42)-CDC42 effector protein (CDC42EP) signaling pathway, a key organizer of the actin cytoskeleton, was previously reported in DLPFC gray matter from subjects with schizophrenia. We examined the integrity of the CDC42-p21-activated serine/threonine protein kinases (PAK)-LIM domain-containing serine/threonine protein kinases (LIMK) signaling pathway in schizophrenia in a layer-specific and cell type-specific fashion in DLPFC deep layer 3.
Using laser microdissection, samples of DLPFC deep layer 3 were collected from 56 matched pairs of subjects with schizophrenia and comparison subjects, and levels of CDC42-PAK-LIMK pathway messenger RNAs were measured by quantitative polymerase chain reaction. These same transcripts also were quantified by microarray in samples of individually microdissected deep layer 3 pyramidal cells from a subset of the same subjects and from monkeys exposed to antipsychotics.
Relative to comparison subjects, CDC42EP4, LIMK1, LIMK2, ARHGDIA, and PAK3 messenger RNA levels were significantly upregulated in subjects with schizophrenia in laminar and cellular samples. In contrast, CDC42 and PAK1 messenger RNA levels were significantly downregulated specifically in deep layer 3 pyramidal cells. These differences were not attributable to psychotropic medications or other comorbid factors.
Findings from the present and prior studies converge on synergistic alterations in CDC42 signaling pathway that could destabilize actin dynamics and produce spine deficits preferentially in deep layer 3 pyramidal cells in schizophrenia.
SCZ Keywordsschizophrenia