Fig. 1. Neural induction in Xenopus ventral ectoderm by ectopic expression of inhibitors of TGFß signals. RNAs encoding transmembrane (1 ng tBMPRIA and tActRIIB), cytoplasmic (0.1 ng Smad6 and Smad7) or nuclear (0.1 ng VP16-Msx1 and Ski) inhibitors of TGFß signaling were co-injected with nßGal (0.1 ng RNA) into one ventral animal blastomere of 32- to 64-cell stage embryos. The embryos were analyzed by Red-Gal staining (red speckled stain) and in situ hybridization of the neural (Sox2 and Sox3), neural crest (Slug) and epidermal (XK70) markers at neurula stages. Inhibitors of both Smad1 and Smad2 signaling (tActRIIB, Smad7 and Ski) induced neural markers efficiently. Among the specific inhibitors of Smad1 signaling, tBMPRIA induced Sox2 and Sox3 weakly, whereas Smad6 and VP16-Msx1 were ineffective in inducing neural markers.