Les cellules des capsules frontières - une niche des cellules souches neurales dans le système nerveux péripherique

The peripheral nervous system (PNS) is formed by neural crest cells (NCC) that migrate out of the neural tube in early mid-gestation. NCC give rise to most of the components of the PNS, including the sensory neurons, glial satellite and Schwann cells. In addition, neural crest cells also give rise to another type of PNS cells, the boundary cap (BC) cells. BC cells form clusters at the surface of the neural tube, at entry and exit points of peripheral nerve roots. Using various genetic tools we were able to trace BC cell progeny during development and to perform their ablation in vivo. The elimination of BC cells allowed us to reveal an unsuspected function of these cells: they are required to maintain the integrity of the spinal cord motor column and in their absence motor neurons translocate their cell bodies along their axons into the periphery. In addition, we have shown that trunk BC-derived cells migrated along peripheral axons and colonized spinal nerve roots and dorsal root ganglia (DRG). All Schwann cell precursors occupying the dorsal roots were derived from BC cells. In the DRG, BC-derived cells were the progenitors of both neurons, mainly nociceptive afferents, and satellite cells. These unexpected observations indicate that BC cells constitute a source of peripheral nervous system (PNS) components that, after the major neural crest ventrolateral migratory stream, feeds a secondary wave of migration to the PNS.