Endocrine Abstracts

Spermatogenesis is crucial for our ability to reproduce. However, it also represents an evolutionary battleground. Genes that emerge during evolution are first expressed in the testis and spermatogenesis heavily depends on the rapidly evolving sex chromosomes. The evolution of spermatogenesis is also reflected by a great variation in testis size among primates and even among our closest relatives – the great apes.To explore the evolution of spermatogenesis we collected testicular specimens and reproductive data on more than 100 species of apes, including all great apes. This extensive resource allows us to assess the efficiency of spermatogenesis among these species quantitatively and to evaluate differences in reproductive hormones. To better understand the molecular processes that affect the evolution of spermatogenesis, we also generated single-nuclei gene-expression data from ~100k testicular cells from 11 species. We identified both evolutionary conserved and divergent patterns of gene expression. Notably, we observed a rapid molecular evolution in late post-meiotic germ cells. In addition, we were able to identify sex-chromosome-specific gene expression in spermatids, indicating recent meiotic drive processes, which are known to impair spermatogenesis. I will highlight our major findings from this extensive dataset and other comparative data on spermatogenesis across primates, with a particular emphasis on human spermatogenesis. The evolution of spermatogenesis can provide valuable insights into the molecular processes critical for its efficiency, potentially shedding light on why human spermatogenesis is relatively poor.