Movie 4.

Time-lapse movie of transplanted midline progenitor targeted HS:DHB-mSc-p2a-H2B-miRFP670 transgenic cells. Midline progenitor targeted transplantation and time-lapse imaging using HS:DHB-mSc-p2a-H2BmiRFP670 donor cells show that the dorsal midline NMPs are in various phases of the cell cycle but arrest in G1 before entering the notochord domain. The left and right movies are from the same timelapse showing either only HS:DHB-mSc-p2a-H2BmiRFP670 donor cells (left movie, only DHB-mSc is shown), or HS:DHB-mSc-p2a-H2BmiRFP670 cells (green) in the context of the host embryo (right movie). The white arrow points to a cell in the posterior floor-plate region that is moving posteriorly as it transitions from S to G2 to M phase before dividing, at which point the two daughter cells are in G1 phase and begin entering the notochord. Scale bar = 20μm.