Pitx2 and Wnt/PCP signaling in left-right asymmetric gut morphogenesis

描述（由申请人提供）：脊椎动物消化道形成左右不对称环和手性旋转，这对正常生理功能至关重要。这些迷人的解剖特征的扰动是危及生命的先天性缺陷的发展的基础。在早期胚胎中，“左”与“右”的初始决定表现为独特的左右不对称基因表达模式，包括转录因子Pitx 2的左限制表达，这是正常不对称器官形态发生所需的。然而，这种分子的不对称性，然后产生发育器官内的形态不对称性的机制仍然知之甚少。初步数据表明，驱动非洲爪蟾原肠管（PGT）中的组织伸长和上皮形态发生的内胚层细胞重排受Wnt/平面细胞极性（Wnt/PCP）信号传导的支配，并受Pitx 2表达的调节。本提案的目的是确定Pitx 2和Wnt/PCP信号在调节内胚层细胞形状、粘附和/或重排中的单独和组合作用，所述内胚层细胞形状、粘附和/或重排在消化道中左右不对称解剖结构的发展过程中。将采用功能丧失和获得策略，包括使用已开发用于侧，阶段和组织特异性时空调节Wnt-PCP和Pitx 2在非洲爪蟾肠管中表达的新型光活化试剂。具体目标1是确定Wnt-PCP信号传导是否调节肠形态发生期间内胚层中的细胞形状、粘附和重排。目的2是确定不对称Pitx 2表达是否控制肠道左侧的这些参数。目的3是确定Pitx 2在不对称肠道形态发生中的功能是否由Wnt-PCP信号转导介导。成功完成拟议的研究将提供独特的见解不对称器官形态发生的未解决的机制，通过连接左右不对称基因表达模式的关键机制不对称器官发育。 公共卫生相关性：拟议的工作将阐明目前未知的病因常见的消化器官出生缺陷，如肠旋转不良，狭窄或闭塞的消化道，先天性短肠。这项研究的结果也将对Pitx 2和Wnt信号在多个对称和不对称器官的形态发生中的相互关系以及在上皮-间充质转化中的相互关系产生重要而广泛的影响，这些上皮-间充质转化驱动发育，维持肠道上皮稳态，并成为消化道和其他上皮肿瘤转移进展的基础。

DESCRIPTION (provided by applicant): The vertebrate digestive tract develops left-right asymmetric loops and chiral rotations that are essential for normal physiological function. Perturbations of these fascinating anatomical features underlie the development of life-threatening congenital defects. In the early embryo, the initial determination of "left" versus "right" is manifest as unique left-right asymmetric gene expression patterns, including the left-limited expression of the transcription factor, Pitx2, which is required for normal asymmetric organ morphogenesis. However, the mechanism by which this molecular asymmetry then engenders morphological asymmetries within developing organs remains poorly understood. Preliminary data indicate that the endoderm cell rearrangements that drive tissue elongation and epithelial morphogenesis in the Xenopus primitive gut tube (PGT) are governed by Wnt/Planar Cell Polarity (Wnt/PCP) signaling, and are modulated by Pitx2 expression. The objective of this proposal is to determine the individual and combined roles of Pitx2 and Wnt/PCP signaling in regulating endoderm cell shape, adhesion and/or rearrangement during the development of left-right asymmetric anatomy in the digestive tract. Loss- and gain-of-function strategies will be employed, including the use of novel photoactivatable reagents that have been developed for side-, stage-, and tissue-specific spatiotemporal modulation of Wnt-PCP and Pitx2 expression in the Xenopus gut tube. Specific Aim 1 is to determine whether Wnt-PCP signaling regulates cell shape, adhesion and rearrangement in the endoderm during gut morphogenesis. Aim 2 is to determine whether asymmetric Pitx2 expression controls these parameters on the left side of the gut tube. Aim 3 is to determine whether the function of Pitx2 in asymmetric gut morphogenesis is mediated by Wnt-PCP signaling. Successful completion of the proposed research will provide unique insight into the unsolved mechanisms of asymmetric organ morphogenesis, by linking left-right asymmetric gene expression patterns to key mechanisms of asymmetric organ development. PUBLIC HEALTH RELEVANCE: The proposed work will illuminate the currently unknown etiology of common digestive organ birth defects, such as intestinal malrotation, narrowing or occlusion of the digestive tract, and congenital short bowel. The results of this research will also have significant, broad implications for the interrelationship of Pitx2 and Wnt signaling in the morphogenesis of multiple symmetric and asymmetric organs, and in the epithelial-mesenchymal transitions that drive development, maintain gut epithelial homeostasis, and underlie metastatic progression in tumors of the digestive and other epithelia.