The lateral line of fishes is a sensory organ composed of neuromasts spread along the side of the fish; via the lateral line, the fish sense nearby movements and thus can detect predator and prey. The neuromasts originate from placodes in the head, from which precursors migrate in stereotypical patterns across the surface of the fish. David et al., studying lateral line formation in the zebrafish, find that the path of travel is dictated by interactions between CXCR4b and SDF1a, homologs, respectively, of a receptor and ligand that are involved in lymphocyte migration. An SDF1a-demarcated pathway is laid down for the migrating lateral line primordium, whose successful navigation depends on expression of the receptor, CXCR4b. The growth cones of sensory neuron axons journey along with the migrating primordium and eventually form the nerve for the lateral line. Although SDF1a expression defines the path of migration, the direction of migration is likely defined by other factors. -- PJH
Proc. Natl. Acad. Sci. U.S.A. 99, 16297 (2002).
