Fig. 7. The lack of contribution of Sox17–/– ES cells in the gut endoderm in the chimera. ROSA26-derived cells are positive for X-gal staining (blue staining), while the ES clone (Sox17–/–)-derived cells are negative. (A,E) Whole mount view of chimaeric embryos with the high contribution of Sox17–/– ES cells and non-chimaeric littermates (right) at 8.25 (A) and 9.5 (E) dpc. (E) Three chimeras with various degrees of mutant ES cell contribution: one chimera with high mutant ES cell contribution displays no axis rotation (upper left), while two other chimeras containing moderately high mutant ES cell contribution are slightly retarded in posterior trunk development [one shows delayed axis rotation (lower left)]. The broken arrows show the plane of the sectioning image in the designated plate. In E, red arrowheads show the posterior gut endoderm, which was composed mostly of the ROSA26 (Sox17+/+) host-derived cells. (B-D,F-K) Transverse sections of chimaeric embryos at 8.25 (B-D) and 9.5 (F-K) dpc. Sox17–/– ES cells were excluded from the posterior or mid- and hindgut endoderm, which is mainly composed of ROSA26 host-derived cells (B-D,F,G,J,K). Sox17–/– mutant cells can contribute to the anterior or foregut endoderm (open arrows in B,C,H,I). The chimeras with the high mutant ES cell contribution display a reduction in cell population of the posterior definitive endoderm (B,C) or embryonic gut (F). Arrowheads show the border between visceral endoderm and definitive endoderm. The broken rectangle encompasses the area magnified in the designated plate. fg, foregut; hg, hindgut; mg, midgut; ve, visceral endoderm. Scale bars: 100 µm.
