Deciphering the cellular and molecular mechanisms underlying mammalian sperm-egg fusion

在2022财年，我以第一作者身份发表了3篇研究论文和1篇综述文章。在Tang， Lu et al. 2022 PNAS中，我们通过x射线晶体学解析了人TMEM95的晶体结构，并生成了针对人TMEM95和IZUMO1的单克隆抗体。为了研究TMEM95的分子功能，我们利用了人类精子可以使无带金仓鼠卵受精的特性。利用抗体的Fab片段，我们发现IZUMO1 Fab片段可以破坏精子与卵子的结合，这与我们最近在小鼠和大鼠身上的发现相吻合（Matsumura et al. 2022 Front Cell Dev Biol）。相比之下，TMEM95 fab不影响精子与卵子的结合，但会减少精子与卵子的融合，这表明TMEM95的作用与IZUMO1不同。进一步，我们设计了TMEM95- fc融合蛋白，发现重组蛋白与仓鼠卵质膜结合，表明TMEM95具有卵受体。在Lu et al. 2023 PNAS中，我们发现1700029I15Rik，一种定位于内质网的II型跨膜蛋白，调节精卵相互作用所需的顶体膜糖蛋白的生物合成。该途径独立于calmegin介导的精子质膜蛋白的生物合成，表明顶体和质膜蛋白是在时空中加工的。此外，在Lu et al. (2023) Andrology中，我们报道了ADAD2与其他rna结合蛋白（如MIWI， RNF17）联合调节睾丸中piRNA的生物发生。此外，ADAD2在粗线精母细胞中与RNF17形成新的颗粒并稳定RNF17。

In the fiscal year of 2022, I published three research articles and one review article as the first author.In Tang, Lu et al. 2022 PNAS, we resolved the crystal structure of human TMEM95 by X-ray crystallography and generated monoclonal antibodies against human TMEM95 and IZUMO1. To investigate the molecular function of TMEM95, we exploited the nature that human sperm can fertilize zona-free golden hamster eggs. Using Fab fragments of the antibodies, we found that IZUMO1 Fabs ablate sperm-egg binding, in corroboration with our recent finding in mice and rats (Matsumura et al. 2022 Front Cell Dev Biol). In contrast, TMEM95 Fabs do not affect sperm-egg binding, but reduce sperm-egg fusion, suggesting that TMEM95 plays a role distinct to IZUMO1. Further, we engineered TMEM95-Fc fusion protein and discovered that the recombinant protein binds the hamster egg plasma membrane, indicating that TMEM95 has an egg receptor.In Lu et al. 2023 PNAS, we discovered that 1700029I15Rik, a type II transmembrane protein localized to the ER, regulates the biosynthesis of acrosomal membrane glycoproteins required for sperm-egg interaction. This pathway is independent from Calmegin-mediated biosynthesis of sperm plasma membrane proteins, suggesting that acrosomal and plasma membrane proteins are processed in a spatiotemporal manner.Additionally, in Lu et al. (2023) Andrology, we reported that ADAD2, in association with other RNA-binding proteins (e.g., MIWI, RNF17), regulates piRNA biogenesis in testis. Moreover, ADAD2 forms novel granules with and stabilizes RNF17 in pachytene spermatocytes.