Migration of crest-derived cells from gut: gut influence on spinal cord development

The technique of backtransplantation was used to investigate the developmental potential of neural crest cells that have migrated to and colonized the bowel. Segments of chimaeric gut in which only the crest-derived cells were of quail origin, were grafted between somites and neural tube of younger chick host either at truncal (somites 18-24) or at rhombencephalic level. Quail neural crest-derived cells were identified in the spinal cord, spinal roots and ganglia, sympathetic ganglia and the adrenals, cranial sensory ganglia according to the level selected for the graft. These experiments demonstrate that crest-derived cells, having previously migrated to the gut, retained the ability to migrate to distant sites into a younger host. The chimaeric gut transplants induced a unilateral increase in the host's neural tube as it had been previously revealed after quail gut, skeletal, and cardiac muscle backtransplantation. Moreover, our experiments demonstrate that the number of the motor neuron progenitors is affected when spinal cord and gut experimentally developed in close contact. These observations support the hypothesis that gut smooth muscle as striated muscles releases a short range diffusible factor that induces proliferative effects on the neuroepithelial cells. The growth-promoting effect occurs during the time neurons are actively generated. It must still be determined whether such extrinsically derived factors participate in the regulation of cell proliferation in the central nervous system.