Seeing tube formation

Makoto Kamei, Brant Weinstein (NIH, Bethesda, MD), and colleagues have visualized in vivo tubule formation. As in previous in vitro experiments, large vacuoles fuse to form a tubule lumen that passes through an individual cell. Many such cells adhere in a line to form a blood vessel.

The researchers took advantage of the transparency of zebrafish to look at vessels emerging from the dorsal aorta. Initially, they saw highly dynamic vacuoles that appeared and disappeared. The vacuoles then fused together and enlarged to take up most of the cell volume, thus forming the lumen.

Quantum dots injected into the circulation got into the lumen formed by each cell in turn. Preliminary evidence suggests that vacuoles form independently in each cell, but enlargement may be a progressive process: the cells nearest...