Movie 2

Dynamic ERK activity in Fgf4 mutant cells stimulated with recombinant FGF4. Time-lapse imaging of Fgf4 mutant cells expressing the ERK-KTR sensor cultured without FGF stimulation (top left), or stimulated with 2.5 ng/ml (top right), 5 ng/ml (bottom left), and 20 ng/ml FGF4 (bottom right). Frame rate is 20 s, total duration is 82 min. Scale bar: 20 μm.