Fig. 5. cm-BMP7 mRNA blocks Smad1 phosphorylation but not Smad2 phosphorylation. Wild-type embryos at the 8-cell stage were injected into one ventral blastomere with 600 pg of cm-BMP7, cm-Xnr2 or Xnr2 mRNAs. Embryos were cultured to stage 10 and frozen in groups of 5 for a western blot. Embryos were processed as described by Lee et al. (Lee et al., 2001). The blot was probed for both phosphorylated Smad1 and Smad2 protein. cm-BMP7 mRNA-injected embryos had reduced expression of PSmad1 compared to uninjected controls, while PSmad2 was unaffected (lane 2). In comparison cm-Xnr2 mRNA reduced Smad2 phosphorylation and increased PSmad1 (lane 3), while Xnr2 mRNA increased PSmad2 and reduced PSmad1.