Role of cdx genes and RA in regionalizing the endoderm

描述(由申请人提供)： 这项建议的广泛目标是研究CDX基因和维甲酸(RA)在斑马鱼中肠区域化中的作用，特别是强调胰腺和肝脏。RA信号已被证明是斑马鱼胰腺和肝脏所必需的，并且RA在胰腺发育中的作用在脊椎动物中是保守的。RA在这种情况下发挥作用的机制尚不清楚。对中胚层和外胚层的研究表明，RA在CDX转录因子的上游发挥作用，而CDX转录因子又向下游的HOX基因传递信号。我的初步实验已经证实，cdx4是胰腺沿消化道正常定位所必需的。我的总体策略是检验胰腺定位依赖于整合来自前部的RA信号和来自后部的CDX信号的工作假说。我将使用功能丧失的方法研究cdx4和cdx2在内胚层区域化中的作用。由于CDX基因已被证明在其他系统中发挥协同作用，我将研究CDX4和CDX2在内胚层模式形成过程中是否发挥协同作用。利用细胞移植，我将产生嵌合胚胎，以确定cdx4是否自主地与非细胞地自主地影响胰腺命运。最后，我将研究RA信号在利用功能丧失途径调节CDX基因中的作用以及外源性RA的治疗。

DESCRIPTION (provided by applicant): The broad objective of this proposal is to examine the roles of cdx genes and retinoic acid (RA) in regionalizing the zebrafish midgut, with particular emphasis on the pancreas and liver. RA signaling has been shown to be necessary to specify the zebrafish pancreas and liver, and the role of RA in pancreas development is conserved across vertebrates. The mechanism whereby RA functions in this context is unknown. Studies on mesoderm and ectoderm have suggested that RA functions upstream of Cdx transcription factors, which in turn signal to downstream hox genes. My preliminary experiments have established that cdx4 is required for normal pancreas localization along the digestive tract. My general strategy is to test the working hypothesis that pancreas localization relies on integrating anteriorally-derived RA signals and posteriorally-derived Cdx signals. I will investigate the roles of cdx4 and cdx2 in regionalizing the endoderm using loss-of-function approaches. Since Cdx genes have been shown to function synergistically in other systems, I will investigate whether cdx4 and cdx2 function synergistically during endoderm patterning. Using cell transplantation I will generate chimeric embryos to determine whether cdx4 influences pancreatic fate cell-autonomously versus non-cell-autonomously. Finally, I will investigate the role of RA signaling in regulating Cdx genes utilizing loss-of-function approaches as well as treatment with exogenous RA.