Lumbo-sacral neural crest contributes to the avian enteric nervous system independently of vagal neural crest.

Abstract

Most of the avian enteric nervous system is derived from the vagal neural crest, but a minority of the neural cells in the hindgut, and to an even lesser extent in the midgut, are of lumbo-sacral crest origin. Since the lumbo-sacral contribution was not detected or deemed negligible in the absence of vagal cells, it had been hypothesised that lumbo-sacral neural crest cells require vagal crest cells to contribute to the enteric nervous system. In contrast, zonal aganglionosis, a rare congenital human bowel disease led to the opposite suggestion, that lumbo-sacral cells could compensate for the absence of vagal cells to construct a complete enteric nervous system. To test these notions, we combined E4 chick midgut and hindgut, isolated prior to arrival of neural precursors, with E1. 7 chick vagal and/or E2.7 quail lumbo-sacral neural tube as crest donors, and grafted these to the chorio-allantoic membrane of E9 chick hosts. Double and triple immuno-labelling for quail cells (QCPNA), neural crest cells (HNK-1), neurons and neurites (neurofilament) and glial cells (GFAP) indicated that vagal crest cells produced neurons and glia in large ganglia throughout the entire intestinal tissues. Lumbo-sacral crest contributed small numbers of neurons and glial cells in the presence or absence of vagal cells, chiefly in colorectum, but not in nearby small intestinal tissue. Thus for production of enteric neural cells the avian lumbo-sacral neural crest neither requires the vagal neural crest, nor significantly compensates for its lack. However, enteric neurogenesis of lumbo-sacral cells requires the hindgut microenvironment, whereas that of vagal cells is not restricted to a particular intestinal region.