| Development of the Enteric Nervous System |
| The ENS is a unique part of the nervous system |
| Quail-chick interspecies chimeras reveal the migration pathways of crest-derived cells |
| DiI-labeled sacral crest cells colonize the post-umbilical bowel |
| Slide 5 |
| Microenvironmental signals determine the fates of crest-derived cells |
| Slide 7 |
| Congenital aganglionosis causes pseudoobstruction |
| Crest-derived cells require Edn3 (ET-3) and Ednrb (ETB) to complete their colonization of the gut |
| Megacolon occurs in mice that lack edn3 (ET-3) |
| The terminal colon of ET-3-deficient mice is aganglionic |
| Co-cultured sources of crest fail to colonize presumptive end3ls gut |
| Presumptive aganglionic gut from edn3ls mice cannot be entered by quail crest cells |
| The terminal colon is normally colonized in end3ls <> WT chimeric mice |
| Edn3 inhibits the development of neurons from crest-derived precursors |
| Crest-derived cells are present in the proximal bowel of edn3-deficient mice but do not enter the terminal gut |
| Exogenous Edn3 enables crest-derived cells to enter the terminal colon of Edn3-deficient mice |
| Exogenous ET-3 allows crest-derived cells to colonize the entire colon in vitro |
| Ectopic ganglia develop in the pelvis of endls mice |
| Ret and Ednrb interact in humans and in mice (mice tested to verify human data) |
| Enteric neurons are Ret-dependent |
| The GDNF family of growth factors activate Ret |
| Specific transcription and growth factors define stages in ENS development |
| The earlier a gene acts in development, the more massive the defect that follows its deletion |
| Genes associated with Hirschsprung’s disease |
| Crest-derived cells are isolated by immunoselection. |
| Neurons develop in cultures of isolated crest-derived cells. |
| GDNF is mitogenic and promotes neurogenesis at E12 |
| Promotion of neurogenesis by GDNF decreases at E14; neurogenic response to NT-3 is acquired |
| Slide 30 |
| Crest-derived cells colonize the bowel and then migrate from the gut to the pancreas. |
| Crest-derived cells migrate in the outer gut mesenchyme; the submucosal plexus forms secondarily. |
| mRNA encoding netrin-1 is found in E13 mouse gut and pancreas. |
| Transcripts encoding netrin receptors are expressed in the developing gut and pancreas |
| Crest-derived cells migrate from explants of bowel toward transfected cells expressing netrin-1. |
| Crest-derived cells migrate toward cells that secrete netrin-1. |
| Crest-derived cells isolated from chick gut migrate toward co-cultured netrin-1-expressing cells. |
| Slide 38 |
| Antibodies to DCC block the inward migration of crest-derived cells in chick gut explants. |
| Antibodies to DCC inhibit the migration of crest-derived cells from gut toward pancreas. |
| The pancreas of DCC -/- mice is aganglionic |
| Vagal axons entering the stomach at E13 are DCC-immunoreactive |
| Summary & Conclusions |