Developmental Genetics of the Mammalian Ovary

哺乳动物卵巢的发育遗传学

• 批准号: 6503225
• 负责人: JURRIEN DEAN
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6503225
• 关键词: animal breeding; animal genetic material tag; cell differentiation; developmental genetics; egg /ovum; embryogenesis; female; fertilization; gene expression; genetic library; genetically modified animals; germ cells; graafian follicles; human genetic material tag; laboratory mouse; mammalian embryology; molecular cloning; oogenesis; ovary; protein structure; reproductive development; sex differentiation; sperm; transcription factor; zona pellucida glycoproteins

Mammalian female germ cells must successfully complete developmental programs to initial folliculogenesis that lead to mature gametes capable of fertilization and the transfer of genetic material to the next generation. At birth the ovary contains its full complement of germ cells, each surrounded by a single layer of granulosa cells which together form the primordial follicles. We have identified a novel, oocyte-specific, basic helix-loop-helix transcription factor, FIG-alpha (Factor In the Germline, alpha) and mouse lines have been established in which the single-copy Fig-alpha gene has been disrupted. Female mice lacking FIG-alpha are sterile because of germ cell depletion secondary to an inability to form primordial follicles. Identification of downstream targets of FIG-alpha should provide additional insights into the molecular basis of follicle formation. After the onset of folliculogenesis, FIG-alpha also modulates the expression of the single-copy genes that encode ZP1, ZP2 and ZP3. Normally, the three zona glycoproteins are secreted during folliculogenesis to form the zona pellucida, an extracellular matrix that mediates order-specific sperm binding to the egg (e.g., human sperm will not bind to the mouse zona pellucida). Using transgenesis, we have determined that mouse ZP1 is not required for formation of the zona pellucida, order-specific sperm binding or fertility. In contrast, both ZP2 and ZP3 are required for stable matrix formation without which mice are infertile. Although the replacement of either mouse ZP2, mouse ZP3 or both with their human homologue restores the zona pellucida matrix, it does not affect the specificity of sperm binding. Breeding studies to establish mouse lines expressing all three human zona proteins or mutant forms of the mouse zona proteins are being pursued to further investigate the molecular basis of sperm-egg interactions. Late in oogenesis the oocyte becomes transcriptionally inactive and much of the maternal RNA is degraded during meiotic maturation and ovulation. At fertilization, both gametes are transcriptionally inert and the major activation of the embryonic genome occurs at the two-cell stage. The sperm brings little but its genome to fertilization and the activation of early development programs must depend on maternal factors. MATER (Maternal Antigen That Embryos Require) is a cytoplasmic protein that is present in growing oocytes and persists in early embryos. Mice lacking MATER have normal folliculogenesis and ovulate eggs. Although fertilization takes place, embryos do not progress beyond the early cleavage stage. Males are unaffected and MATER represents a maternal effect gene product critical for mammalian development. Investigations are underway to determine its role in transition of the terminally differentiated germ cell into the totipotent stem cells of the early embryo.

哺乳动物的雌性生殖细胞必须成功地完成从最初的卵泡发生到成熟配子的发育程序，这些配子能够受精并将遗传物质转移到下一代。在出生时，卵巢包含完整的生殖细胞，每个生殖细胞被一层颗粒细胞包围，这些颗粒细胞共同形成原始卵泡。我们已经鉴定出一种新的、卵母细胞特异的碱性螺旋-环-螺旋转录因子FIG-α(种系中的因子，α)，并且已经建立了单拷贝的FIG-α基因已经被破坏的小鼠系。缺乏FIG-α的雌性小鼠是不育的，因为生殖细胞枯竭，继而无法形成原始卵泡。识别FIG-α的下游靶点应该能为卵泡形成的分子基础提供更多的见解。在卵泡发生开始后，FIG-α还调节编码ZP1、ZP2和ZP3的单拷贝基因的表达。正常情况下，这三种透明带糖蛋白在卵泡发生过程中分泌形成透明带，这是一种细胞外基质，介导特定顺序的精子与卵子结合(例如，人类精子不会与小鼠透明带结合)。通过转基因，我们已经确定小鼠ZP1不是透明带形成、特定顺序精子结合或生育所必需的。相比之下，ZP2和ZP3都是稳定的基质形成所必需的，如果没有稳定的基质形成，小鼠就不能生育。尽管用小鼠ZP2、小鼠ZP3或两者的人类同源物替换可以恢复透明带基质，但不影响精子结合的特异性。目前正在进行育种研究，以建立表达所有三种人类透明带蛋白或突变形式的小鼠透明带蛋白的小鼠品系，以进一步研究精子-卵子相互作用的分子基础。在卵子发生的后期，卵母细胞在转录上变得不活跃，在减数分裂成熟和排卵期间，母体的大部分RNA被降解。在受精时，两个配子在转录上都是惰性的，胚胎基因组的主要激活发生在两细胞阶段。精子除了它的基因组外，对受精几乎没有什么影响，早期发育计划的激活必须取决于母体因素。Mater(胚胎所需的母体抗原)是一种细胞质蛋白，存在于发育中的卵母细胞中，并在早期胚胎中持续存在。缺乏物质的小鼠有正常的卵泡发生和排卵。虽然受精发生了，但胚胎不会超过早期卵裂阶段。雄性不受影响，MATER代表着一种对哺乳动物发育至关重要的母性效应基因产物。目前正在进行研究，以确定它在将终末分化的生殖细胞转变为早期胚胎的全能干细胞中所起的作用。