EPITHELIAL/MESENCHYMAL TRANSFORMATION IN PALATOGENESIS

二次上颚融合的一个关键事件是中线内侧边缘上皮的消失。我们实验室的研究使用细胞谱系分析来追踪内侧边缘上皮细胞的命运，并记录这些细胞经历表型转变并作为间充质细胞保持活力。对表型转化的分子控制研究已经确定tf - β 3是一个重要的调节分子。纯合子tgf - β 3敲除小鼠在不补充外源tgf - β 3的情况下不能在器官培养中融合。这些发现导致假设，tgf - β 3是在腭融合过程中启动腭架内边缘上皮细胞上皮-间质转化程序的主要效应分子。这一假设将通过四个具体目标进行检验；1. 探讨tgf - β 3在胚胎发育过程中MEE细胞型特异性表型标记物表达模式中的作用；2. 表征tgf - β 3在腭壁接触和上皮间质转化发生前调控细胞周期和MEE细胞增殖的机制；3. 研究生长因子与其细胞表面受体结合后MEE的细胞内信号通路；4. 评估tgf - β 3对基质金属蛋白酶在基质金属蛋白酶在基质金属蛋白酶在基质金属蛋白酶在基质金属蛋白酶在基质金属蛋白酶在基质金属蛋白酶在基质金属蛋白酶之间的调节作用。确定腭融合过程中必不可少的分子机制将导致未来可能的应用，以确定人类颅面出生缺陷的机制，制定产前诊断策略，建立颅面出生缺陷的家族风险，确定颅面致畸物的作用机制，减少人类颅面出生缺陷的发生率。

A critical event in the fusion of the secondary palate is the disappearance of the medial edge epithelium from the midline. Studies in our laboratory have used cell lineage analysis to trace the fate of the medial edge epithelial cells and document that these cells undergo a phenotypic transitions and remain viable as mesenchymal cells. Investigations of the molecular control of the phenotypic transformation have identified TF-beta3 as an important regulating molecule. Homozygous TGF-beta3 knock-out mice do not fuse in organ culture without supplementation of exogenouse TGF-beta3. These findings have led to the hypothesis, TGF-beta3 is a primary effectors molecule responsible for initiating the program of epithelial-mesenchymal transformation in the palatal shelf medial edge epithelial cells during palatal fusion. This hypothesis will be tested by four Specific Aims; 1. To determine the role of TGF-beta3 in the pattern of expression of cell-type specific phenotypic markers in the MEE during palatogenesis; 2. To characterize the mechanism of TGF-beta3 regulation of the cell cycle and MEE cell proliferation prior to palatal shelf contact and the onset of epithelial-mesenchymal transformations; 3. To examine the intracellular signalling pathway in the MEE following binding of the growth factor to its cell surface receptor; 4. To evaluate TGF-beta3 regulation of matrix metalloproteinases in the mesenchyme underlying the MEE responsible for degradation of the basement membrane. Identification of molecular mechanisms essential to the process of palatal fusion will result in future possible applications to determining the mechanisms underlying human craniofacial birth defects, developing prenatal diagnosis strategies, establishing familial risk of craniofacial birth defects, determining the mechanism of action of craniofacial teratogens and reducing the incidence of human craniofacial birth defects.