Effect of transgene copy number on survival in the G93A SOD1 transgenic mouse model of ALS

Novel insights into RAGE signaling pathways during the progression of amyotrophic lateral sclerosis in RAGE-deficient SOD1 G93A mice

Amyotrophic lateral sclerosis (ALS) is neurodegenerative disease characterized by a progressive loss of motor neurons resulting in paralysis and muscle atrophy. One of the most prospective hypothesis on the ALS pathogenesis suggests that excessive inflammation and advanced glycation end-products (AGEs) accumulation play a crucial role in the development of ALS in patients and SOD1 G93A mice. Hence, we may speculate that RAGE, receptor for advanced glycation end-products and its proinflammatory ligands such as: HMGB1, S100B and CML contribute to ALS pathogenesis. The aim of our studies was to decipher the role of RAGE as well as provide insight into RAGE signaling pathways during the progression of ALS in SOD1 G93A and RAGE-deficient SOD1 G93A mice. In our study, we observed alternations in molecular pattern of proinflammatory RAGE ligands during progression of disease in RAGE KO SOD1 G93A mice compared to SOD1 G93A mice. Moreover, we observed that the amount of beta actin (ACTB) as well as Glial fibrillary acidic protein (GFAP) was elevated in SOD1 G93A mice when compared to mice with deletion of RAGE. These data contributes to our understanding of implications of RAGE and its ligands in pathogenesis of ALS and highlight potential targeted therapeutic interventions at the early stage of this devastating disease. Moreover, inhibition of the molecular cross-talk between RAGE and its proinflammatory ligands may abolish neuroinflammation, gliosis and motor neuron damage in SOD1 G93A mice. Hence, we hypothesize that attenuated interaction of RAGE with its proinflammatory ligands may improve well-being and health status during ALS in SOD1 G93A mice. Therefore, we emphasize that the inhibition of RAGE signaling pathway may be a therapeutic target for neurodegenerative diseases.

Insights on the Multifaceted Roles of Wild-Type and Mutated Superoxide Dismutase 1 in Amyotrophic Lateral Sclerosis Pathogenesis

Amyotrophic Lateral Sclerosis (ALS) is a progressive motor neurodegenerative disease. Cell damage in ALS is the result of many different, largely unknown, pathogenetic mechanisms. Astrocytes and microglial cells play a critical role also for their ability to enhance a deranged inflammatory response. Excitotoxicity, due to excessive glutamate levels and increased intracellular Ca2+ concentration, has also been proposed to play a key role in ALS pathogenesis/progression. Reactive Oxygen Species (ROS) behave as key second messengers for multiple receptor/ligand interactions. ROS-dependent regulatory networks are usually mediated by peroxides. Superoxide Dismutase 1 (SOD1) physiologically mediates intracellular peroxide generation. About 10% of ALS subjects show a familial disease associated with different gain-of-function SOD1 mutations. The occurrence of sporadic ALS, not clearly associated with SOD1 defects, has been also described. SOD1-dependent pathways have been involved in neuron functional network as well as in immune-response regulation. Both, neuron depolarization and antigen-dependent T-cell activation mediate SOD1 exocytosis, inducing increased interaction of the enzyme with a complex molecular network involved in the regulation of neuron functional activity and immune response. Here, alteration of SOD1-dependent pathways mediating increased intracellular Ca2+ levels, altered mitochondria functions and defective inflammatory process regulation have been proposed to be relevant for ALS pathogenesis/progression.

Up-regulation of cholesterol synthesis pathways and limited neurodegeneration in a knock-in Sod1 mutant mouse model of ALS

Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disorder affecting brain and spinal cord motor neurons. Mutations in the copper/zinc superoxide dismutase gene ( SOD1 ) are associated with ∼20% of inherited and 1-2% of sporadic ALS cases. Much has been learned from mice expressing transgenic copies of mutant SOD1, which typically involve high-level transgene expression, thereby differing from ALS patients expressing one mutant gene copy. To generate a model that more closely represents patient gene expression, we created a knock-in point mutation (G85R, a human ALS-causing mutation) in the endogenous mouse Sod1 gene, leading to mutant SOD1 G85R protein expression. Heterozygous Sod1 G85R mutant mice resemble wild type, whereas homozygous mutants have reduced body weight and lifespan, a mild neurodegenerative phenotype, and express very low mutant SOD1 protein levels with no detectable SOD1 activity. Homozygous mutants exhibit partial neuromuscular junction denervation at 3-4 months of age. Spinal cord motor neuron transcriptome analyses of homozygous Sod1 G85R mice revealed up-regulation of cholesterol synthesis pathway genes compared to wild type. Transcriptome and phenotypic features of these mice are similar to Sod1 knock-out mice, suggesting the Sod1 G85R phenotype is largely driven by loss of SOD1 function. By contrast, cholesterol synthesis genes are down-regulated in severely affected human TgSOD1 G93A transgenic mice at 4 months. Our analyses implicate dysregulation of cholesterol or related lipid pathway genes in ALS pathogenesis. The Sod1 G85R knock-in mouse is a useful ALS model to examine the importance of SOD1 activity in control of cholesterol homeostasis and motor neuron survival.

SIGNIFICANCE STATEMENT

Amyotrophic lateral sclerosis is a devastating disease involving the progressive loss of motor neurons and motor function for which there is currently no cure. Understanding biological mechanisms leading to motor neuron death is critical for developing new treatments. Using a new knock-in mutant mouse model carrying a Sod1 mutation that causes ALS in patients, and in the mouse, causes a limited neurodegenerative phenotype similar to Sod1 loss-of-function, we show that cholesterol synthesis pathway genes are up-regulated in mutant motor neurons, whereas the same genes are down-regulated in transgenic SOD1 mice with a severe phenotype. Our data implicate dysregulation of cholesterol or other related lipid genes in ALS pathogenesis and provide new insights that could contribute to strategies for disease intervention.

Oral Treatment with d-RD2RD2 Impedes Early Disease Mechanisms in SOD1*G93A Transgenic Mice but Does Not Prolong Survival

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease affecting upper and lower motor neurons, thus, progressing to complete muscle loss until the patient dies from respiratory arrest. The disease is not curable, and patients die approximately 2-5 years after diagnosis. Studying the underlying disease mechanisms to get access to new treatment options is, therefore, essential for patients' benefit. However, so far, only three drugs that alleviate the symptoms have been approved by the U.S. Food and Drug Administration (FDA). A new drug candidate for the treatment of ALS is the all-d-enantiomeric peptide RD2RD2. In this study, we investigated the therapeutic effect of RD2RD2 in two setups. First, we analyzed disease progression and survival in 7 week-old B6.Cg-Tg(SOD1*G93A)1Gur/J mice. Second, we confirmed the result of the survival analysis in the B6SJL-Tg(SOD1*G93A)1Gur/J mouse line. Shortly before disease onset, the mice were treated daily with an oral dose of 50 mg/kg body weight. Treatment with RD2RD2 led to a delayed disease onset and reduced motor phenotype as shown using the SHIRPA test, the splay reflex test, and the pole test, but did not affect survival. In conclusion, RD2RD2 has the ability to delay the onset of symptoms.

Hemizygous Granzyme A Mice Expressing the hSOD1G93A Transgene Show Slightly Extended Lifespan

Granzyme A (gzmA), a serine protease involved in the modulation of the inflammatory immune response, is found at an elevated level in the serum from ALS patients. However, the influence of gzmA on the progression of ALS remains unclear. The aim of our work was to assess whether the absence of gzmA in an ALS murine model could help slow down the progression of the disease. Homozygous and hemizygous gzmA-deficient mice expressing the hSOD1G93A transgene were generated, and survival of these mice was monitored. Subsequently, gene and protein expression of inflammatory and oxidative stress markers was measured in the spinal cord and quadriceps of these mice. We observed the longest lifespan in gzmA+/- mice. GzmA gene and protein expression was downregulated in the spinal cord and serum from gmzA+/- mice, confirming that the increased survival of hemizygous mice is correlated with lower levels of gzmA. In addition, mRNA and protein levels of glutathione reductase (GSR), involved in oxidative stress, were found downregulated in the spinal cord and quadriceps of gmzA+/- mice, together with lower IL-1β and IL-6 mRNA levels in hemyzigous mice. In summary, our findings indicate for the first time that reduced levels, but not the absence, of gzmA could slightly ameliorate the disease progression in this animal model.

Identification of quantitative trait loci for survival in the mutant dynactin p150Glued mouse model of motor neuron disease

Amyotrophic lateral sclerosis (ALS) is the most common degenerative motor neuron disorder. Although most cases of ALS are sporadic, 5-10% of cases are familial, with mutations associated with over 40 genes. There is variation of ALS symptoms within families carrying the same mutation; the disease may develop in one sibling and not in another despite the presence of the mutation in both. Although the cause of this phenotypic variation is unknown, it is likely related to genetic modifiers of disease expression. The identification of ALS causing genes has led to the development of transgenic mouse models of motor neuron disease. Similar to families with familial ALS, there are background-dependent differences in disease phenotype in transgenic mouse models of ALS suggesting that, as in human ALS, differences in phenotype may be ascribed to genetic modifiers. These genetic modifiers may not cause ALS rather their expression either exacerbates or ameliorates the effect of the mutant ALS causing genes. We have reported that in both the G93A-hSOD1 and G59S-hDCTN1 mouse models, SJL mice demonstrated a more severe phenotype than C57BL6 mice. From reciprocal intercrosses between G93A-hSOD1 transgenic mice on SJL and C57BL6 strains, we identified a major quantitative trait locus (QTL) on mouse chromosome 17 that results in a significant shift in lifespan. In this study we generated reciprocal intercrosses between transgenic G59S-hDCTN1 mice on SJL and C57BL6 strains and identified survival QTLs on mouse chromosomes 17 and 18. The chromosome 17 survival QTL on G93A-hSOD1 and G59S-hDCTN1 mice partly overlap, suggesting that the genetic modifiers located in this region may be shared by these two ALS models despite the fact that motor neuron degeneration is caused by mutations in different proteins. The overlapping region contains eighty-seven genes with non-synonymous variations predicted to be deleterious and/or damaging. Two genes in this segment, NOTCH3 and Safb/SAFB1, have been associated with motor neuron disease. The identification of genetic modifiers of motor neuron disease, especially those modifiers that are shared by SOD1 and dynactin-1 transgenic mice, may result in the identification of novel targets for therapies that can alter the course of this devastating illness.

Chlorovirus ATCV-1 Accelerates Motor Deterioration in SOD1-G93A Transgenic Mice and Its SOD1 Augments Induction of Inflammatory Factors From Murine Macrophages

Background

Genetically polymorphic Superoxide Dismutase 1 G93A (SOD1-G93A) underlies one form of familial Amyotrophic Lateral Sclerosis (ALS). Exposures from viruses may also contribute to ALS, possibly by stimulating immune factors, such as IL-6, Interferon Stimulated Genes, and Nitric Oxide. Recently, chlorovirus ATCV-1, which encodes a SOD1, was shown to replicate in macrophages and induce inflammatory factors.

Objective

This study aimed to determine if ATCV-1 influences development of motor degeneration in an ALS mouse model and to assess whether SOD1 of ATCV-1 influences production of inflammatory factors from macrophages.

Methods

Sera from sporadic ALS patients were screened for antibody to ATCV-1. Active or inactivated ATCV-1, saline, or a viral mimetic, polyinosinic:polycytidylic acid (poly I:C) were injected intracranially into transgenic mice expressing human SOD1-G93A- or C57Bl/6 mice. RAW264.7 mouse macrophage cells were transfected with a plasmid vector expressing ATCV-1 SOD1 or an empty vector prior to stimulation with poly I:C with or without Interferon-gamma (IFN-γ).

Results

Serum from sporadic ALS patients had significantly more IgG1 antibody directed against ATCV-1 than healthy controls. Infection of SOD1-G93A mice with active ATCV-1 significantly accelerated onset of motor loss, as measured by tail paralysis, hind limb tucking, righting reflex, and latency to fall in a hanging cage-lid test, but did not significantly affect mortality when compared to saline-treated transgenics. By contrast, poly I:C treatment significantly lengthened survival time but only minimally slowed onset of motor loss, while heat-inactivated ATCV-1 did not affect motor loss or survival. ATCV-1 SOD1 significantly increased expression of IL-6, IL-10, ISG promoter activity, and production of Nitric Oxide from RAW264.7 cells.

Conclusion

ATCV-1 chlorovirus encoding an endogenous SOD1 accelerates pathogenesis but not mortality, while poly I:C that stimulates antiviral immune responses delays mortality in an ALS mouse model. ATCV-1 SOD1 enhances induction of inflammatory factors from macrophages.

Pridopidine modifies disease phenotype in a SOD1 mouse model of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a lethal and incurable neurodegenerative disease due to the loss of upper and lower motor neurons, which leads to muscle weakness, atrophy, and paralysis. Sigma‐1 receptor (σ‐1R) is a ligand‐operated protein that exhibits pro‐survival and anti‐apoptotic properties. In addition, mutations in its codifying gene are linked to development of juvenile ALS pointing to an important role in ALS. Here, we investigated the disease‐modifying effects of pridopidine, a σ‐1R agonist, using a delayed onset SOD1 G93A mouse model of ALS. Mice were administered a continuous release of pridopidine (3.0 mg/kg/day) for 4 weeks starting before the appearance of any sign of muscle weakness. Mice were monitored weekly and several behavioural tests were used to evaluate muscle strength, motor coordination and gait patterns. Pridopidine‐treated SOD1 G93A mice showed genotype‐specific effects with the prevention of cachexia. In addition, these effects exhibited significant improvement of motor behaviour 5 weeks after treatment ended. However, the survival of the animals was not extended. In summary, these results show that pridopidine can modify the disease phenotype of ALS‐associated cachexia and motor deficits in a SOD1 G93A mouse model.

Generation and analysis of innovative genomically humanized knockin SOD1, TARDBP (TDP-43), and FUS mouse models

Amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) is a fatal neurodegenerative disorder, and continued innovation is needed for improved understanding and for developing therapeutics. We have created next-generation genomically humanized knockin mouse models, by replacing the mouse genomic region of Sod1, Tardbp (TDP-43), and Fus, with their human orthologs, preserving human protein biochemistry and splicing with exons and introns intact. We establish a new standard of large knockin allele quality control, demonstrating the utility of indirect capture for enrichment of a genomic region of interest followed by Oxford Nanopore sequencing. Extensive analysis shows that homozygous humanized animals only express human protein at endogenous levels. Characterization of humanized FUS animals showed that they are phenotypically normal throughout their lifespan. These humanized strains are vital for preclinical assessment of interventions and serve as templates for the addition of coding or non-coding human ALS/FTD mutations to dissect disease pathomechanisms, in a physiological context.

The Long-Term Clinical Course of Canine Degenerative Myelopathy and Therapeutic Potential of Curcumin

Canine degenerative myelopathy (DM), recognized as a spontaneous model of amyotrophic lateral sclerosis, is known as a late-onset progressive degenerative disease of the spinal cord. Because of the progressive nature of DM, many dogs are elected to be euthanized, resulting in limited information on the end-stage clinical presentation. We investigated the long-term clinical course from diagnosis to natural death to further deepen our understanding of the entire clinical picture of this disease. Because curcumin was administered in some cases, the therapeutic effect of curcumin on DM was also examined. Forty dogs included in this study were client-owned Pembroke Welsh Corgis with a definitive diagnosis of DM by necropsy and histopathology. Dogs were excluded from this study if they died from another disease or were elected to be euthanized. Information on the long-term clinical symptoms of DM was investigated based on a questionnaire, which was collected from the dog owners. Urinary incontinence and respiratory disorder were observed in most dogs, as was respiratory impairment-correlated death. In contrast, signs consistent with brainstem dysfunction were noticed at the terminal stage in a small portion of dogs. Although further studies with more cases are needed, the results of this study suggest that administration of curcumin is effective in slowing the progression of DM.

Sex-dependent effects of amyloid precursor-like protein 2 in the SOD1-G37R transgenic mouse model of MND

Motor neurone disease (MND) is a neurodegenerative disorder characterised by progressive destruction of motor neurons, muscle paralysis and death. The amyloid precursor protein (APP) is highly expressed in the central nervous system and has been shown to modulate disease outcomes in MND. APP is part of a gene family that includes the amyloid precursor-like protein 1 (APLP1) and 2 (APLP2) genes. In the present study, we investigated the role of APLP2 in MND through the examination of human spinal cord tissue and by crossing APLP2 knockout mice with the superoxide dismutase 1 (SOD1-G37R) transgenic mouse model of MND. We found the expression of APLP2 is elevated in the spinal cord from human cases of MND and that this feature of the human disease is reproduced in SOD1-G37R mice at the End-stage of their MND-like phenotype progression. APLP2 deletion in SOD1-G37R mice significantly delayed disease progression and increased the survival of female SOD1-G37R mice. Molecular and biochemical analysis showed female SOD1-G37R:APLP2-/- mice displayed improved innervation of the neuromuscular junction, ameliorated atrophy of muscle fibres with increased APP protein expression levels in the gastrocnemius muscle. These results indicate a sex-dependent role for APLP2 in mutant SOD1-mediated MND and further support the APP family as a potential target for further investigation into the cause and regulation of MND.

Oral Treatment with RD2RD2 Impedes Development of Motoric Phenotype and Delays Symptom Onset in SOD1G93A Transgenic Mice

Neuroinflammation is a pathological hallmark of several neurodegenerative disorders and plays a key role in the pathogenesis of amyotrophic lateral sclerosis (ALS). It has been implicated as driver of disease progression and is observed in ALS patients, as well as in the transgenic SOD1^G93A mouse model. Here, we explore and validate the therapeutic potential of the d-enantiomeric peptide RD2RD2 upon oral administration in SOD1^G93A mice. Transgenic mice were treated daily with RD2RD2 or placebo for 10 weeks and phenotype progression was followed with several behavioural tests. At the end of the study, plasma cytokine levels and glia cell markers in brain and spinal cord were analysed. Treatment resulted in a significantly increased performance in behavioural and motor coordination tests and a decelerated neurodegenerative phenotype in RD2RD2-treated SOD1^G93A mice. Additionally, we observed retardation of the average disease onset. Treatment of SOD1^G93A mice led to significant reduction in glial cell activation and a rescue of neurons. Analysis of plasma revealed normalisation of several cytokines in samples of RD2RD2-treated SOD1^G93A mice towards the levels of non-transgenic mice. In conclusion, these findings qualify RD2RD2 to be considered for further development and testing towards a disease modifying ALS treatment.

BAC transgenic mice to study the expression of P2X2 and P2Y1 receptors

Extracellular purines are important signaling molecules involved in numerous physiological and pathological processes via the activation of P2 receptors. Information about the spatial and temporal P2 receptor (P2R) expression and its regulation remains crucial for the understanding of the role of P2Rs in health and disease. To identify cells carrying P2X2Rs in situ, we have generated BAC transgenic mice that express the P2X2R subunits as fluorescent fusion protein (P2X2-TagRFP). In addition, we generated a BAC P2Y₁R TagRFP reporter mouse expressing a TagRFP reporter for the P2RY1 gene expression. We demonstrate expression of the P2X2R in a subset of DRG neurons, the brain stem, the hippocampus, as well as on Purkinje neurons of the cerebellum. However, the weak fluorescence intensity in our P2X2R-TagRFP mouse precluded tracking of living cells. Our P2Y₁R reporter mice confirmed the widespread expression of the P2RY1 gene in the CNS and indicate for the first time P2RY1 gene expression in mouse Purkinje cells, which so far has only been described in rats and humans. Our P2R transgenic models have advanced the understanding of purinergic transmission, but BAC transgenic models appeared not always to be straightforward and permanent reliable. We noticed a loss of fluorescence intensity, which depended on the number of progeny generations. These problems are discussed and may help to provide more successful animal models, even if in future more versatile and adaptable nuclease-mediated genome-editing techniques will be the methods of choice.

A Systematic Review of Oropharyngeal Dysphagia Models in Rodents

Oropharyngeal dysphagia is a condition characterized by swallowing difficulty in the mouth and pharynx, which can be due to various factors. Animal models of oropharyngeal dysphagia are essential to confirm the cause-specific symptoms, pathological findings, and the effect of treatment. Recently, various animal models of dysphagia have been reported. The purpose of this review is to organize the rodent models of oropharyngeal dysphagia reported to date. The articles were obtained from Medline, Embase, and the Cochrane library, and selected following the PRISMA guideline. The animal models in which oropharyngeal dysphagia was induced in rats or mice were selected and classified based on the diseases causing oropharyngeal dysphagia. The animal used, method of inducing dysphagia, and screening methods and results were collected from the selected 37 articles. Various rodent models of oropharyngeal dysphagia provide distinctive information on atypical swallowing. Applying and analyzing the treatment in rodent models of dysphagia induced from various causes is an essential process to develop symptom-specific treatments. Therefore, the results of this study provide fundamental and important data for selecting appropriate animal models to study dysphagia.

Implication of post-translationally modified SOD1 in pathological aging

Why certain people relish healthy aging throughout their life span while others suffer pathological consequences? In this review, we focus on some of the dominant paradigms of pathological aging, such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), and Parkinson's disease (PD), and predict that the antioxidant superoxide dismutase 1 (SOD1), when post-translationally modified by aging-associated oxidative stress, acts as a mechanism to accelerated aging in these age-related neurodegenerative diseases. Oxidative modifications of natively reduced SOD1 induce pathological confirmations such as misfolding, leading to a subsequent formation of monomeric, oligomeric, and multimeric aggregates. Misfolded SOD1 propagates like prions from cell to cell. These modified conformations are detected in brain tissues in ALS, AD, and PD, and are considered a contributing factor to their initial pathogenesis. We have also elaborated on oxidative stress-induced non-native modifications of SOD1 and offered a logistic argument on their global implication in accelerated or pathological aging in the context of ALS, AD, and PD.

Protein disulfide isomerase ERp57 protects early muscle denervation in experimental ALS

Amyotrophic lateral sclerosis (ALS) is a progressive fatal neurodegenerative disease that affects motoneurons. Mutations in superoxide dismutase 1 (SOD1) have been described as a causative genetic factor for ALS. Mice overexpressing ALS-linked mutant SOD1 develop ALS symptoms accompanied by histopathological alterations and protein aggregation. The protein disulfide isomerase family member ERp57 is one of the main up-regulated proteins in tissue of ALS patients and mutant SOD1 mice, whereas point mutations in ERp57 were described as possible risk factors to develop the disease. ERp57 catalyzes disulfide bond formation and isomerization in the endoplasmic reticulum (ER), constituting a central component of protein quality control mechanisms. However, the actual contribution of ERp57 to ALS pathogenesis remained to be defined. Here, we studied the consequences of overexpressing ERp57 in experimental ALS using mutant SOD1 mice. Double transgenic SOD1G93A/ERp57WT animals presented delayed deterioration of electrophysiological activity and maintained muscle innervation compared to single transgenic SOD1G93A littermates at early-symptomatic stage, along with improved motor performance without affecting survival. The overexpression of ERp57 reduced mutant SOD1 aggregation, but only at disease end-stage, dissociating its role as an anti-aggregation factor from the protection of neuromuscular junctions. Instead, proteomic analysis revealed that the neuroprotective effects of ERp57 overexpression correlated with increased levels of synaptic and actin cytoskeleton proteins in the spinal cord. Taken together, our results suggest that ERp57 operates as a disease modifier at early stages by maintaining motoneuron connectivity.

Trifluoroethanol Partially Unfolds G93A SOD1 Leading to Protein Aggregation: A Study by Native Mass Spectrometry and FPOP Protein Footprinting

Misfolding of Cu, Zn superoxide dismutase (SOD1) variants may lead to protein aggregation and ultimately amyotrophic lateral sclerosis (ALS). The mechanism and protein conformational changes during this process are complex and remain unclear. To study SOD1 variant aggregation at the molecular level and in solution, we chemically induced aggregation of a mutant variant (G93A SOD1) with trifluoroethanol (TFE) and used both native mass spectrometry (MS) to analyze the intact protein and fast photochemical oxidation of proteins (FPOP) to characterize the structural changes induced by TFE. We found partially unfolded G93A SOD1 monomers prior to oligomerization and identified regions of the N-terminus, C-terminus, and strands β5, β6 accountable for the partial unfolding. We propose that exposure of hydrophobic interfaces of these unstructured regions serves as a precursor to aggregation. Our results provide a possible mechanism and molecular basis for ALS-linked SOD1 misfolding and aggregation.

Absence of Receptor for Advanced Glycation End Product (RAGE) Reduces Inflammation and Extends Survival in the hSOD1G93A Mouse Model of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal and rapidly progressing motor neuron degenerative disease that is without effective treatment. The receptor for advanced glycation end products (RAGE) is a major component of the innate immune system that has been implicated in ALS pathogenesis. However, the contribution of RAGE signalling to the neuroinflammation that underlies ALS neurodegeneration remains unknown. The present study therefore generated SOD1^G93A mice lacking RAGE and compared them with SOD1^G93A transgenic ALS mice in respect to disease progression (i.e. body weight, survival and muscle strength), neuroinflammation and denervation markers in the spinal cord and tibialis anterior muscle. We found that complete absence of RAGE signalling exerted a protective effect on SOD1^G93A pathology, slowing disease progression and significantly extending survival by ~ 3 weeks and improving motor function (rotarod and grip strength). This was associated with reduced microgliosis, cytokines, innate immune factors (complement, TLRs, inflammasomes), and oxidative stress in the spinal cord, and a reduction of denervation markers in the tibialis anterior muscle. We also documented that RAGE mRNA expression was significantly increased in the spinal cord and muscles of preclinical SOD1 and TDP43 models of ALS, supporting a widespread involvement for RAGE in ALS pathology. In summary, our results indicate that RAGE signalling drives neuroinflammation and contributes to neurodegeneration in ALS and highlights RAGE as a potential immune therapeutic target for ALS.

The deletion of mutant SOD1 via CRISPR/Cas9/sgRNA prolongs survival in an amyotrophic lateral sclerosis mouse model

The superoxide dismutase 1 (SOD1) mutation is one of the most notable causes of amyotrophic lateral sclerosis (ALS), and modifying the mutant SOD1 gene is the best approach for the treatment of patients with ALS linked to the mutations in this gene. Clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (Cas9)/sgRNA delivered by the adeno-associated virus (AAV) system is a powerful tool for genome editing in the central nervous system (CNS). Here, we tested the capacity of the AAV-SaCas9-sgRNA system to modify mutant SOD1 in SOD1G93A transgenic mice and found that AAV9-SaCas9-sgRNA5 deleted the SOD1 gene, improved the lifespan of SOD1G93A mice by 54.6%, and notably ameliorated the performance of ALS transgenic mice. An immunochemical analysis showed that the expression of mutant SOD1 was very weak in motor neurons expressing SaCas9-sgRNA5. Consequently, the area showing muscle atrophy was more notably restored in the group treated with SaCas9-sgRNA5 compared with the group treated with SaCas9-sgLacZ. In addition, deep sequencing did not show the indel mutation in the gene highly matched to sgRNA5. Hence, AAV9-SaCas9-sgRNA-based gene editing is a feasible potential treatment for patients with ALS linked to SOD1 mutations.

Modeling cell-autonomous motor neuron phenotypes in ALS using iPSCs

Amyotrophic lateral sclerosis (ALS) is an aggressive and uniformly fatal degenerative disease of the motor nervous system. In order to understand underlying disease mechanisms, researchers leverage a host of in vivo and in vitro models, including yeast, worms, flies, zebrafish, mice, and more recently, human induced pluripotent stem cells (iPSCs) derived from ALS patients. While mouse models have been the main workhorse of preclinical ALS research, the development of iPSCs provides a new opportunity to explore molecular phenotypes of ALS within human cells. Importantly, this technology enables modeling of both familial and sporadic ALS in the relevant human genetic backgrounds, as well as a personalized or targeted approach to therapy development. Harnessing these powerful tools requires addressing numerous challenges, including different variance components associated with iPSCs and motor neurons as well as concomitant limits of reductionist approaches. In order to overcome these obstacles, optimization of protocols and assays, confirmation of phenotype robustness at scale, and validation of findings in human tissue and genetics will cement the role for iPSC models as a valuable complement to animal models in ALS and more broadly among neurodegenerative diseases.

Hyperexcitability in Cultured Cortical Neuron Networks from the G93A-SOD1 Amyotrophic Lateral Sclerosis Model Mouse and its Molecular Correlates

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease affecting the corticospinal tract and leading to motor neuron death. According to a recent study, magnetic resonance imaging-visible changes suggestive of neurodegeneration seem absent in the motor cortex of G93A-SOD1 ALS mice. However, it has not yet been ascertained whether the cortical neural activity is intact, or alterations are present, perhaps even from an early stage. Here, cortical neurons from this model were isolated at post-natal day 1 and cultured on multielectrode arrays. Their activity was studied with a comprehensive pool of neurophysiological analyses probing excitability, criticality and network architecture, alongside immunocytochemistry and molecular investigations. Significant hyperexcitability was visible through increased network firing rate and bursting, whereas topological changes in the synchronization patterns were apparently absent. The number of dendritic spines was increased, accompanied by elevated transcriptional levels of the DLG4 gene, NMDA receptor 1 and the early pro-apoptotic APAF1 gene. The extracellular Na⁺, Ca²⁺, K⁺ and Cl^- concentrations were elevated, pointing to perturbations in the culture micro-environment. Our findings highlight remarkable early changes in ALS cortical neuron activity and physiology. These changes suggest that the causative factors of hyperexcitability and associated toxicity could become established much earlier than the appearance of disease symptoms, with implications for the discovery of new hypothetical therapeutic targets.

Optimizing the Translational Value of Mouse Models of ALS for Dysphagia Therapeutic Discovery

The goal of this study was to compare dysphagia phenotypes in low and high copy number (LCN and HCN) transgenic superoxide dismutase 1 (SOD1) mouse models of ALS to accelerate the discovery of novel and effective treatments for dysphagia and early amyotrophic lateral sclerosis (ALS) diagnosis. Clinicopathological features of dysphagia were characterized in individual transgenic mice and age-matched controls utilizing videofluoroscopy in conjunction with postmortem assays of the tongue and hypoglossal nucleus. Quantitative PCR accurately differentiated HCN-SOD1 and LCN-SOD1 mice and nontransgenic controls. All HCN-SOD1 mice developed stereotypical paralysis in both hindlimbs. In contrast, LCN-SOD1 mice displayed wide variability in fore- and hindlimb involvement. Lick rate, swallow rate, inter-swallow interval, and pharyngeal transit time were significantly altered in both HCN-SOD1 and LCN-SOD1 mice compared to controls. Tongue weight, tongue dorsum surface area, total tongue length, and caudal tongue length were significantly reduced only in the LCN-SOD1 mice compared to age-matched controls. LCN-SOD1 mice with lower body weights had smaller/lighter weight tongues, and those with forelimb paralysis and slower lick rates died at a younger age. LCN-SOD1 mice had a 32% loss of hypoglossal neurons, which differed significantly when compared to age-matched control mice. These novel findings for LCN-SOD1 mice are congruent with reported dysphagia and associated tongue atrophy and hypoglossal nucleus pathology in human ALS patients, thus highlighting the translational potential of this mouse model in ALS research.

Myelin degeneration induced by mutant superoxide dismutase 1 accumulation promotes amyotrophic lateral sclerosis

Myelin is a specialized membrane that wraps around nerve fibers and is essential for normal axonal conduction in neurons. In the central nervous system, oligodendrocytes are responsible for myelin formation. Recent studies have reported pathological abnormalities in oligodendrocytes in human patients with amyotrophic lateral sclerosis (ALS) and a mouse model of ALS expressing the G93A mutation of the human superoxide dismutase 1 (mtSOD1). However, it is unclear whether oligodendrocyte pathology in ALS represents the primary dysfunction induced by mtSOD1 and how mtSOD1 contributes to oligodendrocyte degeneration and ALS pathogenesis. We analyzed GAL4-VP16-UAS transgenic zebrafish selectively expressing mtSOD1 in mature oligodendrocytes. We observed that mtSOD1 directly induced oligodendrocyte degeneration by disrupting the myelin sheath and downregulating monocarboxylate transporter 1 (MCT1), thereby causing spinal motor neuron degeneration. Pathological changes observed in this transgenic zebrafish were similar to the pathology observed in the SOD1^G93A mouse model of ALS, which is characterized by expression of mtSOD1 in all cells. In addition, oligodendrocyte dysfunction induced by mtSOD1 was associated with anxiety-related behavioral abnormalities, learning impairments, and motor defects in the early symptomatic stage. We also found that treatment with potassium channel inhibitors rescued behavioral abnormalities without rescuing MCT1 expression, suggesting that myelin disruption induces behavioral abnormalities independently of MCT1. These results indicate that mtSOD1-induced dysfunction of mature oligodendrocytes is sufficient to induce motor neuron degeneration, thus informing future therapeutic strategies targeted at oligodendrocytes in ALS.

Klotho Is Neuroprotective in the Superoxide Dismutase (SOD1G93A) Mouse Model of ALS

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by the loss of motor neurons in the brain and spinal cord. ALS neuropathology is associated with increased oxidative stress, excitotoxicity, and inflammation. We and others reported that the anti-aging and cognition-enhancing protein Klotho is a neuroprotective, antioxidative, anti-inflammatory, and promyelinating protein. In mice, its absence leads to an extremely shortened life span and to multiple phenotypes resembling human aging, including motor and hippocampal neurodegeneration and cognitive impairment. In contrast, its overexpression extends life span, enhances cognition, and confers resistance against oxidative stress; it also reduces premature mortality and cognitive and behavioral abnormalities in an animal model for Alzheimer's disease (AD). These pleiotropic beneficial properties of Klotho suggest that Klotho could be a potent therapeutic target for preventing neurodegeneration in ALS. Klotho overexpression in the SOD1 mouse model of ALS resulted in delayed onset and progression of the disease and extended survival that was more prominent in females than in males. Klotho reduced the expression of neuroinflammatory markers and prevented neuronal loss with the more profound effect in the spinal cord than in the motor cortex. The effect of Klotho was accompanied by reduced expression of proinflammatory cytokines and enhanced the expression of antioxidative and promyelinating factors in the motor cortex and spinal cord of Klotho × SOD1 compared to SOD1 mice. Our study provides evidence that increased levels of Klotho alleviate ALS-associated pathology in the SOD1 mouse model and may serve as a basis for developing Klotho-based therapeutic strategies for ALS.

Motor Neuron Susceptibility in ALS/FTD

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the death of both upper and lower motor neurons (MNs) in the brain, brainstem and spinal cord. The neurodegenerative mechanisms leading to MN loss in ALS are not fully understood. Importantly, the reasons why MNs are specifically targeted in this disorder are unclear, when the proteins associated genetically or pathologically with ALS are expressed ubiquitously. Furthermore, MNs themselves are not affected equally; specific MNs subpopulations are more susceptible than others in both animal models and human patients. Corticospinal MNs and lower somatic MNs, which innervate voluntary muscles, degenerate more readily than specific subgroups of lower MNs, which remain resistant to degeneration, reflecting the clinical manifestations of ALS. In this review, we discuss the possible factors intrinsic to MNs that render them uniquely susceptible to neurodegeneration in ALS. We also speculate why some MN subpopulations are more vulnerable than others, focusing on both their molecular and physiological properties. Finally, we review the anatomical network and neuronal microenvironment as determinants of MN subtype vulnerability and hence the progression of ALS.

A High-throughput qPCR-based Method to Genotype the SOD1G93A Mouse Model for Relative Copy Number

The most commonly used mouse model in ALS preclinical research expresses multiple copies of the human SOD1 (G93A) transgene. During the course of breeding, successive generations of mice can lose copies of the transgene. Because shorter lifespan of these mice is dependent on transgene copy number, it is essential to ensure that no low-copy, and therefore longer-lived, mice are included in preclinical studies. Existing techniques for SOD1^G93A mouse genotyping are broadly based on creating a standard curve using a reference gene and deducing the relative amount of SOD1 by comparison with the standard curve. This type of technique is used in Alexander et al. (2004) , Vieira et al. (2017) and Maier et al. (2018) . However, it is not described in detail (see Note 1). This paper provides a detailed protocol for determining the relative copy number of the human SOD1 transgene. Briefly, the protocol involves first the extraction of high-quality genomic DNA from mouse ear tissue, creation of a genomic DNA concentration-based standard curve, and qPCR analysis of up to 88 samples at once alongside the standard curve with Gapdh as a reference gene. Analysis involves the normalization of each unknown sample using the standard curve followed by determination of the copy number of the sample relative to the cohort median. This protocol has been optimized to produce high-quality genomic DNA and consistent results, and the relative copy number cutoffs have been optimized and validated empirically by comparison of relative copy number and mouse lifespan.

Intrathecal delivery of recombinant AAV1 encoding hepatocyte growth factor improves motor functions and protects neuromuscular system in the nerve crush and SOD1-G93A transgenic mouse models

Amyotrophic lateral sclerosis (ALS) is a fatal neuromuscular disease resulting from motor neuron degeneration that causes muscle weakness, paralysis, and eventually respiratory failure. We investigated whether recombinant adeno-associated virus encoding human hepatocyte growth factor (rAAV-HGF) could generate beneficial effects in two mouse models with neuromuscular problems when intrathecally delivered to the subarachnoid space. We chose AAV serotype 1 (rAAV1) based on the expression levels and distribution of HGF protein in the lumbar spinal cord (LSC). After a single intrathecal (IT) injection of rAAV1-HGF, the protein level of HGF in the LSC peaked on day 14 and thereafter gradually decreased over the next 14 weeks. rAAV1-HGF was initially tested in the mouse nerve crush model. IT injection of rAAV1-HGF improved mouse hindlimb strength and rotarod performance, while histological analyses showed that the length of regenerated axons was increased and the structure of the neuromuscular junction (NMJ) was restored. rAAV1-HGF was also evaluated in the SOD1-G93A transgenic (TG) mouse model. Again, rAAV1-HGF not only improved motor performance but also increased the survival rate. Moreover, the number and diameter of spinal motor neurons (SMNs) were increased, and the shape of the NMJs restored. Data from in vitro motor cortical culture experiments indicated that treatment with recombinant HGF protein (rHGF) increased the axon length of corticospinal motor neurons (CSMNs). When cultures were treated with an ERK inhibitor, the effects of HGF on axon elongation, protein aggregation, and oxidative stress were suppressed, indicating that ERK phosphorylation played an important role(s). Taken together, our results suggested that HGF might play an important role(s) in delaying disease progression in the SOD1-G93A TG mouse model by reducing oxidative stress through the control of ERK phosphorylation.

The UPR-PERK pathway is not a promising therapeutic target for mutant SOD1-induced ALS

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease, characterized by motor neuron death in the brain and spinal cord. Mutations in the Cu/Zn superoxide dismutase (SOD1) gene account for ~20% of all familial ALS forms, corresponding to 1%-2% of all ALS cases. One of the suggested mechanisms by which mutant SOD1 (mtSOD1) exerts its toxic effects involves intracellular accumulation of abnormal mtSOD1 aggregates, which trigger endoplasmic reticulum (ER) stress and activate its adaptive signal transduction pathways, including the unfolded protein response (UPR). PERK, an eIF2α kinase, is central to the UPR and is the most rapidly activated pathway in response to ER stress. Previous reports using mtSOD1 transgenic mice indicated that genetic or pharmacological enhancement of the UPR-PERK pathway may be effective in treating ALS. We investigated the response to PERK haploinsufficiency, and the response to deficiency of its downstream effectors GADD34 and CHOP, in five distinct lines of mtSOD1 mice. We demonstrate that, in contrast to a previously published study, PERK haploinsufficiency has no effect on disease in all mtSOD1 lines examined. We also show that deficiency of GADD34, which enhances the UPR by prolonging the phosphorylation of eIF2α, does not ameliorate disease in these mtSOD1 mouse lines. Finally, we demonstrate that genetic ablation of CHOP transcription factor, which is known to be pro-apoptotic, does not ameliorate disease in mtSOD1 mice. Cumulatively, our studies reveal that neither genetic inhibition of the UPR via ablation of PERK, nor genetic UPR enhancement via ablation of GADD34, is beneficial for mtSOD1-induced motor neuron disease. Therefore, the PERK pathway is not a likely target for therapeutic intervention in mtSOD1-induced ALS.

Therapeutic blockade of HMGB1 reduces early motor deficits, but not survival in the SOD1G93A mouse model of amyotrophic lateral sclerosis

Background

Amyotrophic lateral sclerosis (ALS) is a fatal and rapidly progressing neurodegenerative disease without effective treatment. The receptor for advanced glycation end products (RAGE) and the toll-like receptor (TLR) system are major components of the innate immune system, which have been implicated in ALS pathology. Extracellularly released high-mobility group box 1 (HMGB1) is a pleiotropic danger-associated molecular pattern (DAMP), and is an endogenous ligand for both RAGE and TLR4.

Methods

The present study examined the effect of HMGB1 inhibition on disease progression in the preclinical SOD1^G93A transgenic mouse model of ALS using a potent anti-HMGB1 antibody (2G7), which targets the extracellular DAMP form of HMGB1.

Results

We found that chronic intraperitoneal dosing of the anti-HMGB1 antibody to SOD1^G93A mice transiently improved hind-limb grip strength early in the disease, but did not extend survival. Anti-HMGB1 treatment also reduced tumour necrosis factor α and complement C5a receptor 1 gene expression in the spinal cord, but did not affect overall glial activation.

Conclusions

In summary, our results indicate that therapeutic targeting of an extracellular DAMP, HMGB1, improves early motor dysfunction, but overall has limited efficacy in the SOD1^G93A mouse model of ALS.

MAP4K4 Activation Mediates Motor Neuron Degeneration in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease affecting both upper and lower motor neurons (MNs). To date, its underlying mechanisms have yet to be clarified completely, and there are no truly effective treatments. Here, we show that MAP4K4, a MAP kinase family member, regulates MN death, with its suppression not only promoting survival but preventing neurite degeneration and decreasing mutant SOD1 levels through autophagy activation. Moreover, we report that MAP4K4 signaling specifically modulates MN viability via phosphorylated JNK3 and activation of the canonical c-Jun apoptotic pathway. Finally, we show the feasibility of MAP4K4 as a drug target by using an available MAP4K4-specific inhibitor, which improves survival of ESC and/or iPSC-derived MNs and MNs cultured from mouse spinal cords. In summary, our studies highlight a MAP4K4-initiated signaling cascade that induces MN degeneration, shedding light on the mechanism underlying MN degeneration and providing a druggable target for ALS therapeutics.

SOD1/Rag2 Mice with Low Copy Number of SOD1 Gene as a New Long-Living Immunodeficient Model of ALS

The most recent research concerning amyotrophic lateral sclerosis (ALS) emphasizes the role of glia in disease development. Thus, one can suspect that the effective therapeutic strategy in treatment of ALS would be replacement of defective glia. One of the basic problems with human glial progenitors (hGRPs) replacement strategies is the time needed for the cells to become fully functional in vivo. The lifespan of most popular high copy number SOD1 mutant mice might be too short to acknowledge benefits of transplanted cells. We focused on developing immunodeficient rag2-/- model of ALS with lower number of transgene copies and longer lifespan. The obtained hSOD1/rag2 double mutant mice have been characterized. QPCR analysis revealed that copy number of hSOD1 transgene varied in our colony (4-8 copies). The difference in transgene copy number may be translated to significant impact on the lifespan. The death of long- and short-living hSOD1/rag2 mice is preceded by muscular weakness as early as one month before death. Importantly, based on magnetic resonance imaging we identified that mutant mice demonstrated abnormalities within the medullar motor nuclei. To conclude, we developed long-living double mutant hSOD1/rag2 mice, which could be a promising model for testing therapeutic utility of human stem cells.

Transgenic and physiological mouse models give insights into different aspects of amyotrophic lateral sclerosis

A wide range of genetic mouse models is available to help researchers dissect human disease mechanisms. Each type of model has its own distinctive characteristics arising from the nature of the introduced mutation, as well as from the specific changes to the gene of interest. Here, we review the current range of mouse models with mutations in genes causative for the human neurodegenerative disease amyotrophic lateral sclerosis. We focus on the two main types of available mutants: transgenic mice and those that express mutant genes at physiological levels from gene targeting or from chemical mutagenesis. We compare the phenotypes for genes in which the two classes of model exist, to illustrate what they can teach us about different aspects of the disease, noting that informative models may not necessarily mimic the full trajectory of the human condition. Transgenic models can greatly overexpress mutant or wild-type proteins, giving us insight into protein deposition mechanisms, whereas models expressing mutant genes at physiological levels may develop slowly progressing phenotypes but illustrate early-stage disease processes. Although no mouse models fully recapitulate the human condition, almost all help researchers to understand normal and abnormal biological processes, providing that the individual characteristics of each model type, and how these may affect the interpretation of the data generated from each model, are considered and appreciated.

Muscle specific kinase (MuSK) activation preserves neuromuscular junctions in the diaphragm but is not sufficient to provide a functional benefit in the SOD1G93A mouse model of ALS

Amyotrophic lateral sclerosis (ALS), a neurodegenerative disease affecting motor neurons, is characterized by rapid decline of motor function and ultimately respiratory failure. As motor neuron death occurs late in the disease, therapeutics that prevent the initial disassembly of the neuromuscular junction may offer optimal functional benefit and delay disease progression. To test this hypothesis, we treated the SOD1^G93A mouse model of ALS with an agonist antibody to muscle specific kinase (MuSK), a receptor tyrosine kinase required for the formation and maintenance of the neuromuscular junction. Chronic MuSK antibody treatment fully preserved innervation of the neuromuscular junction when compared with control-treated mice; however, no preservation of diaphragm function, motor neurons, or survival benefit was detected. These data show that anatomical preservation of neuromuscular junctions in the diaphragm via MuSK activation does not correlate with functional benefit in SOD1^G93A mice, suggesting caution in employing MuSK activation as a therapeutic strategy for ALS patients.

Motor neuron degeneration, severe myopathy and TDP-43 increase in a transgenic pig model of SOD1-linked familiar ALS

Amyotrophic Lateral Sclerosis (ALS) is a neural disorder gradually leading to paralysis of the whole body. Alterations in superoxide dismutase SOD1 gene have been linked with several variants of familial ALS. Here, we investigated a transgenic (Tg) cloned swine model expressing the human pathological hSOD1^G93A allele. As in patients, these Tg pigs transmitted the disease to the progeny with an autosomal dominant trait and showed ALS onset from about 27 months of age. Post mortem analysis revealed motor neuron (MN) degeneration, gliosis and hSOD1 protein aggregates in brainstem and spinal cord. Severe skeletal muscle pathology including necrosis and inflammation was observed at the end stage, as well. Remarkably, as in human patients, these Tg pigs showed a quite long presymptomatic phase in which gradually increasing amounts of TDP-43 were detected in peripheral blood mononuclear cells. Thus, this transgenic swine model opens the unique opportunity to investigate ALS biomarkers even before disease onset other than testing novel drugs and possible medical devices.

Effects of Intraoperative Vagal Nerve Stimulation on the Gastrointestinal Microbiome in a Mouse Model of Amyotrophic Lateral Sclerosis

The gastrointestinal microbiota (GM) plays a fundamental role in health and disease and contributes to the bidirectional signaling between the gastrointestinal system and brain. The direct line of communication between these organ systems is through the vagus nerve. Therefore, vagal nerve stimulation (VNS), a commonly used technique for multiple disorders, has potential to modulate the enteric microbiota, enabling investigation and possibly treatment of numerous neurologic disorders in which the microbiota has been linked with disease. Here we investigate the effect of VNS in a mouse model of amyotrophic lateral sclerosis (ALS). B6SJL-Tg(SOD1*G93A)^dl1Gur (SOD1^dl) and wildtype mice underwent ventral neck surgery to access the vagus nerve. During surgery, the experimental group received 1 h of VNS, whereas the sham group underwent 1 h of sham treatment. The third (control) group did not undergo any surgical manipulation. Fecal samples were collected before surgery and at 8 d after the initial collection. Microbial DNA was sequenced to determine the GM profiles at both time points. GM profiles did not differ between genotypes at either the initial or end point. In addition, VNS did not alter GM populations, according to the parameters chosen in this study, indicating that this short intraoperative treatment is safe and has no lasting effects on the GM. Future studies are warranted to determine whether different stimulation parameters or chronic use of VNS affect GM profiles.

Prolonged Voluntary Running Negatively Affects Survival and Disease Prognosis of Male SOD1G93A Low-Copy Transgenic Mice

Amyotrophic Lateral Sclerosis (ALS) is a disease in which physical activity plays a controversial role. Epidemiological studies indicate an association between intense exercise and risk of developing ALS. To study the impact of physical activity on ALS, mouse models rely mostly on forced exercise. In this study we hypothesized that voluntary wheel running could represent a better model of the influence of exercise in the pathogenesis of ALS. We used an automated home-cage running-wheel system that enables individual monitoring of performance. To verify the effect of voluntary running on disease progression, prognosis and survival as well as motor functions, we challenged SOD1G93A low-copy male and female mice on one (1 RW, at age 24 weeks) or multiple (3 RW) running sessions at age 13, 18, and 24 weeks. In parallel we measured performance on Rotarod and Grip strength tests at different ages. Several parameters were analyzed through Principal Component Analysis in order to detect what indices correlate and may be useful for deeper understanding of the relation between exercise and disease development. We found mutant male mice more negatively affected than females by prolonged and repeated exercise. SOD1G93A low-copy male mice showed shorter survival, increased body weight loss and poorer disease prognosis when exposed to multiple running sessions. These findings could encourage the investigation of the pathogenetic mechanisms underlying the supposedly increased risk to develop ALS in humans engaged in specific and intense exercise activities.

Modelling amyotrophic lateral sclerosis: progress and possibilities

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder that primarily affects the motor system and presents with progressive muscle weakness. Most patients survive for only 2-5 years after disease onset, often due to failure of the respiratory muscles. ALS is a familial disease in ∼10% of patients, with the remaining 90% developing sporadic ALS. Over the past decade, major advances have been made in our understanding of the genetics and neuropathology of ALS. To date, around 20 genes are associated with ALS, with the most common causes of typical ALS associated with mutations in SOD1, TARDBP, FUS and C9orf72. Advances in our understanding of the genetic basis of ALS have led to the creation of different models of this disease. The molecular pathways that have emerged from these systems are more heterogeneous than previously anticipated, ranging from protein aggregation and defects in multiple key cellular processes in neurons, to dysfunction of surrounding non-neuronal cells. Here, we review the different model systems used to study ALS and discuss how they have contributed to our current knowledge of ALS disease mechanisms. A better understanding of emerging disease pathways, the detrimental effects of the various gene mutations and the causes underlying motor neuron denegation in sporadic ALS will accelerate progress in the development of novel treatments.

Summary: In this Review, Ludo Van Den Bosch and colleagues discuss the different model systems for studying ALS and how they have contributed to our current understanding of the etiology and pathology of this neurodegenerative disease.

Expression profile of pattern recognition receptors in skeletal muscle of SOD1(G93A) amyotrophic lateral sclerosis (ALS) mice and sporadic ALS patients

AIMS

Amyotrophic lateral sclerosis (ALS) is characterized by degeneration of motoneurons and progressive muscle wasting. Inflammatory processes, mediated by non-neuronal cells, such as glial cells, are known to contribute to disease progression. Inflammasomes consist of pattern recognition receptors (PRRs), apoptosis-associated speck-like protein (ASC) and caspase 1 and are essential for interleukin (IL) processing and a rapid immune response after tissue damage. Recently, we described inflammasome activation in the spinal cord of ALS patients and in SOD1^(G93A) ALS mice. Since pathological changes in the skeletal muscle are early events in ALS, we hypothesized that PRRs might be abnormally expressed in muscle fibre degeneration.

METHODS

Western blot analysis, real-time PCR and immunohistochemistry were performed with muscle tissue from presymptomatic and early-symptomatic male SOD1^(G93A) mice and with muscle biopsies of control and sporadic ALS (sALS) patients. Analysed PRRs include nucleotide-binding oligomerization domain-like (NOD-like) receptor protein 1 (NLRP1), NLR protein 3 (NLRP3), NLR family CARD domain-containing 4 (NLRC4) and absent in melanoma 2. Additionally, expression levels of ASC, caspase 1, interleukin 1 beta (IL1β) and interleukin 18 (IL18) were evaluated.

RESULTS

Expression of PRRs and ASC was detected in murine and human tissue. The PRR NLRC4, caspase 1 and IL1β were significantly elevated in denervated muscle of SOD1^(G93A) mice and sALS patients. Furthermore, levels of caspase 1 and IL1β were already increased in presymptomatic animals.

CONCLUSION

Our findings suggest that increased inflammasome activation may be involved in skeletal muscle pathology in ALS. Furthermore, elevated levels of NLRC4, caspase 1 and IL1β reflect early changes in the skeletal muscle and may contribute to the denervation process.

Intrathecal Injection of scAAV9-hIGF1 Prolongs the Survival of ALS Model Mice by Inhibiting the NF-kB Pathway

Amyotrophic lateral sclerosis (ALS) is a chronic, fatal neurodegenerative disorder characterized by the progressive loss of upper and lower motor neurons. Currently, there is no effective drug for ALS. Recent studies in ALS model mice have shown that insulin-like growth factor-1 (IGF1) may be a promising therapeutic drug. We demonstrate that self-complementary adeno-associated virus serum type 9 encoding the human IGF1 (scAAV9-hIGF1) could significantly postpone the onset and slow down the progression of the disease owning to inhibiting the NF-κB signaling pathway. Furthermore, the results were supported by experiments in which the CRISPR/Cas9 system was used to knock-down IGF1 in ALS mice (mIGF1). Our data indicate that IGF1-mediated suppression of NF-κB activation in microglia is a novel molecular mechanism underlying MN death in ALS. It provides new insight into IGF1 and points toward novel therapeutic targets of IGF1 in ALS.

Insertional Mutagenesis Confounds the Mechanism of the Morbid Phenotype of a PLNR9C Transgenic Mouse Line

BACKGROUND

A mouse line with heterozygous transgenic expression of phospholamban carrying a substitution of cysteine for arginine 9 (TgPLN^R9C) under the control of α-myosin heavy chain (αMHC) promoter features dilated cardiomyopathy, heart failure, and premature death.

METHODS AND RESULTS

Determination of transgene chromosomal localization by conventional methods shows that in this line the transgenic array of 13 PLN^R9C expression cassettes, arranged in a head-to-tail tandem orientation, have integrated into the bidirectional promoter of the αMHC (Myh6) gene and the gene for the regulatory noncoding RNA Myheart (Mhrt), both of which are known to be involved in cardiac development and pathology. Expression of the noncoding RNA Mhrt in TgPLN^R9C mice exhibits profound deregulation, despite the presence of the second, intact allele.

CONCLUSIONS

The TgPLN^R9C mouse strain is, in the best case, a functionally ambiguous phenocopy of the human PLN^R9C heterozygote, because a similar constellation of genetically programmed events can not occur in a patient. Publications featuring "cardiac-specific overexpression" are focused on the phenotype and typically forgo the definition of the transgene integration site or transgene temporal expression profile, so caution should be exercised in attributing clinical relevance to pathologic phenomena observed in αMHC-driven transgenes.

Intramuscular Delivery of scAAV9-hIGF1 Prolongs Survival in the hSOD1G93A ALS Mouse Model via Upregulation of D-Amino Acid Oxidase

Self-complementary adeno-associated viral vector 9 (scAAV9) has been confirmed to be an efficient AAV serotype for gene transfer to the central nervous system (CNS). Neurotrophic factors have been considered to be therapeutic targets for amyotrophic lateral sclerosis (ALS). In the present study, we intramuscularly injected scAAV9 encoding human insulin-like growth factor 1 (hIGF1) into an hSOD1G93A ALS mouse model. We observed that scAAV9-hIGF1 significantly reduced the loss of motor neurons of the anterior horn in the lumbar spinal cord and delayed muscle atrophy in ALS mice. Importantly, IGF1 significantly delayed disease onset and prolonged the life span of ALS mice. In addition, scAAV9-hIGF1 protected motor neurons from apoptosis through upregulation of D-amino acid oxidase (DAO), which controls the level of D-serine. Moreover, to further verify these results, we used CRISPR-Cas9 system to target the central nervous system knockdown of IGF1. This experiment supported the continued investigation of neurotrophic factor gene therapies targeting the central nervous system as a potential treatment for ALS.

Characterisation of the pathogenic effects of the in vivo expression of an ALS-linked mutation in D-amino acid oxidase: Phenotype and loss of spinal cord motor neurons

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset neuromuscular disorder characterised by selective loss of motor neurons leading to fatal paralysis. Current therapeutic approaches are limited in their effectiveness. Substantial advances in understanding ALS disease mechanisms has come from the identification of pathogenic mutations in dominantly inherited familial ALS (FALS). We previously reported a coding mutation in D-amino acid oxidase (DAO^R199W) associated with FALS. DAO metabolises D-serine, an essential co-agonist at the N-Methyl-D-aspartic acid glutamate receptor subtype (NMDAR). Using primary motor neuron cultures or motor neuron cell lines we demonstrated that expression of DAO^R199W, promoted the formation of ubiquitinated protein aggregates, activated autophagy and increased apoptosis. The aim of this study was to characterise the effects of DAO^R199Win vivo, using transgenic mice overexpressing DAO^R199W. Marked abnormal motor features, e.g. kyphosis, were evident in mice expressing DAO^R199W, which were associated with a significant loss (19%) of lumbar spinal cord motor neurons, analysed at 14 months. When separated by gender, this effect was greater in females (26%; p< 0.0132). In addition, we crossed the DAO^R199W transgenic mouse line with the SOD1^G93A mouse model of ALS to determine whether the effects of SOD1^G93A were potentiated in the double transgenic line (DAO^R199W/SOD1^G93A). Although overall survival was not affected, onset of neurological signs was significantly earlier in female double transgenic animals than their female SOD1^G93A littermates (125 days vs 131 days, P = 0.0239). In summary, some significant in vivo effects of DAO^R199W on motor neuron function (i.e. kyphosis and loss of motor neurons) were detected which were most marked in females and could contribute to the earlier onset of neurological signs in double transgenic females compared to SOD1^G93A littermates, highlighting the importance of recognizing gender effects present in animal models of ALS.

25-Hydroxycholesterol is involved in the pathogenesis of amyotrophic lateral sclerosis

This study aimed to evaluate the levels of three major hydroxycholesterols (24-, 25-, and 27-hydroxycholesterols) in the serum and cerebrospinal fluid (CSF) of patients with amyotrophic lateral sclerosis (ALS), as well as to show their role in the pathogenesis of ALS experimental models. The level of 25-hydroxycholesterol were higher in untreated ALS patients (n = 30) than in controls without ALS (n = 33) and ALS patients treated with riluzole (n = 9) both in their serum and CSF. The level of 25-hydroxycholesterol in the serum of ALS patients were significantly associated with their disease severity and rate of progression. In the motor neuron-like cell line (NSC34) with the human mutant G93A superoxide dismutase 1 gene (mSOD1-G93A), 25-hydroxycholesterol induced motor neuronal death/ apoptosis via glycogen synthase kinase-3β and liver X receptor pathways; riluzole treatment attenuated these effects. The expressions of enzymes that synthesize 25-hydroxycholesterol were significantly increased in the brains of early symptomatic mSOD1G93A mice. Our data, obtained from patients with ALS, a cellular model of ALS, and an animal model of ALS, suggests that 25-hydroxycholesterol could be actively involved in the pathogenesis of ALS, mostly in the early symptomatic disease stage, by mediating neuronal apoptosis.

Postneonatal Mortality and Liver Changes in Cloned Pigs Associated with Human Tumor Necrosis Factor Receptor I-Fc and Human Heme Oxygenase-1 Overexpression

Soluble human tumor necrosis factor (shTNFRI-Fc) and human heme oxygenase 1 (hHO-1) are key regulators for protection against oxidative and inflammatory injury for xenotransplantation. Somatic cells with more than 10 copy numbers of shTNFRI-Fc and hHO-1 were employed in somatic cell nuclear transfer to generate cloned pigs, thereby resulting in seven cloned piglets. However, produced piglets were all dead within 24 hours after birth. Obviously, postnatal death with liver apoptosis was reported in the higher copy number of shTNFRI-Fc and hHO-1 piglets. In liver, the transcript levels of ferritin heavy chain, light chain, transferrin, and inducible nitric oxide synthase were significantly highly expressed compared to those of lower copy number of shTNFRI-Fc and hHO-1 piglets (P < 0.05). Also, H₂O₂ contents were increased, and superoxide dismutase was significantly lower in the higher copy number of shTNFRI-Fc and hHO-1 piglets (P < 0.05). These results indicate that TNFRI-Fc and hHO-1 overexpression may apparently induce free iron in the liver and exert oxidative stress by enhancing reactive oxygen species production and block normal postneonatal liver metabolism.

MRI reveals therapeutical efficacy of stem cells: An experimental study on the SOD1(G93A) animal model

PURPOSE

The first part of the experiment identifies and validates MRI biomarkers distinctive of the disease progression in the transgenic superoxide dismutase gene (SOD1(G93A)) animal model. The second part assesses the efficacy of a mesenchymal stem cell-based therapy through the MRI biomarkers previously defined.

METHODS

The first part identifies MRI differences between SOD1(G93A) and healthy mice. The second part of the experiment follows the disease evolution of stem cell-treated and non-stem-cell treated SOD1(G93A) mice. The analysis focused on voxel-based morphometry and T2 mapping on the brain tissues, and T2-weighted imaging and diffusion tensor imaging (DTI) on the hind limbs.

RESULTS

Comparing diseased mice to healthy control revealed gray matter alterations in the brainstem area, accompanied by increased T2 relaxation time. Differences in muscle volume, muscle signal intensity, fractional anisotropy, axial diffusivity, and radial diffusivity were measured in the hind limbs. In the comparison between stem cell-treated mice and nontreated ones, differences in muscle volume, muscle signal intensity, and DTI-derived maps were found.

CONCLUSION

MRI-derived biomarkers can be used to identify differences between stem cell-treated and nontreated SOD1(G93A) mice. Magn Reson Med 79:459-469, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Loss of Ranbp2 in motoneurons causes disruption of nucleocytoplasmic and chemokine signaling, proteostasis of hnRNPH3 and Mmp28, and development of amyotrophic lateral sclerosis-like syndromes

The pathogenic drivers of sporadic and familial motor neuron disease (MND), such amyotrophic lateral sclerosis (ALS), are unknown. MND impairs the Ran GTPase cycle, which controls nucleocytoplasmic transport, ribostasis and proteostasis; however, cause-effect mechanisms of Ran GTPase modulators in motoneuron pathobiology have remained elusive. The cytosolic and peripheral nucleoporin Ranbp2 is a crucial regulator of the Ran GTPase cycle and of the proteostasis of neurological disease-prone substrates, but the roles of Ranbp2 in motoneuron biology and disease remain unknown. This study shows that conditional ablation of Ranbp2 in mouse Thy1 motoneurons causes ALS syndromes with hypoactivity followed by hindlimb paralysis, respiratory distress and, ultimately, death. These phenotypes are accompanied by: a decline in the nerve conduction velocity, free fatty acids and phophatidylcholine of the sciatic nerve; a reduction in the g-ratios of sciatic and phrenic nerves; and hypertrophy of motoneurons. Furthermore, Ranbp2 loss disrupts the nucleocytoplasmic partitioning of the import and export nuclear receptors importin β and exportin 1, respectively, Ran GTPase and histone deacetylase 4. Whole-transcriptome, proteomic and cellular analyses uncovered that the chemokine receptor Cxcr4, its antagonizing ligands Cxcl12 and Cxcl14, and effector, latent and activated Stat3 all undergo early autocrine and proteostatic deregulation, and intracellular sequestration and aggregation as a result of Ranbp2 loss in motoneurons. These effects were accompanied by paracrine and autocrine neuroglial deregulation of hnRNPH3 proteostasis in sciatic nerve and motoneurons, respectively, and post-transcriptional downregulation of metalloproteinase 28 in the sciatic nerve. Mechanistically, our results demonstrate that Ranbp2 controls nucleocytoplasmic, chemokine and metalloproteinase 28 signaling, and proteostasis of substrates that are crucial to motoneuronal homeostasis and whose impairments by loss of Ranbp2 drive ALS-like syndromes.

Summary: Loss of Ranbp2 in spinal motoneurons drives ALS syndromes in mice and Ranbp2 functions in nucleocytoplasmic trafficking, proteostasis and chemokine signaling uncover novel therapeutic targets and mechanisms for motoneuron disease.

Human SOD1 ALS Mutations in a Drosophila Knock-In Model Cause Severe Phenotypes and Reveal Dosage-Sensitive Gain- and Loss-of-Function Components

Amyotrophic Lateral Sclerosis (ALS) is the most common adult-onset motor neuron disease and familial forms can be caused by numerous dominant mutations of the copper-zinc superoxide dismutase 1 (SOD1) gene. Substantial efforts have been invested in studying SOD1-ALS transgenic animal models; yet, the molecular mechanisms by which ALS-mutant SOD1 protein acquires toxicity are not well understood. ALS-like phenotypes in animal models are highly dependent on transgene dosage. Thus, issues of whether the ALS-like phenotypes of these models stem from overexpression of mutant alleles or from aspects of the SOD1 mutation itself are not easily deconvolved. To address concerns about levels of mutant SOD1 in disease pathogenesis, we have genetically engineered four human ALS-causing SOD1 point mutations (G37R, H48R, H71Y, and G85R) into the endogenous locus of Drosophila SOD1 (dsod) via ends-out homologous recombination and analyzed the resulting molecular, biochemical, and behavioral phenotypes. Contrary to previous transgenic models, we have recapitulated ALS-like phenotypes without overexpression of the mutant protein. Drosophila carrying homozygous mutations rendering SOD1 protein enzymatically inactive (G85R, H48R, and H71Y) exhibited neurodegeneration, locomotor deficits, and shortened life span. The mutation retaining enzymatic activity (G37R) was phenotypically indistinguishable from controls. While the observed mutant dsod phenotypes were recessive, a gain-of-function component was uncovered through dosage studies and comparisons with age-matched dsod null animals, which failed to show severe locomotor defects or nerve degeneration. We conclude that the Drosophila knock-in model captures important aspects of human SOD1-based ALS and provides a powerful and useful tool for further genetic studies.

αCAR IGF-1 vector targeting of motor neurons ameliorates disease progression in ALS mice

OBJECTIVE

We have previously described the generation of coxsackievirus and adenovirus receptor (α CAR)-targeted vector, and shown that intramuscular delivery in mouse leg muscles resulted in specific retrograde transduction of lumbar-motor neurons (MNs). Here, we utilized the α CAR-targeted vector to investigate the in vivo neuroprotective effects of lentivirally expressed IGF-1 for inducing neuronal survival and ameliorating the neuropathology and behavioral phenotypes of the SOD1^G93A mouse model of ALS.

METHODS

We produced cell factories of IGF-1 expressing lentiviral vectors (LVs) bearing α CAR or Vesicular Stomatitis Virus glycoprotein (VSV-G) on their surface so as to compare neuroprotection from MN transduced versus muscle transduced cells. We performed intramuscular delivery of either α CAR IGF-1 or VSVG IGF-1 LVs into key muscles of SOD1^G93A mice prior to disease onset at day 28. Motor performance, coordination and gait analysis were assessed weekly.

RESULTS

We observed substantial therapeutic efficacy only with the α CAR IGF-1 LV pretreatment with up to 50% extension of survival compared to controls. α CAR IGF-1 LV-treated animals retained muscle tone and had better motor performance during their prolonged survival. Histological analysis of spinal cord samples at end-stage further confirmed that α CAR IGF-1 LV treatment delays disease onset by increasing MN survival compared with age-matched controls. Intrastriatal injection of α CAR eGFP LV in rats leads to transduction of neurons and glia locally and neurons in olfactory bulb distally.

INTERPRETATION

Our data are indicative of the efficacy of the α CAR IGF-1 LV in this model and support its candidacy for early noninvasive neuroprotective therapy in ALS.