The Ly6/uPAR protein Bouncer is necessary and sufficient for species-specific fertilization

Ly6/uPAR蛋白Bouncer对于物种特异性受精是充分且必要的

摘要：有性生殖的基础就是受精，然而受精的分子机制所知甚少。在此，我们鉴定出卵母细胞表达的Ly6/uPAR蛋白，并将其称为Bouncer，是斑马鱼中一个重要的受精因子。我们发现膜结合的Bouncer介导着精卵结合，因此对于精子进入卵子是必要的。有趣的是，Bouncer不仅对于精卵相互作用是必要的，而且足够使得斑马鱼和青鳉不同物种间受精，斑马鱼及青鳉早在1.5亿年前就出现种属分离。因此我们的研究鉴定了Bouncer作为鱼类中物种特异性受精的关键决定性因子。Bouncer在四足动物中的最亲近的同系物是SPACA4,在体内受精的脊椎动物中SPACA4仅存在雄性性腺中，表明我们在鱼类的发现与人类生物学相关。

关键词：受精  物种特异性 精卵相互作用 斑马鱼
Abstract Fertilization is fundamental for sexual reproduction, yet its molecular mechanisms are poorly understood. Here, we identify an oocyte-expressed Ly6/uPAR protein, which we call Bouncer, as a crucial fertilization factor in zebrafish. We show that membrane-bound Bouncer mediates sperm-egg binding and is thus essential for sperm entry into the egg. Remarkably, Bouncer is not only required for sperm-egg interaction, but also sufficient to allow cross-species fertilization between zebrafish and medaka, two fish species that diverged over 150 million years ago. Our study thus identifies Bouncer as a key determinant of species-specific fertilization in fish. Bouncer’s closest homolog in tetrapods, SPACA4, is restricted to the male gonad in internally fertilizing vertebrates, suggesting that our findings in fish have relevance to human biology.

Keywords: fertilization, species-specificity, sperm-egg interaction, zebrafish