Molecular analysis of cell differentiation and morphogenesis by mesoderm inducing factor

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There are several lines of evidence that activin is a crucial molecules for mesoderm induction in early Xenopus and newt embryos. Three isoforms of activins A,B and B,were demonstrated to be present at least in part as a complex with abundant follistatin in early Xenopus embryos (stage 1-5). Animal-half blastomeres from the late 8-cell stage Xenopus embryo respond to activin, and there are prepatterns in ventral and dorsal cells from very early stages. Histological differentiation of the pronephric tubules on the presumptive ectoderm were induced by the mixture of activin A and retinoic acid. The induced pronephric tubules showed exactly the same expression stage and pattem for both marker genes, Xlim 1 and Xlcaax-1, as compares to that of normal embryos. Activin and follistatin protein were found to be localized uniformly in yolk platelets. Some kind of genes, sonic hedgehog, HMG and GS genes, are cloned related with neural formation.