Guest seminar by Florent Murat (postponed)

Summary

The testis produces gametes through spermatogenesis and evolves rapidly at the morphological and molecular level in mammals, probably due to the evolutionary pressure on males to be reproductively successful. However, the molecular evolution of different spermatogenic cell types in mammals remains largely unknown. Here we report evolutionary analyses of mononuclear transcriptomic data for testes from 11 species that span the three major mammalian lineages (eutherians, marsupials, and monotremes) and birds (the evolutionary outgroup), and include seven primates. We find that rapid testis evolution was driven by accelerated rates of gene expression changes, amino acid substitutions, and novel genes in late spermatogenic stages, likely facilitated by reduced pleiotropic constraints, haploid selection, and transcriptionally permissive chromatin. We identify temporal expression changes of individual genes across species and conserved expression programs controlling ancestral spermatogenic processes. Genes expressed predominantly in spermatogonia (germ cells fueling spermatogenesis) and Sertoli cells (somatic support) accumulated on X chromosomes during evolution, presumably due to selective forces are beneficial to males. Further work has identified transcriptomic differences between X- and Y-bearing spermatids and found that meiotic sex chromosome inactivation (MSCI) also occurs in monotremes and is therefore common to mammalian sex chromosome systems. Thus, the mechanism of meiotic silencing of non-synapsed chromatin, which underlies MSCI, is an ancestral feature of mammals. Our study sheds light on the molecular evolution of spermatogenesis and associated selective forces, and provides a resource for the study of mammalian testis biology.
Participation (for SAPS non-members)

• Registration mandatory by email

Contact :

• Hervé Acloque

Reference:

Murat, F., Mbengue, N., Winge, S.B. et al. The molecular evolution of spermatogenesis across mammals. Nature 613, 308–316 (2023). https://doi.org/10.1038/s41586-022-05547-7