The cis-regulatory effect on CHRNA5 mRNA expression in frontal cortex from individuals of African ancestry is the same as observed in frontal cortex from individuals of European ancestry. In populations of European ancestry variants that alter CHRNA5 mRNA expression levels are in an extensive linkage disequilibrium bin spanning ∼200 kb, with correlation coefficient (r2) of 0.7. In populations of African ancestry they fell into 7 bins (r2≥0.7) (Table S1), allowing us to map the functional variants influencing CHRNA5 mRNA expression to a ∼9 kb region upstream of the CHRNA5 transcription start site (−22.3 kb to −13.2 kb at AUG of CHRNA5).
