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

描述（申请人提供）：脊椎动物消化道发育左右不对称循环和手性旋转，这是正常生理功能所必需的。这些迷人的解剖特征的扰动是危及生命的先天性缺陷发展的基础。在胚胎早期，“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Pitx2的左受限表达，这是正常不对称器官形态发生所必需的。然而，这种分子不对称在发育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，驱动非洲爪蟾原始肠管（PGT）组织伸长和上皮形态发生的内胚层细胞重排受Wnt/Planar cell Polarity （Wnt/PCP）信号调控，并受Pitx2表达调节。本研究的目的是确定Pitx2和Wnt/PCP信号在消化道左右不对称解剖发展过程中调节内胚层细胞形状、粘附和/或重排中的单独和联合作用。将采用功能丧失和功能获得策略，包括使用新型光激活试剂，这些试剂已开发用于爪蟾肠管中Wnt-PCP和Pitx2表达的侧、期和组织特异性时空调节。特异性目的1是确定Wnt-PCP信号是否在肠道形态发生过程中调节内胚层的细胞形状、粘附和重排。目的2是确定不对称Pitx2表达是否控制肠管左侧的这些参数。目的3是确定Pitx2在不对称肠形态发生中的功能是否由Wnt-PCP信号介导。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，该研究的成功完成将为尚未解决的不对称器官形态发生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.