Figure 6

Cubilin inactivation disrupts embryonic visceral endoderm (emVE) dispersal. Whole mount image of immunofluorescence for Sox17 (red) in Afp-GFP VE reporter embryo (green). (A–A”) By E7.25 egressing definitive endoderm (DE) cells robustly express Sox17 (Sox17^high) but lack GFP expression. (a) Cross section showing Sox17^highGFP⁻ DE cells at the surface of the embryo. Arrowheads mark the leading edge of the mesodermal wings. (B–B”) In Cubn^0/0 embryos, transgenic for the Afp-GFP VE reporter the number of Sox17^highGFP⁻ DE cells is greatly diminished. (b1,b2) Cross sections show a quasi absence of egressing DE cells. Whole mount image of immunofluorescence for Foxa2 (red) and Afp-GFP VE reporter embryo (green). (C–C”) By E7.25 Foxa2 is expressed in emVE and DE precursors. (c) Cross section showing intermixed Foxa2 + GFP⁻ and Foxa2 + GFP⁺ cells. Low levels of Foxa2 are also found in the primitive streak (PS) or in cells leaving the PS. (D–D”) In Cubn mutants, the Foxa2 + GFP⁺ cell cohort (emVE) is predominant. (d1,d2) Cross sections confirming the abundance of Foxa2 + GFP⁺ cells at the surface of the embryo. Foxa2-positive cells are observed at the level of the PS. Scale bars: 20 μm.