TGFb and Cardiac Neural Crest Cell Fate and Function

描述(由申请人提供)：该项目阐述了在主动脉和肺动脉干形成过程中的信号传递过程，然后在这些血管的成熟和维持过程中。对这些过程的更好理解可能会为这些过程出错时发生的畸形提供诊断或治疗机会。我们在小鼠中进行了II型TGFb受体基因(TGFBR2)的神经峰特异性破坏，以研究TGFb信号在发育中的心脏流出道血管形成和成熟中的作用。突变胚胎具有永存动脉干(PTA)和主动脉弓中断(IAA-B)；在妊娠后期，动脉导管神经脊来源的血管壁的弹性基质变得紊乱，导致血管壁扩张(动脉瘤)。解释这些缺陷的中心前提是神经脊细胞的行为是由局部信号事件决定的，神经脊细胞直接对这些信号做出反应，而TGFb就是这样的信号之一。具体目标1：确定神经脊细胞中缺乏TGFb信号导致PTA的机制。在这一目标中，我们将识别和表征在神经脊来源的平滑肌细胞中被错误调控的基因的作用；我们还将解决对TGFb受体下游Smad依赖的信号通路的需求。具体目的2：探讨视黄酸和视黄酸受体在房室间隔形成中的作用，以及该通路与TGFb信号通路的潜在趋同性。视黄酸受体基因的突变导致了与TGFBR2突变体几乎相同的PTA缺陷。我们将定义维甲酸信号发生的组织，并解决RA和TGFb信号通路在流出道分离过程中的会聚问题。具体目标3：探讨TGFb信号在血管壁成熟中的作用。在这个目标中，我们将研究血管壁变形的开始，解决中胚层来源的与神经脊来源的平滑肌中需要TGFb信号转导的程度，并解决血管扩张是否直接或间接地源于机械损伤的血管壁。

DESCRIPTION (provided by applicant): This project addresses signaling processes during formation of the aorta and pulmonary trunk, and then in the maturation and maintenance of these vessels. A greater understanding of these processes might lead to diagnostic or therapeutic opportunities for malformations that occur when these processes go awry. We have undertaken neural crest-specific disruption of the type II TGFb receptor gene (Tgfbr2) in mice, to address the role of TGFb signaling in the formation and maturation of the outflow tract vessels of the developing heart. Mutant embryos have persistent truncus arteriosus (PTA) and interrupted aortic arch (IAA- B); later in gestation, the elastic matrix of the neural crest-derived vessel wall of the ductus arteriosus becomes disorganized, leading to vessel wall dilation (aneurysm). The central premise to explain these defects is that the behavior of neural crest cells is dictated by local signaling events, that neural crest cells respond directly to these signals, and that TGFb is one such signal. Specific Aim 1: To identify mechanisms by which absence of TGFb signaling in neural crest cells results in PTA. In this Aim, we will identify and characterize the role of genes that are misregulated in neural crest- derived smooth muscle cells; we will also address the requirement for Smad-dependent signaling pathways downstream of the TGFb receptor. Specific Aim 2: To address the role of retinoic acid and RA receptors in the formation of the A/P septum, and the potential convergence of this pathway with TGFb signaling pathways. Mutation of retinoic acid receptor genes leads to a virtually identical PTA defect as in Tgfbr2 mutants. We will define the tissue in which retinoic acid signaling occurs, and address the convergence of RA and TGFb signaling pathways in the process of outflow tract septation. Specific Aim 3: To address the role of TGFb signaling in vessel wall maturation. In this Aim, we will study the onset of vascular wall deformation, address the extent to which TGFb signal transduction is required in mesodermally-derived vs. neural crest-derived smooth muscle and resolve whether vessel dilation results directly or indirectly from a mechanically impaired vessel wall.