Nonisotopic single strand conformation analysis of the 5α-reductase type 2 gene for the diagnosis of 5α-reductase deficiency

5α-Reductase deficiency is a rare autosomal recessive disorder of defective virilization in karyotypic males due to reduced conversion of testosterone to dihydrotestosterone. The gene encoding the affected 5α- reductase type 2 enzyme has recently been cloned, and mutations within the coding region have been discovered as the cause of this disease. We address the possibility of a rapid nonradioactive molecular genetic screening technique for initial diagnosis and report different point mutations in this gene in eight unrelated patients with clinical features of 5α-reductase deficiency. For molecular genetic analysis, DNA from peripheral blood leukocytes was studied. The coding region of the 5α-reductase type 2 gene was characterized by exon-specific PCR amplification, nonradioactive single strand conformation analysis, and direct sequencing. In seven patients, homozygous point mutations were identified (Leu⁵⁵-Gln, ΔMet¹⁵⁷, Gly¹⁹⁶-Ser, Arg²²⁷-Gln, Ala²²⁸-Thr, and His²³-Arg). One individual was a compound heterozygote carrier of two mutations (Ile¹¹²-Asn and Gln¹²⁶-Arg). We conclude that molecular genetic characterization of point mutations in the 5α-reductase type 2 gene may be used as an additional valuable procedure for the diagnosis of this disorder.