Protein expression profiling of postmortem brain in schizophrenia

Surface enhanced laser desorption/ionization time of flight mass spectrometry (SELDI-TOF-MS) enables the sensitive, high-throughput protein profiling of complex biological mixtures. In combination with bioinformatics, this technology has the potential to identify combinations of spectral peaks that can differentiate individuals with a particular disease from normal controls. SELDI-TOF-MS was used to screen postmortem tissue derived from the dorsolateral prefrontal cortex of individuals with schizophrenia (n = 34) and matched controls (n = 35), obtained from the Stanley Foundation Neuropathology Consortium. Tissue samples were homogenized in urea buffer, applied to four different chip arrays which possess different chromatographic surfaces, and analyzed using the Ciphergen ProteinChip Biomarkers System (Model PBS II). Protein expression profiles of the schizophrenia and control groups were compared and analyzed using the Ciphergen Express (CE) and Biomarker Patterns Software (BPS) package. We detected several protein peaks whose intensities differed between the schizophrenia and control groups to a highly significant degree. A combination of these peaks was capable of distinguishing between schizophrenia and controls with a sensitivity and specificity of about 70%. The classification model that distinguished schizophrenia from controls was complex, suggesting that the biochemical abnormalities underlying schizophrenia are heterogeneous. Our results suggest that SELDI-TOF-MS has the potential for distinguishing individuals with schizophrenia from normal controls and may eventually lead to a better understanding of the classification, diagnosis and pathogenesis of this disorder.