Smith W C, Harland R M
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Cell. 1991 Nov 15;67(4):753-65. doi: 10.1016/0092-8674(91)90070-f.
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.
从原肠胚cDNA文库中进行表达克隆，鉴定出Wnt家族成员Xwnt-8在非洲爪蟾胚胎中具有诱导背轴形成的活性。显微注射Xwnt-8 mRNA能够挽救因紫外线照射而腹化的胚胎中背侧完整的前后轴发育。在32细胞期将其注射到边缘或植物极卵裂球中时，胚胎中均观察到轴诱导现象。接受Xwnt-8 mRNA的植物极卵裂球产生的后代并非参与诱导的背轴形成，而是形成内胚层，这一结果与Xwnt-8使细胞充当Nieuwkoop中心（正常背轴形成的植物极诱导成分）而非斯佩曼组织者（直接形成背侧中胚层的诱导背侧边缘区成分）相一致。正常情况下在原肠胚中期和神经胚胚胎腹侧表达的Xwnt-8，注射后似乎模拟了在发育早期起作用的母体编码的背侧中胚层诱导因子。
