Argonaute proteins orchestrate Meiotic Sex Chromosome Inactivation and timing of the spermatogenic transcriptional program [Multiome]

Here, we demonstrate that AGO3 and AGO4, but not AGO2, localize to the sex chromatin of pachytene spermatocytes, where they are required for the transcriptional silencing of XY-linked genes that characterizes Meiotic Sex Chromosome Inactivation (MSCI). Previous findings showed that deletion of Ago4 (Ago4-/-) mildly impairs MSCI and normal spermatozoa production.

By contrast, loss of Ago3 (Ago3-/-) does not produce these defects, while combined deletion of Ago1, Ago3, and Ago4 (Ago413-/-) leads to severely reduced fertility, accompanied by disrupted autosomal and sex chromosome gene regulation and altered chromatin accessibility in spermatocytes. In Ago413-/- mice, premature overexpression of spermiogenesis genes during prophase I results in reduced sperm production, abnormal sperm morphology, and impaired fertilization capacity.