Fu J, Jiang M, Mirando AJ et al.Reciprocal regulation of Wnt and Gpr177/mouse Wntless is required for embryonic axis formation. Proc Natl Acad Sci USA 106:18598-18603

Department of Biomedical Genetics, Center for Oral Biology, James P Wilmot Cancer Center, University of Rochester Medical Center, 601 Elmwood Avenue, Box 611, Rochester, NY 14642, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 11/2009; 106(44):18598-603. DOI: 10.1073/pnas.0904894106
Source: PubMed


Members of the Wnt family are secreted glycoproteins that trigger cellular signals essential for proper development of organisms. Cellular signaling induced by Wnt proteins is involved in diverse developmental processes and human diseases. Previous studies have generated an enormous wealth of knowledge on the events in signal-receiving cells. However, relatively little is known about the making of Wnt in signal-producing cells. Here, we describe that Gpr177, the mouse orthologue of Drosophila Wls, is expressed during formation of embryonic axes. Embryos with deficient Gpr177 exhibit defects in establishment of the body axis, a phenotype highly reminiscent to the loss of Wnt3. Although many different mammalian Wnt proteins are required for a wide range of developmental processes, the Wnt3 ablation exhibits the earliest developmental abnormality. This suggests that the Gpr177-mediated Wnt production cannot be substituted. As a direct target of Wnt, Gpr177 is activated by beta-catenin and LEF/TCF-dependent transcription. This activation alters the cellular distributions of Gpr177 which binds to Wnt proteins and assists their sorting and secretion in a feedback regulatory mechanism. Our findings demonstrate that the loss of Gpr177 affects Wnt production in the signal-producing cells, leading to alterations of Wnt signaling in the signal-receiving cells. A reciprocal regulation of Wnt and Gpr177 is essential for the patterning of the anterior-posterior axis during mammalian development.

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Available from: Anthony J Mirando, Oct 05, 2015
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    • "When Wls is inactivated, cells are unable to secrete Wnts, and the effects of Wnt signal depletion on homeostasis of a tissue can be evaluated. This genetic approach carries with it a caveat: global elimination of Wls results in embryonic lethality (Fu et al. 2009); therefore, a conditional approach must be used in order for animals to reach the postnatal period. For example, alveolar bone osteoblasts (Fig. 2E, F) express Osteocalcin (Ocn; Fig. 2G and see Takano- Yamamoto et al. 1994; Lim, Liu, Cheng, Hunter, et al. 2014). "
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    ABSTRACT: A new field of dental medicine seeks to exploit nature's solution for repairing damaged tissues, through the process of regeneration. Most adult mammalian tissues have limited regenerative capacities, but in lower vertebrates, the molecular machinery for regeneration is an elemental part of their genetic makeup. Accumulating data suggest that the molecular pathways responsible for the regenerative capacity of teleosts, amphibians, and reptiles have fallen into disuse in mammals but that they can be "jumpstarted" by the selective activation of key molecules. The Wnt family of secreted proteins constitutes one such critical pathway: Wnt proteins rank among the most potent and ubiquitous stem cell self-renewing factors, with tremendous potential for promoting human tissue regeneration. Wnt reporter and lineage-tracing strains of mice have been employed to create molecular maps of Wnt responsiveness in the craniofacial tissues, and these patterns of Wnt signaling colocalize with stem/progenitor populations in the rodent incisor apex, the dental pulp, the alveolar bone, the periodontal ligament, the cementum, and oral mucosa. The importance of Wnt signaling in both the maintenance and healing of these craniofacial tissues is summarized, and the therapeutic potential of Wnt-based strategies to accelerate healing through activation of endogenous stem cells is highlighted. © International & American Associations for Dental Research 2015.
    Journal of dental research 08/2015; DOI:10.1177/0022034515599772 · 4.14 Impact Factor
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    • "Rab8a deletion decreases Gpr177 trafficking to the cell surface in vivo To further explore whether Gpr177 traffic was affected in Wnt producers in vivo, we performed immunogold labeling of Gpr177 in Rab8a +/+ and Rab8a −/− mouse intestines. The specificity of the Gpr177 antibody (Fu et al., 2009) was affirmed by a 90%, 91% and 93% reduction in gold particles in the ER, the non-ER vesicular compartment and the plasma membrane, respectively, of Gpr177-deficient cells (supplementary material Fig. S6) as Fig. 3. Rab8a deletion impairs canonical Wnt signaling in intestines. (A) Quantitative RT-PCR showed reduced Tcf1, Olfm4, Axin2 and Ascl2 expression in Rab8a −/− intestines. "
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    ABSTRACT: Communication between stem and niche supporting cells maintains the homeostasis of adult tissues. Wnt signaling is a crucial regulator of the stem cell niche, but the mechanism that governs Wnt ligand delivery in this compartment has not been fully investigated. We identified that Wnt secretion is partly dependent on Rab8a-mediated anterograde transport of Gpr177 (wntless), a Wnt-specific transmembrane transporter. Gpr177 binds to Rab8a, depletion of which compromises Gpr177 traffic, thereby weakening the secretion of multiple Wnts. Analyses of generic Wnt/β-catenin targets in Rab8a knockout mouse intestinal crypts indicate reduced signaling activities; maturation of Paneth cells - a Wnt-dependent cell type - is severely affected. Rab8a knockout crypts show an expansion of Lgr5(+) and Hopx(+) cells in vivo. However, in vitro, the knockout enteroids exhibit significantly weakened growth that can be partly restored by exogenous Wnts or Gsk3β inhibitors. Immunogold labeling and surface protein isolation identified decreased plasma membrane localization of Gpr177 in Rab8a knockout Paneth cells and fibroblasts. Upon stimulation by exogenous Wnts, Rab8a-deficient cells show ligand-induced Lrp6 phosphorylation and transcriptional reporter activation. Rab8a thus controls Wnt delivery in producing cells and is crucial for Paneth cell maturation. Our data highlight the profound tissue plasticity that occurs in response to stress induced by depletion of a stem cell niche signal. © 2015. Published by The Company of Biologists Ltd.
    Development 05/2015; 128(13). DOI:10.1242/dev.121046 · 6.46 Impact Factor
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    • "At E10.5 and beyond, the expression of Wls in the mesenchyme and distal retinal rim that can be observed in control mice (Fig. 2C,D,G,I,K) is diminished in Le-cre; Wls fl/fl mice (Fig. 2E,F,H,J,L). This suggests that ectodermderived Wnt ligands indirectly regulate the expression of Wls in the adjacent tissues and is consistent with the suggestion that Wls is a Wnt/β-catenin pathway target gene (Fu et al., 2009). "
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    ABSTRACT: The Wnt/β-catenin response pathway is central to many developmental processes. Here, we assessed the role of Wnt signaling in early eye development using the mouse as a model system. We showed that the surface ectoderm region that includes the lens placode expressed 12 out of 19 possible Wnt ligands. When these activities were suppressed by conditional deletion of wntless (Le-cre; Wls(fl/fl)) there were dramatic consequences that included a saucer-shaped optic cup, ventral coloboma, and a deficiency of periocular mesenchyme. This phenotype shared features with that produced when the Wnt/β-catenin pathway co-receptor Lrp6 is mutated or when retinoic acid (RA) signaling in the eye is compromised. Consistent with this, microarray and cell fate marker analysis identified a series of expression changes in genes known to be regulated by RA or by the Wnt/β-catenin pathway. Using pathway reporters, we showed that Wnt ligands from the surface ectoderm directly or indirectly elicit a Wnt/β-catenin response in retinal pigment epithelium (RPE) progenitors near the optic cup rim. In Le-cre; Wls(fl/fl) mice, the numbers of RPE cells are reduced and this can explain, using the principle of the bimetallic strip, the curvature of the optic cup. These data thus establish a novel hypothesis to explain how differential cell numbers in a bilayered epithelium can lead to shape change. © 2015. Published by The Company of Biologists Ltd.
    Development 03/2015; 142(5):972-82. DOI:10.1242/dev.120022 · 6.46 Impact Factor
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