Fig. 5

Endoderm expression of Jagged induces Notch activity and lineage specification. a Schematic of transplant approach to generate endoderm chimeras. At the one-cell stage, wild type Tp1:GFP donor embryos were injected with rhodamine dextran for lineage tracing and sox32 mRNA for conversion to endoderm. At late blastula stage, donor cells were transplanted into Tp1:GFP host embryos that had been injected with antisense MO’s to knockdown Jag1a and Jag1b. (a, bottom panel) Example of endoderm chimeric embryo demonstrating rhodamine dextran labeled donor cells (red) localized primarily to the sox17:GFP⁺ (green) host gut endoderm region. b, c Immunofluorescence analysis of chimeric host pancreas (b) and liver (c) generated by the approach described in a demonstrating a rescue of Notch signaling in Jag1b/Jag2b compromised embryos by endoderm cells with wild type expression of Jag1b/Jag2b. Tp1:GFP⁺ cells (green) are only observed in regions of these organs with wild type donor cells (red) but not in regions without donor cells (yellow asterisks), (d, e) (representative samples, n = 10 embryos. Samples pooled from 2 experiments). Rescued Tp1:GFP⁺ cells found without rhodamine dextran (red, white arrows and arrowhead), are always directly associated with rhodamine dextran + cells. All rescued Tp1:GFP + host cells are Nkx6.1⁺ (blue) in the pancreas (d) and Alcama⁺ (blue) in the liver (e), indicating that they are of the duct lineage. Scale bars 250 μM a, and 25 μM (b–e)