Fig. 3. The biomechanical patterning of an early bilaterian embryo.

a Apical accumulation of Myo-II (in green) triggers mesoderm and posterior endoderm invaginations, and is biochemically patterned by the expression of Fog in early Drosophila embryos. Antero-posterior cross-cut view of the embryo. b Pre-patterning of Fog and T48 expression by Dorsal and Twist in the mesoderm, and Rho-dependent activation of Myo-II medio-apical accumulation downstream of Fog and T48. T = 0’ is the beginning of mesoderm invagination. Dorso-ventral cross-cut view of the embryo. c Biochemically patterned Myo-II anisotropy in morphogenetic movements of convergent-extension in Drosophila embryos, prepatterned by the antero-posterior polarity genes Bicoid and Nanos, and pair-rule genes Eve and Runt, adapted from³⁵. Antero-posterior surface view of the embryo.