Expression of Sox9 in granulosa cells lacking the estrogen receptors, ERalpha and ERbeta.

Ovaries from adult mice lacking both estrogen receptors ERalpha and ERbeta (ERalphabetaKO mice) contain abnormal cells sharing morphologic features with Sertoli cells, which are located mainly in the interstitial compartment. We show here that these cells express the Sertoli cell markers TIF1beta, TIF2, and Sox9. In ERalphabetaKO ovaries, Sox9 is expressed by granulosa cells before the morphologic appearance of Sertoli cells, but neither by granulosa cell precursors nor by non-Sertolian interstitial cells. These findings suggest that functional Sertoli cells can transdifferentiate from mature granulosa cells devoid of estrogen receptors as a result of Sox9 expression.