A Multi-cell, Multi-scale Model of Vertebrate Segmentation and Somite Formation
(A) Sketch of an experimental image of a chick embryo at HH stage 10 (dorsal view). Anterior end to the top and posterior end to the bottom. The modeled tissue extends approximately eight somite lengths posterior to the differentiation front. Cells in the modeled region have little intercellular ECM, so they contact each other directly. They adhere to one another and have limited motility. They do not transcribe fgf8 or wnt3a mRNA, though they translate FGF8 and Wnt3a protein from the temporally decaying mRNA. Each PSM cell contains a segmentation-clock network submodel that couples the clock submodels in neighboring cells via contact-dependent Delta/Notch signaling. (B, C, D) Initial model conditions, visualizing (B) cell types, (C) [FGF8] and (D) [Lfng]. Not shown: initially, the constraining walls extend the full AP length of the simulation. (E, F, G) The modeled PSM after reaching its full length (at 720 min), visualizing (E) cell types, (F) [FGF8] and (G) [Lfng]. The patterns present in the full-length PSM arise spontaneously from the model's behavior. The first, ill-formed somite to the anterior of the full-length PSM results from the model's non-biological initial conditions. Parameters are the same as in the reference simulation (Figure 7). In (B–G) white color indicates cell boundaries. Scale bars: (A) 330 µm (B–G) 40 µm. For more information see INTRODUCTION: Two-dimensional model of the PSM and METHODS: Initial conditions.