Muscle and intestine innexins with muscle Deg/Enac channels promote muscle coordination and embryo elongation.

Body axis elongation represents a fundamental morphogenetic process in development, which involves cell shape changes powered by mechanical forces. How mechanically interconnected tissues coordinate in organismal development remains largely unexplored. During C. elegans elongation, cyclic forces generated by muscle contractions induce remodeling of adherens junctions and the actin cytoskeleton in the epidermis, facilitating gradual embryo lengthening. While previous studies have identified key players in epidermal cells, understanding how muscle cells coordinate their activity for proper embryo elongation remains unsolved. Using a Calcium sensor to monitor muscle activity during elongation, we identified two cells in each muscle quadrant with a leader cell function that orchestrate muscle activity within their respective quadrants. Strikingly, ablation of these cells halted muscle contractions and delayed elongation. A targeted RNAi screen focusing on communication channels identified two innexins and two Deg channels regulating muscle activity, which proved required for normal embryonic elongation. Interestingly, one innexin exhibits specific expression in intestinal cells. Our findings provide novel insights into how embryonic body wall muscles coordinate their activity and how interconnected tissues ensure proper morphogenesis.