CRANIOFACIAL MORPHOGENESIS IN ZEBRAFISH

颅面畸形是由发育过程中的错误引起的，当胚胎的基因不能正常工作时就会发生这种畸形。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颅面疾病的基础是必不可少的。斑马鱼为这类研究提供了一个有用的动物模型：斑马鱼胚胎适合于发育和遗传研究。它的胚胎头颅骨骼与人类有相当多的相似之处。斑马鱼和人类骨骼发育模式的基因在进化过程中高度保守，因此从斑马鱼身上获得的理解可以直接应用于人类的发育。这个建议是严格检查斑马鱼胚胎发育的一个时期，当细胞形成面部骨骼的雏形时，大约一天。“形态发生级联”假说提出，在遗传控制下，咽部弓原基中的神经嵴来源细胞经历了一系列短暂的重排，每一步都细化了骨骼的预模式。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细胞，这些细胞将形成特定的面部骨骼元素。第二个目标是直接观察完整胚胎中的细胞，用共聚焦显微镜（4d分析）进行延时记录，以了解预测的细胞重排是否发生，以及精确地如何发生。这两个目标的完成将揭示细胞行为，建立个体元素的头部骨骼。第三个具体目标是通过分析颅面突变体和同源克隆基因来研究级联遗传。从层次上讲，上游调控基因已经被这些技术识别出来，主要的重点将是识别和表征在级联过程中执行下游步骤的新基因。

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.