COMT genotype is associated with differential expression of muscarinic M1 receptors in human cortex

Catechol-O-methyltransferase (COMT) genotype has been associated with varying levels of cognitive functioning and an altered risk of schizophrenia. COMT regulates the breakdown of catecholamines, particularly dopamine, which is thought critical in maintaining cognitive function and the aetiology of schizophrenia. This hypothesis gained support from reports that the VAL allele at rs4680 was associated with poorer performance on cognitive tests and a slightly increased risk of schizophrenia. More recently, genotype at rs4818, part of a hapblock with rs4680, has been shown to impact on cognitive ability more than genotype at rs4680 but, as yet, not the risk for schizophrenia. Here, we determined if COMT genotype at rs4680 or rs4818, as well as rs165519 and rs737865, two synonymous single nucleotide polymorphisms (SNPs) with no known functional consequences, were associated with an altered risk of schizophrenia and if genotype at the four COMT SNPs was related to expression of the cortical muscarinic M1 receptor (CHRM1) because the expression of the cortical CHRM1 has been reported to be lower in schizophrenia and is important in maintaining cognitive functioning in humans. We report that the variation in gene sequence at the four COMT SNPs studied was not associated with an altered the risk of schizophrenia but genotype at rs4680 and rs4818, but not rs165519 and rs737865, were associated with varying levels of cortical CHRM1 expression in the human dorsolateral prefrontal cortex (DLPFC). These data are the first to suggest that levels of CHRM1 in the human DLPFC are, in part, determined by COMT gene sequence. © 2016 Wiley Periodicals, Inc.