Movie 3

Live imaging of Fucci cell cycle reporter shows that IK cells rearrange dynamically in the E11.5+12h molar placode
Fluorescence confocal microscopy time-lapse of an embryonic mouse E11.5 whole-mount mandible explant imaged for 12h, showing the contribution of cell cycle stages to molar placode and initial budding morphogenesis on a high single cell resolution. Image stacks were taken at 20min intervals, and the playback speed here is five frames per second. The movie shows a volume rendering of cell cycle indicator Fucci G₁/G₀ nuclei (red) and S/G₂/M (green). First, an overview of the mandible at the start of imaging seen from the mesenchymal side toward the epithelium, then a close up of the developing molar placode (IK, open circle) followed by both channels merged and separately. Individual cell tracks are shown as a dragon tail rendering showing a subset of twenty subsequent points in each track, IK G₁/G₀ (red), S/G₂/M (green). The IK G₁/G₀ cells moved toward the mesial front area of the bud. The IK cells stayed in G₁/G₀ phase and drove proliferation locally in the adjacent cells, posterior to the knot, to initiate the invagination of the epithelium. The bud S/G₂/M cells showed little movement.