Movie 1.

Endodermal cells display junctional changes and polarized cellular protrusions during endoderm C&E in control embryos at 7-12s. Confocal time-lapse experiment was performed on Tg(sox17:memGFP/H2A-mCherry) embryos at 7-12s using Zeiss LSM880 confocal microscope with a LD C-Apo 20×/NA0.8. Images were acquired at 5 min intervals and the movie plays at 4 frames/sec. Green lines: Type 3 junctions (T3), mediolaterally shrinking junctions; Red lines: Type 1 junctions (T1), anterior-posteriorly expanding junctions; Dashed yellow lines: rosettes; Yellow arrows: the leading edge of the endodermal cells that squeezed between neighboring cells; Green arrowheads: cellular protrusions in the leading edge of endoderm cells at the midline.