Physics of lumen coarsening and blastocoel formation
Early embryos are shaped via a series of cell divisions, shape changes and rearrangements leading generally to a stereotypical blastula structure before gastrulation. I will summarize our recent analysis and modeling efforts to decipher the self-organizing principles of the mouse embryo morphogenesis, combining 3D numerical simulations with simple concepts of softmatter physics (1-3). Pre-implantation mammalian embryogenesis leads to the blastocyst, a structure composed of an epithelial layer surrounding an inner mass of cells and a fluid-filled cavity. In a collaborative efforts with biologists, we demonstrated in the past years that differential changes in cell surface tensions are sufficient to drive the process of compaction at 8-cell stage (1) and the formation of the inner-cell mass at the 8-to-16 cells transition (2). Here I will focus on the formation and positioning of the blastocoel cavity after the 32-cell stage. I will present our recent results demonstrating that the blastocoel forms by hydraulic fracturing of cell-cell contacts into hundreds of microlumens, which then coarsen into a single cavity though hydro-osmotic luminal fluid exchange (3).
(1) Maître, J. L., Niwayama, R., Turlier, H., Nédélec, F., & Hiiragi, T. Pulsatile cell- autonomous contractility drives compaction in the mouse embryo. Nat. Cell Biol. 17, 849-855 (2015). (2) Maître, J. L., Turlier, H., Illukkumbura, R., Eismann, B., Niwayama, R., Nédélec, F., & Hiiragi, T. Asymmetric division of contractile domains couples cell positioning and fate specification. Nature, 536, 344-348 (2016). (3) Dumortier, J., Le Verge-Serandour, M., Tortorelli, A. F., Mielke, A., de Plater, L., Turlier*, H., & Maitre*, J.L. Hydraulic fracturing and active coarsening position the lumen of the mouse blastocyst. Science, 365, 465-468 (2019).
Center for Interdisciplinary Research in Biology, Collège de France