Fig. 4. Mechanical induction of specification in bilaterian early embryogenesis and development.
a i Ectopic mechanical induction of the expression of the endomesoderm twist gene and Twist protein in response to soft (on the order of 10%) global lateral deformation of Drosophila embryos. Similar results were obtained for snail gene expression (not shown). ii Mechanical stimulation of Twist expression in the presumptive anterior midgut of the Drosophila embryo, in response to its compression by the morphogenetic movement of germ-band extension at gastrulation. Adapted from49,51. b Mesoderm invagination maintains Twist expression via the mechanical stimulation of the β-catenin pathway, by Y654-βcat mechanotransductive phosphorylation leading to translocation of β-cat from the junctions to the cytoplasm. c Periodic compression and buckling of the epidermis epithelial cells after condensation of the underlying dermis cells leads to mechanical activation of Y654β-cat phosphorylation, upstream of Fgf20 expression that specifies feather follicle primordia formation during chicken development. Adapted from55.