Project description:Downregulation of expression and activity levels of the astroglial glutamate transporter EAAT2 is thought to be implicated in motor neuron excitotoxicity in amyotrophic lateral sclerosis (ALS). We previously reported that EAAT2 is cleaved by caspase-3 at the cytosolic C-terminus domain, impairing the transport activity and generating a proteolytic fragment found to be SUMO1 conjugated (CTE-SUMO1). We show here that this fragment accumulates in the nucleus of spinal cord astrocytes in vivo throughout the disease stages of the SOD1-G93A mouse model of ALS. In vitro expression in spinal cord astrocytes of the C-terminus peptide of EAAT2 (CTE), which was artificially fused to SUMO1 (CTE-SUMO1fus) to mimic the endogenous SUMOylation reaction, recapitulates the nuclear accumulation of the fragment seen in vivo and causes caspase-3 activation and axonal growth impairment in motor neuron-derived NSC-34 cells and primary motor neurons co-cultured with CTE-SUMO1fus-expressing spinal cord astrocytes. This indicates that CTE-SUMO1fus could trigger non-cell autonomous mechanisms of neurodegeneration. Prolonged nuclear accumulation of CTE-SUMO1fus in astrocytes leads to their degeneration, although the time frame of the cell-autonomous toxicity is longer than the one for the indirect toxic effect on motor neurons. As more evidence on the implication of SUMO substrates in neurodegenerative diseases emerges, our observations strongly suggest that the nuclear accumulation in spinal cord astrocytes of a SUMOylated proteolytic fragment of the astroglial glutamate transporter EAAT2 could take part to the pathogenesis of ALS and suggest a novel, unconventional role for EAAT2 in motor neuron degeneration in ALS. Comparison is made between the toxic fragment (SUMO) and the same fragment without lysines that can be sumo-ylated (CTE). Four replicates have been performed for each sample group.
Project description:Downregulation of expression and activity levels of the astroglial glutamate transporter EAAT2 is thought to be implicated in motor neuron excitotoxicity in amyotrophic lateral sclerosis (ALS). We previously reported that EAAT2 is cleaved by caspase-3 at the cytosolic C-terminus domain, impairing the transport activity and generating a proteolytic fragment found to be SUMO1 conjugated (CTE-SUMO1). We show here that this fragment accumulates in the nucleus of spinal cord astrocytes in vivo throughout the disease stages of the SOD1-G93A mouse model of ALS. In vitro expression in spinal cord astrocytes of the C-terminus peptide of EAAT2 (CTE), which was artificially fused to SUMO1 (CTE-SUMO1fus) to mimic the endogenous SUMOylation reaction, recapitulates the nuclear accumulation of the fragment seen in vivo and causes caspase-3 activation and axonal growth impairment in motor neuron-derived NSC-34 cells and primary motor neurons co-cultured with CTE-SUMO1fus-expressing spinal cord astrocytes. This indicates that CTE-SUMO1fus could trigger non-cell autonomous mechanisms of neurodegeneration. Prolonged nuclear accumulation of CTE-SUMO1fus in astrocytes leads to their degeneration, although the time frame of the cell-autonomous toxicity is longer than the one for the indirect toxic effect on motor neurons. As more evidence on the implication of SUMO substrates in neurodegenerative diseases emerges, our observations strongly suggest that the nuclear accumulation in spinal cord astrocytes of a SUMOylated proteolytic fragment of the astroglial glutamate transporter EAAT2 could take part to the pathogenesis of ALS and suggest a novel, unconventional role for EAAT2 in motor neuron degeneration in ALS.
Project description:Mechanisms underlying motor neuron degeneration in amyotrophic lateral sclerosis (ALS) are yet unclear. Specific deletion of the ER-component membralin in astrocytes manifested postnatal motor defects and lethality in mice, causing the accumulation of extracellular glutamate through reducing the glutamate transporter EAAT2. Restoring EAAT2 levels in membralin KO astrocytes limited astrocyte-dependent excitotoxicity in motor neurons. Transcriptomic profiles from mouse astrocytic membralin KO motor cortex indicateed significant perturbation in KEGG pathway components related to ALS, including downregulation of Eaat2 and upregulation of Tnfrsf1a. Changes in gene expression with membralin deletion also overlapped with mouse ALS models and reactive astrocytes. Our results shown that activation of TNF receptor (TNFR1)-NFkB pathway known to suppress Eaat2 transcription was upregulated with membralin deletion. Further, reduced membralin and EAAT2 levels correlated with disease progression in spinal cord from SOD1-mutant mouse models, and reductions in membralin/EAAT2 were observed in human ALS spinal cord. Importantly, overexpression of membralin in SOD1G93A astrocytes decreased TNFR1 levels and increased EAAT2 expression, and improved motor neuron survival. Importantly, upregulation of membralin in SOD1G93A mice significantly prolonged mouse survival. Together, our study provides a mechanism for ALS pathogenesis where membralin limits glutamatergic neurotoxicity, suggesting that modulating membralin has potential in ALS therapy
Project description:Spinal motor axons traverse large distances to innervate target muscle, and thus require local control of cellular events for proper functioning of the distal axon. To interrogate axon-specific processes we developed Axon-seq, a refined method incorporating microfluidic devices and stringent bioinformatic quality controls. Axon-seq demonstrates improved sensitivity and accuracy in whole-transcriptome sequencing of axons compared to previously published studies. Importantly, we show that axon transcriptomes are distinct from those of somas, displaying fewer detected genes and no contaminating astrocytic markers. We identified >5,000 transcripts in stem cell-derived spinal motor axons required for local oxidative energy production and ribosome generation. Axons contained unique transcription factor mRNAs, e.g. Ybx1, with implications for local axonal functions. Cross-comparison with existing mouse motor axon datasets, as well as our own human motor axon data identified a common axon transcriptome. As motor axons degenerate in amyotrophic lateral sclerosis (ALS), we investigated their response to the disease-causing SOD1G93A mutation, identifying 121 ALS-dysregulated transcripts. Several of these are implicated in axonal and dendritic outgrowth, including Nrp1, Dbn1, and Nek1, a known ALS-causing gene. In conclusion, Axon-seq proves a robust and improved method for RNA-seq of axons, furthers our understanding of peripheral axon biology, and identifies novel therapeutic targets to maintain neural connectivity in disease.
Project description:Amyotrophic Lateral Sclerosis (ALS) is a rare neurodegenerative disease characterized by motor neuron dysfunction and loss, leading to progressive paralysis and death. A portion of ALS cases is caused by mutation of the proteasome shuttle factor Ubiquilin 2 (UBQLN2), but the molecular pathway leading from UBQLN2 dysfunction to neurodegenerative disease remains unclear. Here, we demonstrate a major function of UBQLN2 in regulating activity of the domesticated gag-pol retrotransposon ‘paternally expressed gene 10’ (PEG10) in human cells and tissues. UBQLN2 exclusively facilitates degradation of the frameshifted gag-pol form of PEG10 through recognition of a unique polyproline repeat. In cells, the PEG10 gag-pol protein cleaves itself in a mechanism reminiscent of retrotransposon self-processing to generate a liberated ‘nucleocapsid’ fragment, which uniquely localizes to the nucleus. Overexpression of the nucleocapsid fragment upregulates transcription of neuronal genes involved in axon remodeling, which were also affected in sporadic ALS (sALS) patient tissues. Finally, proteomics of spinal cords from ALS patients revealed that PEG10 gag-pol is significantly elevated in disease compared to healthy controls. These findings implicate the retrotransposon-like activity of PEG10 as a contributing mechanism in ALS through regulation of neuronal gene expression, and restraint of PEG10 as a primary function of UBQLN2.
Project description:Background: Amyotrophic lateral sclerosis (ALS) is a devastating disorder of the central nervous system that leads to progressive loss of upper and lower motor neurons. Most cases are sporadic and of unknown aetiology. In this study, we screened 71 patients with sporadic ALS for the presence of DNA copy number variations, in order to identify novel candidate disease genes. Methods: We have used sub-megabase resolution BAC array comparative genomic hybridisation to detect genomic imbalances in our ALS patient cohort. In order to distinguish phenotypically neutral copy number variations occurring frequently in the normal population from disease-associated aberrations, we screened our results against both the Database of Genomic Variants and a reference data set of approximately 700 normal individuals and probands with other disorders analysed in our laboratory. Aberrations with potential relevance for disease aetiology were verified by oligo array CGH. Findings: In 71 patients with sporadic ALS, we identified a total of six duplications and seven deletions that scored above our threshold. Twelve of these thirteen variations were smaller than 1Mb. Seven were observed exclusively in ALS patients and thus likely play causal roles in the disorder. Analysis of these regions highlighted, for example, the SLC1A7 (EAAT5) glutamate transporter and the kinesin family member KIF9 as good positional and functional candidate genes for ALS. Interpretation: Non-polymorphic sub-microscopic duplications and deletions observable by array CGH are frequent in patients with sporadic ALS. Analysis of such aberrations serves as an excellent starting point in deciphering the aetiology of this complex disease. Keywords: array CGH A cohort of 71 ALS patients was analysed by means of a submegabase resolution BAC array. No replicates were included. Experiments were done without dye swap.
Project description:Gene expression changes in spinal motor neurons of the SOD1G93A-transgenic model for ALS after treatment with G-CSF. To gain insight into the mode of action of G-CSF, we performed gene expression profiling on isolated lumbar motor neurons from SOD1G93A mice, the most frequently studied animal model for ALS, with and without G-CSF treatment. A first group of SOD1G93A and WT mice was included in the study at week 11 of age when SOD1G93A mice present no signs of motor dysfunction but subtle signs of denervation detectable by electromyography. The second cohort of mice was treated with G-CSF or vehicle from week 11 to week 15. At the time of study completion, SOD1G93A mice presented clear motor impairment and motor neuron degeneration is documented. This design should provide information on genes altered in motor neurons of SOD1G93A mice from the clinically non-symptomatic to an early symptomatic stage, and give insight into genes influenced by G-CSF treatment. We sampled 300 motoneurons per mouse spinal cord by laser microdissection.
Project description:<p>Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a fatal and devastating neurodegenerative disorder that causes the progressive death of upper and lower motor neurons. Although many efforts have been done to elucidate molecular factors involved in the onset and progression of the disorder, the causes of ALS are yet unknown and undefined. Transcriptome studies, based mostly on microarrays, have revealed multiple perturbations of the motor neuron function, supporting the current idea that several cellular events contribute to the pathobiology of the disease, including mitochondrial dysfunction, enhanced apoptosis, glutamate-mediated excitotoxicity, free radical injury, protein misfolding, abnormal calcium metabolism and altered axonal transport. In the present study, we have deeply sequenced the whole transcriptome of ventral horns of the human lumbar spinal cord from matched control and ALS post-mortem donors. Whole exome sequencing from the same donors has also been performed to exclude known genetic variants associated to the familiar form of ALS. In addition, to characterize the ALS transcriptome we have sequenced the RNA fraction at low molecular weight in the same tissues and individuals. Genomic and transcriptomic reads have been generated using the Illumina HiSeq2000 sequencer.</p>
Project description:Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease marked by motor neuron loss and TDP‑43 proteinopathy, but its upstream causes remain unclear. We identify a distinct signature of oxidized phosphatidylcholines (PC‑OxPL) in the cerebrospinal fluid (CSF) of sporadic ALS (sALS) patients and show that APOE-containing particles are their main carriers. In human iPSC‑derived motor neurons, PC‑OxPL induces disease‑related transcriptional changes and TDP‑43 pathology, establishing it as a driver of ALS‑like neurodegeneration in vitro. To counteract this toxicity, we engineered PC‑OxPL‑VecTab®, an AAV‑delivered single‑chain antibody fragment that targets PC‑OxPL neoepitopes. PC‑OxPL‑VecTab® neutralizes PC‑OxPL–induced neurotoxicity, reduces TDP‑43 aggregation, and prevents motor neuron loss and behavioral deficits in an sALS CSF transfer mouse model. Intrathecal delivery in minipigs achieved broad motor neuron transduction at therapeutic levels, supporting translational potential. These findings position PC‑OxPL as a mechanistic contributor to ALS and establish PC‑OxPL‑VecTab® as a first‑in‑class upstream therapeutic candidate with relevance to other neurodegenerative diseases driven by PC‑OxPL toxicity.