The Multicopy Gene Sly Represses the Sex Chromosomes in the Male Mouse Germline after Meiosis

Studies of mice with Y chromosome long arm deficiencies suggest that the male-specific region (MSYq) encodes information required for sperm differentiation and postmeiotic sex chromatin repression (PSCR). Several genes have been identified on MSYq, but because they are present in more than 40 copies each, their functions cannot be investigated using traditional gene targeting. Here, we generate transgenic mice producing small interfering RNAs that specifically target the transcripts of the MSYq-encoded multicopy gene Sly (Sycp3-like Y-linked). Microarray analyses performed on these Sly-deficient males and on MSYq-deficient males show a remarkable up-regulation of sex chromosome genes in spermatids. Two sets of samples were examined: (1) Total RNA isolated from separated round spermatids of young adult males (8 weeks postpartum) with Yq deletions or shSLY targeted knockdown, compared to age- and strain-matched controls. (2) Total RNA isolated from whole testis of juvenile males (17 days post partum) with shSLY targeted knockdown, compared to age- and strain-matched controls.