Section: Highlights of the Year

Highlights of the Year

• To obtain efficient data-structures from segmented images that can be used for later physical simulations, we developed a computational tool, DRACO-STEM, that interprets cell population images as 3D cell meshes. DRACO-STEM has been released as an independent package to enable biomechanical simulations on real-world data [33].

• Modeling cell fate decisions during Acsidian embryo development. Canalization of developmental processes ensures the reproducibility and robustness of embryogenesis within each species. In its extreme form, found in ascidians, early embryonic cell lineages are invariant between embryos within and between species, despite rapid genomic divergence. To resolve this paradox, we used live light-sheet imaging to quantify individual cell behaviors in digitalized embryos and explore the forces that canalize their development. This quantitative approach revealed that individual cell geometries and cell contacts are strongly constrained, and that these constraints are tightly linked to the control of fate specification by local cell inductions. While in vertebrates ligand concentration usually controls cell inductions, we found that this role is fulfilled in ascidians by the area of contacts between signaling and responding cells. We propose that the duality between geometric and genetic control of inductions contributes to the counterintuitive inverse correlation between geometric and genetic variability during embryogenesis [Submitted in Dec 2017].