Figure 12. Role of Yap1/Wwtr1 in somite stage morphogenesis.

(A) Yap1 and Wwtr1 are expressed specifically in the presumptive epidermis and notochord (light blue), where they promote cell adhesion and Fn assembly (orange). These processes are essential for both the movement of presumptive epidermal cells dorsally and ventrally to form the MFF, and for force transmission of the underlying tissues to allow the elongation of the posterior body. (B) At the midline, cells are converging from either side and push against each other to form the dorsal (shown) and ventral MFFs. We propose that adhesion to Fn is required for cells to be able to create the necessary force to allow them to generate the MFF. The presomitic mesoderm is shown in red and the neural tube is green.