Functional analysis of four CYP21 mutations from Spanish patients with congenital adrenal hyperplasia

Deleterious mutations in the CYP21 (steroid 21-hydroxylase) gene cause cong enital adrenal hyperplasia (CAH). These mutations usually result from recom binations between CYP21 and an adjacent pseudogene, CYP21P, including delet ions and transfers of deleterious mutations from CYP21P to CYP21 (gene conv ersions). Additional rare mutations that are not gene conversions account f or 5-10% of al-hydroxylase deficiency alleles. Recently, four novel CYP21 p oint mutations leading to amino acid changes were identified in a populatio n of 57 Spanish families with CAH. A nonsense mutation, K74X, was also iden tified. The enzymatic activities of al-hydroxylase mutants G90V, G178A, G29 1C, and R354H were examined in transiently transfected CHOP cells using pro gesterone and 17 alpha-hydroxyprogesterone as substrates. The G90V, G291C, and R354H mutations effectively eliminated al-hydroxylase activity. However , the G178A mutant retained significant activity when 17 alpha-hydroxyproge sterone was the substrate. These results correlate well with the identifica tion of G90V, G291C, and R354H in patients with severe "salt-wasting" disea se and G178A in a patient with the milder simple virilizing form. (C) 1999 Academic Press.