SMAD MEDIATED SIGNALING DURING LUNG MORPHOGENESIS

对肺的分子胚胎学的研究可能对肺发育、损伤和疾病的分子机制提供重要的新的理解。我们已经证明了转化生长因子-β受体介导的自分泌/旁分泌信号负向调节早期肺发育。最近对Smad家族信号转导蛋白的发现揭示了转化生长因子-β信号从细胞膜到细胞核的新机制，我们的初步数据表明，Smad介导的信号调节小鼠肺分支的形态发生和细胞分化。假设：特定的Smad基因表达调节转化生长因子-β信号，从而指导早期小鼠胚胎肺分支的形态发生。目的：1.明确Smad基因在胚胎肺发育过程中的发育和时空表达(I)体内和(II)肺外植体培养。目的：采用(I)“功能丧失”和(Ii)“功能获得”策略，研究转化生长因子-β途径限制性的Smad2和Smad3在无血清培养中调节胚胎肺分支形态发生和细胞分化的分子机制。目的3.明确反馈抑制蛋白Smad6和Smad7在胚胎肺分支形态发生过程中的生物学功能。(I)肺组织培养中，Smad6和Smad7基因的表达模式将被描述为时间和剂量依赖的转化生长因子-β诱导的抑制性Smad6和Smad7基因的表达模式。(Ii)抑制Smad6和Smad7在肺发育过程中对转化生长因子-β信号转导的拮抗机制将在胚胎肺培养中确定。控制肺形态发生的新分子机制及其对人类健康的意义：目前的提议将定义Smad介导的信号调节胚胎肺分支形态发生的新分子机制。该项目的结果将为新的治疗策略提供新的理论基础，以调节肺发育、损伤、修复和疾病过程中的转化生长因子-β信号。

Studies of the molecular embryology of the lung are likely to provide significant new understanding of the molecular mechanisms of lung development, injury and disease. We have demonstrated that TGF-beta receptor-mediated autocrine/paracrine signaling negatively regulates early lung development. The recent identification of the Smad family signal transducer proteins has unraveled new mechanisms by which TGF-beta signals from the cell membrane to the nucleus, and our preliminary data show that Smad-mediated signaling modulates mouse lung branching morphogenesis and cytodifferentiation. Hypothesis: Specific Smad gene expression regulates TGF-beta signaling, and thus instructs early mouse embryonic lung branching morphogenesis. Specific Aims: Aim 1. To define the developmental and temporo-spatial expression of Smad genes during embryonic lung development (i) in vivo and (ii) in lung explant culture. Aim 2. To determine the molecular mechanism of TGF-beta pathway- restricted Smad2 and Smad3 in regulating embryonic pulmonary branching morphogenesis and cytodifferentiation in serumless culture using both (i) "loss-of-function" and (ii) "gain-of- function" strategies. Aim 3. To define the biological function of the feedback inhibitory Smad6 and Smad7 proteins during embryonic lung branching morphogenesis in culture. (i) Time- and dose-dependent TGF-beta-induced inhibitory Smad6 and Smad7 gene expression patterns will be delineated in lung explant culture. (ii) The antagonistic mechanism by inhibitory Smad6 and Smad7 on TGF-beta signaling during lung development will be determined in embryonic lung culture. Novel molecular mechanisms to control lung morphogenesis and significance to human health: The current proposal will define novel molecular mechanisms in which Smad-mediated signaling regulates embryonic lung branching morphogenesis. The results of this project will provide new rationales for novel therapeutic strategies to modulate TGF-beta signaling during lung development, injury, repair, and disease.