CRANIOFACIAL MORPHOGENESIS IN ZEBRAFISH

颅面畸形是由发育错误引起的，当形成胚胎图案的基因不能正常运作时，就会发生这种情况。了解面部骨骼是如何形成的，以及控制其形成的基因，对于最终理解遗传性头面部疾病的基础是至关重要的。斑马鱼为这类研究提供了一个有用的动物模型：斑马鱼胚胎适合进行发育和遗传研究。它的胚胎头骨与人类有相当大的相似之处。斑马鱼和人类骨骼发育的基因在进化过程中高度保守，因此从斑马鱼获得的理解可以直接应用于人类发育。这项提议是对斑马鱼胚胎发育的大约一天的时间进行批判性的研究，当时细胞形成了面部骨骼的雏形。一种“形态发生级联”假说认为，在遗传控制下，咽弓原基中的神经脊来源细胞经历了一系列短暂的重排，在每一步中，都会完善骨骼的预构型。第一个具体目标是通过在级联的连续步骤中绘制命运图来识别将形成特定面部骨骼元素的细胞。第二个目标是通过用共焦显微镜(4D分析)进行延时记录，直接观察完整胚胎中的细胞，以了解预测的细胞重排是否发生以及准确地如何发生。这两个目标的实现将揭示构成头部骨骼各个元素的细胞行为。第三个具体目标是通过分析通过同源克隆的头面部突变和模式基因，从遗传学角度研究级联基因。这些技术已经层层识别了上游调控基因，主要重点将是识别和表征执行级联反应中较晚的下游步骤的新基因。

Craniofacial malformations arise by errors in development, as can occur when genes that pattern the embryo do not function correctly. Learning about how the facial skeleton forms, as well as the genes that control its formation, is essential for the eventual understanding of the bases of inherited craniofacial disorders. The zebrafish provides a useful animal model for such studies: The zebrafish embryo is amenable for developmental and genetic investigation. Its embryonic head skeleton shares considerable similarity with that of humans. Genes that pattern zebrafish and human skeletal development have been highly conserved during evolution, hence understanding gained from zebrafish can apply directly to human development. This proposal is to examine critically a period of about a day of embryonic development in the zebrafish when cells form the rudiments of the facial skeleton. A "morphogenetic cascade" hypothesis proposes that, under genetic control, neural crest-derived cells in the pharyngeal arch primordia undergo a short series of rearrangements that, at each step, refine skeletal prepatterning. The first specific aim is to identify the cells, by fate mapping at successive steps of the cascade, that will form specific facial skeletal elements. The second aim is to watch the cells in the intact embryo directly, by making time-lapse recordings with a confocal microscope (4d-analysis), to learn whether and precisely how the predicted cellular rearrangements occur. Accomplishment of these two aims will reveal the cellular behaviors that build individual elements of the head skeleton. The third specific aim is to study the cascade genetically, by analyzing craniofacial mutants and patterning genes cloned by homology. Hierarchically upstream regulatory genes have already been identified by these techniques and the principal focus will be to identify and characterize new genes that execute that later, downstream, steps in the cascade.