This is a very exciting paper. 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 sensory neurons, glial satellite and Schwann cells. In addition, NCC also give rise to another type of PNS cell called the boundary cap (BC) cell. BC cells form clusters on the surface of the neural tube at entry and exit points of peripheral nerve roots. Using various genetic tools the authors were able to trace BC cell progeny during development and to ablate the cells in vivo. BC cell elimination revealed that they have an unsuspected function; the cells maintain integrity of the motor column in the spinal cord. In their absence, motor neurons translocate their cell bodies along their axons into the periphery. In addition, trunk BC-derived cells migrate along peripheral axons and colonized spinal nerve roots and dorsal root ganglia (DRG). All Schwann cell precursors are found in dorsal roots are derived from BC cells. In the DRG, BC cells are progenitors of neurons (mainly nociceptive afferents) and satellite cells.

These unexpected observations indicate that BC cells are a source of PNS components that, following the major neural crest ventrolateral migratory stream, feed a secondary wave of migration to the PNS.

17 references.