piRNA 3'末端加尾修饰在哺乳动物精子发生中的功能机制研究

piRNA是动物生殖细胞特异表达的小分子非编码RNA，通过与PIWI蛋白结合，形成PIWI/piRNA复合物，发挥沉默转座子、调控编码基因等功能，为生殖细胞发育所必需。RNA 3'末端非模板加尾是常见的RNA修饰，广泛参与RNA的加工成熟、功能调控及降解代谢，但目前还不清楚piRNA是否存在非模板加尾现象。我们的前期研究结果发现，小鼠PIWI（MIWI）结合piRNA中，有约16%存在3'末端加尾修饰，且绝大多数为单个加U尾；初步实验结果表明，TUT4/7可能参与了piRNA 3'末端加U尾修饰。本项目将在前期研究基础上，系统鉴定小鼠雄性生殖细胞中piRNA 3'末端加尾修饰的特性，深入研究piRNA 3'末端加尾修饰的生成机制及其在精子发生中的生物学功能，并探索其异常调控与男性不育症的相关性。项目研究结果将揭示piRNA加尾的功能机制，可为相关男性不育症的诊治提供理论基础和方法策略。

PIWI-interacting RNAs (piRNAs) are an animal germline-specific class of small non-coding RNAs. They associate with PIWI proteins to form PIWI/piRNA complexes, which silence transposable elements and regulate gene expression in germ cells, playing essential roles for germline development and gametogenesis. RNA tailing, i.e. addition of non-templated nucleotides to the 3'end of RNA, is one of the most frequent type of RNA modifications, which is widely involved in regulation of RNA metabolisms, including the processing and maturation, function, and degradation. However, it remains unclear whether non-templated tailing occurs in piRNAs. Our preliminary results showed that ~16% of mouse PIWI (MIWI)-interacting piRNAs possessed 3'tailing, among which most tailings are the mono (U) tailing. We further found that TUT4/7 are likely responsible for the mono(U) tailing of piRNAs. In this research plan, we will systematically identify the characteristics of 3'tailed-piRNAs, investigate the molecular mechanisms underlying piRNA 3'tailing and physiological function of mouse 3'tailed-piRNAs during spermatogenesis, and explore the clinical relevance of dysregulation of piRNA 3'tailing in human male infertility. The obtained results will uncover the role and mechanism of piRNA 3'tailing and may provide new targets and strategies for the diagnosis and therapeutics of human male infertility.