Regulation of Wolffian duct development in patients with complete androgen insensitivity syndrome
SE Hannema, H Martin & IA Hughes
Wolffian duct (WD) development is believed to be testosterone dependent. However, patients with complete androgen insensitivity syndrome (CAIS) and a causative mutation in the androgen receptor (AR) still develop WDs. Exceptions to this observation are those patients with severe N-terminal mutations. We investigated the role of the AR in WD development in these patients.
AR expression in genital skin fibroblasts (GSF) from eleven patients with CAIS was studied by Western hybridisation. Substitution mutations and single amino acid deletions led to normal AR expression, whereas premature stopcodons led to low or undetectable AR levels, possibly by rapid degradation of truncated proteins.
Five mutations were recreated in vitro (Y223X, G371X, deletion F582, G724D and D864N). When expressed in COS-1 cells truncated ARs were detectable. Transactivation assays utilising a dual luciferase reporter system showed that transactivation activity of ARs with a C-terminal substitution mutation was decreased, but present at high concentrations of 5alpha-dihydrotestosterone (DHT). Mutations in the N-terminus and DNA-binding domain prevented any response to DHT.
As ARs with C-terminal substitution mutations are expressed at normal levels in GSF and have been shown to transactivate at high concentrations of androgen, they may stabilise the WD in response to the high local concentrations of testosterone. Alternative explanations for WD development in CAIS patients include ligand-independent activation of the AR. Further experiments designed to investigate ligand-independent activity of the AR in CAIS are underway.