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.

中文翻译：

---

JUNO 蛋白包被珠：预测牛精子受精能力的潜在工具

尽管通过了最低限度的解冻后质量控制检查，但 AI 中心的公牛之间的生育能力存在相当大的差异。开发一种可靠的体外测试来预测公牛的生育能力，可以识别和选择高生育能力的公牛，而无需求助于测试授精。深入了解受精的分子基础是开发此类测试或测试组合的先决条件。迄今为止，JUNO 是唯一一种被描述为参与配子结合的卵母细胞质膜受体，精子中的伴侣 IZUMO1 是已知的。尽管这种相互作用在哺乳动物中似乎是保守的，但尚未在包括牛在内的某些物种中得到证实。此外，尚未测试结合和生育能力之间的关联。这里，我们提出了一种基于涂有牛重组 JUNO 蛋白 (BJUNO) 的磁性琼脂糖凝胶珠的精子结合试验，以研究精子结合。公牛精子与 BJUNO 特异性结合，表明 JUNO-IZUMO1 相互作用在牛中是保守的。此外，该测定能够区分附睾和射出的精子。最后，对于来自低与高田间生育力公牛的冻融精子，与 BJUNO 结合的精子细胞数量显着降低。总之，我们的发现记录了一种新的有效精子结合试验，可预测哺乳动物精子功能并研究特定蛋白质在配子识别和融合中的作用。公牛精子与 BJUNO 特异性结合，表明 JUNO-IZUMO1 相互作用在牛中是保守的。此外，该测定能够区分附睾和射出的精子。最后，对于来自低与高田间生育力公牛的冻融精子，与 BJUNO 结合的精子细胞数量显着降低。总之，我们的发现记录了一种新的有效精子结合试验，可预测哺乳动物精子功能并研究特定蛋白质在配子识别和融合中的作用。公牛精子与 BJUNO 特异性结合，表明 JUNO-IZUMO1 相互作用在牛中是保守的。此外，该测定能够区分附睾和射出的精子。最后，对于来自低与高田间生育力公牛的冻融精子，与 BJUNO 结合的精子细胞数量显着降低。总之，我们的发现记录了一种新的有效精子结合试验，可预测哺乳动物精子功能并研究特定蛋白质在配子识别和融合中的作用。