Fig. 1: Avian gastrulation.
From: Control of tissue flows and embryo geometry in avian gastrulation
A Avian morphogenesis involves convergent extension of the presumptive mesendoderm to form the primitive streak (PS), shape change of the embryo proper (EP), and extraembryonic (EE) expansion driven by edge cells (EC) crawling on the vitelline membrane. Myosin activity drives isotropic apical constriction throughout the EP and directs mesendoderm intercalations. Mesendoderm cells actively ingress at the PS, marking the anterior-posterior (A-P) axis. Cyan in insets marks elevated myosin activity. B The Dynamic Morphoskeleton of avian gastrulation. Repellers (R1 and R2) mark initial (t0) locations of cells that maximally separate by final time tf.The Attractor marks final (tf) locations where cells maximally converge during [t0, tf]. The domain of attraction marks the initial cell positions that converge to the Attractor. R1 lies on the EP-EE boundary, R2 bisects the presumptive mesendoderm, and the Attractor marks the PS. C–E Active nematic tensor dynamics (Eq. (1c)). C Flow coupling: Actomyosin cables (cyan nematic elements) reorient and align passively with the local flow (black). Vorticity rotates (left), while shear can rotate and both increase (middle) or decrease (right) nematic order. D Actomyosin cables align active junctions through mechanosensitive myosin redistribution, increasing nematic order. E Nematic order passively relaxes without activity or flow, decreasing nematic order.
