Meiotic sex chromosome inactivation within mouse spermatogenesis

Meiotic sex chromosome inactivation (MSCI) is an essential epigenetic process, which transcriptionally silences X and Y chromosomes during spermatogenesis. It is accompanied by substantial chromatin remodeling resulting in a formation of so called sex or XY body, which is a characteristic of male pachytene spermatocytes. In spite of MSCI indispensability for male fertility, its biological role and molecular nature still remain rather unclear. However, the described link between chromosomal asynapsis and transcriptional silencing demonstrated that MSCI is tightly associated with the asynapsis of largely non-homologous sex chromosomes and is a specific form of more general mechanism called meiotic silencing of unsynapsed chromatin (MSUC). The essential role of MSCI was demonstrated using mouse models, such as carriers of X- autosome translocations, where anomalous synapsis of sex chromosomes leads to impairment of MSCI and male sterility. Intriguingly, the exclusive spermatogenic arrest is a hallmark of not only X-autosome translocations but even various autosomal rearrangements, including autosomal translocations, inversions, or other structural mutations. Because the rearranged autosomes often intimately associate with the sex body, it..