Abstract
The enteric nervous system (ENS) is mainly derived from vagal neural crest cells (NCC) that arise at the level of somites 1-7. To understand how the size and composition of the NCC progenitor pool affects ENS development, we reduced the number of NCC by ablating the neural tube adjacent to somites 3-6 to produce aganglionic gut. We then back-transplanted various somite lengths of quail neural tube into the ablated region to determine the 'tipping point', whereby sufficient progenitors were available for complete ENS formation. The addition of one somite length of either vagal, sacral or trunk neural tube into embryos that had the neural tube ablated adjacent to somites 3-6, resulted in ENS formation along the entire gut. Although these additional cells contributed to the progenitor pool, the quail NCC from different axial levels retained their intrinsic identities with respect to their ability to form the ENS; vagal NCC formed most of the ENS, sacral NCC contributed a limited number of ENS cells, and trunk NCC did not contribute to the ENS. As one somite length of vagal NCC was found to comprise almost the entire ENS, we ablated all of the vagal neural crest and back-transplanted one somite length of vagal neural tube from the level of somite 1 or somite 3 into the vagal region at the position of somite 3. NCC from somite 3 formed the ENS along the entire gut, whereas NCC from somite 1 did not. Intrinsic differences, such as an increased capacity for proliferation, as demonstrated in vitro and in vivo, appear to underlie the ability of somite 3 NCC to form the entire ENS.
Highlights
The enteric nervous system (ENS) in avian embryos is derived predominantly from vagal neural crest cells (NCC) that emigrate from the neural tube at the level of somites 1-7 (Burns et al, 2000; Burns and Le Douarin, 1998; Epstein et al, 1994; Le Douarin and Teillet, 1973; Yntema and Hammond, 1954)
Once the hindgut is colonised by vagal NCC, a second population, which delaminates from the sacral neural crest caudal to the 28th pair of somites, forms the Nerve of Remak (NoR) that extends along the dorsal wall of the gut and enters the hindgut (Burns and Le Douarin, 1998)
By the 17ss, there was an extensive concentration of NCC at the base of somites 1-3, posterior to the branchial arches that abut another group of NCC that have migrated from the post-otic region of the neural tube (Fig. 1B,BЈ)
Summary
The ENS in avian embryos is derived predominantly from vagal NCC that emigrate from the neural tube at the level of somites 1-7 (Burns et al, 2000; Burns and Le Douarin, 1998; Epstein et al, 1994; Le Douarin and Teillet, 1973; Yntema and Hammond, 1954). These cells exit the neural tube at embryonic day (E) 1.5 and migrate ventrally within the embryo reaching the foregut by E4, from where they travel in a rostrocaudal direction to colonise the entire length of the gut by E8.5 (Burns, 2005; Burns and Le Douarin, 1998).
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