Y chromosome damage underlies testicular abnormalities in ATR-X syndrome

ATR-X (alpha thalassemia, mental retardation, X-linked) syndrome is a severe developmental disorder affecting males caused by mutations in the chromatin remodelling gene ATRX. Genital abnormalities in affected boys include hypospadias and ambiguous genitalia, and patients show small poorly formed testes with only a few seminiferous tubules. Our mouse model recapitulated these testicular defects when Atrx was specifically deleted in Sertoli cells (ScAtrxKO). ScAtrxKO mice develop small testes with fewer and discontinuous tubules due to G2/M arrest and apoptosis of Sertoli cells. Here, we investigated the mechanism underlying the Sertoli cell defects in ATR-X syndrome. In healthy male control mice, Sertoli cell nuclei contain a single novel "GATA4 PML nuclear body (NB)" that strongly expresses the transcription factor GATA4, as well as ATRX and its binding partner DAXX. The GATA4 PML NB co-localizes with heterochromatin protein HP1 and PH3 (a marker of chromosome condensation), and with the short arm of the Y chromosome (Yp). In contrast, ScAtrxKO Sertoli cells contain a single giant GATA4 PML NB, frequently associated with DNA double-strand breaks in G2/M-arrested Sertoli cells that underwent apoptosis. HP1 and PH3 were absent from the giant GATA4 foci suggesting a local failure in heterochromatin formation and chromosome condensation. Our data indicate that in Sertoli cells, ATRX protects a chromosomal region of Yp from DNA damage, probably during replication stress, and thus protects Sertoli cells from cell death. We discuss Y chromosome damage as a novel mechanism for testicular failure and the potential role of GATA4 during this process. Disclosure SummaryThe authors have nothing to disclose.