Requirement of signalling by receptor tyrosine kinase RET for the directed migration of enteric nervous system progenitor cells during mammalian embryogenesis

Abstract

The majority of neurones and glia of the enteric nervous system (ENS) are derived from the vagal neural crest. Shortly after emigration from the neural tube, ENS progenitors invade the anterior foregut and, migrating in a rostrocaudal direction, colonise in an orderly fashion the rest of the foregut, the midgut and the hindgut. We provide evidence that activation of the receptor tyrosine kinase RET by glial cell line-derived neurotrophic factor (GDNF) is required for the directional migration of ENS progenitors towards and within the gut wall. We find that neural crest-derived cells present within foetal small intestine explants migrate towards an exogenous source of GDNF in a RET-dependent fashion. Consistent with an in vivo role of GDNF in the migration of ENS progenitors, we demonstrate that Gdnf is expressed at high levels in the gut of mouse embryos in a spatially and temporally regulated manner. Thus, during invasion of the foregut by vagal-derived neural crest cells, expression of Gdnf was restricted to the mesenchyme of the stomach, ahead of the invading NC cells. Twenty-four hours later and as the ENS progenitors were colonising the midgut,Gdnf expression was upregulated in a more posterior region —the caecum anlage. In further support of a role of endogenous GDNF in enteric neural crest cell migration, we find that in explant cultures GDNF produced by caecum is sufficient to attract NC cells residing in more anterior gut segments. In addition, two independently generated loss-of-function alleles of murine Ret, Ret.k— and miRet51, result in characteristic defects of neural crest cell migration within the developing gut. Finally, we identify phosphatidylinositol-3 kinase and the mitogen-activated protein kinase signalling pathways as playing crucial roles in the migratory response of enteric neural crest cells to GDNF.

Ret loss-of-function decreases neural crest progenitor proliferation and restricts developmental fate potential during enteric nervous system development

“…To assess cell-type-specific roles for Ret in the developing ENS, we used a previously described mouse line harboring a Ret -null fluorescent reporter allele ( Ret CFP ) (Uesaka et al 2008). All ENCDCs express Ret during early development (Natarajan et al 2002) allowing for their isolation via this reporter system. We sorted Ret expressing ENCDC via FACS to decipher the cell autonomous effect of Ret LoF.…”

“…One of the key factors involved in the migration of ENCDCs into the developing gut, and their differentiation into enteric neurons and glia, is the receptor tyrosine kinase RET (Natarajan et al 2002; Lasrado et al 2017). RET expression in ENCDCs promotes proliferation and cell survival via the MAPK and PI3K/AKT pathways (Mulligan 2014).…”

TALPID3/KIAA0586 Regulates Multiple Aspects of Neuromuscular Patterning During Gastrointestinal Development in Animal Models and Human

“…TALPID3 and Rac1 have a comparable function in vesicular trafficking ( Stenmark, 2009 ), centrosome regulation ( May et al, 2014 ) and in cell-matrix interactions ( Thomas et al, 2010 ). Rac1 is also downstream of RET, a tyrosine kinase receptor essential for ENS development ( Natarajan et al, 2002 ; Fu et al, 2010 ; Mulligan, 2014 ).…”

“…This phenotype has been attributed to a combination of reduced Hh signaling and increased Ret tyrosine kinase signaling ( Biau et al, 2013 ). The Ret tyrosine kinase is essential for ENS development ( Natarajan et al, 2002 ).…”

Schwann Cells in Digestive System Disorders

“…Hepatic innervation differs from that of the gastrointestinal tract, although the liver is formed from the foregut during embryonic development. The liver itself does not contain ENS or other intrinsic neurons derived from NC, perhaps due to very low expression levels of GDNF, a known NC chemoattractant in the developing gut [ 174 , 185 ].…”