Physical forces drive C. elegans embryonic deformation

The abnormal development of embryos is closely linked to abnormal cell division and elongation, but the underlying mechanism remains to be elucidated. The embryonic development of C elegans embryo is different because it occurs without cell proliferation or cell rearrangement. Here, we focus on a spectacular 4-fold elongation that is achieved approximately 3 hours before the egg shell hatches and results from active filament networks. The body shape is represented by an inhomogeneous cylinder, which allows us to assess the active stresses induced by the actomyosin network located in the cortex and the muscles in ventral position near the epidermis. By considering the specific embryo configuration, we can quantitatively obtain the contractile forces induced by actomyosin filaments and muscles for a bending torsion event with defined curvature. We find that the active stress induced by actomyosin molecular motors or muscles increases with elongation and bending curvature, while also varying with radius. Both elongation and torsional deformation contribute to increased moment magnitudes that explain the dynamics of the embryo in the egg. Our results highlight the complex interplay between biomechanical factors in modulating embryonic deformation.