MorphoPace: Understanding the conserved mechanisms pacing morphogenesis

Animal development relies on the timely succession of different differentiation, in which cells acquire a certain identity and function, and morphogenetic, in which cells are placed in the part of the animal body, steps. These conserved steps follow a highly stereotypical timing among animals of the same species, but, remarkably, it varies significantly across species. For example, gastrulation, the first morphogenetic movement shaping the embryo, takes 2.5x longer in medaka (Oryzias latipes) than zebrafish (Danio rerio) in the same conditions. Although these differences are well known, it remains unclear how time is kept during development. Recent work has shown that molecular differences between species define the pace of differentiation. It is unclear, however, how these scale up to set the pace of morphogenesis, a collective process that happens across embryos, and set by active cell movements and resisting tissue material properties. With this project, I aim to understand these pace morphogenesis, by comparing gastrulation in two fish species: zebrafish and medaka. Since the latter species remains undescribed, I will first characterize mesendoderm internalization, the opening act of gastrulation. I will map single-cell properties and tissue-scale features, and use a theoretical physics model to make predictions about timing differences between species. Secondly, I will define whether pace is intrinsic to the cells, or set by the native environment, by transplanting cells between embryos of different species, and using zebrafish-medaka hybrids. Finally, I will manipulate the pace of internalization by modulating both intrinsic forces and the tissue state. Altogether, this project will build a way to understand morphogenesis by comparing different fish species, which have broad implications in biology, physics and evolution by uncovering how embryos time development across teleost fish, the largest and most diverse class of vertebrates in the planet.