Adenylate kinase 9 is essential for sperm function and male fertility in mammals
Despite passing routine laboratory tests for semen quality, bulls used in artificial insemination exhibit significant variation in fertility. Routine analysis of fertility data identified a dairy bull with extreme subfertility (10% pregnancy rate). To characterize the subfertility phenotype, a range of in vitro, in vivo, and molecular assays were carried out. Sperm from the subfertile bull exhibited reduced motility and severely reduced caffeine-induced hyperactivation compared to controls. Ability to penetrate the zona pellucida, cleavage rate, cleavage kinetics, and blastocyst yield after IVF or AI were significantly lower than in control bulls. Whole-genome sequencing from semen and RNA sequencing of testis tissue revealed a critical mutation in adenylate kinase 9 (AK9) that impaired splicing, leading to a premature termination codon and a severely truncated protein. Mice deficient in AK9 were generated to further investigate the function of the gene; knockout males were phenotypically indistinguishable from their wild-type littermates but produced immotile sperm that were incapable of normal fertilization. These sperm exhibited numerous abnormalities, including a low ATP concentration and reduced motility. RNA-seq analysis of their testis revealed differential gene expression of components of the axoneme and sperm flagellum as well as steroid metabolic processes. Sperm ultrastructural analysis showed a high percentage of sperm with abnormal flagella. Combined bovine and murine data indicate the essential metabolic role of AK9 in sperm motility and/or hyperactivation, which in turn affects sperm binding and penetration of the zona pellucida. Thus, AK9 has been found to be directly implicated in impaired male fertility in mammals.
An integrated multidisciplinary approach to revolutionise dairy cattle breeding, through the application of state-of-the-art technology to advance the identification, sexual maturation, fertility and availability of semen from genetically elite sires
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PublicationPNAS, 2023, 120 (42) e2305712120
PublisherNational Academy of Sciences
Other Funding informationThis work was funded by Science Foundation Ireland to P.L., S.F. and D.A.K (Project 16/IA/4474). X.M.M., A.L.-V., and H.P. received financial support from Swissgenetics, Zollikofen, Switzerland (https://swissge?netics.ch/), the Swiss NSF (310030 185229), and through an ETH Research Grant. A.G.-A., P.N.-L., M. Maroto, R.F.-G., and E.P. were supported by Grant PID2021-122507OB-I00, and M.B.-A., M.A by Grant PID2021-123091NB-C21, both funded by MCIN/AEI/10.13039/501100011033/ and European Union NextGenerationEU/PRTR. J.M.S. was funded by Talent Attraction Program of the Comunidad de Madrid (ATI2019-T2-BIO-12966). P.N.-L. was supported by a pre-doctoral fellowship from the Spanish Ministry of Science and Innovation (MICINN) (PRE2019-088813).
Department or School
- Biological Sciences