Fig. 4.

Bipotential neuromesodermal cells segregate rapidly during mid to late gastrulation. (A) In silico tracking of cells within the multi-view reconstruction was performed to follow lineage segregation from 30% epiboly. A custom MATLAB-based tool was developed to allow for the extraction of tracking data. Tracks were selected separately (n=100) in marginal and animal subgroups and visualized on top of 75% epiboly stage nuclei as a reference (purple). Cells were selected and tracked forwards in time, then scored based on expression or absence of mezzo:eGFP marking mesoderm. (B) An example track demonstrating a number of cell divisions and the two terminal divisions, one scored as both neural and one as a bi-fated NMp. In total 102 tracks were validated, with 36 terminal divisions scored. (C) Frequencies of cell divisions per track. (D) Of the 36 terminal divisions, 11 demonstrated contributions to both the neural and mesodermal compartment, with a remaining eight contributing to only neural and 17 to only the mesoderm. (E-F) From the animal and lateral views, the bi-fated cells are clearly intermixed with mono-fated cells. The fated cells are shown overlaid on the animal view image and then expanded in the schematic. Asterisk in E indicates the first mezzo:eGFP-positive cells and therefore the dorsal-most aspect of the marginal zone.