Epithelial to mesenchymal transition (EMT) is a morphogenetic process in which cells lose their
epithelial characteristics and gain mesenchymal properties, and is fundamental for many tissue
remodeling events in developmental and pathological conditions. Although general cell biology of
EMT has been well-described, how it is executed in diverse biological settings depends largely on
individual context, and as a consequence, regulatory points for each EMT may vary. Here we discuss
developmental and cellular events involved in chick gastrulation EMT. Regulated disruption of
epithelial cell/basement membrane (BM) interaction is a critical early step. This takes place after
molecular specification of mesoderm cell fate, but before the disruption of tight junctions. The
epithelial cell/BM interaction is mediated by small GTPase RhoA and through the regulation of basal
microtubule dynamics. We propose that EMT is not regulated as a single morphogenetic event.
Components of EMT in different settings may share similar regulatory mechanisms, but the sequence
of their execution and critical regulatory points vary for each EMT.