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

描述(申请人提供)：脊椎动物的消化道形成左右不对称的环和手性旋转，这对正常的生理功能是必不可少的。这些令人着迷的解剖特征的扰动是危及生命的先天性缺陷发生的基础。在早期胚胎中，“左”与“右”的最初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Pitx2的左限表达，这是正常不对称器官形态发生所必需的。然而，这种分子不对称随后在发育中的器官中产生形态不对称的机制仍然知之甚少。初步数据表明，在非洲爪哇原始肠管(PGT)中，驱动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)信号控制，并受Pitx2表达的调控。本研究的目的是确定在消化道左右不对称解剖发育过程中，Pitx2和Wnt/PCP信号在调节内胚层细胞形态、黏附和/或重排中的单独和联合作用。将采用功能丧失和功能获得的策略，包括使用已经开发的新型光激活试剂，用于在非洲爪哇肠道管中对Wnt-PCP和Pitx2的表达进行侧向、阶段和组织特异性的时空调节。具体目的1是确定Wnt-PCP信号在肠道形态发生过程中是否调节内胚层细胞的形状、黏附和重排。目的2是确定不对称的Pitx2表达是否控制了肠管左侧的这些参数。目的3确定Pitx2在非对称肠道形态发生中的作用是否由Wnt-PCP信号转导。这项拟议的研究的成功完成将通过将左右不对称基因表达模式与不对称器官发育的关键机制联系起来，为了解不对称器官形态发生的未解决机制提供独特的见解。

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.