UCLA

Schizophrenia and bipolar disorder are substantially heritable psychiatric illnesses. This study examined peripheral gene expression in an initial sample recruited in Sweden consisting of 35 individuals with schizophrenia and their unaffected co-twins, 24 individuals with bipolar disorder and their unaffected co-twins, and 60 control twins without a history of significant psychiatric illness. Results were confirmed with a secondary sample of 18 individuals with schizophrenia and their unaffected co-twins and 37 non-psychiatric control twins recruited in Finland. Expression in peripheral blood lymphocytes was measured using the Illumina Human WG6 v3.0 gene chip. A cognitive endophenotype was used to screen for genes that varied in relation to cognition out of the genome-wide panel. Results of the mixed-model ANOVA revealed 28 genes showed a significant association with cognitive performance at a corrected α = 0.05 and 47 at a corrected α = 0.10. Twelve of these genes showed significantly decreased expression in patients with schizophrenia and five showed decreased expression in patients with bipolar disorder compared to controls. Nine genes also showed decreased expression in the unaffected co-twins of patients with schizophrenia compared to controls. All twelve genes also showed decreased expression in the secondary sample of patients with schizophrenia. Further research is necessary to determine the relationship between decreased peripheral expression of these genes and expression levels in the central nervous system and relationships with other factors such as duration of illness and psychotropic medication use.