Nampt在小鼠卵母细胞发育过程中的作用及机制研究

Poor oocyte quality is a main cause of miscarriage, infertility and birth defects. It has been reported that NAD is not only an important co-enzyme during oxidation-reduction reaction, but also an essential factor for many enzymes such as Sirtuins. Nampt is a critical rate-limiting enzyme in the NAD salvage pathway, and its role during oocyte development remains completely unknown. Our previous work has shown that, in vitro knockdown or pharmacological inhibition of Nampt mouse oocytes results in the arrest of meiotic maturation, with the failure of spindle assembly and chromosome congression, indicating the possible role of Nampt during oocyte development. In this project, we set out to investigate how Nampt modulates oogenesis and oocyte aging by employing the conditional knockout mouse model. Our findings will be beneficial for improving oocyte quality, preventing reproductive diseases and birth defects.

卵子质量低劣是导致自然流产、不孕不育和出生缺陷的一个重要因素。烟酰胺腺嘌呤二核苷酸(nicotinamide adenine dinucleotide，NAD)不仅是氧化还原反应中重要的辅酶，而且还是包括Sirtuin家族在内的很多酶类的必需辅因子。烟酰胺磷酸核糖转移酶(nicotinamide phosphoribosyltransferase,Nampt)是NAD 补救合成途径的关键限速酶。我们的前期工作表明，通过抑制剂处理和Morpholino注射的方法，发现降低Nampt活性或者表达水平导致小鼠卵母细胞成熟阻滞，并且出现纺锤体组装失败和染色体无法聚集排列，暗示Nampt可能在卵母细胞发育过程中发挥了作用。本项目拟进一步应用卵母细胞特异性敲除小鼠模型，深入揭示Nampt调控卵母细胞发生和老化的分子机制，为改善卵子质量，预防生殖疾病和出生缺陷提供理论基础和分子靶标。

卵子质量低劣是导致自然流产、不孕不育和出生缺陷的一个重要因素。烟酰胺腺嘌呤二核苷酸(nicotinamide adenine dinucleotide，NAD)不仅是氧化还原反应中重要的辅酶，而且还是包括Sirtuin家族在内的很多酶类的必需辅因子。烟酰胺磷酸核糖转移酶(nicotinamide phosphoribosyltransferase,Nampt)是NAD补救合成途径的关键限速酶。首先我们在肥胖小鼠卵母细胞中鉴定到NAD+浓度显著降低，NAD+合成通路关键酶NAMPT的表达量在肥胖小鼠卵母细胞中显著低于对照组小鼠卵母细胞中的表达量。在对照组小鼠卵母细胞中特异性敲降NAMPT后会导致卵母细胞成熟阻滞，并伴随着纺锤体组装异常及染色体排列紊乱；同时，在肥胖组组小鼠卵母细胞中过表达NAMPT或体外培养过程中添加烟碱酸会有效的提高卵母细胞的成熟率及成熟质量，例如ROS水平降低、纺锤体组装及染色体排列趋于正常水平等。以上的结果揭示了NAMPT蛋白水平减少可能是导致肥胖小鼠卵母细胞质量受损的一个重要原因，同时我们也发现NAMPT-NAD+-ROS是调控肥胖小鼠早期胚胎发育的关键通路，为改善肥胖小鼠的卵母细胞成熟质量及胚胎体外培养体系提供了一个新的思路。

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