Regulation of tissue morphodynamics: an important role for actomyosin contractility

Abstract

Forces arising from contractile actomyosin filaments help shape tissue form during morphogenesis. Developmental events that result from actomyosin contractility include tissue elongation, bending, budding, and collective migration. Here, we highlight recent insights into these morphogenetic processes from the perspective of actomyosin contractility as a key regulator. Emphasis is placed on a range of results obtained through live imaging, culture, and computational methods. Combining these approaches in the future has the potential to generate a robust, quantitative understanding of tissue morphodynamics.

Figure 1. Contraction of actomyosin filaments generates tissue-scale changes in shape

(a) Filamentous actin, crosslinking proteins (not shown), and non-muscle myosin II form contractile actomyosin filaments, shown in the zonula adherens belt (orange structures) within an epithelium. (b) Local increases in planar polarized contractility (see yellow cell borders) result in preferential remodeling of cell junctions (to white cell borders) during convergent extension. (c) Apically-localized actomyosin contractility decreases the area of the apical membrane to drive budding and epithelial sheet bending.

Figure 2. Actomyosin contractility regulates many developmental processes

(a) Convergent extension elongates the germband during Drosophila gastrulation. (b) Apical constriction initiates budding during airway branching morphogenesis in the embryonic chicken lung. (c) Contractility-dependent collective migration sculpts the 3D mammary ductal architecture during mammary branching morphogenesis.

Figure 3. Computational modeling can quantify the underlying physical forces acting on cells during morphogenesis

(a) In vertex models, cells are often modeled as 2D polygons representing a slice through the cell at the adherens belt. The movement of each vertex is related to the force acting on that vertex, which is a function of actomyosin contractility, adhesion to neighboring cells, and the elasticity of the membrane. See [9] for more information. (b) A recent model of epithelial morphology expands the force balance into 3D to represent changes in tissue shape as stable points in the underlying mechanical equations.