Argonaute proteins regulate the timing of the spermatogenic transcriptional program.

Argonaute proteins are best known for their role in microRNA-mediated post-transcriptional gene silencing. Here, we show that AGO3 and AGO4, but not AGO2, localize to the sex chromatin of pachytene spermatocytes where they are required for transcriptional silencing of XY-linked genes, known as Meiotic Sex Chromosome Inactivation (MSCI). Using an Ago413 -/- mouse, we show that AGO3 and AGO4 are key regulators of spermatogenesis, orchestrating expression of meiosis-related genes during prophase I while maintaining silencing of spermiogenesis genes. Premature overexpression of spermiogenesis genes during prophase I in Ago413 -/- mice results in subfertility, altered sperm morphology and reduced fertilization capability. We also identify BRG1, a BAF complex subunit, as an AGO3 interactor. Loss of AGO3 and AGO4 results in increased BRG1 in spermatocytes, suggesting that AGO3 aids in removing BRG1 from the XY chromatin to achieve MSCI and demonstrating a meiotic role for AGO3 in transcriptional control through the chromatin remodeling machinery.