Fig. 9

Insulin signaling blockade in ECB donor cells promotes Insulin expression and host β cell regeneration. (A-D′) Merged and single channel confocal projections of transplanted Tg(sox17:GFP) donor ECBs in β cell-ablated host larvae stained for GFP (green), Insulin (red) and Glucagon (white) at 2 days post transplantation (dpt). (B-B′, D-D′) Higher magnification of boxed region in panels A-A′ and C-C′, respectively. In (A-B′) donor cells were injected with sox32 mRNA only; in (C-D′) donor ECBs had been zygotically-injected with sox32 and dnIRS2 mRNAs. Cells derived from the ECB transplant are bounded by a dotted yellow line and the principal islet (pi) of the host is indicated by a red arrow. (E) Quantification of Insulin+ β cells in donor ECBs that were transplanted into β cell ablated hosts; dnIRS2 (n=11), +dnIRS2 (n=10). Blockade of insulin signaling with dnIRS2 increased the production of insulin-positive β cells. (F) Quantification of host-derived regenerated β cells in the principal islet (pi) after transplantation with no cells (sham control, n=12), donor ECBs injected with sox32 mRNA alone (n=11), or ECBs injected with sox32 plus dnIRS2 mRNAs (n=11). (G) Model for the role of insulin signaling in regulating β cell differentiation and reciprocal interactions between transplanted endoderm-committed blastomeres and the host environment. Student′s t-test was used in E and one-way ANOVA was used in F to determine significance. Abbreviation: pi, host larvae principal islet at 2 days post β cell ablation.