Fig. 1. Nkx2.5 and Gata-4 are expressed in the splanchnic mesoderm of the pharyngeal floor. (A) Whole-mount (stage 14) chick embryos after in situ hybridization for Nkx2.5. (B) Diagram illustrating the distal cardiac outflow tract as it is seen in A. The broken line indicates the plane of section seen in C,E. (C) Nkx2.5 mRNA can be seen in the caudal wall of the distal cardiac outflow tract (oft) and in the mesenchyme dorsal and caudal to the cardiac outflow tract (pharynx, p). (D,E) In situ hybridization showing expression of GATA-4 in the region where Nkx2.5 is expressed (arrow in D). Scale bars: 100 µm in A,C,E; 50 µm in D.