@article {Khairy029355, author = {Khaled Khairy and William Lemon and Fernando Amat and Philipp J. Keller}, title = {Continuum mechanics modeling of Drosophila mesoderm invagination based on spherical harmonics accounts for long-range tissue remodeling}, elocation-id = {029355}, year = {2015}, doi = {10.1101/029355}, publisher = {Cold Spring Harbor Laboratory}, abstract = {Mechanics plays a key role in the development of higher organisms. For example, during fruit-fly gastrulation, local forces generated by the acto-myosin meshwork in the region of the future mesoderm lead to formation of a ventral tissue fold. The process is accompanied by substantial changes in cell shape and long-range cell movements whose origin is not understood.It has proven difficult to model the link between local forces, generated at the subcellular level, and global tissue deformation. Here, we adopt an approach first developed for lipid bilayers and cell membranes, in which we model force-generation at the cytoskeletal level as resulting in local changes in preferred tissue curvature. The continuum mechanics problem can thus be completely formulated in terms of tissue strains, which is desirable since mechanical forces themselves are often unknown. The solution then yields global morphogenetic predictions that accommodate the tendency towards this local preferred curvature. Computer simulations, especially in three dimensions, face the additional challenge of high complexity of shapes, gene expression patterns, and mechanical constraints. Our computational framework, which we call SPHARM-MECH, extends a three-dimensional spherical harmonics parameterization known as SPHARM to address this challenge.Using SPHARM-MECH in combination with whole-embryo light-sheet-based live imaging, we study mesoderm invagination in the fruit-fly embryo. Our analysis reveals a striking correlation between calculated and observed tissue movements, predicts the observed cell shape anisotropy on the ventral side of the embryo, and suggests an active mechanical role of the mesoderm invagination process in supporting the first phase of germ-band extension.}, URL = {https://www.biorxiv.org/content/early/2015/10/16/029355}, eprint = {https://www.biorxiv.org/content/early/2015/10/16/029355.full.pdf}, journal = {bioRxiv} }