A new familial mutation in the SRY gene (Arg133Gly)

Abstract

Mutations in the testis-determining gene SRY result in XY sex reversal with pure gonadal dysgenesis (PGD). Most of the SRY mutations affect the HMG domain of SRY which plays a central role in DNA binding and bending activity of SRY. The arginine at codon 133 is conserved in the SRY gene of all studied species. It is part of the basic C-terminal region of the HMG box, which was proposed to provide nuclear localization signal. A de novo Arg133Trp mutation was described in two unrelated patients with pure gonadal dysgenesis. Impaired nuclear localization of SRY was proposed as a cause of organogenesis failure for mutations affecting Arg133. Here we describe a novel mutation that affects codon 133 of the SRY gene, resulting in an arginine to glycine substitution in the protein. It was detected in a 17 years old girl with primary amenorrhea, non-mosaic 46,XY karyotype and bilateral gonadoblastoma. The Arg133Gly mutation in the SRY gene was also detected in patient’s father, who is a phenotipically normal male. However, the mutation was not found in the SRY gene of 90 other males, thus excluding the possibility of a common polymorphism. Our report of familial Arg133Gly mutation suggests that replacement of Arg 133 of the SRY is not sufficient for impaired organogenesis and emphasizes the importance of modifier genes in the sex determination pathway.