Internalization of multiple cells during C. elegans gastrulation depends on common cytoskeletal mechanisms but different cell polarity and cell fate regulators.

Understanding the links between developmental patterning mechanisms and force-producing cytoskeletal mechanisms is a central goal in studies of morphogenesis. Gastrulation is the first morphogenetic event in the development of many organisms. Gastrulation involves the internalization of surface cells, often driven by the contraction of actomyosin networks that are deployed with spatial precision-both in specific cells and in a polarized manner within each cell. These cytoskeletal mechanisms rely on different cell fate and cell polarity regulators in different organisms. Caenorhabditis elegans gastrulation presents an opportunity to examine the extent to which diverse mechanisms may be used by dozens of cells that are internalized at distinct times within a single organism. We identified 66 cells that are internalized in C. elegans gastrulation, many of which were not known previously to gastrulate. To gain mechanistic insights into how these cells internalize, we genetically manipulated cell fate, cell polarity and cytoskeletal regulators and determined the effects on cell internalization. We found that cells of distinct lineages depend on common actomyosin-based mechanisms to gastrulate, but different cell fate regulators, and, surprisingly, different cell polarity regulators. We conclude that diverse cell fate and cell polarity regulators control common mechanisms of morphogenesis in C. elegans. The results highlight the variety of developmental patterning mechanisms that can be associated with common cytoskeletal mechanisms in the morphogenesis of an animal embryo.