Movie 4

Leader-follower cell switching in 3D spheroid invasion.
3D spheroid invasion of MDA-MB-231-FUCCI cells in collagen I was imaged every hour over 43 hours. Individual red- and green-FUCCI, as well as overlay channels are shown. G1 cell initiates (white arrow) and leads (magenta arrow) the invasion strand; following transition to G2, new leader cells in G1 take over (magenta arrows). Scale bar 50 μm.