The Role of TGF-Beta3 in Palatogenesis

描述(申请人提供)：腭裂是人类最常见的出生缺陷之一。我们和其他人已经证明，转化生长因子-3(转化生长因子-3)在小鼠和人类的腭部上皮融合中起着关键作用。转化生长因子-β3信号失灵导致腭部内侧缘上皮不能消失，从而导致完全发育的腭架不能融合。在这笔赠款的前几年，我们已经表明，转化生长因子-β信号在腭部上皮和腭间充质中都是必需的，以实现适当的腭架生长、图案化和融合。因此，我们的结果表明，转化生长因子-β3在腭裂形成中的作用比先前认为的更广泛和更复杂。基于最近的发现和我们的初步数据，我们提出了一个总体假设，即特定的、模块化的、远程调控元件负责将转化生长因子3的表达靶向到融合前的腭部上皮。这种上皮特异性表达的转化生长因子β3，反过来，诱导Smad4依赖(典型)和Smad4非典型(非典型)信号事件，与间充质的转化生长因子-3信号一起，成功的腭部融合所需。在特定的目标1中，我们提出了一种假设，即腭侧缘上皮细胞中的转化生长因子β3转录受远距离5‘和/或3’增强子的调控。在特定的目标2中，我们提出了一种假说，即转化生长因子β激活的激酶-1(Tak1)与Smad4介导的信号通路共同作用，诱导转化生长因子β3诱导的细胞周期停滞和随后的腭部上皮细胞凋亡。在特定目标3中，我们建议检验这样的假设：在TGFB3缺失突变体中，转化生长因子β和Notch信号之间的不平衡导致细胞周期抑制因子的表达减弱，最终导致腭裂；最后，在特定目标4中，我们建议检验假设，即转化生长因子β3通过调节预灌合腭架的适当模式，在腭间充质中发挥先前意想不到的作用。我们独特的实验模型和最先进的策略将使我们能够定义规范和非规范的转化生长因子-β信号在腭裂形成中的作用。总的来说，拟议的实验可能对试图了解人类腭裂综合征的分子基础至关重要。 公共卫生相关性：腭裂是人类最常见的先天性出生缺陷之一。拟议的研究剖析了转化生长因子-β信号在腭裂发病机制中的作用。我们预计，拟议的研究将对理解导致人类腭裂综合征的潜在分子机制具有重要意义。

DESCRIPTION (provided by applicant): Cleft palate is among the most common birth defects in humans. We and others have shown that transforming growth factor-¿3 (Tgf-¿3) plays a critical role in palatal epithelial fusion both in mice and in humans. Failure in Tgf-¿3 signaling leads to a condition in which the palatal medial edge epithelium fails to disappear, and subsequently fully- grown palatal shelves fail to fuse. During previous funding years of this grant, we have shown that Tgf-¿ signaling is required both in the palatal epithelium and in the palatal mesenchyme for appropriate palatal shelf growth, patterning and fusion. Consequently, our results suggest that the role of Tgf-¿3 during palatogenesis is broader and more complex than previously thought. Based on the recent findings and our preliminary data, we have formulated an overall hypothesis that specific, modular, long-distance regulatory elements are responsible of targeting Tgf¿3 expression to the prefusion palatal epithelium. This epithelial-specific expression of Tgf¿3, in turn, induces both Smad4-dependent (canonical) and Smad4-independent (non-canonical) signaling events in the palatal epithelium that are together with the mesenchymal Tgf-¿3 signaling, required for successful palatal fusion. In specific aim 1, we propose to test the hypothesis that Tgf¿3 transcription in palatal medial edge epithelial cells is regulated by distant 5' and/or 3' enhancers. In specific aim 2, we propose to test the hypothesis that Tgf-¿-activated kinase-1 (Tak1) functions together with the Smad4-mediated signaling pathway to induce Tgf-¿3-induced cell cycle arrest and subsequent apoptosis in palatal epithelial cells. In specific aim 3, we propose to test the hypothesis that in Tgfb3 null mutants, imbalance between Tgf-¿ and Notch signaling leads to an attenuated expression of cell cycle inhibitors ultimately resulting in cleft palate, and finally, in specific aim 4, we propose to test the hypothesis that Tgf-¿3 plays a previously unexpected role in the palatal mesenchyme by regulating appropriate patterning of prefusion palatal shelves. Our unique experimental models and state-of-art strategy will allow us to define to the role of canonical and non-canonical Tgf-¿ signaling during palatogenesis. Collectively, the proposed experiments are likely to be of critical importance in attempting to understand the molecular basis of the cleft palate syndrome in humans. PUBLIC HEALTH RELEVANCE: Cleft palate is one of the most common congenital birth defects in humans. The proposed studies dissect the role of a transforming growth factor-beta signaling in the pathogenesis of cleft palate. We expect that the proposed studies will be important in understanding of the underlying molecular mechanisms that lead to the cleft palate syndrome in humans.