Fig. 4

Inhibition of Notch-signaling dramatically induces precocious secondary islet formation. (A–E) Confocal images of 5 dpf micro-dissected pancreata. (A) Tg(Tp1bglob:hmgb1-mCherry)^jh11; Tg(P0-pax6b:GFP)^ulg515 untreated larva display pax6b expressing cells (green) localized only to the principal islet (◄), and PNCs (red) around the islet and through the middle of the pancreatic tail. (B and C) The same compound transgenic larvae, when treated with 100 μM DAPT from 3 dpf to 5 dpf, show a dramatic loss of PNCs concurrent with the appearance of Pax6b endocrine cells along the pancreatic tail. (B) Represents a typical result and (C) an extreme example. (D) Tg(T2Kins:mCherry)^jh2; Tg(gcga:GFP)^ia1 larva show a principal islet containing β-cells (red) surrounded by α-cells (green). (E) DAPT treatment causes appearance of numerous α- and a few β-cells (→) along the tail of the pancreas. (F) Larvae of transgenic lines that mark early pan-endocrine cells [Tg(P0-pax6b:eGFP)^ulg515], α-cells [Tg(gcga:GFP) ^ia1] and β-cells [Tg(T2Kins:mCherry)^jh2] were examined at three time points for the number of secondary islets. By treating with 100 μM of DAPT, significantly more secondary islets were observed. Within either the treated or untreated groups, more pax6b expressing islets were observed, and at an early development time, than either other marker. The marker for β-cells was the most infrequently observed.