Screening for mutations in candidate genes for hypospadias

Hypospadias, a condition with a frontally placed urethral orifice on the pe nis, is the most common malformation in males. During fetal development sev eral components are necessary for normal male genital development. Testoste rone and dihydrotestosterone act via the androgen receptor but a defective receptor function results in different degrees of genital malformations. Te stosterone-5 alpha-reductase converts testosterone to dihydrotestosterone, which is crucial for normal differentiation, and a total lack of this enzym e results, in syndromes with hypospadias. The Wilms' tumour 1 (WT1) gene is expressed in the fetal gonad and genital malformations can occur due to WT 1 gene mutations. These genes are therefore strong candidate genes for hypo spadias. We have analysed 35 boys with hypopadias and one girl diagnosed as with complete androgen insensitivity syndrome, using exon by exon polymera ce chain reaction (PCR) amplification of the AR, WT1 and 5 alpha-reductase genes and screened for point mutations and performed subsequent DNA sequenc ing. No mutations in any of these genes were found in the 26 patients with isolated hypospadias. Two patients with severe hypospadias with cryptorchid ism were found to carry mutations in the androgen receptor gene. Also the g irl with clinically diagnosed complete androgen insensitivity was found to be homozygous for a splice mutation in the 5 alpha-reductase gene. In summa ry, mutations in the WT1, AR and 5 alpha-reductase genes are not common cau ses of isolated hypospadias.