Molecular mechanisms underlying trachea formation and the pathology of tracheomalacia and complete tracheal rings

气管支气管软化症(TBM)和完全性气管环(CTR)是先天性疾病，其特征是 气管软骨和肌肉异常，并与高发病率和死亡率相关。重型颅脑损伤的病因探讨 和CTR知之甚少，目前的干预措施仅限于侵入性手术和姑息治疗。这个 本申请的首要目标是确定先天性疾病的潜在分子机制。 影响气管发育的。我们发表的研究表明呼吸内胚层在心脏疾病中具有重要作用。 确定气管间充质的背腹组织在软骨和平滑肌的位置 发展起来的。Wls(Wnless)的内皮性缺失(Wnless)，这是分泌Wnt配体所必需的货物受体， 导致缺乏气管软骨，被组织异常的平滑肌肉取代，类似于TBM 病理学。我们的RNA测序分析确定Notom和Bmp4是气管中的候选Wnt靶基因 调节WLS上皮下游软骨和气管平滑肌形成的间充质 诱导信号。我们假设Notom通过抑制规范的Wnt信号而起作用 同时促进气管间充质所需的非规范Wnt和BMP信号转导 差异化。因此，Notom是WNT信号输出的一种新的调节模型的核心，其中 上皮性Wnt配体首先促进Wnt/b-catenin信号转导，然后将其关闭以允许非典型性Wnt 活动。为了检验中心假说，我们将：SA1：确定诺图姆促进的机制 气管软骨形成。利用新的小鼠模型和体外研究，我们将确定在多大程度上 Notom的缺失或过表达影响Wnt/b-catenin依赖和独立的信号活性，以及 Notom、Wnt5a和Wnt-b-catenin之间的上位作用形成软骨。SA2：通过以下方式定义机制 Bmp4和Wnt信号相互作用介导气管间充质细胞命运。在活体和EX中表演 体内研究我们将确定Wnt/b-catenin是否与BMP协同作用，通过诱导 Notom和Wnt5a/Ror2的表达以及Notom和Bmp4是否协同抑制异位肌肉。 腹侧气管间充质。SA3：验证上皮性Wnt信号引导细胞骨架的假设 气管平滑肌的组织。我们将检查1)正常的Wnt配体是否来自上皮细胞 通过调控成肌细胞基因表达直接促进成肌细胞骨架组织；2)上皮细胞 WNT配体激活非规范间充质Wnt信号，通过Ror2介导成肌细胞 细胞骨架组织。拟议的研究将确定关键的分子信号通路， 气管的形态发生，将有助于阐明TBM和CTR的病理机制。因此，这些研究将为 为更好地诊断和治疗先天性和结构性气管缺陷奠定了基础。

Tracheobronchomalacia (TBM) and Complete Tracheal Rings (CTR), are congenital conditions characterized by abnormal tracheal cartilage and muscle and associated with high morbidity and mortality. The etiologies of TBM and CTR are poorly understood, and current interventions are limited to invasive surgery and palliative care. The overarching goal of the present application is to define underlying molecular mechanisms of congenital diseases affecting trachea development. Our published studies demonstrated a critical role for respiratory endoderm in determining the dorsal-ventral organization of the tracheal mesenchyme where cartilage and smooth muscle developed. Endodermal deletion of Wls (Wntless), a cargo receptor necessary for secretion of Wnt ligands, results in lack of tracheal cartilage that is replaced by abnormally organized smooth muscle, resembling TBM pathology. Our RNA Sequencing analysis identified Notum, and Bmp4, as candidate Wnt target genes in tracheal mesenchyme that regulate cartilage and trachealis smooth muscle formation downstream of epithelial Wls- induced signaling. We hypothesize that Notum acts by suppressing canonical Wnt signaling while simultaneously promoting non-canonical Wnt and BMP signaling required for tracheal mesenchyme differentiation. Thus, Notum is at the core of a novel model of regulation for the output of Wnt signaling wherein epithelial Wnt ligands first promote Wnt/b-catenin signaling and then turn it off to allow for non-canonical Wnt activity. To test the central hypothesis, we will: SA1: To determine the mechanism by which Notum promotes tracheal cartilage formation. Using novel mouse model and ex vivo studies, we will determine the extent to which deletion or overexpression of Notum affects Wnt/b-catenin dependent and independent signaling activity, and the epistasis among Notum, Wnt5a, and Wnt-b-catenin to pattern cartilage. SA2: To define the mechanism by which Bmp4 and Wnt signaling interact to mediate cell fate of tracheal mesenchyme. Performing in vivo and ex vivo studies we will determine whether Wnt/b- catenin synergizes with BMP to promote cartilage by inducing Notum and Wnt5a/Ror2 expression; and whether Notum and Bmp4 cooperate to repress ectopic muscle in ventral tracheal mesenchyme. SA3: To test the hypothesis that epithelial Wnt signaling directs cytoskeletal organization of trachealis smooth muscle. We will examine whether 1) canonical Wnt ligands from the epithelia act directly to promote myoblast cytoskeletal organization by regulating myogenic gene expression; 2) epithelial Wnt ligands activate non-canonical mesenchymal Wnt signaling working via Ror2 to mediate myoblast cytoskeletal organization. The proposed studies will identify critical molecular signaling pathways that mediate tracheal morphogenesis and will shed light on the pathology of TBM and CTR. Thus, these studies will lay the foundation for better diagnosis and therapeutic management of congenital and structural defects of the trachea.