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. Author manuscript; available in PMC: 2012 Apr 26.
Published in final edited form as: Curr Biol. 2011 Apr 14;21(8):712–717. doi: 10.1016/j.cub.2011.03.041

Figure 3. Inhibition of Ptf1a activity induces ectopic endocrine gene expression.

Figure 3

(A) elastase:cre-Ptf1aEN, heat-inducible overexpression of Engrailed-Ptf1a in an elastase3l:Cre restricted domain. Expression of Cre in acinar cells excises the EBFP2-STOP cassette and perm its heat-inducible expression of Engrailed -Ptf1a. (B–K′) Confocal sections through pancreata marked with immuno-fluorescence (D–E′) or fluorescent transgenes (F–K′). Scale bars = 20μm. (B–E′) Tg(ela3l:cre); (hsp70l:loxP:mCherrySTOP:loxP:H2B-GFP) embryos were heat-shocked at 60 hpf (B,B′) or 4.5 dpf (C–E′) and analyzed 24 h post heat-shock. (F–I′) elastase:cre-Ptf1aEN (F,F′,H,H′,J,J′) and Tg(ela3l:cre) negative control embryos (G,G′,I,I′,K,K′) were heat-shocked at 4.5 dpf and analyzed at 5.5 dpf (H–I′) or 6.5 dpf (F–G′, J–K′). (B,B′) Tg(ela3l:cre) did not mark pancreatic cells by 60 hpf (dotted outline). (C,C′) By 4.5 dpf, Tg(ela3l:cre) marked a large fraction of pancreatic cells (dotted outline). Cells that were marked by Tg(ela3l:cre) at 4.5 dpf co-expressed the acinar marker Elastase (D,D′, arrow ) but never co-expressed the endocrine marker Insulin (E,E′) at 5.5 d pf. (F,F′) elastase:cre-Ptf1aEN induction caused down-regulation of Tg(elastase:eGFP) expression in a subset of acinar cells (F′, inset). Some acinar cells that expressed low levels of Tg(elastase:eGFP) co-expressed Tg(insulin:d sRED) (F, inset). (G,G′) Tg(insulin:d sRED) expression was neverdetected in Tg(ela3l:cre) negative controls. (H–I′) elastase:cre-Ptf1aEN expression induced expression of the endocrine progenitor marker Tg(pax6b:eGFP) in cells outside of the principal islet (arrow s, H,H′). In Tg(ela3l:cre) negative controls at this stage, Tg(pax6b:eGFP) was expressed in the principal islet and in endocrine cells that differentiated in the extra-pancreatic duct (arrow head s, I,I′). (J–K′) elastase:cre-Ptf1aEN also induced Tg(gcga:GFP) expression in the exocrine compartment (J,J′), whereas Tg(gcga:GFP) expression was restricted to the principal islet in Tg(ela3l:cre) negative controls (K,K′).