A NONSENSE MUTATION (TGG[TRP(116)]-]TAG [STOP]) IN CYP11B1 CAUSES STEROID 11-BETA-HYDROXYLASE DEFICIENCY

Steroid 11 beta-hydroxylase deficiency (11 beta OHD), an autosomal rec essive hereditary disease, accounts for 5-8% of cases of congenital ad renal hyperplasia. In this study, we carried out a molecular genetic a nalysis of CYP11B1 encoding steroid 11 beta-hydroxylase (P450c11) from a Japanese patient affected with this disease. Nucleotide sequence an alysis of polymerase chain reaction-amplified products of the patient' s genome revealed the occurrence of a stop codon in exon 2 due to a po int mutation, TGG --> TAG (Trp(116) --> Stop). To further analyze the role of CYP11B2 encoding steroid 18-hydroxylase (P450c18) in the 11 be ta OHD patient, CYP11B2 of the patient was also amplified and sequence d. In contrast to CYP11B1, there was no mutation in CYP11B2. Restricti on fragment length polymorphism analysis indicated that the 11 beta OH D patient is homozygous and his unaffected parents are heterozygous fo r the mutation. When a cDNA corresponding to CYP11B1 of the 11 beta OH D patient was transfected into COS-7 cells, steroid 11 beta-hydroxylas e activity was not detectable in mitochondria of the cells. These resu lts demonstrate that intact P450c11 was not produced at all due to the nonsense mutation in CYP11B1 of the patient without any mutation in C YP11B2.