title: Cell-autonomous signal transduction in the Xenopus egg Wnt/β-catenin pathway.
abstract: Wnt proteins are thought to bind to their receptors on the cell surfaces of neighboring cells. Wnt8 likely substitutes for the dorsal determinants in Xenopus embryos to dorsalize early embryos via the Wnt/β-catenin pathway. Here, we show that Wnt8 can dorsalize Xenopus embryos working cell autonomously. Wnt8 mRNA was injected into a cleavage-stage blastomere, and the subcellular distribution of Wnt8 protein was analyzed. Wnt8 protein was predominantly found in the endoplasmic reticulum (ER) and resided at the periphery of the cells; however, this protein was restricted to the mRNA-injected cellular region as shown by lineage tracing. A mutant Wnt8 that contained an ER retention signal (Wnt8-KDEL) could dorsalize Xenopus embryos. Finally, Wnt8-induced dorsalization occurred only in cells injected with Wnt8 mRNA. These experiments suggest that the Wnt8 protein acts within the cell, likely in the ER or on the cell surface in an autocrine manner for dorsalization.
authors.affiliation: Department of Chemistry and Bioscience, Faculty of Science, Kagoshima University, Kagoshima, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Motomura
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Narita
authors.forename: Yuya
authors.initials: Y
authors.lastname: Nasu
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Kato
authors.forename: Ayako
authors.initials: A
authors.lastname: Sedohara
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Nishimatsu
authors.forename: Masao
authors.initials: M
authors.lastname: Sakai
mesh_terms: D000818:Animals; D019898:Autocrine Communication / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000378:metabolism*; D021382:Protein Sorting Signals / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051153:Wnt Proteins / Q000096:biosynthesis / Q000235:genetics; D060449:Wnt Signaling Pathway / Q000502:physiology*; D029867:Xenopus Proteins / Q000096:biosynthesis / Q000235:genetics; D014982:Xenopus laevis; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D021382:Protein Sorting Signals; D012333:RNA, Messenger; D051153:Wnt Proteins; D029867:Xenopus Proteins; D051176:beta Catenin; C495248:wnt8a protein, Xenopus
keywords: KDEL; Wnt; Xenopus; endoplasmic reticulum; immunohistochemistry