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Among these new approaches, the most widespread at present is based on the study of proteins, molecules involved in cell structure and function. In mature spermatozoa, very few new proteins are produced: thus, only those already present at the time of ejaculation will ensure all the functions of the spermatozoa, thus constituting a good reflection of their quality.

Towards the identification of new markers
However, male fertility is not only about the ability of spermatozoa to fertilize an oocyte. It is also necessary that the molecules transmitted by the spermatozoon to the future embryo allow its proper development. While historically scientists thought that only the oocyte could influence the early development of the embryo, recent work in invertebrates and mammals has shown that spermatozoa also have a role to play. This influence is exerted via particular RNAs which are not at the origin of the production of proteins but which regulate the expression of other genes. The function of these RNAs, which are present in small quantities in spermatozoa, has long been neglected, but we now know that they are involved in the expression of genes in the newly formed embryo.
In mammals, these RNAs differ according to sperm motility and more globally to the fertility of the individual, suggesting their use as new fertility markers. However, no study has shown the presence of such RNAs in avian spermatozoa. INRAE researchers have therefore developed a protocol to detect them, proving that they are also present in birds. Further studies are currently underway to explore the link between these RNAs and rooster fertility, in order to better understand their influence on embryo development and potentially complete our fertility assessment tools in this species.

A help for the preservation of biodiversity
Research on male fertility is also of interest in a very specific field: cryopreservation, a process that allows cells to be preserved at very low temperatures. This process is crucial for the different programs of biodiversity conservation of species and breeds, of which the national program CRB Anim dedicated to domestic species is a part. In roosters, cryopreservation of semen strongly reduces the fertilization capacity of spermatozoa. INRAE researchers have demonstrated a strong modification of sperm proteins before and after cryopreservation, contributing to this impact on sperm quality. Studies are currently underway to determine if a similar impact can be observed on the RNA present in these male gametes. By identifying the molecules affected by cryopreservation, scientists hope to be able to improve the fertilizing capacity of frozen seeds in the future, and thus improve biodiversity conservation programs.

Contact

• Anais Carvalho
• Presse : Laurent Cario