Cui X M, Shuler C F
The University of Southern California, School of Dentistry, Center for Craniofacial Molecular Biology, Los Angeles 90089, USA.
Int J Dev Biol. 2000 Jun;44(4):397-402.
During palatal fusion, the medial edge epithelial cells (MEE) but not the oral/nasal palatal epithelium, selectively undergo epithelial-mesenchymal transformation. It is known that this process is regulated, at least in part, by endogenous TGF-beta3. One conceivable mechanism is that restricted expression of TGF-beta receptors (TbetaRs) in a subpopulation of cells may localize TGF-beta responsiveness (Brown et al., 1999). However, TGF-beta type II receptor (TbetaR-II) is expressed by all palatal epithelial cells during palatal fusion (Cui et al., 1998) and therefore cannot localize TGF-beta3 responsiveness. To investigate the role of TGF-beta type III receptor (TbetaR-III) in MEE transformation, we examined the expression pattern of TbetaR-III in the developing palate from E12 to E15 mice in vivo and in vitro by immunohistochemistry and compared the expression pattern to that of type I receptor (TbetaR-I). The expression of TbetaR-III was temporo-spatially restricted to the MEE during palatal fusion, while the expression of TbetaR-I was primarily localized in all palatal epithelia, consistent with the expression patterns of TbetaR-II and TGF-beta3 (Cui et al., 1998). These results support our hypothesis that TbetaR-III localizes and mediates the developmental role of TGF-beta3 on MEE transformation by specific expression in the MEE. TbetaR-III may modulate TGF-beta3 binding to TbetaR-II in the MEE cells to locally enhance TGF-beta3 autocrine signaling through the TbetaR-I/TbetaR-II receptor complex, which contributes to MEE selective epithelial-mesenchymal transformation.
在腭融合过程中，内侧边缘上皮细胞（MEE）而非口腔/鼻腔腭上皮细胞选择性地经历上皮-间充质转化。已知该过程至少部分受内源性TGF-β3调控。一种可能的机制是，TGF-β受体（TβRs）在细胞亚群中的限制性表达可能使TGF-β反应性定位（Brown等人，1999年）。然而，在腭融合期间，所有腭上皮细胞均表达TGF-β II型受体（TβR-II）（Cui等人，1998年），因此无法使TGF-β3反应性定位。为了研究TGF-β III型受体（TβR-III）在MEE转化中的作用，我们通过免疫组织化学在体内和体外检测了E12至E15小鼠发育中的腭中TβR-III的表达模式，并将其表达模式与I型受体（TβR-I）的表达模式进行比较。在腭融合期间，TβR-III的表达在时间和空间上局限于MEE，而TβR-I的表达主要定位于所有腭上皮，这与TβR-II和TGF-β3的表达模式一致（Cui等人，1998年）。这些结果支持了我们的假设，即TβR-III通过在MEE中的特异性表达来定位并介导TGF-β3对MEE转化的发育作用。TβR-III可能调节TGF-β3与MEE细胞中TβR-II的结合，以通过TβR-I/TβR-II受体复合物局部增强TGF-β3自分泌信号传导，这有助于MEE选择性上皮-间充质转化。
