A novel splice site mutation in the androgen receptor gene results in exon skipping and a non-functional truncated protein

Abstract

Mutations of the androgen receptor (AR) gene and protein are associated with complete androgen insensitivity syndromes (CAIS) in individuals with XY genotypes causing them to develop as phenotypic females. Splice site mutations of the AR gene are very rare and in this report we describe the consequences of a novel G→A mutation at the exon 7/intron 7 splice junction of the AR gene that resulted in CAIS in two siblings. Reverse transcriptase-polymerase chain reaction (RT-PCR) of the AR transcript in patient's fibroblasts was performed and sequencing of the product showed omission of exon 7, with exon 6 being spliced directly to exon 8. This resulted in a shift of the reading frame and the introduction of a premature stop codon 10 amino acids into exon 8. Immunoblot analyses showed that the resultant AR protein was partially deleted in its C-terminal region and was ~ 1.5 kDa smaller than the wild type. This truncated AR was non-functional as it was unable to bind its physiological ligand (dihydrotestosterone) in androgen-binding assays. This is the first documentation of a point mutation in the AR gene which causes exon skipping and proves that the mutation is the cause of CAIS in our two subjects.