Fig. 3. Snail genes are a convergence point in EMT induction. Numerous signalling pathways induce the epithelial to mesenchymal transition (EMT), and all have been shown to activate the expression of Snail genes. Below each extracellular signal are the tissues and processes in which they have been studied. In addition to being tightly regulated at the transcriptional level, Snail activity is also regulated by its subcellular localisation, which is governed by at least two kinases GSK3 and PAK1, and by the zinc-finger transporter LIV1. (See text for details.) AMF, autocrine motility factor; E-cad, E-cadherin; EGF, epidermal growth factor; FGF, fibroblast growth factor; BMP, bone morphogenetic protein; ILK, integrin-linked kinase; MTA3, metastasis-associated protein 3; PAK1; p21-activated kinase; TGFß, transforming growth factor ß; PTH(rP)R, parathyroid hormone related peptide receptor; SCF, stem cell factor.