Duband J L, Monier F, Delannet M, Newgreen D
Laboratoire de Biologie Cellulaire du Développement, Institut Jacques-Monod, Université Paris, France.
Acta Anat (Basel). 1995;154(1):63-78. doi: 10.1159/000147752.
The neural crest is the organ system whose presence defines vertebrates. The onset of migration of neural crest cells is an archetypal epithelium to mesenchyme transition (EMT), and this event identifies the cell lineage. Little is known yet of the establishment of the neural crest, although the zinc finger gene Slug seems to be involved in specifying EMT competence. The details, especially the temporal order of events in neural crest EMT, vary between different species and between different axial levels, but several important features have emerged from observations in situ and experiments in vitro and in vivo. EMT seems to be strongly associated with decrease in cell-cell adhesion, and particularly with loss of N-cadherin on the surface of neural crest cells at the time of onset of migration. The related adhesion molecule T-cadherin is also present, but correlated changes have not yet been described, while the unrelated adhesion molecule N-CAM also declines on neural crest cells, but with a time course unrelated to EMT. The extracellular matrix is also important: EMT-related changes in matrix receptor (i.e. integrin) activity are recorded in avian crest cells, while the nature of the matrix itself changes in urodele amphibians. Changes in cell shape and in cell motility also occur at the time of EMT, consistent with changes in the cytoskeleton. These concerted changes can be triggered by TGF-beta family growth factors, of which dorsalin-I appears particularly important. These may act through pathways involving controlled alterations in phosphorylation to effect the complex of responses that make up EMT. Although much remains to be understood, the spatiotemporal definability of this system makes it a very useful model for studying EMTs in general.
神经嵴是脊椎动物特有的器官系统。神经嵴细胞迁移的开始是一种典型的上皮细胞向间充质细胞转变（EMT），这一事件确定了细胞谱系。尽管锌指基因Slug似乎参与了EMT能力的确定，但目前对神经嵴的形成了解甚少。神经嵴EMT中事件的细节，尤其是时间顺序，在不同物种和不同轴位之间有所不同，但通过原位观察以及体外和体内实验已经发现了几个重要特征。EMT似乎与细胞间黏附的减少密切相关，特别是在迁移开始时神经嵴细胞表面N-钙黏蛋白的丧失。相关的黏附分子T-钙黏蛋白也存在，但尚未描述其相关变化，而不相关的黏附分子N-CAM在神经嵴细胞上也会减少，但时间进程与EMT无关。细胞外基质也很重要：在鸟类嵴细胞中记录到了基质受体（即整合素）活性与EMT相关的变化，而在有尾两栖动物中基质本身的性质发生了变化。在EMT时细胞形状和细胞运动性也会发生变化，这与细胞骨架的变化一致。这些协同变化可由TGF-β家族生长因子触发，其中背侧素-I似乎尤为重要。这些因子可能通过涉及磷酸化受控改变的途径来影响构成EMT的复杂反应。尽管仍有许多有待了解的地方，但该系统的时空可定义性使其成为研究一般EMT的非常有用的模型。
