Lineage-specific Cell Communication During Sea Urchin Development

在海胆胚胎中，有5个不变的谱系领域——未来的胎外胚层、未来的口腔外胚层、植物板、成骨间质和小微粒。除了独特的基因表达模式外，这些区域还由个体细胞谱系历史和不同细胞类型的产生来定义。形成这些区域的谱系在第6次分裂时彼此完全分离，空间受限的基因表达在一到两次分裂后开始。在除成骨间质外的所有区域中，作为每个区域的祖细胞的创始细胞通过与其他细胞的细胞内相互作用实现独特的基因表达模式。以下研究旨在确定区域内特定细胞类型的创始细胞的谱系和命运；探讨与邻近细胞相互作用在建立特定区域中的特定功能意义；并测试主要信号转导系统在区域和细胞类型规范中的作用。提出的实验分为以下几类：1。笼型荧光素-葡聚糖示踪植物板和神经元谱系。2. 用细胞烧蚀法研究细胞谱系和细胞相互作用。3. 引入外源5 -羟色胺配体-受体系统引起的异常表型的分子表征。4. 异位刺激已知谱系特定卵裂球PI信号转导系统的发育后果（使用5 -羟色胺受体）。5. 第二信使蛋白水平升高对整个胚胎和单个卵裂球的影响。6. 外源受体激酶在全胚胎和单个细胞中的表达对发育的影响。

In the sea urchin embryo there are five territories of invariant lineage - the prospective aboral ectoderm, the prospective oral ectoderm the vegetal plate, the skeletogenic mesenchyme and the small micromeres. In addition to a unique pattern of gene expression, these territories are defined by individual cell lineage histories and generation of distinct cell types. The lineages forming these territories are completely segregated from each other by the 6th cleavage and spatially restricted gene expression begins one or two divisions later. In all the territories except the skeletogenic mesenchyme, the founder cells that are the progenitors of each territory achieve unique patterns of gene expression by means of intracellular interactions with other cells. The following studies are designed to determine the lineage and fate of founder cells for specific cell types within territories; to investigate the specific functional significance of interactions with neighboring cells in establishing certain of the territories; and to test the role of major signal transduction systems in the specification of territories and cell types. The proposed experiments fall into the following categories: 1. Vegetal plate and neuronal lineage tracing with caged flourescein- dextran. 2. Cell lineage and cell interaction studied by means of cell ablation. 3. Molecular characterization of abnormal phenotypes derived from introduction of a foreign serotonin ligand- receptor system. 4. Developmental consequences of ectopic stimulation of the PI signal transduction system in specific blastomeres of known lineage (using the serotonin receptor). 5. The effects of elevated levels of second messengers in whole embryos and individual blastomeres. 6. Developmental effects of the expression of foreign receptor kinases in whole embryos and individual cells.