Gpx5 - An antioxidant enzyme protects sperm
Gpx5 (glutathione peroxidase 5), an antioxidant protein that protects the immature sperm cells once they have left the testis has been identified by the unit GReD (INSERM CNRS University of Clermont-Ferrand). The discovery of Joel Drevet and his team established the link between oxidative stress and post-testicular degradation of the DNA of male gametes. These results, which portend a significant clinical impact especially for medically assisted procreation (PMA), published in the Journal of Clinical Investigation (JCI).

Sperm are formed in the testes and, on leaving the latter to mature within the epididymis where they acquire their fertilizing capacity. During these stages of maturation, the fragile sperm are subject to oxidative stress, provoking damage of membrane lipids to DNA. To prevent such oxidative damage during ripening and storage between two ejaculations, gametes are partially protected by - Gpx5 - an antioxidant enzyme secreted by the epididymal epithelium.

The study shows that male mice lacking this protein were morphologically normal sperm and fully capable of fertilizing an egg. But when we cross the wild females with these males deficient Gpx5, abnormally high rates of developmental defects, an increased number of abortions and perinatal mortality were recorded. What causes it? Further analysis of sperm from animals without Gpx5 show oxidative damage to sperm DNA: DNA is unpacked and tends to fragment.

John Aitken of the University of Newcastle (Australia) said in a comment for the article that these results have significant clinical impact in the context of the fertility of human aging and technology to PMA. If these data are confirmed in humans, several applications could be envisaged for the diagnosis and correction of post-testicular infertility. In the field of medically assisted procreation, these results would protect the seeds during thawing before artificial insemination and, more generally, to better take into account the state of fragmentation of sperm DNA technology in the LDCs.

Genetics Unit, reproduction and development, UMR CNRS 6247 - Unit Inserm931, University of Clermont-Ferrand 1 and 2.

Bibliography: Epididymis Seleno-independent glutathione peroxidase 5 maintains sperm DNA integrity in mice.
E. Chabory, C. Damon, A. Lenoir, G. Kauselmann, H. Kern, B. Zevnik, C. Garrel, F. Saez, R. Cadet, J. Henry Berger, M. Schoor, U. Gottwald, U. Habenicht, J. R. Drevet and P. Vernet. GPX5 protects the family jewels. J. Aitken Published in Journal of Clinical Investigation, July 2009


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