Injected Xwnt-8 RNA acts early in Xenopus embryos to promote formation of a vegetal dorsalizing center.
Expression cloning from a pool of gastrula cDNAs identified the Wnt family member Xwnt-8 as having dorsal axis-inducing activity in Xenopus embryos. Microinjected Xwnt-8 mRNA was able to rescue the development of a dorsally complete anterior-posterior axis in embryos ventralized by exposure to UV light. Axis induction was observed in embryos injected in either marginal or vegetal blastomeres at the 32-cell stage. Vegetal blastomeres receiving Xwnt-8 mRNA contributed progeny not to the induced dorsal axis, but to the endoderm, a result consistent with Xwnt-8 causing cells to act as a Nieuwkoop center (the vegetal-inducing component of normal dorsal axis formation), rather than as a Spemann organizer (the induced dorsal marginal zone component that directly forms the dorsal mesoderm). Xwnt-8, which is normally expressed ventrally in midgastrula and neurula embryos, appears to mimic, when injected, maternally encoded dorsal mesoderm-inducing factors that act early in development.
Smith
W C
WC
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Harland
R M
RM
D000818:Animals; D015152:Blotting, Northern; D002712:Chlorides / Q000494:pharmacology; D004627:Embryonic Induction / Q000187:drug effects / Q000528:radiation effects; D015870:Gene Expression; D008094:Lithium / Q000494:pharmacology; D018021:Lithium Chloride; D008845:Microinjections; D009024:Morphogenesis / Q000187:drug effects / Q000528:radiation effects; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000235:genetics*; D014466:Ultraviolet Rays; D014982:Xenopus laevis / Q000196:embryology*
D002712:Chlorides; D012333:RNA, Messenger; D008094:Lithium; D018021:Lithium Chloride