Characterization of a genotype previously designated as CYP2A6 D-type:: CYP2A6*4B, another entire gene deletion allele of the CYP2A6 gene in Japanese

CYP2A6 is known as an enzyme responsible for the metabolism of several clincally used drugs such as tegafur. Previously, we found two novel genotypes of the CYP2A6 gene, D-type and E-type, and the E-type was clarified to be homozygous for the CYP2A6* 4A allele. On the other hand, since the D-type was reported to lack regions from at least intron 5 to a part of exon 9 of the CYP2A6 gene, it caused a misunderstanding that the D-type would be a partial CYP2A6 gene-deleted allele. In this paper, we demonstrate that the D-type is a genotype heterozygous for the CYP2A6*4A and another novel entire CYP2A6 gene-deleted allele, CYP2A6*4B, by analyzing a Japanese family including parents genotyped as the CYP2A6*4A/4A and CYP2A6* 1A/*4B, respectively.