JUNO protein coated beads: A potential tool to predict bovine sperm fertilizing ability

• Published in: Theriogenology 2020-10, Vol.155, p.168-175
• Main Authors: Hamze, Julieta Gabriela, Sánchez, José María, O’Callaghan, Elena, McDonald, Michael, Bermejo-Álvarez, Pablo, Romar, Raquel, Lonergan, Patrick, Jiménez-Movilla, María
• Format: Article
• Language: English
• Subjects: Cattle; Fertility; JUNO; Sperm binding
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/j.theriogenology.2020.05.025

Considerable variation in fertility exists between bulls in AI centres, despite passing minimum post-thaw quality control checks. The development of a reliable in vitro test to predict bull fertility could enable the identification and selection of high fertility bulls, without the need to resort to test inseminations. An in-depth knowledge of the molecular basis of fertilization is a prerequisite to the development of such a test or combination of tests. To date, JUNO is the only oocyte plasma membrane receptor described to be involved in gamete binding for which the partner in the sperm, IZUMO1, is known. Despite the fact that this interaction appears to be conserved among mammals, it has not been confirmed yet in some species including cattle. Furthermore, an association between binding and fertility has not been tested. Here, we propose a sperm-binding assay based on magnetic sepharose beads coated with bovine recombinant JUNO protein (BJUNO) to study sperm binding. Bull sperm bound specifically to BJUNO demonstrating that the JUNO-IZUMO1 interaction is conserved in cattle. Moreover, the assay was able to distinguish between epididymal and ejaculated sperm. Lastly, the number of sperm cells bound to BJUNO was significantly lower for frozen-thawed sperm from bulls of low vs high field fertility. In conclusion, our findings document a novel valid sperm-binding assay to predict mammalian sperm function and to investigate the role of specific proteins involved in gamete recognition and fusion. •Recombinant bovine JUNO beads support sperm binding.•Fresh ejaculated bull sperm bind specifically to JUNO beads and the mean number of sperms bound increases over time.•Sperm binding to JUNO beads is able to distinguish between epididymal and ejaculated sperm.•Sperm binding to JUNO beads is able to distinguish between subfertile (TMEM95 deficient bull sperm) and fertile sperm.•Sperm binding to JUNO beads is able to distinguish between High and Low fertility ejaculates.