Fig. 2.

Fig. 2. Lineage tracing showed limited Notch-responsive duct–to–endocrine cells conversion at the principal islet.

(A and B) Tg(tp1:CreERT2) was crossed to two different color-switch lines under the control of ubiquitin B promoter. H2BmCherry/mCherry expression was specifically induced in tp1⁺ Notch-responsive ducts and their progenies with 20 μM 4-OHT administered from 3 to 4 dpf, as visualized with Z-projections 6 dpf. Yellow, white, and cyan dashed lines indicate the pancreata, Notch-responsive intrapancreatic ducts, and non–Notch-responsive duct anterior to the principal islet, respectively. Scale bars, 100 μm. (C and D) Schematics and confocal Z-projections of tp1 lineage–traced cells under β cell ablation condition. Tentative overlap in the Z-projection (the mCherry⁺ cell indicated by orange arrow) was confirmed to not coexpress Sst1.1 and insulin (Ins) in single planes. Scale bars, 40 μm. The yellow and blue dashed lines indicate the principal islet and extra- and intermediate pancreatic duct, respectively. (E and F) Long-term lineage tracing in tp1:CreERT2;ubi:Switch with 4-OHT treatment 3 to 4 dpf. Confocal Z-projections of pancreatic head (E) and tail (F) 23 dpf. Yellow dashed lines indicate the principal islet. Scale bars, 40 μm. (G and H) cftr:Gal4;UAS:EGFP;tp1:H2BmCherry indicate cftr⁺ cells 6 dpf (G) and 22 dpf (H). The ductal cells are highlighted using cyan dashed lines. Scale bars, 40 μm. (I and J) cftr:Gal4;UAS:EGFP;UAS:Cre;ubi:Switch indicate cftr⁺ lineage traced cells 14 dpf (I) and 20 dpf (J). Yellow dashed lines in (I) indicate the pancreatic head (magnifications in right panels). The yellow arrow points to lineage-traced endocrine cells. Yellow arrows in (J) indicate lineage-traced Gcg⁺ cells in head and tail regions. Scale bars, 40 μm.