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Endogenous miRNA-200b/c activity and regulation explored by a functional dual fluorescence reporter

ABSTRACT: Since their discovery, microRNAs (miRNA)s have been widely studied in almost every field of biology and medicine, leading to the identification of important gene regulation circuits and cellular mechanisms. However, investigations are generally focused on the analysis of their downstream targets and biological functions in overexpression and knockdown approaches, while miRNAs endogenous levels and activity remain poorly investigated. Here, we used the cellular plasticity-regulating process of epithelial-to-mesenchymal transition (EMT) as a model to show the efficacy of a plasmid-based fluorescent sensor to separate cells with distinct EMT signatures, based on miR-200b/c activity. The system was further combined with a CRISPR-Cas9 screening platform to unbiasedly identify miR-200b/c upstream regulating genes. The sensor allows to infer miRNAs fundamental biological properties, as profiling of sorted cells indicated miR-200b/c as a molecular switch between EMT differentiation and proliferation, and suggested a role for metabolic enzymes in miR-200/EMT regulation. Analysis of miRNAs’ endogenous levels and activity could lead to a better comprehension of their biological role in physiology and disease.

ORGANISM(S): Homo sapiens

PROVIDER: GSE154429 | GEO | 2020/12/01

REPOSITORIES: GEO

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Project description:MiRNA molecules are important post-transcriptional regulators of gene expression in the brain function. Altered miRNA profiles could represent a defensive response against the pathogenesis of neurodegenerative disorders, such as Alzheimer's disease (AD). Endogenous miRNAs have lower toxic effects than other gene silencing methods, thus enhancing the expression of defensive miRNA could be an effective therapy. However, little is known about the potential of targeting miRNAs for the treatment of AD. Here, we examined the function of the miR-200 family (miR-200a, -141, -429, -200b, -200c), identified using miRNA microarray analysis of cortical tissue from Tg2576 transgenic mice. In murine primary neurons, we found that upregulation of miR-200b or -200c was induced by the addition of amyloid beta (Aβ). Neurons transfected with miR-200b or -200c reduced secretion of Aβ in conditioned medium. Moreover, mice infused with miR-200b/c into the brain were relieved of memory impairments induced by intracerebroventricular injection of oligomeric Aβ, and demonstrated proper spatial learning in the Barnes maze. To gain further understanding of the relationship between miR-200b/c and Aβ, we identified target mRNAs via an RNA-binding protein immunoprecipitation-microarray assay. Western blot analysis showed that expression of ribosomal protein S6 kinase B1 (S6K1), a candidate target, was inhibited by miR-200c. S6K1, a downstream effector of mammalian target of rapamycin (mTOR), serves as a negative feedback mediator that phosphorylates insulin receptor substrate 1 at serine residues (IRS-1pSer). S6K1-dependent IRS-1pSer suppresses insulin signaling leading to insulin resistance, which is frequently observed in AD brains. Notably, miR-200b/c transfection of SH-SY5Y cells reduced the levels of IRS-1pSer. This finding indicates that miR-200b/c has the potential to alleviate insulin resistance via modulation of S6K1. Taken together, miR-200b/c may contribute to reduce Aβ secretion and Aβ-induced cognitive impairment by promoting insulin signaling.

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Endogenous miRNA-200b/c activity and regulation explored by a functional dual fluorescence reporter

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