Fig. 3. Rescue of endodermal markers in MZoep by Cripto protein injection at different times. (A) Experimental procedure. Synchronized MZoep embryos were injected with Cripto protein together with rhodamine dextran as a tracer at appropriate stages (from high to 40% epiboly). Subsequently, embryos exhibiting homogeneous rhodamine fluorescence were sorted, fixed and analysed by in situ hybridization (B-S). (B-N) Lateral (C-E,G-I,N) or dorsal views. At 80% epiboly, four different classes of expression pattern of cas (B-E), sox17 (F-I) and foxa2 (J-N) can be identified in Cripto-injected MZoep embryos. When Cripto was injected at 40% epiboly, most embryos do not express foxa2 in endodermal cells but still express it in axial mesoderm (M). (O-S) Staining of fkd7 in Cripto-injected MZoep embryos at 30 hpf. Anterior to the left. Four classes were also defined. (O) Class I exhibits almost normal expression of fkd7 in the pharynx (white arrow) and in the gut (black arrow). (P) Class II exhibits incomplete expression of fkd7, often lacking the pharyngeal endoderm (white arrow) but have an almost normal expression in the gut (black arrow). Class III has only a few fkd7 positive cells (Q, arrow). Class IV shows no endodermal fkd7 staining (R,S).
