线粒体DNA突变影响雌性生殖的机制研究

The oocyte is the major determinant of female reproduction. Mitochondrion, as the richest organelle in oocyte, plays an important role in the reproductive process, with influence on germ cell development and quality as well as embryonic development. Meanwhile，mitochondria damage have been widely reported in aging and metabolic diseases induced female fertility decline. While previous studies just suggested a link between mitochondrial function and female reproduction, it lacked direct, experimental evidence. We now address this question by using mtDNA mutaor mice, to investigate the causative link between mtDNA mutation and female reproduction, and the underlying mechanisms. Our preliminary results indicated a substantial loss of fertility in mtDNA mutator mice. Increased mtDNA mutation adversely affects the function integrity of electron transfer chain, which impairs ATP production and ROS balance. Therefore, we postulated mtDNA mutation induced energy deficiency and oxidative stress disrupted oocyte competence for maturation and subsequent early embryonic development, and ultimately led to premature infertility. Here by using mtDNA mutator mouse model, we will perform molecular, cellular and biochemical analysis to test the hypothesis above and uncover the molecular mechanism of mtDNA mutation in female reproduction, and to provide theoretical basis and molecular targets for improving reproductive defects caused by mitochondrial dysfunction.

卵母细胞是雌性生殖的关键。线粒体作为卵母细胞中最丰富的细胞器，在生殖细胞的发育和质量以及胚胎发育等过程中发挥重要作用。同时，线粒体损伤在衰老等疾病引起雌性生殖减退中广泛报道。基于以往的研究缺乏线粒体功能障碍引起雌性生殖缺陷的直接实验证据。为此，我们借助mtDNA突变小鼠模型来探讨mtDNA突变对雌性生殖的影响和机制。初步实验证实，雌性mtDNA突变鼠生育力减退。基于mtDNA突变对其编码呼吸链蛋白功能的影响，我们推测，mtDNA突变影响其编码呼吸链蛋白的功能，引起能量不足和氧化应激，从而破坏了卵母细胞成熟和维持后续胚胎发育的潜能，并最终引起雌性过早不育。本研究将以mtDNA突变鼠（PolgAmut/mut）为模型，应用遗传学、分子生物学和细胞生物学等手段，拟对上述设想予以验证，以揭示线粒体DNA突变对雌性生殖的影响和机制，为改善线粒体功能障碍引起的生殖缺陷提供理论基础和分子靶标。

线粒体广泛参与雌性生殖过程，但线粒体DNA (mtDNA)突变在卵母细胞中的功能仍然未知。在本项目的资助下，我们通过采用mtDNA突变体(Polgm)小鼠模型发现来自Polgm卵母细胞的植入后胚胎存在胎儿生长迟缓和胎盘功能障碍。值得注意的是，Polgm卵母细胞显示出DNA甲基化的整体缺失;受精后，合子基因组去甲基化不足，基因表达失调。纺锤体-染色体交换实验表明，Polgm卵母细胞中的细胞质因子是导致这种表观遗传重塑缺陷的原因。此外，代谢组学分析发现Polgm小鼠卵母细胞中α-酮戊二酸(αKG)水平显著降低。重要的是，添加αKG可以恢复Polgm胚胎的DNA甲基化状态和转录活性，从而防止发育缺陷。我们的发现揭示了卵母细胞mtDNA突变在胚胎发生过程中控制表观遗传重编程和基因表达的重要作用。αKG作为治疗线粒体功能障碍相关生育能力下降的潜在药物值得进一步评价。