Cell migration is crucial to animal development: cells are often born far from where they and their progenitors need to end up. Although many regulators and drivers of migration have been described, how cells know when to stop migrating is less well understood. In the C. elegans larva, the QR neuroblast migrates from posterior to anterior and on this journey undergoes three rounds of cell division. Wnt receptor expression arrests progenitor migration; this expression is regulated not by spatial cues, but by a temporal mechanism. Now, Clément Dubois, Shivam Gupta, Andrew Mugler and Marie-Anne Félix investigate the robustness of QR migration arrest to genetic and environmental variation. They first show that the variance in final position of QR.pax (the final QR progenitors) is similar to other long-migrating neurons. The position of QR.pax varies in mutant strains with different body sizes (such that, in larger bodies, QR.pax is found more posteriorly, and vice versa), but a partial compensation mechanism acting specifically on cell velocity limits this effect. Early developmental arrest considerably increases variance of QR.pax position, and its mean is displaced following temperature shift. Finally, using wild isolates, the authors identify significant natural variation in QR.pax position that cannot be explained either by variation in body size or by sampling latitude. This work thus gives new insights into the genetic and environmental influences on migration arrest.
