Meiotic Consequences of Genetic Extension of Unsynapsed Autosomal Chromatin

We investigated the influence of extension of autosomal asynapsis on expression profiles during spermatogenesis. We used the mouse autosomal translocation T(16;17)43H (abbreviated T43H) and t12 haplotype, a natural variant of Chr 17 encompassing four adjacent non-overlapping inversions proximal to the T43H translocation breakpoint, as a model. The presence of t12 haplotype in trans to the T43H translocation resulted in stringent spermatogenic block and in more complete silencing of genes surrounding the T43H translocation break. Strikingly, silencing of the unsynapsed autosomal chromatin preceded the inactivation of the sex chromosomes (MSCI) and was apparent already in the population of pre-mid pachytene spermatocytes and testes of 15 days old males. Populations of pre-mid-pachytene spermatocytes were isolated from Ttf+/+T43H and t12+/+T43 males in three biological replicates. Their expression was compared to two biological replicates of the populations of pre-mid pachytene spermatocytes and mid-late pachytene spermatocytes obtained from C57BL/10J fertile males. Independently, testicular RNA was isolated from 15 days old Ttf+/+T43H and t12+/+T43 males in three biological replicates and the expression was compared to the testicular expression of two 15 days old C57BL/6J males.