The transgenic line Tg(ptf1a:GFP) marks a subset of neurons within the larval ENS. Maximum projection confocal stacks at (A-A′′) 4 dpf, (B-B′′) 5 dpf and (C-C′′) 6 dpf depicting ptf1a:GFP⁺ and Hu⁺ cells within the midgut (dashed lines), scale bar: 70 microns, for A-C. (D) Bar graph illustrating total number of ptf1a:GFP⁺ cells in the gut from 4 dpf to 6 dpf, error bars represent s.e.m., n=6. (E) Maximum intensity confocal projection along the z-axis reveals that ptf1a:GFP⁺/Hu⁺ cells co-localize in a concentric pattern along the gut tube at 6 dpf, scale bar: 100 microns. (F) Lateral view of a 6 dpf ptf1a:GFP⁺ larval fish. (G, H) Ventrolateral view following whole mount in situ hybridization against ptf1a reveals that ptf1a localizes to the brain, pancreas and midgut of 6 dpf larvae. (I) Bar graph illustrating the percentage of total Hu⁺ neurons that are ptf1a:GFP⁺ in the midgut at 5 dpf and 6 dpf, error bars represent s.e.m., n = 6. Int. bulb-intestinal bulb.

ptf1a:GFP⁺ cells co-localize with the neuronal marker acetylated tubulin in the gut. Maximum projection confocal stacks at (A-A′′) 4 dpf, (B-B′′) 5 dpf and (C-C′′) 6 dpf depicting ptf1a:GFP⁺ and Acetylated tubulin⁺ cells within the midgut (dashed lines), scale bar: 70 microns.

ptf1a:GFP cells are largely serotonergic enteric neurons that are derived from the neural crest. Maximum projection confocal stack of the midgut (A-A′′) reveal that ptf1a:GFP⁺ cells co-localize with the neurotransmitter 5HT at 6 dpf. (B-B′′) Images of live triple transgenic larval fish, ptf1a:GFP;-4725sox10:Cre;elf1a:loxp-GFP-loxp-dsRedpA, shows that ptf1a:GFP⁺ cells are neural crest derived. Scale bar: 70 µm.