TRIM28-dependent SUMOylation protects the adult ovary from activation of the testicular pathway.

Gonadal sexual fate in mammals is determined during embryonic development and must be actively maintained in adulthood. In the mouse ovary, oestrogen receptors and FOXL2 protect ovarian granulosa cells from transdifferentiation into Sertoli cells, their testicular counterpart. However, the mechanism underlying their protective effect is unknown. Here, we show that TRIM28 is required to prevent female-to-male sex reversal of the mouse ovary after birth. We found that upon loss of Trim28, ovarian granulosa cells transdifferentiate to Sertoli cells through an intermediate cell type, different from gonadal embryonic progenitors. TRIM28 is recruited on chromatin in the proximity of FOXL2 to maintain the ovarian pathway and to repress testicular-specific genes. The role of TRIM28 in ovarian maintenance depends on its E3-SUMO ligase activity that regulates the sex-specific SUMOylation profile of ovarian-specific genes. Our study identifies TRIM28 as a key factor in protecting the adult ovary from the testicular pathway. Gonadal fate in mammals is determined during embryogenesis and is actively maintained in adulthood. This study shows that E3-SUMO ligase activity of TRIM28 is required for ovarian identity maintenance and testicular-specific gene repression in mouse adult ovary; in its absence, ovarian granulosa cells transdifferentiate to Sertoli cells. [ABSTRACT FROM AUTHOR]