EPITHELIAL/MESENCHYMAL TRANSFORMATION IN PALATOGENESIS

继发性腭裂融合的一个关键事件是内侧缘上皮从中线消失。我们实验室的研究已经使用细胞谱系分析来追踪内侧边缘上皮细胞的命运，并证明这些细胞经历了表型转变并仍然作为间充质细胞存活。表型转化的分子调控研究表明，Tf-beta3是一种重要的调控分子。如果没有外源性转化生长因子-β3的补充，纯合的转化生长因子-β3基因敲除的小鼠不会在器官培养中融合。这些发现导致了一种假说，在腭裂融合过程中，转化生长因子-β3是启动腭架内侧缘上皮细胞向间充质转化程序的主要效应分子。这一假说将通过四个特定的目标来验证：1.确定转化生长因子-β3在腭裂形成过程中的MEE细胞类型特异性表型标志物表达模式中的作用；2.表征在腭架接触和上皮-间充质转化开始之前，转化生长因子-β3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在MEE中的细胞内信号转导途径；4.评价转化生长因子-β3对MEE下负责基底膜降解的间质中基质金属蛋白酶的调节。对腭裂融合过程中重要分子机制的识别将在确定人类头面部出生缺陷的机制、开发产前诊断策略、确定颅面出生缺陷的家族风险、确定颅面畸形菌的作用机制和降低人类头面部出生缺陷的发生率方面具有潜在的应用前景。

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.