Cell clusters follow the leaders

Organogenesis requires the collective movement of large groups of cells during development. According to a new study by Petra Haas and Darren Gilmour (European Molecular Biology Laboratory, Heidelberg, Germany), one such mass transit is directed by a few leader cells that respond to a chemokine signal to guide the trek and keep the marching troops in formation.

The cluster of about 100 cells that forms the posterior lateral line primordium (pLLP), the progenitor of the zebrafish mechanosensory organ, marches down a stripe of the stroma-derived factor 1 (SDF1) chemokine. Time-lapse imaging showed that the tissue's trajectory was controlled by cells that extended filopodia on the leading outer edge of the pLLP. For the column of cells to move, only leader cells required Cxcr4b, the SDF1 receptor;...