Our previous studies in frontal cortices of European ancestry demonstrated significant cis-regulatory effects on the CHRNA5 mRNA levels. In contrast only modest variation in CHRNA3 or CHRNB4 mRNA levels were detected in our sample and these were not associated with SNP variation. In this study, we focused on CHRNA5. We first examined the CHRNA5 mRNA variability in frontal cortices derived from 49 African Americans and confirmed our previous observation in other ethnic population. Further, we quantified CHRNA5 allelic mRNA expression in frontal cortices derived from 66 European Australians, 45 European Americans, and 49 African Americans, to investigate the putative cis-regulatory variants that affect mRNA expression of this gene. Because several cis-regulatory variants for CHRNA5 mRNA expression are located in the PSMA4 gene region, we also examined the influence of these variants on PSMA4 mRNA expression to clarify whether the cis-regulatory effect is specific for CHRNA5 mRNA expression.
