Roles for GFRα1 receptors in zebrafish enteric nervous system development

Abstract

Components of the zebrafish GDNF receptor complex are expressed very early in the development of enteric nervous system precursors, and are already present as these cells begin to enter the gut and migrate caudally along its length. Both gfra1a and gfra1b as well as ret are expressed at this time, while gfra2 expression, the receptor component that binds the GDNF-related ligand neurturin, is not detected until the precursors have migrated along the gut. Gfra genes are also expressed in regions of the zebrafish brain and peripheral ganglia, expression domains conserved with other species. Enteric neurons are eliminated after injection with antisense morpholino oligonucleotides against ret or against both Gfra1 orthologs, but are not affected by antisense oligonucleotides against gfra2. Blocking GDNF signaling prevents migration of enteric neuron precursors, which remain positioned at the anterior end of the gut. Phenotypes induced by injection of antisense morpholinos against both Gfra orthologs can be rescued by introduction of mRNA for gfra1a or for gfra2, suggesting that GFRα1 and GFRα2 are functionally equivalent.

Kit‐like immunoreactivity in the zebrafish gastrointestinal tract reveals putative ICC

“…Smooth muscle cells are evident at 50 hr post fertilization (hpf) and the longitudinal and circular muscle layers are well established by 96 hpf (Wallace et al, 2005a). Enteric neurons are observed by 72 hpf, completely populate the GI tract by 96 hpf, and increase in number to 120 hpf (Kelsh and Eisen, 2000;Shepherd et al, 2004). Therefore, both enteric neurons and smooth muscle cells appear well established by 5 dpf, coinciding with observations of spontaneous GI contractions and feeding (Holmberg et al, 2004).…”

“…Spontaneous contractions of the zebrafish GI tract begin at 4 dpf, coinciding with the development of enteric neurons, but the possibility for ICC contributing to the development of rhythmic contractions has not been explored (Kelsh and Eisen, 2000;Shepherd et al, 2004;Wallace et al, 2005b). Kit expression was identified in the GI tract of paraformaldehydefixed zebrafish larvae.…”

lessenencodes a zebrafishtrap100required for enteric nervous system development

“…Clutches of incrossed 96 hpf embryos were fixed and processed for immunocytochemistry using anti Hu mAb 16A11. The number of enteric neurons was determined in a 10-somite segment of the intestine extending anteriorly from the end of the yolk extension as described previously (Shepherd et al, 2004).…”

“…Digoxigeninlabelled and fluorescein-labelled riboprobes were synthesized from templates linearized with BamHI using T7 RNA polymerase for trap100. Other digoxigenin-labelled riboprobes used in this study were synthesized from templates linearized and transcribed as follows: crestin (Rubinstein et al, 2000), SacI and T7; phox2b (Shepherd et al, 2004), NotI and T7; dlx2a (Akimenko et al, 1994) and foxn1 (Schorpp et al, 2002), BamHI and T7; rag1 (Willett et al, 1997), HindII and T7; epha4 (Xu et al, 1995), EcoRI and T3; hoxb4 (Prince et al, 1998), KpnI and T3; ifbp (Andre et al, 2000), trypsin (Mayer and Fishman, 2003), pax9 (Nornes et al, 1996) and gata6 (Pack et al, 1996), SalI and T7; foxa2 (Strahle et al, 1993), SacI and T3; ptc1 (Concordet et al, 1996), BamHI and T3; shh (Ekker et al, 1995), HindII and T7; ret (Bisgrove et al, 1997), NotI and T7; and gfra1a (Shepherd et al, 2001) and nos1 (previously nnos) (Poon et al, 2003), NotI and Sp6. Digoxigenin-labelled probes were visualized with NBT/BCIP coloration reactions, while fluorescein-labelled riboprobe was visualized with Fast Red (Roche).…”

“…In zebrafish, differentiated enteric neurons can be first detected at the anterior end of the intestine immunocytochemically at 72 hpf (Bisgrove et al, 1997;Kelsh and Eisen, 2000;Shepherd et al, 2001;Shepherd et al, 2004). By 96 hpf, enteric neurons can be identified along the complete length of the intestine.…”