Isolation of Novel Mutations Affecting the Mouse Embryo

描述（由申请人提供）：在哺乳动物早期发育过程中，一系列形态发生运动确定了前后体轴，产生胚层，组织中线并拉长胚胎，以产生正确的组织和器官的空间排列。关于细胞间信号在发育过程中如何控制细胞和组织的这些行为，我们知之甚少。在这里，遗传学方法被用来定义调节这些形态发生事件的蛋白质和基因网络。一个正向遗传筛选已经成功地鉴定了大量的化学诱导突变，破坏胚胎的形态发生。小鼠分子遗传学的工具已被用来确定负责突变体发育缺陷的基因。这些基因中的大多数以前没有被研究过。这种方法将继续下去：在筛选中发现的其他突变体将被表征，集中的基于报告者的筛选将识别更多调节胚胎形态发生的基因。为了从单一基因转移到调节形态发生的基因网络，实验将确定在屏幕中识别的肌动蛋白调节因子如何与发育信号联系起来。在筛选中发现的突变将用于确定控制两种胚胎组织（淋巴结和神经板）形态发生的基因网络。胚胎结是中线组织和左右不对称所必需的。Notch信号和FERM结构域蛋白Lulu/ epb4.1 . 15都是节点正常形成所必需的。实验将测试Notch信号是否通过Lulu介导的肌动蛋白重排来控制节点形态发生，或者Notch信号是否需要Lulu。神经板进入神经管的闭合依赖于平面极性通路的信号传导。基因实验表明，另一种肌动蛋白调节因子Cofilin1可能介导平面极性依赖性细胞重组，实验将验证这一假设。这些研究将为理解哺乳动物发育过程中细胞间信号与细胞行为之间的遗传网络提供基础。出生缺陷是由形态发生错误引起的。所提出的研究将确定基因和机制，负责先天性畸形，如倒位和神经管缺陷。此外，指导胚胎形态发生的基因在转移中也起着至关重要的作用。例如，Cofilin1和其他肌动蛋白调节因子在转移过程中上调，促进肿瘤细胞的运动。拟议的研究将确定这些肌动蛋白调节因子如何在完整的胚胎和组织中发挥作用，这肯定与它们在肿瘤转移中的作用相似。公共卫生相关性：哺乳动物的正常发育和肿瘤的异常发育受指导细胞迁移和细胞重排的细胞间信号的调节。这些过程的破坏会导致出生缺陷和转移。遗传实验将定义在哺乳动物发育过程中，调节细胞行为以响应细胞外信号的蛋白质和基因网络。

DESCRIPTION (provided by applicant): During early mammalian development, a sequence of morphogenetic movements define the anterior-posterior body axis, create the germ layers, organize the midline and elongate the embryo to generate the correct spatial arrangement of tissues and organs. Little is known about how intercellular signals control these behaviors of cells and tissues during development. Here, genetic approaches are used to define the proteins and gene networks that regulate these morphogenetic events. A forward genetic screen has successfully identified a large number of chemically-induced mutations that disrupt morphogenesis of the embryo. The tools of mouse molecular genetics have been used to identify the genes responsible for the developmental defects of the mutants. Most of these genes had not been studied previously. This approach will be continued: additional mutants identified in the screen will be characterized and focused reporter-based screens will identify more of the genes that regulate embryonic morphogenesis. To move from single genes to the gene networks that regulate morphogenesis, experiments will determine how actin regulators identified in the screen are linked to developmental signals. Mutations identified in the screen will be used to define the gene networks that control morphogenesis in two embryonic tissues, the node and the neural plate. The embryonic node is required for organization of the midline and for left-right asymmetry. Both Notch signaling and the FERM domain protein Lulu/Epb4.1l5 are required for the proper formation of the node. Experiments will test whether Notch signaling controls node morphogenesis through Lulu-mediated actin rearrangements or if Lulu is required for Notch signaling. Closure of the neural plate into the neural tube depends on signaling by the planar polarity pathway. Genetic experiments suggest that Cofilin1, another actin regulator, may mediate planar polarity-dependent cell reorganization, and experiments will test this hypothesis. These studies will provide a foundation for understanding the genetic networks that link intercellular signals to cell behavior during mammalian development. Birth defects are caused by errors in morphogenesis. The proposed studies will define the genes and mechanisms that are responsible for congenital malformations such as situs inversus and neural tube defects. In addition, the same genes that direct embryonic morphogenesis are of critical importance in metastasis. For example, Cofilin1 and other actin regulators are upregulated during metastasis and promote the movement of tumor cells. The proposed studies will define how these actin regulators function in the intact embryos and tissues, which is certain to parallel their roles in tumor metastasis. PUBLIC HEALTH RELEVANCE: Normal mammalian development and the abnormal development of tumors are regulated by intercellular signals that direct cell migration and cell rearrangements. Disruption of these processes leads to birth defects and metastasis. Genetic experiments will define proteins and gene networks that regulate cell behavior in response to extracellular signals during mammalian development.