COLONIZATION OF THE BOWEL BY NEURAL CREST-DERIVED CELLS RE-MIGRATING FROM FOREGUT BACKTRANSPLANTED TO VAGAL OR SACRAL REGIONS OF HOST EMBRYOS

The enteric nervous system (ENS) in avian embryos is formed. by cells that migrate to the bowel from vagal and sacral regions of the neural crest. Experiments were carried out to evaluate the developmental pote ntial of crest-derived cells at the time they colonize the gut. Backtr ansplantation of E4 quail foregut (or control aneuronal hindgut) was u sed to determine whether crest-derived cells that have previously colo nized the bowel are capable of following defined neural crest migratio n pathways in host embryos. Vagal and sacral, but not truncal, backgra fts provided donor cells for the host's bowel. These cells were immuno stained by the neural crest marker, NC-1, restricted to the ENS, and a ppeared only when foregut was backgrafted; therefore, they were crest- derived. In order for cells to migrate to the host's bowel, backgrafts evidently had to be located in the vicinity of the neuraxis at the ti me crest-derived cells exited from them. When vagal grafts moved away from the neuraxis, crest-derived donor cells colonized cephalic gangli a and the vagus nerves near the grafts; however, such cells did not mi grate down the vagi to the host's gut. Sacral backgrafts provided cres t-derived cells for the bowel only if the donor gut was transplanted p rior to the formation of somite 28, at the level of the disappearing p rimitive streak. Cells from vagal backgrafts were capable of reaching the host's cloaca, but backgrafts placed at a sacral level colonized o nly the postumbilical bowel. In addition, donor cells proliferated ext ensively within the host's gut. Whenever the host's gut was colonized, donor crest-derived cells were also found in non-enteric targets incl uding nerves, cephalic (vagal backgrafts), or sympathetic (sacral back grafts) ganglia; however, donor cells did not form ectomesenchyme or m elanocytes. These data suggest that (i) crest-derived cells that have colonized the bowel remain capable of re-migrating and following defin ed neural crest migration pathways in host embryos; (ii) remigrating c ells must enter these pathways at their start; (iii) the gut stimulate s the proliferation of enteric crest-derived cells; (iv) vagal crest-d erived cells can follow sacral pathways to reach enteric, Remak's, or sympathetic ganglia; and (v) the migration of crest-derived cells with in the gut is determined more by the route they follow to reach the bo wel than by their level of origin in the neural crest. (C) 1993 Wiley- Liss, Inc.