Male infertility: the treatment by observing the yeast?

Humans and yeast have one thing in common: they use the same molecular process to ensure the integrity of their genetic heritage during reproduction. That's what researchers have discovered the CNRS, Inserm and Université Joseph Fourier in Grenoble.

 These last 50 years, male fertility has been declining. Men have lost half of their sperm in a half-century, probably because of pollutants. But the fragility of the remaining sperm is also responsible for this situation. If they carry the DNA is damaged, it prevents the development of a healthy embryo.

During their journey to the ovum in the female body, the sperm undergo changes in temperature and other chemical attacks. To withstand these conditions, DNA is compacted during spermatogenesis: it loses about 90% of its volume. At the molecular level, this means the loss of histone molecules around which DNA is wound, in favor of smaller, protamines. Defects in the process of compaction are responsible for many cases of male infertility. They were highlighted by the presence of histones remaining in the DNA of sperm.

The team KHOCHBIN Saadi, Director of Research Studies, compared the molecular steps of compaction in mice to those that occur during sporulation in yeast, a unicellular fungus. This mechanism of spore dispersal as he responds to a need to protect the genetic aggressions against the environment. From a functional standpoint, it is comparable to compaction during spermatogenesis. What researchers discovered is that it is also a molecular point of view. Before they are replaced by protamines, histones have already undergone a chemical change called hyperacetylation. She is the signal that initiates the compaction. Researchers have highlighted the existence of this hyperacetylation in yeast and a similar molecular factor in yeast and humans, which acts on histone acetylation.

This study suggests that the sperm has evolved from the simpler process of sporulation, while retaining the same molecular principles. But more importantly, sporulation in yeast, a simple system to study, will serve as a model for understanding spermatogenesis and study human diseases affecting male fertility.