Down-Regulation of a Male-Specific H3K4 Demethylase, <i>KDM5D</i>, Impairs Cardiomyocyte Differentiation

Despite the small number of Y chromosome genes, their adequate expression is required for regulation of transcription, translation, and protein stability in males, not just for sex determination. In addition to the role in male fertility, the Y chromosome has a significant role in the development and sexual dimorphism of healthy and disease phenotypes. We observed that <i>KDM5D</i> along with its X-counterpart, <i>KDM5C</i>, are up-regulated during the cardiac mesoderm stage of development. Down-regulation of <i>KDM5D</i> using siRNA resulted in accumulation of differentiating cells in the S-phase of the cell cycle and impaired progression to cardiomyocytes as reflected by an altered expression pattern of cardiac progenitor specific markers. Furthermore, while control cells started spontaneous beating at a normal physiological range on day 7 of differentiation induction, no spontaneous beating was observed in <i>KDM5D</i> down-regulated cells. Interestingly, the knockdown of <i>KDM5D</i> had no significant effect on the expression level of its X-counterpart, <i>KDM5C</i>. Thus, we suggest that <i>KDM5D</i>, in cooperation with its X homologue as a dose-sensitive gene, may have an important role in cardiomyocyte differentiation. Our study presents further evidence on the contribution of Y chromosome genes to sex-dependent development outside of sex determination.