Fig. 3 pitx2 expression in Xenopus is activated in response to Nodal. (A) Animal cap assay showing induction of pitx2 expression in response to Xnr-1 overexpression. Embryos at the four-cell stage were microinjected at the animal pole in each blastomere with 50 pg of Xnr-1 mRNA. Animal caps were removed at stage 7, treated continuously with 10 μg/ml cycloheximide, and analyzed at stage 9 in parallel with untreated control caps for the expression of Xbra, goosecoid, pitx2b, pitx2c, and histone H4. While Xnr-1 induces Xbra and goosecoid expression in absence of protein synthesis, treatment with cycloheximide prevents the strong activation of pitx2c and pitx2b expression.
Reprinted from Developmental Biology, 229(2), Faucourt, M., Houliston, E., Besnardeau, L., Kimelman, D., and Lepage, T., The pitx2 homeobox protein is required early for endoderm formation and nodal signaling, 287-306, Copyright (2001) with permission from Elsevier. Full text @ Dev. Biol.