Extended Data Fig. 1: Expression of hepato-pancreato-biliary markers during early cell fate specification.

a, Images of mouse embryos at the indicated somite stages (ss) taken using a Zeiss Stemi 2000 stereomicroscope. Scale bar, 1mm. b, Representative confocal whole‐mount immunofluorescence (IF) images of embryos stained for Prox1. In addition to the ventral foregut region (VFG), Prox1 is expressed in the developing heart tube (HT) from 6ss onwards. Scale bar, 100μm. c–e, Representative confocal IF images of the VFG in E8.5-E8.75 (8-13ss) embryos. VFG shown as whole‐mount in frontal (c) or lateral (d) views or in transverse cryosections (e). Prox1 (red), Pdx1 (blue), and Sox17 (green) mark hepatic (Prox1⁺) and pancreato-biliary (Prox1⁺/Pdx1⁺/Sox17⁺) progenitors in the VFG (outlined by dotted line). Insets in c, e show higher magnifications of boxed regions in grey scale for Pdx1 channel. Right panels in d show Pdx1 channel in grey scale highlighting the onset of Pdx1 expression at the VFG lip. Hoechst dye was used as nuclear counterstain. Scale bars, 100μm. f, Scatter plot showing the ratio of LV versus PB cell counts (n = 166 embryos). Quantification of cell numbers in LV and PB buds was performed on IF stained cryosections (see Fig. 1b). Data are representative of 3 or more biologically independent experiments with similar results.

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