A SNP in the ABCC11 gene is the determinant of human earwax type

Human earwax consists of wet and dry types. Dry earwax isfrequent in East Asians, whereas wet earwax is common inother populations. Here we show that a SNP, 538G-A(rs17822931), in the ABCC11 gene is responsible fordetermination of earwax type. The AA genotype corresponds todry earwax, and GA and GG to wet type. A 27-bp deletion inABCC11 exon 29 was also found in a few individuals of Asianancestry. A functional assay demonstrated that cells with alleleA show a lower excretory activity for cGMP than those withallele G. The allele A frequency shows a north-south and east-west downward geographical gradient; worldwide, it is highestin Chinese and Koreans, and a common dry-type haplotype isretained among various ethnic populations. These suggest thatthe allele A arose in northeast Asia and thereafter spreadthrough the world. The 538G-A SNP is the first exampleof DNA polymorphism determining a visible genetic trait.Earwax (cerumen) is a secretory product of ceruminous apocrineglands. Human earwax is a mendelian trait consisting of wet and drytypes