Analysis of CYP21 coding polymorphisms in three ethnic populations: Further evidence of nonamplifying CYP21 alleles among whites

Background: Adrenal steroid 21-hydroxylase is essential for the synthesis of both mineralocorticoids and glucocorticoids. The gene for this enzyme, CYP21, contains several frequent coding polymorphisms. Because of its essential function in steroid synthesis, polymorphisms in this enzyme might influence a variety of disease processes. However, before disease-association studies are performed, it is important to understand the frequency of these polymorphisms among normal individuals. Methods: Using polymerase chain reaction (PCR) with restriction enzyme digestion or size length polymorphism analysis, we measured the frequencies of the +Leu(10), Arg102Lys, and Ser268Thr polymorphisms in CYP21 in healthy whites, blacks, and Indian Americans. The subjects were all young female college students participating in a study of relative risks for cardiovascular disease in these populations. Results: The frequency of each polymorphism among whites, blacks, and Indian Americans were as follows: +Leu(10), 0.55, 0.96, 0.75; Arg102, 0.63, 0.97, 0.82; and Ser268, 0.92, 0.68, 0.79, respectively. With the exception of the frequencies of the Ser268Thr polymorphism among blacks and Indian Americans, there were significantly different frequencies of each polymorphism among all groups (P < .05). Among whites, the distribution of genotypes for the +Leu(10) and Arg102Lys polymorphisms deviated significantly from expected Hardy-Weinberg values because of an excess of homozygotes. Conclusions: Among the ethnic groups, there are statistically significant differences in the frequencies of these common coding polymorphisms in CYP21 that need to be considered in disease-association studies. Deviation from Hardy-Weinberg distributions might be explained by allelic dropout during PCR, a phenomenon previously reported at this locus.