Regulation of α7-nicotinic receptor subunit and α7-like gene expression in the prefrontal cortex of patients with bipolar disorder and schizophrenia

Objective: The alpha 7-nicotinic receptor subunit gene (CHRNA7) is located at chromosome 15q13-14, a region previously linked with schizophrenia. Genetic association and mRNA expression studies also implicate CHRNA7 in schizophrenia. The CHRNA7 gene has a partial duplication that constitutes the alpha 7-like nicotinic receptor gene (CHRFAM7A). We hypothesized that major psychoses could affect the expression of both CHRNA7 and CHRFAM7A. Method: CHRNA7 and CHRFAM7A mRNA levels were measured in postmortem prefrontal cortex (donated by the Stanley Foundation) from subjects with schizophrenia, bipolar disorder and unaffected controls (n = 35 each). Results: The mRNA levels of alpha7 and alpha 7-like genes have a positive correlation overall (r = 0.25; P = 0.009), however, there is no significant difference in the expression of CHRNA7 among the three diagnostic groups. Conclusion: This correlation is driven by the bipolar group (r = 0.43; P = 0.009), and is absent in schizophrenia and unaffected controls, suggesting an alteration in the CHRNA7:CHRFAM7A ratio in bipolar disorder.