Maintenance of mammalian enteric nervous system progenitors by SOX10 and endothelin 3 signalling

Abstract

The transcriptional regulator SOX10 and the signalling molecule endothelin 3 have important roles in the development of the mammalian enteric nervous system (ENS). Using a clonal cell culture system, we show that SOX10 inhibits overt neuronal and glial differentiation of multilineage ENS progenitor cells (EPCs), without interfering with their neurogenic commitment. We also demonstrate that endothelin 3 inhibits reversibly the commitment and differentiation of EPCs along the neurogenic and gliogenic lineages, suggesting a role for this factor in the maintenance of multilineage ENS progenitors. Consistent with such a role, the proportion of Sox10-expressing progenitors in the total population of enteric neural crest cells is reduced in the gut of endothelin 3-deficient embryos. This reduction may be related to the requirement of endothelin signalling for the proliferation of ENS progenitors. The dependence of ENS progenitors on endothelin 3 is more pronounced at the migratory front of enteric neural crest cells, which is associated with relatively high levels of endothelin 3 mRNA. Our findings indicate that SOX10 and endothelin 3 have a crucial role in the maintenance of multilineage enteric nervous system progenitors.

The migratory behavior of immature enteric neurons

“…A sub-population of ENCCs differentiates into neurons as ENCCs are migrating through the developing gut (Baetge and Gershon, 1989;Fairman et al, 1995;Newgreen and Hartley, 1995;Burns and Le Douarin, 1998;Young et al, 1999Young et al, , 2002Barlow et al, 2003;Conner et al, 2003;Kruger et al, 2003;Bondurand et al, 2006). In this time-lapse imaging study using transgenic mice in which immature enteric neurons express GFP, around 50% of immature enteric neurons migrated (defined as moving at least one somal diameter over a minimum period of 2 hours).…”

“…As endothelin-3 signaling inhibits neuronal differentiation in vitro (Hearn et al, 1998;Wu et al, 1999;Bondurand et al, 2006;Nagy and Goldstein, 2006), and as there is a delayed migration of ENCCs along the gut in mice lacking endothelin-3 (Barlow et al, 2003), it has been proposed that endothelin-3 prevents premature neuronal differentiation and facilitates the persistence of a precursor pool for sufficient time to colonize the entire gut (Hearn et al, 1998;Wu et al, 1999;Nagy and Goldstein, 2006). It is implicit in this argument that enteric neuronal differentiation directly inhibits migration, or indirectly inhibits migration by reducing proliferation; proliferation has recently been shown to be essential for migration (Simpson et al, 2007).…”

“…While they are migrating along the gut, a sub-population (10%-20%) of ENCCs starts to express panneuronal markers including neurofilaments, Hu, Tuj1, and PGP9.5 and may be considered immature neurons (Baetge and Gershon, 1989;Fairman et al, 1995;Newgreen and Hartley, 1995;Young et al, 1999Young et al, , 2002Barlow et al, 2003;Conner et al, 2003;Kruger et al, 2003;Bondurand et al, 2006). Immature enteric neurons also transiently express the catecholamine synthetic enzyme, tyrosine hydroxylase (TH) (Teitelman, 1981;Baetge and Gershon, 1989;Baetge et al, 1990a,b;Young et al, 1999).…”

“…In mice lacking endothelin-3 or its receptor Ednrb, the migration of ENCCs along the gut is delayed (Cass et al, 1992;Kapur et al, 1992Kapur et al, , 1993Kapur et al, , 1995Barlow et al, 2003;Kruger et al, 2003). In vitro and in vivo studies have shown that endothelin-3 inhibits the differentiation of ENCCs (Hearn et al, 1998;Wu et al, 1999;Bondurand et al, 2006;Nagy and Goldstein, 2006). However, the mechanisms by which differentiation might affect ENCC migration rate have yet to be established.…”

“…If neuronal differentiation retards the migration of ENCCs directly, endothelin-3 might promote ENCC migration by inhibiting differentiation. As proliferation is essential for ENCC migration (Simpson et al, 2007), endothelin-3 might promote ENCC migration indirectly by increasing the rate of proliferation (Hearn et al, 1998;Bondurand et al, 2006;Nagy and Goldstein, 2006). It is therefore of interest to determine whether immature neurons migrate, and if so, whether they migrate at the same speed as undifferentiated ENCCs.…”