Movie S7.

MMP promotes coalescence of aggregates. (A) Live imaging of cells from a K14-GFP mouse show that the coalescence of aggregates was blocked after the culture was treated by a MMP inhibitor from day 3 to day 5. (B) Coalescence of aggregates was blocked when an MMP inhibitor was added at day 4. Most cells move in the aggregates rather than moving out. (C) Coalescence of aggregates was not influenced when the MMP inhibitor was added at day 6. The epidermal plane can still form when the MMP inhibitor is added at stage 4. (D and E) Live imaging of cells from a Pdgfra-GFP mouse show that aggregates (black blank region) cannot merge after MMP inhibitor treatment. Dermal cells also move at a low velocity.