Project description:The assembly of the mammalian brain is orchestrated by temporally coordinated waves of gene expression. Post-transcriptional regulation of gene expression by microRNAs (miRNAs) is a key aspect of this program. Indeed, deletion of neuron-enriched miRNAs induces strong developmental phenotypes, and miRNA levels are altered in patients with neurodevelopmental disorders. However, the mechanisms used by miRNAs to instruct brain development remain largely unexplored. Here, we identified miR-218 as a critical regulator of hippocampal assembly. MiR-218 is highly expressed in the hippocampus and enriched in both excitatory principal neurons (PNs) and GABAergic inhibitory interneurons (INs). Early life inhibition of miR-218 results in an adult brain with a predisposition to seizures. Changes in gene expression in the absence of miR-218 suggest that network assembly is impaired. Indeed, we find that miR-218 inhibition results in the disruption of early depolarizing GABAergic signaling, structural defects in dendritic spines, and altered intrinsic membrane excitability. Conditional knockout of miR-218 in INs, but not PNs, is sufficient to recapitulate long-term instability. Finally, de-repressing Kif21b and Syt13, two miR-218 targets, phenocopies the effects on early synchronous network activity induced by miR-218 inhibition. Taken together, the data suggest that miR-218 orchestrates formative events in PNs and INs to produce stable networks.
Project description:miRNAs are post-transcriptional repressors with wide variation in cellular abundance across cell types and disease states. Yet, the transcriptomic and biological impact of altering miRNA levels (rather than binary gain or loss) has not been systematically investigated. By genetic combination, we generated an allelic series of mice expressing varying levels of miR-218, a motor neuron-specific miRNA associated with amyotrophic lateral sclerosis (ALS). Modulation of miR-218 dose causes threshold-like neuromuscular synaptogenesis and mouse viability phenotypes and revealed heterogenous dose-response curves of target mRNA repression. A dose-response network analyses unmasked a specific regulon exhibiting an inflection point in repression concomitant with the emergence of motor phenotypes. Furthermore, we find that miR-218 indirectly activates a coherent peripheral neuronal genetic signature and that the magnitude of miR-218 mediated effects varies in distinct motor subpopulations. This work reveals miRNA dose as a potent, non-linear modulator of in vivo mRNA target selection, suggesting how cellular dysfunction might abruptly arise when miRNA levels fall below a critical threshold. For the data uploaded here, motor neurons carrying an Hb9:gfp reporter were FACS isolated based upon GFP expression and used for either bulk or single cell RNA sequencing (10x genomics). Motor neurons were either mouse embryonic stem cell derived motor neurons (ESMNs) or mouse motor neurons from developmental stage E12. ESMN samples carry unique mutations of the miR-218-2 promoter of distinct sizes, or are wild type. E12 motor neurons carry combinations of mutations to either miR-218-1 or miR-218-2 or the promoter for miR-218-2. For single cell RNA sequencing, we have WT and miR-218 double knockout (DKO) motor neurons in duplicate. We also sequenced 4 samples of dorsal root ganglia from E12 mice (DRG1-4).
Project description:Motor-neuron specific microRNA-218 (miR-218) was recently put in the spotlight because of its striking roles in mouse development. However, miR-218 relevance to human motor neuron disease was not yet explored. Here, we demonstrate by neuropathology that miR-218 is abundant in healthy human motor neurons. However, in amyotrophic lateral sclerosis (ALS) motor neurons miR-218 is downregulated and its mRNA targets are reciprocally upregulated (de-repressed). We further identify the potassium channel Kv10.1 as a new miR-218 direct target that controls neuronal activity. In addition, we screened thousands of ALS genomes and identified six rare variants in the human miR-218-2 sequence. Intriguingly, miR-218 gene variants fail to regulate neuron activity, suggesting the importance of this small endogenous RNA for neuronal robustness. The underlying mechanisms involve inhibition of miR-218 biogenesis and reduced processing by DICER. Therefore, miR-218 activity uncovers a previously unappreciated facet of motor neuron specificity that may be particularly susceptible to failure in human ALS, contributes to a view of ALS as a disease with a prominent RNA component and suggests that miR-218 is a potential therapeutic target for motor neuron disease.
Project description:Receptor tyrosine kinase pathway signalings plays a central role in the growth and progression of glioblastoma, a highly aggressive group of brain tumors. We recently reported that miR-218 repression, an essentially uniform feature of human GBM, directly promotes RTK hyperactivation by increasing the expression of key positive signaling effectors, including EGFR, PLCr1, PIK3CA and ARAF. However, enhanced RTK signaling is known to activate compensatory inhibitory feedback mechanisms in both normal and cancer cells. We demonstrate here that miR-218 repression in GBM cells also increases the abundance of additional up stream and downstream signaling mediators, including PDGFRa, RSK2, and S6K1, which collectively funciton to alleviate inhibitory RTK feedback regulation. In turn, RTK signaling suppresses miR-218 expression via STAT3, which binds to the miR-218 locus, along with BCLAF1, to repress its expression. These data identify novel interacting feedback loops by which miR-218 repression promotes increased RTK signaling in high-grade gliomas.
Project description:Noncoding RNAs, especially microRNAs (miRNAs) have been implicated in the regulation of neuronal functions, such as learning, cognition and memory formation. However, the particular miRNAs involved in drug-induced behavioral plasticity are largely unknown. Here we report a novel regulator, miR-218, that inhibits heroin-induced behavioral plasticity. Network propagation-based method revealed several miRNAs that play key roles in drug-addiction, among which, miR-218 was decreased in nucleus accumbens (NAc) after chronic exposure to heroin. Lentiviral overexpression of miR-218 in NAc could inhibit heroin-induced reinforcement in both conditioning place preference (CPP) test and heroin self-administration (SA) experiment. Luciferase activity assay indicated miR-218 could regulate neuroplasticity related genes and directly target Mecp2 3’UTR. Consistently, Mecp2-/y mice exhibited reduced heroin seeking behavior in CPP test. These data reveal a functional role of miR-218 and its target, Mecp2, in the regulation of heroin-induced behavioral plasticity.
Project description:Objective: Fibroblast-like synovial cells (FLS) have multilineage differentiation potential including osteoblasts. We aimed to investigate the role of microRNAs during the osteogenic differentiation of rheumatoid arthritis (RA)-FLS. Methods: MicroRNA(miRNA) array analysis was performed to investigate the differentially expressed miRNAs during the osteogenic differentiation. Expression of miR-218-5p (miR-218) during the osteogenic differentiation was determined by quantitative real-time PCR. Transfection with miR-218 precursor and inhibitor were used to confirm the targets of miR-218 and to analyse the ability of miR-218 to induce osteogenic differentiation. Results: The miRNA array revealed that 12 miRNAs were up-regulated and 24 miRNAs were down-regulated after osteogenic differentiation. We observed that miR-218 rose in the early phase of osteogenic differentiation and then decreased. Micro array analysis revealed the mir-218 modulate the expression of ROBO1 in RA-FLS. The induction of miR-218 in RA-FLS decreased ROBO1 expression, and promoted osteogenic differentiation.