To determine whether SOX7 induced markers of cardiogenesis, fertilized eggs were injected with RNA encoding SOX7-GFP (0.5ng/embryo); animal caps were prepared at stage 8 and analyzed by in situ hybridization when control embryo had reached stage 30. Both Nkx2.5 (A) or MHCα (B) were expressed in discrete domains, one per animal cap; no expression of either gene was observed in cap derived from uninjected embryos (data not shown). C: A similar analysis was carried using RT-PCR. Fertilized eggs were injected with RNA (0.5 ng/embryo) encoding either SOX7-GFP (SOX7), mtSOX7ΔC-VP16 (7ΔCVP16), SOX18β-GFP (SOX18), mtSOX18ΔC-VP16 (18ΔCVP16), or mtSOX17β-GFP (SOX17). Animal caps were prepared and analyzed when controls reached stage 25. Each of the injected RNAs induced the expression of the endodermal marker Edd, but only SOX7 or SOX18 constructs induced markers of cardiogenesis, Nkx2.5, MHCα Tbx5 and TnIc. D: In a similar study, SOX7-GFP and SOX18β-GFP induced expression of the mesodermal markers Snail and Eomesodermin (Eomes). E: The SOX7-GFP and SOX18β-GFP induction of Eomes, Hex and Nkx2.5 expression was blocked by the coinjection of RNA encoding the nodal inhibitor CerS (0.2 ng/embryo).