Fig. 3

Inhibition of RA signaling induces PNCs to differentiate into endocrine cells. (A) Schematic of the nuclear red cre responder, Tg(β-actin:loxP-stop-loxP-hmgb1-mCherry)^jh15. The β-actin promoter/enhancer drives ubiquitous expression. Active Cre induces recombination between the two loxP sites (black triangles) removing the STOP signal (yellow box) and allowing production of Hmgb1-mCherry, a nuclear-red fluorescent protein. The transgene is flanked by Tol2 arms (gray triangles). (B) Experimental timeline of 4OHT-dependent fate mapping. 4OHT was applied 2–3 dpf. Larvae were then exposed to drugs from 3–5 dpf. (C–F) Confocal z-stack projections of dissected pancreata from larvae transgenic for the Notch-responsive creER^T2driver, Tg(Tp1glob:creER^T2)^jh12, the nuclear red cre responder and the endocrine marker, Tg(pax6b:eGFP)^ulg515. These triple transgenic larvae were treated with vehicle (C), 4OHT+DMSO (D), 4OHT+DEAB (E), and 4OHT+DSF (F). The presence of lineage-traced cells (red nuclei) is dependent on 4OHT treatment (D–F). 2° islet cells can be detected in the tail region of larval pancreata after treatment with either DEAB (E) or DSF (F). (E′ and F′) The precocious 2° islet cells are positive for both GFP and mCherry, indicating their PNC origin. Nuclei are counterstained with DAPI (blue). White dashes outline pancreata. Scale Bar, 100 μm.