A novel mutation (N233K) in the transactivating domain and the N756S mutation in the ligand binding domain of the androgen receptor gene are associated with male infertility

OBJECTIVE Resistance to androgens has been suggested as a possible cause of male infertility. This hypothesis is based mainly on binding studies in ge nital skin fibroblasts but the molecular evidence is sparse. DESIGN Molecular studies of the androgen receptor gene were performed in 10 azoo- or oligozoospermic men, presenting with clinical signs of low androg en activity-poor virilization and high serum LH despite elevated testostero ne levels, but without genital malformations. PATIENTS Ten men with serum LH >10 IU/I and testosterone >30 nmol/l as well as a low sperm concentration <20 x 10(6)/ml. MEASUREMENTS Genomic DNA was prepared from peripheral leucocytes and PCR-am plification of the coding region of androgen receptor was performed, follow ed by direct sequencing. Identified mutations were reconstructed by site-di rected mutagenesis and the functional properties of the mutants were analys ed, using transient expression in COS-1 cells and subsequent transactivatio n assays. Hormone binding assays were performed in genital skin fibroblasts from the patients. RESULTS Two of the 10 men were shown to have a mutation in the androgen rec eptor gene. Subject 1, who presented with azoospermia, serum testosterone ( T) 50 nmol/l and LH 20 IU/I, had a mutation in exon 1, changing amino acid asparagine 233 to lysine (N233K). In fibroblasts cultured from genital skin , the receptor affinity for 5<alpha>-dihydrotestosterone (DHT) was normal a s compared to healthy controls, but the receptor-hormone complex was thermo labile at 42 degreesC. Subject 2 exhibited severe oligozoospermia and a sim ilar endocrine pattern (T = 50 nmol/l and LH = 25 run). He had a mutation i n exon 5 changing asparagine 756 to serine (N756S). The affinity for DHT in cultured genital fibroblasts from this patient was reduced. Transactivatio n was abnormal for both mutants, N233K reaching 46% and N756S 38% of wild t ype activity when stimulated with 10 nmol/l DHT. CONCLUSIONS Androgen receptor mutations may affect sperm production without resulting in genital malformations. Thus, in infertile men with a clinical presentation of poor androgen activity and an endocrine profile compatible with androgen resistance, mutations in the androgen receptor should be tak en into consideration.