Neural crest
Prior to delamination, presumptive neural crest cells are initially anchored to neighboring cells by tight junction proteins such as occludin and cell adhesion molecules such as NCAM and N"-"Cadherin. Dorsally expressed BMPs initiate delamination by inducing the expression of the zinc finger protein transcription factors snail, slug, and twist. These factors play a direct role in inducing the epithelial-mesenchymal transition by reducing expression of occludin and N-Cadherin in addition to promoting modification of NCAMs with polysialic acid residues to decrease adhesiveness. Neural crest cells also begin expressing proteases capable of degrading cadherins such as ADAM10 and secreting matrix metalloproteinases (MMPs) that degrade the overlying basal lamina of the neural tube to allow neural crest cells to escape. Additionally, neural crest cells begin expressing integrins that associate with extracellular matrix proteins, including collagen, fibronectin, and laminin, during migration. Once the basal lamina becomes permeable the neural crest cells can begin migrating throughout the embryo.