Transcriptional program of FG and HG progenitors correlates with differential BMP and Wnt signaling. (A) Fate map showing that FG progenitors (yellow) give rise to lungs, liver, pancreas and stomach, whereas HG progenitors (green) give rise to intestine (Chalmers and Slack, 2000). (B) Experimental design. RNA-seq was performed on FG endoderm, FG mesoderm, HG endoderm and HG mesoderm explants dissected from stage NF20 Xenopus embryos. Differentially expressed transcripts were identified by pairwise comparisons of FG (endoderm and mesoderm) versus HG (endoderm and mesoderm), as well as endoderm (FG and HG) versus mesoderm (FG and HG) tissue (log2 FC≤−1 or ≥1, FDR≤5%). (C) Venn diagram showing the intersection of two separate differential expression analyses: FG versus HG and endoderm versus mesoderm, showing mutually exclusive lists of transcripts with enriched expression. (D) Heatmap clustering of the 906 FG-enriched and 987 HG-enriched genes showing expression in the indicated tissues with representative FG (orange) and HG (green) genes listed on the right. (E) In situ hybridization of sagittal bisected stage NF20 embryos with hhex and ventx2.1 marking the FG and HG domains, respectively. (F) BMP and Wnt activity shown by pSmad1 (red) and nuclear (n) β-catenin (red) immunostaining in NF20 embryos. Nuclei staining with DAPI (green). (G) pSmad1 is high in the ventral and low in the dorsal FG and HG, whereas nβ-catenin is low in the FG and high in the HG. FG/fg, foregut; HG/hg, hindgut; endo, endoderm; meso, mesoderm. Scale bars: 100 µm.