Expression Profiling of Fibroblasts Identifies Cell Cycle Abnormalities in Schizophrenia

Abstract

Many previous studies have attempted to gain insight into the underlying pathophysiology of schizophrenia by studying postmortem brain tissues of schizophrenia patients. However, such analyses can be confounded by artifactual features of this approach such as lengthy agonal state and postmortem interval times. As several aspects of schizophrenia are also manifested at the peripheral level in proliferating cell types, we have studied the disorder through systematic transcriptomic and proteomic analyses of skin fibroblasts biopsied from living patients. We performed comparative transcriptomic and proteomic profiling to characterize skin fibroblasts from schizophrenia patients compared to healthy controls. Transcriptomic profiling using cDNA array technology showed that pathways associated with cell cycle regulation and RNA processing were altered in the schizophrenia subjects (n = 12) relative to controls (n = 12). LC-MS(E) proteomic profiling led to identification of 16 proteins that showed significant differences in expression between schizophrenia (n = 11) and control (n = 11) subjects. Analysis in silico revealed that these proteins were also associated with proliferation and cell growth pathways. To validate these findings at the protein level, fibroblast protein extracts were analyzed by Western blotting which confirmed the differential expression of three key proteins associated with these pathways. At the functional level, we confirmed the decreased proliferation phenotype by showing that cultured fibroblasts from schizophrenia subjects (n = 5) incorporated less (3)H-thymidine into their nuclei compared to those from controls (n = 6) by day 4 over an 8 day time course study. Similar abnormalities in cell cycle and growth pathways have been reported to occur in the central nervous system in schizophrenia. These studies demonstrate that fibroblasts obtained from living schizophrenia subjects show alterations in cellular proliferation and growth pathways. Future studies aimed at characterizing such pathways in fibroblasts and other proliferating cell types from schizophrenia patients could elucidate the molecular mechanisms associated with the pathophysiology of schizophrenia and provide a useful model to support drug discovery efforts.

Gene Expression Analysis of Fibroblasts from Patients with Bipolar Disorder

“…Aberrant Ca 2+ signaling is a repeated observation in BD studies [52], and this study indicates that these abnormalities may be related to gene expression alterations in BD patients. Cell cycle alterations are also reported after gene expression profiling of skin fibroblasts from schizophrenic patients and gene expression profiling of olfactory neuroepithelium from BD patients [42,51]. Deregulations in small GTPase signal transduction indicated from this study are in accordance with previous findings concerning the effect of lithium and other antidepressants on second-messenger signaling systems [50].…”

“…Additionally GO terms related to apoptosis were identified, such as downregulation of positive regulation of apoptotic process (CAMK1D, MAPK9, CASP2, FAM162A, FLCN, DDX20, BNIP3L, LPAR1, SLIT2, PRKDC, PPARG, AIFM2) and positive regulation of apoptotic signaling pathway (PIM1, BIRC5, TT28). Expression profile of fibroblasts from schizophrenic patients also concludes to altered expression of mRNA transcripts and proteins related to cell cycle [51]. Gene expression profiling of biopsied olfactory neuroepithelium also identifies genes related to apoptosis and cell cycle.…”

Knockdown of the schizophrenia susceptibility gene TCF4 alters gene expression and proliferation of progenitor cells from the developing human neocortex

“…Several of the differentially expressed genes showing most significant association with schizophrenia in the present MAGMA analy sis have known roles in cell cycling, suggesting that TCF4 could operate through a network of other susceptibility genes involved in neural cell proliferation. Cell cycling disturbances in individuals with schizophrenia are also suggested by observations of altered proliferation of fibroblasts 35 and olfactory biopsy cultures 36 from patients with the disorder as well as reports of differential expression of cell cycle genes in postmortem brain samples from such patients. 37,38 Although, to our knowledge, there are no published data implicating cell cycle dysregulation in individuals with Pitt-Hopkins syndrome, changes in neural progenitor proliferation in the developing neocortex could contribute to the severe intellectual deficits observed in people with this condition.…”

Análise proteômica da esquizofrenia

“…Skin fibroblasts can be biopsied from living patients and can also be used as a source of biomarkers. Using label-free proteomics, the proteomes of 12 SCZ patients were compared to 12 controls leading to the identification of cell cycle proteins as well as energy metabolism and oxidative 18 .…”