Figure 1. Comparison of cranial neural crest and palate EMT. Cranial neural crest (CNC) is derived from a single layer of epithelial cells located at the transition zone between neuroepithelium and surface ectoderm (Weston et al., 2004). The cells have increased Slug, and decreased Sox2 expression. The cells lose cell-cell adhesion molecules [(N-cam or E-Cadherin (E-Cad)] and increase actin (RhoB) and extracellular matrix remodeling (Mmp2) proteins and growth factor receptors (PdgfR). After the crest cells have moved away from the neuroepithelium, they increase expression of the HNK-1 epitope (Del Barrio and Nieto, 2004). Palate EMT requires several more steps than CNC, since the periderm cells are sloughed through apoptosis, two epithelial sheets fuse at the apical membranes, and some cells may move to the oral or nasal epithelium. The cells increase Snail, Tgfß3 signal transduction through Smad2, PI-3 kinase, and MMP, while decreasing E-cadherin. In both tissues, cell adhesion proteins are repressed, and matrix degradation and mesenchymal or tissue-specific proteins are increased. A confocal image of a single optical plane through palatal MEE cells that were labeled with CCFSE and then cultured for 72 hrs demonstrates the extensive remodeling at the seam as cells undergo EMT.