Figure 2

Loss of GATA4 prevents expansion of the liver primordium. H&E staining of Gata4^+/- (A) and Gata4^-/- (B) livers from E9.5 embryos reveals a smaller presumptive liver bud (outlined) and the absence of septum transversum mesenchyme (white arrowhead) in Gata4^-/- embryos. In situ hybridisation identifies abundant Alb1 transcripts in the liver bud of both Gata4^+/- (C) and Gata4^-/- (D) embryos (black grains, white arrowhead), although the distribution of Alb1 positive cells is limited in the liver bud of Gata4^-/- embryos (D). E-J shows immunohistochemistry to identify expression of developmental protein markers. HNF4α (white arrowhead) was present in the liver bud of both Gata4^-/- (E) and Gata4^-/- (F) embryos. WT-1 expression (white arrowhead) marks the presence of the septum transversum mesenchyme adjacent to the liver bud (black arrow) in Gata4^+/- (G) but was not detected in Gata4^-/- (H) embryos. The liver bud (black arrow) in Gata4^+/- (I) and Gata4^-/- (J) embryos is lined by PECAM-positive endothelial cells (white arrowheads). fg, foregut. All images show transverse sections through embryos at the level of the midgut. Scale bar = 50 μM.