Molecular Biology of Mammalian Gametogenesis, Fertilization and Early Development

我们使用小鼠作为研究哺乳动物配子发生和早期胚胎发生的发育生物学的范例。我们的研究重点是性别特异性因子的分子机制，这些因子促进排卵卵和成熟精子的形成，确保受精，并支持早期发育。 配子发生：雌性生殖细胞发育的一个标志是减数分裂期间的不对称细胞分裂，导致含有早期发育所需的母体因子的大的排卵卵。雄性生殖细胞的一个标志是减数分裂后的精子发生，其中圆形精子细胞转化为成熟的、能够受精的活动精子。我们已经确定了一种新的卵母细胞特异性碱性螺旋-环-螺旋转录因子FIGLA（生殖系因子α）的下游靶点，该因子提供了大量关于破坏受精和着床前发育的母体效应的分子基础的信息。我们还鉴定了维持精子干细胞所需的男性特异性核蛋白和成功精子发生和男性生育力所需的粗线期piRNA的表达。 受精：单精受精对哺乳动物的发育至关重要。一个精子是必需的，但两个是致命的。这个机会窗口的主要仲裁者是围绕排卵卵和植入前胚胎的透明细胞。细胞外的人和小鼠透明带分别由四个（huZP1 - 4）或三个（moZP1 - 3）糖蛋白组成。我们已经开发出的模型，其中精卵识别是预测的N-末端的ZP2是由ovastacin，受精后从卵皮质颗粒释放的金属内切蛋白酶切割。分子生物学和小鼠转基因正在被用来验证这些模型，了解更多关于皮质颗粒生物学和研究受精所需的配子的制备。 早期发展：虽然母体效应基因编码植入前发育所需的蛋白质，但成功的胚胎发生也依赖于母体蛋白质和RNA的部分或完全降解。我们已经确定了一个皮质下的母体复合体（SCMC），并确定母体基因编码的个别组件的消融影响卵裂阶段的胚胎发生，防止激活的胚胎基因组，并导致女性不育。我们还确定了泛素-蛋白酶体系统（UPS）部分降解正常发育所需的靶向母体蛋白，并正在研究外泌体在介导与成功发育相关的母体RNA降解中的作用。

We use the mouse as a paradigm for investigating the developmental biology of mammalian gametogenesis and early embryogenesis. Our studies focus on molecular mechanisms of sex-specific factors that promote formation of ovulated eggs and mature spermatozoa, ensure fertilization, and support early development. Gametogenesis: A hallmark of female germ cell development is asymmetric cell divisions during meiosis that result in large, ovulated eggs containing maternal factors necessary for early development. A hallmark of male germ cells is post-meiotic spermiogenesis in which round spermatids are transmogrified into mature, motile spermatozoa capable of fertilization. We have identified downstream targets of a novel, oocyte-specific, basic helix-loop-helix transcription factor, FIGLA (factor in the germline, alpha) which has provided a wealth of information on the molecular basis of maternal effects that disrupt fertilization and pre-implantation development. We also have identified male-specific nuclear proteins that are required for maintenance of sperm stem cells and expression of pachytene piRNAs that are needed for successful spermiogenesis and male fertility. Fertilization: Monospermic fertilization is essential for the onset of mammalian development. One sperm is required, but two are lethal. A major arbiter of this constricted window of opportunity is the zona pellucida that surrounds ovulated eggs and pre-implantation embryos. The extracellular human and mouse zonae pellucidae are composed of four (huZP1-4) or three (moZP1-3) glycoproteins, respectively. We have developed models in which sperm-egg recognition is predicated on the N-terminus of ZP2 that is cleaved by ovastacin, a metalloendoprotease released from egg cortical granules following fertilization. Molecular biology and mouse transgenesis are being used to validate these models, learn more about cortical granule biology and investigate the preparation of gametes necessary for fertilization. Early Development: Although maternal effect genes encode proteins required for pre-implantation development, successful embryogenesis also is dependent on the partial or complete degradation of maternal proteins and RNA. We have identified a subcortical maternal complex (SCMC) and determined that maternal ablation of genes encoding individual components affects cleavage-stage embryogenesis, prevents activation of the embryonic genome and results in female infertility. We also have determined that the ubiquitin-proteasome system (UPS) partially degrades targeted maternal proteins required for normal development and are investigating the role of exosomes in mediating degradation of maternal RNAs associated with successful development.