Chemorepulsion and cell adhesion molecules in patterning initial trajectories of sensory axons

dResearch in the past decade has advanced our knowledge of the key role that diffusible cues play in axonal guidance during development. In higher vertebrates, dorsal root ganglion (DRG) neurons extend axons centrally to the spinal cord through the dorsal root entry zone and peripherally to muscle and skin targets. In this review, we;focus on the role of proximate non-target tissues in the initial stages of DRG axonal growth. In the early stages of development, non-target tissues including the dermamyotome, the notochord, and the ventral spinal cord exert chemorepulsion for DRG axons. We describe how semaphorin 3A, chondroitin sulfate proteogrycans, and cell adhesion molecules participate in chemorepulsion and the Way:they provide spatio-temporal specificity to chemorepulsion. Axon I, chemorepulsion may act not only to shape DRG axonal trajectories but it also affects a variety of other axonal projections in the peripheral and central nervous system. (c) 2005 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.