Lack of association between endornetriosis and the CYP17 MspA1 polymorphism in UK and Japanese populations

Endometriosis is a complex trait, which means that multiple susceptibility genes interact with one another and the environment to produce the phenotype. One of the genes previously implicated in the disease is CYP17; this encodes the enzyme P450c17 alpha, which plays a vital role in steroid biosynthesis in the ovary. The presence of a single nucleotide polymorphism (T-C) in the T-promoter region of the gene creates a new recognition site for the restriction enzyme MspA1 producing a mutant allele (A(2)), which affects circulating estrogen levels. In this study, we compared the frequency of the CYP17 MspA1 polymorphism in two different ethnic populations. DNA was obtained from (1) 94 women with revised American Fertility Society (rAFS) stage III-IV endometriosis and 97 male blood donors in the UK, and (2) 130 women with rAFS stage III-IV endometriosis and 179 female newborn infants in Japan. No significant differences in allele or genotype frequencies were seen in either population. The genotype distribution in the UK population was 33/94 [35.1%] (cases) and 39/97 [40.2%] (controls) for A(1)A(1) (homozygous wild-type); 43/94 [45.7%] (cases) and 44/97 [45.4%] (controls) for A(1)A(2); and 18/94 [19.1%] (cases) and 14/97 [14.4%] (controls) for A(2)A(2). The genotype distribution in the Japanese population was 31/130 [23.9%] (cases) and 57/179 [31.8%] (controls) for A(1)A(1); 73/130 [56.2%] (cases) and 89/179 [49.7%] (controls) for A(1)A(2); and 26/130 [20.0%] (cases) and 33/179 [18.4%] (controls) for A(2)A(2). The CYP17 MspA1 polymorphism is probably not associated with endometriosis in either the UK or the Japanese population.