Expression of insulin and insulin receptors during zebrafish endoderm development. (A) In situ hybridization for insra and insrb in the developing zebrafish embryos. (B–C) Fluorescent in situ hybridization of insrb (red) in Tg(sox17:GFP) endoderm (green) at 48 hpf. Abbreviations: z, zygote; ed, endoderm; p, pancreas; li, liver; in, intestine.