![]() ![]() ![]() The early expression of cVg1 includes a phase broadly related to the known time and site of axis (primitive streak) initiation the initial transcription of cVg1 is centred in the posterior marginal zone (PMZ), a region of the blastoderm known to contain the axial organizing activity at this stage. Results We have characterized an amniote (chick) orthologue of Vg1, cVg1, and examined its developmental expression. This restriction may be involved in the spatial localization of activity required for an organizing role. Site-specific proteolytic processing occurs ubiquitously for most TGF β members, producing the active peptide ligand, but is tightly restricted, by unknown mechanisms, for endogenous Vg protein in Xenopus and zebrafish embryos. In Xenopus, the Vg1 gene is a candidate for the initiator of axis formation: its RNA and protein are broadly but appropriately localized at the start of development, and processed Vg1 protein is a powerful inducer of organized axial tissue in blastular animal caps in vitro and when locally produced in vivo after injection of Vg1 mRNA into blastomeres. Background Genes of the transforming growth factor β (TGF β) superfamily have been implicated in the earliest steps of developmental patterning in vertebrates. ![]()
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