CDYL reinforces male gonadal sex determination through epigenetically repressing <i>Wnt4</i> transcription in mice.

Abstract

In mammals, male and female gonads initially develop from bipotential progenitor cells, which can differentiate into either testicular or ovarian cells. The decision to adopt a testicular or ovarian fate relies on robust genetic forces, i.e., activation of the testis-determining gene <i>Sry</i>, as well as a delicate balance of expression levels for pro-testis and pro-ovary factors. Recently, epigenetic regulation has been found to be a key element in activation of <i>Sry</i>. Nevertheless, the mechanism by which epigenetic regulation controls the expression balance of pro-testis and pro-ovary factors remains unclear. Chromodomain Y-like protein (CDYL) is a reader protein for repressive histone H3 methylation marks. We found that a subpopulation of <i>Cdyl</i>-deficient mice exhibited XY sex reversal. Gene expression analysis revealed that the testis-promoting gene <i>Sox9</i> was downregulated in XY <i>Cdyl</i>-deficient gonads during the sex determination period without affecting <i>Sry</i> expression. Instead, we found that the ovary-promoting gene <i>Wnt4</i> was derepressed in XY <i>Cdyl</i>-deficient gonads prior to and during the sex-determination period. <i>Wnt4</i> heterozygous deficiency restored <i>SOX9</i> expression in <i>Cdyl</i>-deficient XY gonads, indicating that derepressed <i>Wnt4</i> is a cause of the repression of <i>Sox9</i>. We found that CDYL directly bound to the <i>Wnt4</i> promoter and maintained its H3K27me3 levels during the sex-determination period. These findings indicate that CDYL reinforces male gonadal sex determination by repressing the ovary-promoting pathway in mice.