CNRS UMR 6216, Université de la Méditerranée, Developmental Biology Institute of Marseille Luminy, Case 907 Parc Scientifique de Luminy, 13288 Marseille cedex 09, France.
In the spinal cord, developing motor neurons extend their axons into the periphery while their cell bodies remain within the motor columns in the spinal cord. Two recent papers show that this partitioning involves forward and reverse semaphorin-plexin signaling between motor neurons and neural crest boundary cap cells.