β-Catenin has been widely implicated in the regulation of mammalian development and cellular homeostasis. However, the mechanisms by which Wnt/β-catenin signaling components regulate physiological events during brain development remain undetermined. Inactivation of glycogen synthase kinase (GSK)-3β leads to β-catenin accumulation in the nucleus, where it couples with T-cell factor (TCF), an association that is disrupted by ICAT (inhibitor of β-catenin and T cell factor). In this study, we sought to determine whether regulation of ICAT by members of the microRNA-29 family plays a role during neurogenesis and whether deregulation of ICAT results in defective neurogenesis due to impaired β-catenin-mediated signaling. We found that miR-29b, but not miR-29a or 29c, is significantly upregulated in three-dimensionally cultured neural stem cells (NSCs), whereas ICAT is reduced as aged. Treatment with a miR-29b reduced the reporter activity of a luciferase-ICAT 3'-UTR construct whereas a control (scrambled) miRNA oligonucleotide did not, indicating that miR-29b directly targets the 3'-UTR of ICAT. We also found that treatment with miR-29b diminished NSC self-renewal and proliferation, and controlled their fate, directing their differentiation along certain cell lineages. Furthermore, our in vivo results showed that inhibition of miR-29b by in utero electroporation induced a profound defect in corticogenesis during mouse development. Taken together, our results demonstrate that miR-29b plays a pivotal role in fetal mouse neurogenesis by regulating ICAT-mediated Wnt/β-catenin signaling.
Bibliographical noteFunding Information:
Acknowledgements. We thank Drs. Jon Weiner, Stefan Arold, and Debra Meyer for helpful discussions, and H Aguilar and S Han for technical assistance. This work was financially supported by grants from Korea Healthcare Technology R&D Project (HI11C1186) by Ministry for Health, Welfare and Family Affairs, South Korea (to H-SK) and in part by Seoul National University Bundang Hospital Research Fund (03-2012-016). In addition, this work was financially supported by NRF 2013R1A2A2A03016122 (to SC and YS) and Korea Ministry of Environment GT-11-G-02-001-1 (to SC and YS).
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ASJC Scopus subject areas
- Cellular and Molecular Neuroscience
- Cell Biology
- Cancer Research