Fig. 5. An initial lumen is formed within tens of minutes in the absence of cell division or apoptosis but during aggregate rotation. Middle sections of Z-stacks collected between 90 minutes before lumen appearance (–90 minutes) and 120 minutes after lumen appearance (+120 minutes) are shown. Cells of a three-cell aggregate are identified as cell 1, cell 2 and cell 3 (labels shown in the pp-YFP channel). The white arrows in the mRFP-gp135 channel (–90 minutes) depict the borders of the PAP before lumen appearance. The white arrowhead points to the first resolvable lumen (0 minutes). Scale bar: 10 µm. The complete recording is available as supplementary material (supplementary material Movie 2).