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MiR-29b controls fetal mouse neurogenesis by regulating ICAT-mediated Wnt/β-catenin signaling.

ABSTRACT: 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.

SUBMITTER: Shin J

PROVIDER: S-EPMC4237260 | biostudies-other | 2014

REPOSITORIES: biostudies-other

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Project description:BackgroundAcute myeloid leukemia (AML) is initiated and maintained by a unique, small subset of leukemia stem cells (LSCs). LSCs are characterized by unrestricted self-renewal and contribute to the malignancy of leukemia. Aberrant protein fucosylation is associated with AML progression. However, it is still less understood that the miR-29b/Sp1/FUT4 crosstalk involved in the fucosylation-mediated LSCs malignancy in AML.MethodsAML cell lines were sorted by magnetic microbeads to obtain the CD34?+?CD38- sub-population. The key biomarkers for LSCs were identified by flow cytometry. Fucosyltransferase genes were screened by qRT-PCR, and FUT4 was focused. Effect of FUT4 on LSCs malignancy was determined by CCK8 assay, sphere formation assay, immunofluorescence staining, apoptosis and in vivo xenografts experiments. The linkage of FUT4 promoter and Sp1 was confirmed by dual-luciferase reporter gene assay. ChIP-PCR assay was used to show the directly binding of Sp1 and FUT4 promoter. Activity of Wnt//?-catenin pathway was determined by western blot. Overall survival curves were diagrammed by Kaplan-Meier analysis.ResultsHere, the expressional profiles of 11 fucosyltransferase genes were different comparing LSCs and non-LSCs of KG-1a and MOLM13 cells, whereas CD34?+?CD38- cells exhibited higher expression of FUT4. Functionally, alteration of FUT4 in CD34?+?CD38- cells modulated LSCs malignant behaviors both in vitro and in vivo. Transcriptional inhibitor actinomycin D (Act D) or translational inhibitor cycloheximide (CHX) prevented LSCs progression, and Sp1 was identified as the efficient regulator of FUT4 transcription. Moreover, miR-29b directly affected the binding of Sp1 and FUT4 promoter region, which further mediated LSCs proliferation, apoptosis and drug-resistance through fucosylated-CD44 via activation of Wnt/?-catenin pathway. Clinically, Sp1 and FUT4 were up-regulated and positively correlated with poor overall survival of AML patients.ConclusionThese data indicated that miR-29b/Sp1/FUT4 axis promoted the malignant behaviors of LSCs by regulating fucosylated CD44 via Wnt/?-catenin pathway. Identifying LSCs surface markers and targeting LSCs were important for the development of potential therapies in AML.

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MiR-29b controls fetal mouse neurogenesis by regulating ICAT-mediated Wnt/β-catenin signaling.

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