Expression of the transgenes Tg(ins:GFP), Tg(gcga:GFP), Tg(sst2:GFP), and Tg(ins:NTR:mCherry) in the endocrine pancreatic cell types. (A–C) Whole mount immunostaining of 3 dpf transgenic larvae Tg(ins:GFP) demonstrating the selective expression of GFP in beta cells. (D–I) Immunostaining of pancreas sections from adult transgenic fish Tg(gcga:GFP/ins:NTR:mCherry). Glucagon+ cells (see arrows in D–F) express high level of GFP and are not labelled by mCherry, while many insulin expressing cells are labelled by mCherry and by GFP (at slightly lower levels) (see arrowheads in G–I). These data reveal a leaking expression of the gcga:GFP transgene in beta cells. (J–L) ISH performed on pancreas section of adult Tg(sst2:gfp) with sst2 probe followed by immunofluorescence using the GFP antibody; the expression of endogenous sst2 gene co-localize with GFP staining confirming the specific expression of the transgene in delta cells .