Enteric neural crest-derived cells: Origin, identification, migration, and differentiation

Neurons and glial cells forming the enteric nervous system (ENS) arise from neural crest cells that migrate away from two different rostrocaudal levels of the neural axis, the vagal and sacral regions. The vagal region is defined as the post-otic hindbrain level with somites 1–7 (Le Douarin, 1982), and the sacral region is caudal to somite 28 in chick embryos and caudal to somite 24 in embryonic mice. Vagal level neural crest cells give rise to enteric neurons and glial cells throughout the entire gastrointestinal tract. Yntema and Hammond (1954) removed the neural crest and dorsal portion of the neural tube from defined rostrocaudal levels of the neural axis of chick embryos, and then approximately a week later, the embryos were fixed, sectioned, and silver stained to determine if enteric ganglia were present in the gastrointestinal tract. They found that enteric ganglia were absent from the esophagus, stomach, and small and large intestines if the lesions removed neural crest cells from a region commencing 4 somites width rostral to the first somite and extended caudally to the predicted level of the 10th somite. ENS deficits were not observed when any other levels of the neural crest were ablated (Yntema and Hammond, 1954, 1955; Hammond and Yntema, 1947). Thus, vagal level neural crest cells were deduced to be the only, or at least the major, source of the ENS throughout the entire gastrointestinal tract. These results were confirmed by Le Douarin and Teillet (1973, 1974) and Burns and Le Douarin (1998), who found that following replacement of the vagal neural axis, between somites 1–7, of chick embryos with the equivalent region from quail embryos, quail neurons and glial cells were found in ganglia throughout the gastrointestinal tract of the host embryo. More exact studies have shown that most neural cells in the mid- and hindgut of chick embryos are derived from the levels of somites 3–6 (Peters-van der Sanden et al., 1993; Epstein et al., 1994). There may be some species differences, since in mice neural crest cells adjacent to somites 1–4 appear to give rise to enteric neurons throughout the gut, whereas neural crest adjacent to somites 6–7 gives rise to a sub-population of neurons in the foregut, but no other gut region (Durbec et al., 1996; note that Durbec and colleagues define neural crest adjacent to somites 6–7 as “trunk” level neural crest since it also gives rise to dorsal root ganglia). Since Yntema and Hammond (1954) observed no neurons within the gut following ablation of the vagal-level neural crest, it appeared that the vagal neural crest was the sole source of enteric neurons. However, using chick-quail grafts, Le Douarin and Teillet (1973) showed that the sacral-level neural crest contributes some cells to enteric ganglia of the hindgut, although they did not ascertain with molecular markers if the sacral-derived cells were neurons and/or glial cells. In the following 25 years, different studies reached different conclusions as to the contribution of the sacral-level neural crest to the enteric nervous system. In both chick and mouse embryos in which pre-migratory sacral level neural crest cells were labelled with DiI or retroviruses, labelled cells were reported in the hindgut (Pomeranz et al., 1991; Serbedzija et al., 1991), at least 2 days prior to the arrival of vagal neural crest cells. However, variable results were obtained when segments of hindgut were removed prior to the arrival of vagal level cells and grown in culture, or explanted to the chorioallantoic membrane or kidney capsule; most studies reported a complete, or almost complete, absence of enteric neurons in the hindgut (Smith et al., 1977; Allan and Newgreen, 1980; Nishijima et al., 1990; Kapur et al., 1992; Lecoin et al., 1996; Young et al., 1996, 1998a), whereas other studies reported that neurons were present (Rothman and Gershon, 1982; Pomeranz and Gershon, 1990). Following transection of the midgut of chick embryos prior to the arrival of vagal neural crest cells, no enteric neurons were observed in the hindgut (Meijers et al., 1989). Thus, most of these experiments in which the vagal source was absent suggested that sacral neural crest cells do not colonize the hindgut, or that they require the presence of vagal cells in order to colonize the hindgut and form a recognizable ENS, or that they arrive simultaneous to or later than the vagal cells (Allan and Newgreen, 1980). The contribution of sacral level neural crest cells to the ENS in birds was resolved by a detailed study utilizing chick-quail chimeric grafting by Burns and Le Douarin (1998), in which they showed definitively that sacral cells contribute to the ENS in the hindgut. Importantly, they examined the time of arrival of sacral cells into the hindgut, and the phenotypes of the derivatives of sacral neural crest cells. Sacral cells were observed to migrate ventrally by E4.5 to form the pelvic plexus and nerve of Remak. The latter is an extension of the pelvic plexus in the form of a ganglionated chain, which lies in the mesentery adjacent to the dorsal border of the post-umbilical intestine; it is unique to birds. However, the sacral neural crest cells did not immediately continue their migration further ventrally from the nerve of Remak to enter the hindgut; instead, they entered the hindgut approximately 3 days later, around the time that the vagal cells arrived in the hindgut, at E7.5. Sacral cells were found to give rise to neurons and glial cells. Cells derived from the sacral neural crest gave rise to 17% of enteric neurons in the distal hindgut, with their contribution decreasing rostrally to 0.3% in the rostral hindgut. Several important questions remain unresolved about the contribution of sacral neural crest cells to the ENS of the hindgut. The first question is why the sacral cells pause for approximately 3 days in the nerve of Remak prior to entering the hindgut. The gut has been postulated to synthesize chemoattractive that neural crest cells (Le Douarin and and it is that the hindgut these at a later than the and The has been that the presence of vagal level neural crest cells within the hindgut may be to the sacral level neural crest cells to into the hindgut (Allan and Newgreen, 1980; et al., However, a study has shown that following ablation of the vagal level neural the migration of the sacral cells into the hindgut is et al., and of hindgut with sacral cells with and vagal cells have shown the and Newgreen, Thus, if is a chemoattractive in the hindgut, it to be by the and not vagal level neural crest cells. than an absence of chemoattractive to sacral cells into the hindgut, it is also that the of sacral cells into the hindgut is to a of the hindgut. study has shown that the of the of chick embryos a that is a of the and in other of the nervous system have that as and neural crest et al., 1996; et al., et al., and showed in extension of from neurons in the nerve of Remak is by of is throughout the of the of the at a later which with the time at which the of the nerve of Remak first enter the of the hindgut, the of to the and and is absent from the and Since the sacral neural crest cells migrate into the hindgut nerve from the nerve of Remak that are into the hindgut and Le Douarin, it is that the of or the time of of the sacral cells into the hindgut. The unresolved question about the contribution of the sacral neural crest to the ENS in the hindgut is the of labelled cells observed in the hindgut following of DiI or a into the sacral neural tube prior to migration of neural crest cells (Pomeranz et al., 1991; Serbedzija et al., 1991), as these cells were observed within the hindgut days prior to the arrival of sacral neural crest cells as reported by Burns and Le Douarin also to be cells derived from the sacral neural crest give rise to of enteric and sacral cells have the to colonize other of gut from the distal hindgut. a contribution from the sacral neural crest to the ENS in the hindgut has been shown in and Le Douarin, the is in in which the or are enteric neurons in most of the gastrointestinal tract caudal to the stomach, but some neurons are present in the distal (Durbec et al., 1996; et al., The most for the of neurons in the distal but not in the small or is that they arise from the sacral-level neural However, as in it that if sacral level neural crest cells do give rise to enteric neurons in the hindgut, they do not enter the hindgut it has been by vagal level neural crest cells. of markers of neural crest cells have been to the of the embryonic mouse gut et al., 1992; Young et al., These studies have shown a of the gut by neural crest labelled cells are not observed in the hindgut prior to the arrival of the cells, which are deduced to be vagal neural crest cells if the hindgut is removed prior to the arrival of vagal crest cells and explanted or no neurons in the of et al., 1990; Kapur et al., 1992; Young et al., 1996, do not have a nerve of but the pelvic plexus is to the distal hindgut in mouse embryos Young et al., 1998a), and it is that sacral neural crest cells migrate into the hindgut, but in the pelvic plexus for as they do in the nerve of Remak in birds. is by the that cells with a to vagal enteric neural crest cells are present in the pelvic plexus adjacent to the distal hindgut of embryonic mice from Young et al., The of vagal-level neural crest cells to colonize the rostral hindgut of mice at and the distal hindgut at around et al., 1992; Young et al., at when the of the vagal cells is within about of the cells within the pelvic plexus that are derived from sacral-level neural crest do not appear to have entered the hindgut most studies have reported an absence of neurons in the hindgut if it is removed and prior to the arrival of vagal neural crest cells and reported neurons were present in of hindgut from mice. Since of the distal hindgut from adjacent is at these it is that the gut also of the pelvic plexus from which into the of neural cells in the gut of mice. The of the gut the migration of cells derived from vagal level neural that are no cells in the hindgut prior to the arrival of vagal neural crest cells. of the hindgut of a mouse cells. The most caudal cells of the of cells derived from the vagal neural crest is approximately from the cells are also present in a in the of the pelvic but do not appear to be any cells within the most caudal of the hindgut adjacent to the pelvic The neural crest of is by and 1980; and However, is also that of neural crest cells are to a prior or from the neural both and and experiments in which neural crest cells are grown in et al., that the of a sub-population of neurons is they from the neural In neural crest cells to appear to be at the time that they from the neural tube and et al., There is also some for of neural crest cells to colonize the level neural crest cells, to somites do not the dorsal and do not give rise to enteric neurons (Le Douarin and However, when quail vagal-level neural crest cells were in to the host chick level neural crest cells, quail cells were present within the gut of the in the post-umbilical small (Le Douarin and et al., Le Douarin and colleagues suggested that vagal neural crest cells are to form the ENS, and to the et al., and and et al., are by pre-migratory cells in the neural which is by neural crest cells, to be by neural and enteric and is by and enteric that the and the cells in the neural tube cells to they are both from the neural tube to the gut, and then the gut neural crest cells are from the cells which they experiments the and migration of neural crest cells the of or the of chick-quail However, a of markers has been that neural crest cells prior to their into enteric neurons and glial cells. These markers are shown in of the markers are by neural crest cells prior to their into the gut whereas other markers are not the cells have arrived within the gut of the first markers of neural cells in the chick was the which an and et al., the time that the was first to neural crest cells, the equivalent and were to a the of neural crest cells et al., and the of cells that is stained with et al., Since and have been to neural cells within the embryonic gut, of chick and quail embryos et al., Pomeranz and Gershon, 1990; Epstein et al., 1991; et al., 1996, and also to neural cells in a of species but not mice or et al., et al., and However, the is also found a of cells not derived from the neural crest, and also et al., and results be with and cells are observed within the somites adjacent to the vagal level neural and the to which the appear to be first the neural crest cells the neural tube et al., the level of somites of an quail embryo. cells are present in the of the dorsal root ganglia and and in some cells that have further ventrally and are entering the that is also observed in around the of neural crest derived cells in the gut of an mouse for and is to the and is the of the are by cells of small from an mouse stained with cells are present in the of the the There are no cells at the of the the plexus later of a from an mouse in which of the cells the The is of both cells and cells and not arise from a of a of the hindgut from an sub-population of the cells has into neurons but most cells do not of gut from an mouse stained with an to and the The two neural crest cells in of are both as is from their The cells that are not neural cells are cells. of a neural that was for and the of is with the of quail and hindgut. Vagal neural enteric neural cells the and post-umbilical to the rostral border of the but no cells are at for in the Sacral neural cells form the nerve of Remak in the dorsal mesentery adjacent to the but do not at into the at any of an in the midgut of an cells in the midgut of an in the of an is by the of the and of the nervous dorsal root ganglia and crest cells at levels of the neural axis of chick and quail embryos both and their from the neural tube et al., is also in the neural tube prior to the of neural crest cells, but is to vagal level neural between and somite and Following is by some dorsal root the ENS, and some ganglia of the chick and The detailed study that examined the migration of sacral-level neural crest cells into the hindgut chimeric grafting to sacral-derived neural crest cells and Le Douarin, than any of the markers shown in is about the of sacral-derived neural crest cells in the prior or their into the hindgut. is in the vagal neural tube of the chick prior to of the neural crest cells, is not by the sacral level neural tube and Sacral cells to the chick hindgut appear to pause in the nerve of Remak for about 3 days prior to entering the hindgut and Le Douarin, and and is shown by cells in the nerve of Remak et al., Epstein et al., 1991; et al., but it is if any of these cells into the hindgut. and are by vagal neural crest cells prior to their into the gut et al., and et al., are in the neural tube the cells but the other are not the cells have the neural is by pre-migratory crest cells of chick embryos it is first in neural crest cells in mice embryos et al., or as et al., et al., et al., and et al., are by enteric and but not dorsal root whereas other as et al., et al., 1993; et al., et al., et al., et al., and et al., et al., are by the of and neurons. is neural crest cells to enter the gut of the or different of cells the of different However, entering the mouse gut, neural crest cells are of two phenotypes et al., of neural cells within the gut that prior to entering the gut, the neural crest cells a of is about the of sacral-level neural crest cells in sacral neural crest cells in the embryonic mouse et al., In cells in the pelvic plexus and et al., 1998a), and if sacral-derived neural crest cells migrate into the hindgut the pelvic plexus vagal cells, sacral-derived cells are also to both of these prior to entering the of the markers by neural cells to the gut are also by the cells within the gut for of cells colonize the embryonic chick and quail gut in a et al., Epstein et al., 1991; et al., et al., and it is that neural cells in the chick gut are is about the of of other neural crest markers by the cells. However, the between and the of the and by neural crest cells as they colonize the gut has been examined et al., the in the mouse et al., mouse and not of the neural cells in the embryonic chick gut appear to or as they are the gut, since cells at the do not or is by vagal neural crest cells both prior to their into the gut, and for days they have entered the gut of embryonic mouse and it is not by neural crest cells in chick embryos prior to or they have entered the gut (Smith et al., However, when neural crest cells are from segments of embryonic chick gut using and then grown in culture, some cells do (Pomeranz et al., 1993; et al., 1994). Sacral neural cells into neurons and glial cells in the hindgut and Le Douarin, However, to is about the of sacral-derived neural crest cells within the chick hindgut prior to their into neurons and glial cells. large of are by vagal neural cells in the embryonic mouse and gut The of the gut by neural cells in mice was first examined in in mice in which the of the the was to of the et al., to be by if not neural crest cells within the gut, and the of the by enteric neurons in are no neurons in the cells almost the cells that is by cells, and for a of than mice with mice that in ENS the of in the migration of neural cells into the gut has been examined Kapur et al., Vagal crest cells the mouse and gut in a Kapur et al., 1992; and Young et al., 1998a), and the the most caudal cells are whereas cells rostral to the are at of The in the of some of these was examined in the embryonic mouse gut et al., and most neural crest cells were found to and but was is also by neural cells within the embryonic and mouse gut et al., et al., is by about of the cells at the et al., In the mouse gut, although have observed the most caudal to be have observed the and most caudal cells are However, at cells further from the in cells are observed in the hindgut. is the absence of cells from the hindgut is to the of the hindgut, or to the of cells. Since cells of the of as and et al., it is that cells to the hindgut they are neurons and have neural cells within the gut appear to and it to be for most of the other markers shown in they are by or a sub-population of neural crest cells, or they are by neurons or glial cells. of of the mouse The cells are also for and The cells form a sub-population of the cells. the most caudal in is not the most caudal is The is by enteric neural cells in the and small and large intestines of embryonic but not the et al., Since sacral-level neural crest cells do not appear to and and since neurons in the arise from neural crest cells adjacent to somites whereas neurons in the of the gastrointestinal tract arise from neural crest cells adjacent to somites 1–4 (Durbec et al., 1996; may be by the most vagal level neural crest cells. The of and in the of the ENS has been and be of the a of different and and the of in in the ENS The to be for ENS are and and and and and and The most of mice in of ENS are mice in which the the or are and mice have no ENS in any region of the gastrointestinal tract et al., et al., et al., Thus, and are for the of enteric neurons and glial cells. However, in other mice in which the ENS is the is mice enteric neurons in the et al., and mice enteric neurons caudal to the et al., et al., 1996; et al., 1996; et al., 1996; et al., et al., and and mice enteric neurons in the and et al., et al., et al., in and of neurons are absent from the et al., et al., whereas in are of enteric neurons in the et al., et al., of neurons in the gastrointestinal tract of some mice. glial derived the presence of enteric neurons in the distal hindgut of and mice. The of of some of these have been The to be for the and of enteric et al., et al., et al., et al., et al., et al., whereas the of the is to that a of to and the entire gastrointestinal tract et al., et al., is for the of neural crest cells, since in cells they the gut et al., However, the by are is for the of and since in is no or in enteric or neural cells et al., The between and is In is by but not by cells in the most rostral ganglia or in the gut, but by is also from the caudal ganglia et al., Since the of is in mice et al., et al., and as is a in the of in some mice et al., it has been that is also in a and et al., However, mice do not have any in their ENS et al., to be for the of neural et al., the of and mice the of of has the and the ENS caudal to the the and the of the ganglia and the ENS in the the mice the and an ENS caudal to the stomach, but the ENS is present in the and caudal ganglia are also However, a results when is There is no ENS in the esophagus, but enteric neurons are present in the and the small and large are also of neurons in the ganglia et al., in of the gastrointestinal the esophagus, and in appear to and et al., 1993; et al., Young et al., and the in the is not to different of the suggested by Durbec et the of the ENS and the nervous system of and mice to be with the rostrocaudal level of the neural axis from which the different of the neural crest adjacent to somites 1–4 give rise to the ENS caudal to the and to the and these are the whereas the ENS in the from neural crest adjacent to somites 6–7 and is The different phenotypes of and mice also that and have in to the and by et et that are neurons in the gut than in the In the small and large of the are of gut these an of glial cells, from an of than neural cells at Thus, in the neural cells within the gut be using with neural crest or by the of for the at any time of the neural cells are cells appear to be the gut, and not to be any region that is a for neural crest cells. In the midgut of chick and mice embryos, neural cells migrate the of the the the plexus form Kapur et al., 1992; et al., 1996; Young et al., 1996; Burns and Le Douarin, the midgut is and and have not (Allan and Newgreen, 1980; et al., cells are not in the of the plexus days later, and the plexus is to arise from a migration from the plexus et al., 1980; et al., In the hindgut of embryonic the of the of neural crest cells within the hindgut and the of the and have not been However, in the of chick embryos, vagal neural crest cells a the of the the plexus and some cells then later migrate to the of the to the region of the plexus and Le Douarin, is that cells in the of the chick migrate a to the than they do in the small by the time that the cells arrive in the large the has days neural cells have a region of the embryonic mouse gut, the cells are with no of in the as the gut in and the cells form The cells to into ganglia are Cells forming a do not arise from a has been by et who found that following of quail gut crest cells into chick embryos neural cells, enteric ganglia within the host that both quail and chick cells. of neurons in a also be using an in in mice for an of mice has of into the and Following in around is in about of cells and most are derived from a the cells of are or in these mice et al., However, enteric ganglia are almost of a of and cells that a not the of a neurons of a within a are also not since within a neurons of a both and cells. of ganglia in the small of the in which enteric neurons and their are labelled with to and neurons with to cells are but at the cells have into recognizable ganglia which ganglia in of the of cells The ENS is of different of neurons that in the of that they and their et al., 1996; and 1996; et al., is about the an neural to into a glial or a of The to some in the of not in the gut, but also in since and mice have of neurons in and enteric ganglia et al., et al., to be for the of some of neurons since mice neurons in the small et al., of enteric neurons at different In embryonic neurons at in the in the hindgut whereas neurons be around and Gershon, and Young et al., and it is that different of enteric neurons are in to that in other of the nervous system and et al., is by some enteric neurons and The gut to the of neurons derived from the neural the gut to the of of neural crest derived cells from gut when for 4 days to of cells and following to the gut neural crest cells appear to be to a of and glial enteric neural cells from or quail embryos are into chick embryos, some cells colonize and ganglia and the nerve of Remak if they are into the level (Rothman et al., 1993; and the cells that contribute to the pelvic ganglia or nerve of Remak a that is of neurons in these the cells that contribute to or ganglia do not an or and the gut is to a in the of different cells to and neurons and appear to a to the the to be neurons or glial cells and In the years, in of ENS have been studies have and that are for the of the ENS in different of the gut, and markers have been that neural cells within the gut prior to their into neurons and glial cells, and the of the gut by neural cells in and be However, are the of within the and are by the and of and the and for with some of the the and also for the and for from the mice.