Identification of a novel mutation (Ala66Thr) of SRY gene causes XY pure gonadal dysgenesis by affecting DNA binding activity and nuclear import

Sex-determining region of the Y chromosome (SRY) gene plays a crucial role in male sexual differentiation and development. Several mutations in the SRY gene have been reported in the high mobility group (HMG) box domain and can cause gonadal dysgenesis symptoms. In this study, we report that a novel missense mutation in the SRY gene, a G to A transition within the HMG box, causes the Ala66Thr amino acid substitution in a female patient presenting 46,XY karyotype with pure gonadal dysgenesis. The G to A base transition was not found in the SRY sequence after the screening of 100 normal males. Furthermore, Ala66Thr mutation drastically reduced the binding capacity of SRY to DNA sequences, whereas wild-type SRY protein showed the normal binding capacity to DNA sequences in vitro. We also found that the mutant SRY protein was partly localized in cytoplasm, whereas wild-type SRY protein was strictly localized in cell nucleus. In addition, we analyzed the three-dimensional structure of SRY protein by homology modeling methods. In conclusion, we identified a novel SRY mutation in a 46,XY female patient with pure gonadal dysgenesis, demonstrating the importance of the Ala66Thr mutation in DNA binding activity and nuclear transport.