Pkdrej, a member of the polycystin-1 gene family, is a testis-specific gene with its encoded protein thought to be located on the sperm surface [1,2,3,4,5]. It is involved in sperm-related functions such as sperm transport and the acrosome reaction, which are crucial steps in the fertilization process [1,2]. These functions suggest its importance in post-copulatory sexual selection [1,2].

Male mice homozygous for a targeted mutation in the Pkdrej allele (Pkdrej(tm/tm)) show reduced reproductive success in competitive mating trials and artificial insemination of mixed-sperm populations. Sperm from these mutant mice take longer to reach the egg/cumulus complex in the oviduct and have a slower development of the zona pellucida-evoked acrosome reaction compared to wild-type males, while the transition to hyperactivated flagellar motility develops similarly in both genotypes. This indicates that Pkdrej controls the timing of fertilization in vivo through effects on sperm transport and exocytotic competence [2]. Among rodents, positive selection was detected in the Pkdrej gene in the family Cricetidae, and there is a positive significant correlation between its evolutionary rates and testes mass relative to body mass, suggesting post-copulatory sexual selection influencing its evolution [1].

In conclusion, Pkdrej plays essential roles in sperm-related functions like sperm transport and the acrosome reaction, which are vital for fertilization. The study of Pkdrej using gene-knockout mouse models has provided insights into its role in post-copulatory sexual selection and the regulation of fertilization steps, contributing to our understanding of the mechanisms underlying reproductive processes [1,2].

References:

1. Vicens, Alberto, Gómez Montoto, Laura, Couso-Ferrer, Francisco, Sutton, Keith A, Roldan, Eduardo R S. 2014. Sexual selection and the adaptive evolution of PKDREJ protein in primates and rodents. In Molecular human reproduction, 21, 146-56. doi:10.1093/molehr/gau095. https://pubmed.ncbi.nlm.nih.gov/25304980/

2. Sutton, Keith A, Jungnickel, Melissa K, Florman, Harvey M. 2008. A polycystin-1 controls postcopulatory reproductive selection in mice. In Proceedings of the National Academy of Sciences of the United States of America, 105, 8661-6. doi:10.1073/pnas.0800603105. https://pubmed.ncbi.nlm.nih.gov/18562295/

3. Sutton, Keith A, Jungnickel, Melissa K, Ward, Christopher J, Harris, Peter C, Florman, Harvey M. . Functional characterization of PKDREJ, a male germ cell-restricted polycystin. In Journal of cellular physiology, 209, 493-500. doi:. https://pubmed.ncbi.nlm.nih.gov/16883570/

4. Butscheid, Yulia, Chubanov, Vladimir, Steger, Klaus, Dietrich, Alexander, Gudermann, Thomas. . Polycystic kidney disease and receptor for egg jelly is a plasma membrane protein of mouse sperm head. In Molecular reproduction and development, 73, 350-60. doi:. https://pubmed.ncbi.nlm.nih.gov/16261614/

5. Hughes, J, Ward, C J, Aspinwall, R, Butler, R, Harris, P C. . Identification of a human homologue of the sea urchin receptor for egg jelly: a polycystic kidney disease-like protein. In Human molecular genetics, 8, 543-9. doi:. https://pubmed.ncbi.nlm.nih.gov/9949214/