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: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:Gene expression profiling has been performed on motor cortex and spinal cord homogenates and of sporadic ALS cases and controls, to identify genes and pathways differentially expressed in ALS. More recent studies have combined the use of laser capture microdissection (LCM) with gene expression profiling to isolate the motor neurons from the surrounding cells, such as microglia and astrocytes, in order to determine those genes differentially expressed in the vulnerable cell population â i.e. motor neuron. The aim of this study was to determine the gene expression profiles from a small subset of cases which all carry mutations in the CHMP2B gene. These mutations have been found to be associated with the lower motor neuron dominant variant of ALS. Expression profiles from isolated motor neurons in CHMP2B-related ALS cases were compared to those from control motor neurons, in order to establish the pathways implicated in CHMP2B-related motor neuronal cell death.
Project description:Microarray analysis has been applied to the study of ALS in order to investigate gene expression in whole spinal cord homogenates of SOD1 G93A mice and human ALS cases, although the massive presence of glial cells and inflammatory factors has made it difficult to define which gene expression changes were motor neuron specific. Recently, laser capture microdissection (LCM), combined with microarray analysis, has allowed the identification of motor neuron specific changes in gene expression in human ALS cases. The aim of the present study is to combine LCM and microarray analysis to study how motor neurons in the spinal cord of transgenic SOD1 G93A mice and transgenic SOD1 WT respond to stimuli determined by the presence of the human mutant protein throughout the evolution of the stages in motor neuron injury Experiment Overall Design: Motor neurons have been isolated from the spinal cord of G93A mice and non transgenic littermates at different time points and the transcription expression profile of the isolated motor neurons has been analysed
Project description:Gene expression profiling has been performed on motor cortex and spinal cord homogenates and of sporadic ALS cases and controls, to identify genes and pathways differentially expressed in ALS. More recent studies have combined the use of laser capture microdissection (LCM) with gene expression profiling to isolate the motor neurons from the surrounding cells, such as microglia and astrocytes, in order to determine those genes differentially expressed in the vulnerable cell population – i.e. motor neuron.
Project description:Recent genetic studies of ALS patients have identified several forms of ALS that are associated with mutations in RNA binding proteins. In animals or cultured cells, such defects broadly affect RNA metabolism. This raises the question of whether all forms of ALS have general effects on RNA metabolism. We tested this hypothesis in a mouse model of ALS that is transgenic for a human disease-causing mutation in the enzyme superoxide dismutase 1 (SOD1). We analyzed RNA from laser-captured spinal cord motor neuron cell bodies of the mutant SOD1 strain, comparing the RNA profile with that from a corresponding wild-type SOD1 transgenic strain. We prepared the samples from animals that were presymptomatic, but which manifested abnormalities at the cellular level that are seen in ALS, including aggregation of the mutant protein in motor neuron cell bodies and defective morphology of neuromuscular junctions, the connections between neuron and muscle. We observed only minor changes in the level and splicing of RNA in the SOD1 mutant animals as compared with wild-type, suggesting that mutant SOD1 produces the toxic effects of ALS by a mechanism that does not involve global RNA disturbance. RNA-Seq of laser microdissection of motor neuron bodies from two biological replicates each of SOD1 YFP (wildtype 592) and SOD1 G85R YFP (737) transgenic mice.
Project description:Microarray analysis has been applied to the study of ALS in order to investigate gene expression in whole spinal cord homogenates of SOD1 G93A mice and human ALS cases, although the massive presence of glial cells and inflammatory factors has made it difficult to define which gene expression changes were motor neuron specific. Recently, laser capture microdissection (LCM), combined with microarray analysis, has allowed the identification of motor neuron specific changes in gene expression in human ALS cases. The aim of the present study is to combine LCM and microarray analysis to study how motor neurons in the spinal cord of transgenic SOD1 G93A mice and transgenic SOD1 WT respond to stimuli determined by the presence of the human mutant protein throughout the evolution of the stages in motor neuron injury Keywords: Murine motor neurons
Project description:To investigate the role of motor neuron autophagy in ALS, we generated mice in which the critical autophagy gene Atg7 was specifically disrupted in motor neurons (Atg7 cKO). We also bred these mice to the SOD1G93A mouse model of ALS. Then we performed RNA sequencing on lumbar spinal cords from these mice to determine how motor neuron autophagy inhibition altered gene expression.
Project description:Amyotrophic Lateral Sclerosis (ALS) results from the selective and progressive degeneration of motor neurons. Although the underlying disease mechanisms remain unknown, glial cells have been implicated in ALS disease progression. Here we examine the effects of glial cell/motor neuron interactions on gene expression, using the hSOD1G93A mouse model of ALS. We detect striking cell autonomous and non-autonomous changes in gene expression in co-cultured motor neurons and glia, revealing that the two cell types profoundly affect each other. In addition, we found a remarkable concordance between the cell culture data, expression profiles of whole spinal cords, and of acutely isolated spinal cord cells, during disease progression in the G93A mouse model, providing validation of the cell culture approach. Bioinformatics analyses identified changes in the expression of specific genes and signaling pathways that may contribute to motor neuron degeneration in ALS, among which are TGF-b signaling pathways. RNA-seq profiles of: 1) 43 Sandwich culture samples at 3 different time points (3, 7 and 14 days), in duplicate, in different combinations of genetic background WT/SOD1_G93A mutant glia and WT/SOD1_G93A mutant neurons; 2) 16 spinal cord samples at 4 different time points, WT and SOD1_G93A mutant.
Project description:Despite the discovery of many genetic risk factors, the cause of the motor neuron death that drives terminal pathology in Amyotrophic Lateral Sclerosis (ALS) remains unknown. We report that the skeletal muscle of ALS patients secretes exosomal vesicles that are specifically toxic to motor neurons. This could not be attributed to a trivial down-stream consequence of muscle denervation. In a study of muscle biopsies and biopsy-derived denervation-naïve differentiated muscle stem cells (myotubes) from 67 human subjects, including healthy and disease controls, ALS myotubes had a consistent signature of disrupted exosome biogenesis and RNA-processing, and their exosomes induced shortened, less branched, neurites, greater death, and disrupted localization of RNA and RNA-processing proteins in motor neurons. Toxicity was dependent on presence of the FUS protein, which is highly expressed in recipient motor neurons. As part of this work, we carried out gene expression analysis of myotubes (differentiated myoblasts) comparing ALS against two other motor neuron disorders as disease controls (SBMA, Spinal and bulbar muscular atrophy; and Spinal Muscular Atrophy Type 4, SMA-IV) and healthy controls.