Effects of sex chromosomes on the developmental potential of the mouse oocyte

性染色体对小鼠卵母细胞发育潜力的影响

• 批准号: RGPIN-2018-04464
• 负责人: TaketoHosotani, Teruko
• 金额: $ 2.62万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=712926
• 关键词: Effects; sex; chromosomes; developmental; potential

My long-term objective is to delineate how sex chromosomes affect the developmental potential of mouse oocytes. In mammalian development, germ cells undergo sexual differentiation according to their gonadal environment, testis or ovary, which is determined by the presence or absence of the Y-linked Sry gene. Therefore, spermatogenesis and oogenesis take place in the presence of XY and XX chromosomes, respectively. The gonadal sex also dictates the phenotypic sex by secretion of sex steroid hormones. When the gonadal sex is reversed, however, the germ cell sex becomes discordant with the chromosomal sex. Both XX males and XY females in humans are infertile, while XY females are fertile in certain rodent species. In Mus musculus, XY females are variably fertile depending on the cause of sex-reversal and genetic background. The B6.YTIR mouse, which develops into an infertile female with an intact Y chromosome, provides an excellent model for studying the effects of sex chromosomes on female fertility. We previously reported that the cause of infertility in the B6.YTIR female is intrinsic to its oocytes; they can reach the Metaphase II (MII) but fail to complete the second meiotic division and rarely develop beyond the zytote-stage after fertilization. This developmental incompetence can be attributed to their defective ooplasm; when XY oocyte nuclei have been transferred into enucleated XX oocytes, the reconstructed oocytes generate healthy offspring. Thus, the Y chromosome in the oocyte makes the ooplasm defective, which leaves the first meiotic division largely intact but disrupts the second meiotic division. In the next 5 years, we will investigate the molecular mechanisms underlying the second meiotic defects in the XY oocyte and investigate the involvement of Y-linked gene(s). (1) To characterize the nature of ooplasmic defects, whether it lies in a deficiency in critical components or the presence of detrimental components, we will transfer a small volume of cytoplasm from an XX oocyte into an XY oocyte or vice versa, followed by maturation in vitro, and examine the second meiotic division after parthenogenic activation (or fertilization). (2) To clarify the molecular mechanism underlying the failure in the second meiotic cytokinesis, we will compare the activity of ARP2/3 pathways, which are essential for maintaining the MII-spindle near the cytokinesis furrow, in XX and XY oocytes before and after activation. (3) To evaluate the role of Y-encoded transcription factor ZFY2 in the ooplasmic defects, we will knock-down its transcripts in the XY oocyte by siRNAs expression in vitro or by shRNAs expression from a transgene in vivo. The results of proposed studies will shed light on the mechanism coordinating the sister-chromatid separation and the second polar body extrusion, and evolution of the Y chromosome associated with the loss of fertility in Mus musculus XY females.

我的长期目标是描述性别染色体如何影响小鼠卵母细胞的发育潜力。在哺乳动物发育中，生殖细胞根据其性腺环境，睾丸或卵巢进行性分化，这取决于存在或不存在Y连锁的SRY基因。因此，分别在XY和XX染色体的情况下进行了精子发生和卵子发生。性腺性别还通过分泌性类固醇激素来决定表型性别。然而，当性腺性别逆转时，生殖细胞性别与染色体性别不一致。人类中的XX男性和XY女性都是不育的，而XY女性在某些啮齿动物物种中都肥沃。在Mus Musculus中，XY女性根据性别反转和遗传背景的原因而变化可变。 B6.ytir小鼠成长为具有完整Y染色体的不育雌性，为研究性染色体对女性生育力的影响提供了一个极好的模型。我们先前报道说，B6.ytir女性在其卵母细胞中的固有原因。他们可以到达中期II（MII），但未能完成第二种减数分裂的分裂，并且在受精后很少出现在Zytote阶段之外。这种发育无能力可以归因于它们的卵子缺陷。当将XY卵母细胞核转移到浓核XX卵母细胞中时，重建的卵母细胞会产生健康的后代。因此，卵母细胞中的Y染色体使卵子有缺陷，这使第一个减数分裂裂片在很大程度上完好无损，但破坏了第二种减数分裂的分裂。在接下来的5年中，我们将研究XY卵母细胞中第二种减数分裂缺陷的分子机制，并研究Y连锁基因的参与。 (1) To characterize the nature of ooplasmic defects, whether it lies in a deficiency in critical components or the presence of detrimental components, we will tr​​ansfer a small volume of cytoplasm from an XX oocyte into an XY oocyte or vice versa, followed by maturation in vitro, and examine the second meiotic division after parthenogenic activation (or fertilization). （2）为了阐明第二种减数分裂细胞因子失败的分子机制，我们将比较ARP2/3途径的活性，ARP2/3途径的活性对于在XX和XY卵母细胞的细胞因子沟附近保持MII纺锤体至关重要。 （3）为了评估Y编码转录因子ZFY2在卵子缺陷中的作用，我们将通过体外或通过体内转基因的shrnas表达在体外表达siRNAS表达在xy卵母细胞中的转录本。拟议的研究的结果将阐明协调姐妹 - 染色剂分离和第二极体挤出的机制，以及与肌肉肌肉中的肌肉丧失相关的Y染色体的演变。