Fig. 8. RA inhibition, cardiac fate maps and Amhc1 expression. (A) RA inhibition by BMS493 10^–4 M changed the HH7 fate map. Anterior precursors (ventricular, conotruncal and vitelline artery) are found at posterior regions of the cardiac field which otherwise contained only sino-atrial (posterior) precursors in the absence of BMS493 (compare with B). (B) Normal HH7 fate map (same data as Fig. 7G). (C) HH7. Bright field/fluorescent overlay of a BMS493-treated embryo injected at a posterior site in the cardiac field, which is normally devoid of ventricular precursors. (D) HH11⁺. Bright field/fluorescent overlay of the embryo in C. DiI is located in the ventricle. (E) Scheme of unilateral, topic, BMS493 treatment at HH6. Three agar cylinders containing BMS493 at 10^–4 M (blue circles) were placed on the endoderm overlying the left lateral mesoderm between Hensen's node and headfold. (F) HH10. AMHC1 in situ hybridization of a BMS493-treated embryo. White arrowhead indicates unilateral inhibition of Amhc1 expression in the left lateral mesoderm.