Fig. 6

Enhanced recovery of beta cell mass in dnmt1 mutants and morphants. (A) Pancreatic beta cell ablation scheme in dnmt1^s872 mutants. 96 hpf Tg(ins:CFP-NTR)^s892 WT and dnmt1 mutant larvae were exposed to MTZ for 24 h , then washed for 48 h  and analyzed at 168 hpf. (B–E) Three-dimensional projections of the primary islet at 168 dpf in WT (B, D) and dnmt1 mutant (C, E) larvae that were untreated (B, C), or ablated with MTZ (D, E). (B, C) WT and dnmt1 mutant islets have a core of Ins+ beta cells surrounded by a mantle of Gcg+ alpha cells. (D) In recovering WT larvae, new beta cells are observed in the islet (arrow). (E) In recovering dnmt1 mutant islets, nearly double the number of beta cells is present, though some appear morphologically abnormal (arrows; compare with panel D). (F) 7.6 ± 1.0 beta cells were observed in recovering WT islets (n = 7), and 14.6 ± 2.0 beta cells were observed in recovering dnmt1 mutant larvae (n = 9; p = 0.014). (G) Pancreatic beta cell ablation scheme in Tg(ins:CFP-NTR)^s892 embryos injected with 2 ng of dnmt1 morpholino (dnmt1-MO). 84 hpf larvae were exposed to MTZ for 24 h , then washed for 24 h  and analysed at 132 hpf. (H–K) Three-dimensional projections of the primary islet at 132 hpf in WT (H, J) and dnmt1-MO injected (I, K) larvae that were untreated (H, I), or ablated with MTZ (J, K). (K) dnmt1-MO injected larvae showed a greater degree of beta cell recovery. (L) 6.5 ± 0.5 beta cells were observed in recovering WT larvae (n = 15), and 9.5 ± 0.6 beta cells were observed in recovering dnmt1-MO injected larvae (n = 22; p = 0.002). Error bars = SEM. Significance assessed by Student′s t-test.