The receptor tyrosine kinase RET regulates hindgut colonization by sacral neural crest cells

Abstract

The enteric nervous system (ENS) is formed from vagal and sacral neural crest cells (NCC). Vagal NCC give rise to most of the ENS along the entire gut, whereas the contribution of sacral NCC is mainly limited to the hindgut. This, and data from heterotopic quail-chick grafting studies, suggests that vagal and sacral NCC have intrinsic differences in their ability to colonize the gut, and/or to respond to signalling cues within the gut environment. To better understand the molecular basis of these differences, we studied the expression of genes known to be essential for ENS formation, in sacral NCC within the chick hindgut. Our results demonstrate that, as in vagal NCC, Sox10, EdnrB, and Ret are expressed in sacral NCC within the gut. Since we did not detect a qualitative difference in expression of these ENS genes we performed DNA microarray analysis of vagal and sacral NCC. Of 11 key ENS genes examined from the total data set, Ret was the only gene identified as being highly differentially expressed, with a fourfold increase in expression in vagal versus sacral NCC. We also found that over-expression of RET in sacral NCC increased their ENS developmental potential such that larger numbers of cells entered the gut earlier in development, thus promoting the fate of sacral NCC towards that of vagal NCC.

Targeted deletion of Hand2 in enteric neural precursor cells affects its functions in neurogenesis, neurotransmitter specification and gangliogenesis, causing functional aganglionosis

“…This idea is supported by mathematical modeling demonstrating that increased proliferation could substitute for a decrease in the initial number of cells colonizing the gut (Zhang et al, 2010) and is reminiscent of the differential proliferative capacity of vagal and sacral neural crest-derived cells (Newgreen et al, 1980;Delalande et al, 2008;Zhang et al, 2010). These results show that both the initial number of precursor cells and differential proliferative capacity accounts for neuron numbers in the ENS (Zhang et al, 2010).…”

Critical numbers of neural crest cells are required in the pathways from the neural tube to the foregut to ensure complete enteric nervous system formation

“…It is possible that we did not see quail trunk NCC in guts of 3-6 ablated embryos because we did not replace the entire vagal neural tube with trunk, as carried out by the authors of this previous work (Le Douarin et al, 1975;Le Douarin and Teillet, 1974). Our recent findings also suggest that levels of Ret expression in the donor NCC from different axial levels could be critical in determining their ENS developmental potential, as sacral NCC, in which Ret was overexpressed by gene electroporation, increased their capacity for migration and became highly invasive of the hindgut (Delalande et al, 2008).…”

“…The BrdU was then washed from the cultures and they were incubated for a further 14 hours in culture media. The following day the cultures were fixed and immunostained with anti-BrdU antibody (Oxford Biotech, UK; 1:300), as previously described (Delalande et al, 2008). The proportion of proliferating NCC was calculated and the mean distance of migration of NCC from the neural tube was determined.…”

Age-dependent changes in the gut environment restrict the invasion of the hindgut by enteric neural progenitors

“…In the fetal gut, sacral crest cells are made up of long, thin strands that project rostrally and contain fewer, more widely spaced cell bodies than do strands from the vagal crest. It is not clear what properties result in their advance or failed expansion, but recent studies suggest a difference in RET expression between vagal-and sacral-derived neural crest may be crucial (Delalande et al, 2008).…”