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A Multi-cell, Multi-scale Model of Vertebrate Segmentation and Somite Formation

Figure 8

Anteriorly traveling Lfng stripes and segmentation-clock period.

(AC) Lfng expression versus AP position and time for different segmentation-clock periods. (A) Increasing the segmentation-clock period to 180 min from the reference simulation period of 90 min decreases the spatial and temporal frequency of Lfng stripes compared to the reference simulation (B). (C) Decreasing the segmentation-clock period to 45 min increases the spatial and temporal frequency of Lfng stripes compared to the reference simulation ([Lfng] axis rescaled for clarity). (D) For a uniform Wnt3a concentration of 0.5 nM, cells' segmentation-clocks oscillate in phase with a period of 90 min. (E) Lfng concentration in a simulation with a segmentation-clock period of 45 min. The distance between the center and anterior (left) peaks is shorter than the distance between the center and posterior (right) peaks. Scale bar 40 µm. Parameters, when not otherwise noted, are equal to those in the reference simulation (Figure 7). The color scale is the same as that in Figure 5 (red indicates high concentration of Lfng and blue low concentrations of Lfng). We increase or decrease the segmentation-clock period by varying how long we integrate the segmentation-clock ODEs during each time step; by doing so, we easily vary the clock period relative to other processes in the simulation without altering parameters within the segmentation-clock submodel or changing the clock response to FGF8, Wnt3a or Delta/Notch signaling. For more information see RESULTS: Reference simulations reproduce key features of wild-type somitogenesis in vivo, The number of high Lfng concentration stripes in the simulated PSM depends on the segmentation-clock period, PSM growth rate and PSM length and Somites form in silico in the absence of traveling gene expression stripes.

Figure 8