ENDOTHELIN-B RECEPTOR IS EXPRESSED BY NEURAL CREST CELLS IN THE AVIANEMBRYO

Disruptions of the genes encoding endothelin 3 (EDN3) and its receptor endothelin-B receptor (EDNRB) in the mouse result in defects of two n eural crest (NC)-derived lineages, the melanocytes, and the enteric ne rvous system, To assess the mechanisms through which the EDN3/EDNRB si gnaling pathway can selectively act on these NC derivatives, we have s tudied the spatiotemporal expression pattern of the EDNRB gene in the avian embryo, a model in which NC development has been extensively stu died, For this purpose, we have cloned the quail homologue of the mamm alian EDNRB cDNA. EDNRB transcripts are present in NC cells before and during their emigration from the neural tube at all levels of the neu raxis. At later developmental stages, the receptor remains abundantly expressed in the peripheral nervous system including the enteric nervo us system. In a previous study, we have shown that EDN3 enhances drama tically the proliferation of NC cells when they are at the pluripotent stage. We propose that the selective effect of EDN3 or EDNRB gene ina ctivation is due to the fact that both melanocytes and enteric nervous system precursors have to colonize large embryonic areas (skin and bo wel) from a relatively small population of precursors that have to exp and considerably in number. It is therefore understandable that a defi cit in one of the growth-promoting pathways of NC cells has more delet erious effects on long-range migrating cells than on the NC derivative s which develop close to the neural primordium like the sensory and sy mpathetic ganglia.