title: Negative regulation of retinal-neurite extension by beta-catenin signaling pathway.
abstract: Although there have been many studies on the regulation of neurite extension in mouse brain, such a mechanism in neural retina has remained to be clarified. To delineate the role of Wnt signaling in retinal development, we used a retrovirus-vector-mediated expression system to express various mutants forms of Wnt signaling members in E17.5 mouse retinal explant cultures, which are an excellent system to examine retinal development in vitro. Expression of constitutively active beta-catenin or Lef-1 in the retinal cells resulted in failure of neurite extension, suggesting that beta-catenin negatively regulates neurite extension in the retina through Lef-1 transcriptional activity. However, proliferation and differentiation of retinal cells into mature retinal cells such as rod-photoreceptor cells and Muller glia cells were not affected by perturbation of the Wnt-Lef-1 pathway. As in retinal cells, activation of beta-catenin-Lef-1 signaling inhibited NGF-induced neurite extension in PC12 cells without affecting their proliferation. Interestingly, the Wnt-Lef-1 signaling pathway suppressed neurite extension without affecting Mek-1 signal activity, which is known to promote neurite extension. We found that MAPK was activated in retinal explant cultures, but that perturbation of MAPK signals did not affect neurite extension. Taken together, our data suggest that the Wnt pathway functions in proper neurite extension by opposing positive signals for promotion of neurite extension that are distinct from those of the MAPK pathway.
authors.affiliation: Department of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ouchi
authors.forename: Yoko
authors.initials: Y
authors.lastname: Tabata
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Arai
authors.forename: Sumiko
authors.initials: S
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D015415:Biomarkers; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D002478:Cells, Cultured; D004622:Embryo, Mammalian / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016501:Neurites / Q000378:metabolism*; D016716:PC12 Cells; D051381:Rats; D012160:Retina / Q000166:cytology* / Q000254:growth & development* / Q000502:physiology; D012190:Retroviridae / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D015415:Biomarkers; C497574:Lef1 protein, mouse; D051821:Lymphoid Enhancer-Binding Factor 1; D051153:Wnt Proteins; D051176:beta Catenin; D020928:Mitogen-Activated Protein Kinases