Cx40 gene region and features of the promoter B SNP. (a) The two alternative transcripts (A and B) of the Cx40 gene GJA5 are illustrated, both sharing a common second coding exon. The positions of the promoter B SNP (rs10465885), the promoter A SNP proxy rs12408178 and each SNP used as an allelic expression imbalance indicator (AEI) are denoted. Linkage disequilibrium relationships (r2) between SNPs are illustrated. (b) Sequence alignment of the promoter region near the promoter B SNP in various mammalian species. The promoter B SNP site (A/G), located at −26 relative to the start site of transcription, is denoted. The overlapping TATA box sequences are underlined, and graphical representations of their respective nucleotide frequency matrices are shown above the sequence.