Screening for mutations in candidate genes for hypospadias

Hypospadias. a condition with a frontally placed urethral orifice on the penis, is the most common malformation in males. During fetal development several components are necessary for normal male genital development. Testosterone and dihydrotestosterone act via the androgen receptor but a defective receptor function results in different degrees of genital malformations. Testosterone-5alpha-reductase converts testosterone to dihydrotestosterone, which is crucial for normal differentiation, and a total lack of this enzyme results, in syndromes with hypospadias. The Wilms' tumour 1 (WT1) gene is expressed in the fetal gonad and genital malformations can occur due to WT1 gene mutations. These genes are therefore strong candidate genes for hypospadias. We have analysed 35 boys with hypopadias and one girl diagnosed as with complete androgen insensitivity syndrome, using exon by exon polymerase chain reaction (PCR) amplification of the AR, WTI and 5alpha-reductase genes and screened for point mutations and performed subsequent DNA sequencing. No mutations in any of these genes were found in the 26 patients with isolated hypospadias. Two patients with severe hypospadias with cryptorchidism were found to carry mutations in the androgen receptor gene. Also the girl with clinically diagnosed complete androgen insensitivity was found to be homozygous for a splice mutation in the 5alpha-reductase gene. In summary, mutations in the WT1, AR and 5alpha-reductase genes are not common causes of isolated hypospadias.