Control of Early Germline Development in C. elegans

描述(由申请人提供)：我的研究团队的长期目标是了解细胞命运的决定，重点是基本的和高度保守的细菌对胞体的决定。生殖细胞必须保持全能和永生，才能产生卵子和精子，以及整个新有机体的一代又一代，而体细胞必须失去这些属性，以便在生物体有限的生命中发挥其特殊作用。我们试图阐明特定生殖细胞的机制，保护这些细胞中的生殖系命运，并对抗体细胞中的生殖系命运。我们的研究结合了模式系统秀丽线虫的强大的遗传学、基因组和分子方法。我的研究小组已经建立了新的范式来规范生殖体决策。我们发现，在胚胎发育过程中，染色质调节因子MES-4表观遗传地将“生殖系记忆”从亲代生殖细胞传递给后代生殖细胞。MES-4即使在胚体细胞中也能促进胚系的发育，但synMuv B染色质调节剂拮抗胚系在胞体中的命运。在后期阶段，随着生殖细胞的发育，生殖系特有的“生殖细胞颗粒”通过对抗体细胞命运来保护生殖系的命运。这一建议的具体目的是阐明MES-4促进生殖系命运、synMuv B蛋白拮抗生殖系命运以及生殖细胞颗粒保护生殖系命运的潜在机制。在目标1中，我们将测试母系生殖系中的转录是否必要且足以启动基因的MES-4标记，MES-4标记是否通过与其产生的染色质修饰在胚胎发生期间传播，以及MES-4‘S在原始生殖细胞中的重要作用是否是指导建立适当的基因表达程序。在目标2中，我们将分析synMuv B因子和MES-4在胚胎基因组中的位置，并确定synMuv B因子是通过改变基因的MES-4标记还是通过改变体细胞中的整体染色质结构来阻断生殖系基因在体细胞中的表达。在目标3中，我们将测试我们的模型，即成年生殖细胞偶尔错误表达体细胞转录物，生殖细胞颗粒通过抑制这些转录物的翻译来保护生殖系的命运，我们将确定缺乏生殖颗粒的生殖细胞是否类似于哺乳动物畸胎瘤，并且除了神经元外，还可以发育成各种体细胞类型。生殖细胞和干细胞具有永生和多能性的特殊性质，都是再生医学的靶点。利用生殖细胞和干细胞的增殖潜力并引导它们发育成所需组织的能力，需要了解促进适当的细胞命运决定和阻止不适当的细胞命运决定的因素和机制。我们对线虫的拟议研究将揭示生殖细胞命运是如何被跨物种保守的因素和过程指定、保护和拮抗的。

DESCRIPTION (provided by applicant): The long-term objectives of my research team are to understand cell fate decisions, with emphasis on the fundamental and deeply conserved germ versus soma decision. Germ cells must remain totipotent and immortal in order to produce eggs and sperm and entire new organism's generation after generation, while somatic cells must lose those properties in order to serve their specialized roles during the finite life of an organism. W seek to elucidate mechanisms that specify germ cells, protect germline fate in those cells, and antagonize germline fate in somatic cells. Our studies combine powerful genetic, genomic, and molecular approaches in the model system Caenorhabditis elegans. My research group has established new paradigms for how the germ-soma decision is regulated. We found that during embryogenesis, the chromatin regulator MES-4 epigenetically transmits the 'memory of germline' from parental to progeny germ cells. MES-4 can promote germline development even in somatic cells of embryos, but the synMuv B chromatin regulators antagonize germline fate in the soma. At later stages, as germ cells develop, germline-specific 'germ granules' protect germline fate by antagonizing somatic fate. The specific aims of this proposal are to elucidate the underlying mechanisms by which MES- 4 promotes germline fate, synMuv B proteins antagonize germline fate, and germ granules protect germline fate. In Aim 1, we will test if transcription in the maternal germ line is necessary and sufficient to initiate MES-4 marking of genes, if MES-4 marking is propagated during embryogenesis by MES-4 binding the chromatin modifications that it generates, and if MES-4's essential role in the primordial germ cells is to guide establishment of the proper program of gene expression. In Aim 2, we will analyze the locations of synMuv B factors compared to MES-4 across the genome in embryos, and determine whether synMuv B factors block expression of germline genes in somatic cells by altering MES-4 marking of genes or by altering global chromatin organization in somatic cells. In Aim 3, we will test our model that adult germ cells occasionally misexpress somatic transcripts and that germ granules protect germline fate by repressing translation of those transcripts, and we will determine whether germ cells that lack germ granules resemble mammalian teratomas and can develop into a variety of somatic cell types in addition to neurons. Germ cells and stem cells share the special properties of immortality and pluripotency, and both are targets of regenerative medicine. The ability to harness the proliferative potential of germ and stem cells and direct them to develop into desired tissues requires knowledge of factors and mechanisms that promote appropriate cell fate decisions and that block inappropriate cell fate decisions. Our proposed studies in C. elegans wil reveal how germ cell fate is specified, protected, and antagonized by factors and processes that are conserved across species.