Accumulation and aggregate formation of mutant superoxide dismutase 1 in canine degenerative myelopathy

Allele and genotype frequencies for primary hereditary cataract, multifocal retinopathy 1, and degenerative myelopathy in Pyrenean Mountain dog from Italy

Pyrenean Mountain Dog (PMD) is an ancient dog breed firstly described in XIV century in the Pyrenees Region and nowadays diffused both in Europe and in the US. Hereditary Cataract (HC), defined as the inherited opacity of the lens, involves clinical signs ranging from reduced vision to glaucoma. A molecular basis of HC was firstly described in Staffordshire Bull Terriers and then reported in multiple canine breeds. The HC-associated variation is a single nucleotide deletion in HSF4 gene that introduces a premature stop codon (c.962del, p.Ala321*). Multifocal Retinopathy 1 (MR) is an ocular disorder characterized by multiple areas of retinal degeneration, caused in various dog breeds (including PMD) by a single nucleotide variant (SNV) in BEST1 gene that generates a premature stop codon (c.73G>A, p.Arg25*). Degenerative Myelopathy (DM) is an adult-onset, progressive neurodegenerative disease and it is associated to a SNV in SOD1 gene causing a change in aminoacidic sequence of the protein (c.118G>A, p.Glu40Lys). This causative variant has been described in various dog breeds, including PMD. Aim of this study was to determine the allele frequencies for the abovementioned three genetic diseases in the Italian breeding PMD population. The survey found no dogs carrying the allele (deletion) associated with HC, while three dogs (6 %) were heterozygous (G/A) for the MR-associated variant, and seven dogs (13 %) were heterozygous (G/A) for the DM-associated alteration, indicating that the variant alleles frequency were 0  %, 3 %, and 7 %, respectively. Appropriate mating management is suggested for the prevention of genetic diseases spreading in the PMD population.

Prevalence of SOD1 allele associated with degenerative myelopathy in canine population in Greece

Canine degenerative myelopathy (CDM) is a late-onset fatal disorder associated with a point mutation of the superoxide dismutase 1 (SOD1) gene (c.118G > A). The purpose of this study was to determine the genotype and allele frequencies of this mutation in 108 dogs, mainly in Belgian Malinois and German Shepherd dogs with (CDM-affected group) and without CDM clinical symptoms (control group) in Greece. Genotyping of the c.118G > A mutation was possible by Sanger sequencing and PCR-RFLP. The observed genotype frequencies for the control group were 89.4% for the homozygous (G/G), 9.6% for the heterozygous (A/G), and 0.96% for the homozygous mutant (A/A) allele. The mutant allele was not common in the Belgian Malinois dogs (allele frequency = 0.029), but quite common in the German Shepherd dogs (allele frequency = 0.138). In the CDM affected group, all 4 dogs were homozygous for the mutant allele. These frequencies were close to those expected, indicating no significant departure from Hardy-Weinberg equilibrium. A strong but not statistically significant association between the mutant allele and CDM was observed. A previously identified deletion upstream of the mutation of interest was found at a high frequency (0.361) in the population.

Intrinsic structural vulnerability in the hydrophobic core induces species-specific aggregation of canine SOD1 with degenerative myelopathy-linked E40K mutation

Canine degenerative myelopathy (DM), a fatal neurodegenerative disease in dogs, shares clinical and genetic features with amyotrophic lateral sclerosis (ALS), a human motor neuron disease. Mutations in the SOD1 gene encoding Cu/Zn superoxide dismutase (SOD1) cause canine DM and a subset of inherited human ALS. The most frequent DM causative mutation is homozygous E40K mutation which induces the aggregation of canine SOD1 but not of human SOD1. However, the mechanism through which canine E40K mutation induces species-specific aggregation of SOD1 remains unknown. By screening human/canine chimeric SOD1s, we identified that the humanized mutation of the 117th residue (M117L), encoded by exon 4, significantly reduced aggregation propensity of canine SOD1^E40K. Conversely, introducing a mutation of leucine 117 to methionine, a residue homologous to canine, promoted E40K-dependent aggregation in human SOD1. M117L mutation improved protein stability and reduced cytotoxicity of canine SOD1^E40K. Furthermore, crystal structural analysis of canine SOD1 proteins revealed that M117L increased the packing within the hydrophobic core of the β-barrel structure, contributing to the increased protein stability. Our findings indicate that the structural vulnerability derived intrinsically from Met 117 in the hydrophobic core of the β-barrel structure induces E40K-dependent species-specific aggregation in canine SOD1.

The incidence of genetic disease alleles in Australian Shepherd dog breed in European countries

Genetic disease control is generally not given the importance it deserves. Information about what percentage of individuals carry a disorder-causing mutation is crucial for breeders to produce healthy offspring and maintain a healthy dog population of a particular breed. This study aims to provide information about the incidence of mutant alleles for the most frequently occurring hereditary diseases in the Australian Shepherd dog breed (AS). The samples were collected during a 10-years period (2012-2022) in the European population of the AS. Mutant alleles and incidence were calculated from all the obtained data for all the diseases, specifically: collie eye anomaly (9.71%), canine multifocal retinopathy type 1 (0.53%), hereditary cataract (11.64%), progressive rod-cone degeneration (1.58%), degenerative myelopathy (11.77%) and bob-tail/short-tail (31.74%). Our data provide more information to dog breeders to support their effort to limit the spread of hereditary diseases.

Molecular Mechanisms of Aggregation of Canine SOD1 E40K Amyloidogenic Mutant Protein

Canine degenerative myelopathy (DM) is a human amyotrophic lateral sclerosis (ALS)-like neurodegenerative disease. It is a unique, naturally occurring animal model of human ALS. Canine DM is associated with the aggregation of canine superoxide dismutase 1 (cSOD1), which is similar to human ALS. Almost 100% of cases in dogs are familial, and the E40K mutation in cSOD1 is a major causative mutation of DM. Therefore, it is important to understand the molecular mechanisms underlying cSOD1(E40K) aggregation. To address this, we first analyzed the structural model of wild type cSOD1. Interactions were evident between amino acid E40 and K91. Therefore, the mutation at residue E40 causes loss of the interaction and may destabilize the native structure of cSOD1. Differential scanning fluorimetry revealed that the E40K mutant was less stable than the wild type. Moreover, stability could be recovered by the E40K and K91E double mutation. Acceleration of amyloid fibril formation in vitro and aggregate formation in cells of cSOD1(E40K) was also suppressed by the introduction of this double mutation in thioflavin T fluorescence assay results and in transfectant cells, respectively. These results clearly show the importance of the interaction between amino acid residues E40 and K91 in cSOD1 for the stability of the native structure and aggregation.

The inhibitory effects of MIF on accumulation of canine degenerative myelopathy-associated mutant SOD1 aggregation

Canine degenerative myelopathy (DM) is a progressive neurodegenerative disorder, which is commonly associated with c.118G > A (p. E40K) missense mutation in the superoxide dismutase 1 (SOD1) gene. Mutant SOD1 protein (SOD1E40K) is likely to be misfolded, acquire insolubility, aggregate in the cytoplasm of neural cells, and lead to degeneration of the nervous tissues. Along with a chaperone activity, macrophage migration inhibitory factor (MIF) is a multifunctional protein that has been shown to directly inhibit human mutant SOD1 misfolding and enhance survival of mutant SOD1-expressing motor neurons. The purpose of this study was to determine whether MIF also inhibits DM-related SOD1E40K misfolding and accumulation of SOD1 aggregates. Human embryonic kidney 293A cells were transfected SOD1cWT or SOD1E40K with or without MIF. The percentages of cells containing transfected SOD1 aggregates were measured by immunocytochemistry, and the amount of SOD1E40K in the insoluble fraction was evaluated by immunoblotting. The percentage of cells with SOD1E40K aggregates and the amount of insoluble SOD1E40K protein decreased in the presence of MIF. Because the chaperone activity of MIF assists in SOD1E40K folding and enhances the refolding and degradation of misfolded SOD1E40K, the results of this study suggests that MIF regulates the accumulation of SOD1 aggregates by its chaperone activity. We propose that enhancing intracellular MIF chaperone activity could be an effective therapeutic strategy for DM.

Molecular Epidemiological Survey for Degenerative Myelopathy in German Shepherd Dogs in Japan: Allele Frequency and Clinical Progression Rate

Canine degenerative myelopathy (DM) is an adult-onset, chronic, progressive neurodegenerative disease reported in multiple canine breeds, including the German Shepherd Dog (GSD). Clinical signs include progressive motor neuron paralysis, which begins in the pelvic limbs and eventually leads to respiratory distress, which may necessitate euthanasia. A common DM-associated mutation is a single nucleotide substitution that causes an amino acid substitution (c.118G>A, p.E40K) in the canine SOD1 gene. This SOD1 mutation and the clinical progression rate of A/A risk genotype in the Japanese GSD population have not been analyzed before. Therefore, the aim of this study was to determine the frequency of the mutated allele and analyze the clinical progression rate in the Japanese GSD population. We studied 541 GSDs registered with the Japanese German Shepherd Dog Registration Society between 2000 and 2019. Genotyping was performed using real-time PCR with DNA extracted from the hair roots of each dog. The study revealed 330 G/G dogs (61%), 184 G/A dogs (34%), and 27 A/A dogs (5%), indicating a frequency of the mutant allele of 0.220, which are in Hardy−Weinberg equilibrium. We analyzed the clinical signs in A/A dogs with an age limit of 10 years based on information obtained from the dogs’ owners. Of the seven A/A dogs older than 10 years, owners reported DM-related clinical signs, indicating a clinical progression rate of 100%. These results, further genotyping, and thorough clinical examinations of SOD1 A/A risk genotype will help control and prevent DM in the Japanese GSD population.

Novel oxindole compounds inhibit the aggregation of amyloidogenic proteins associated with neurodegenerative diseases

Amyloidogenic proteins form aggregates in cells, thereby leading to neurodegenerative disorders, including Alzheimer's and prion's disease, amyotrophic lateral sclerosis (ALS) in humans, and degenerative myelopathy (DM) and cognitive dysfunction in dogs. Hence, many small-molecule compounds have been screened to examine their inhibitory effects on amyloidogenic protein aggregation. However, no effective drug suitable for transition to clinical use has been found. Here we examined several novel oxindole compounds (GIF compounds) for their inhibitory effects on aggregate formation of the canine mutant superoxide dismutase 1 (cSOD1 E40K), a causative mutation resulting in DM, using Thioflavin-T fluorescence. Most GIF compounds inhibited the aggregation of cSOD1 E40K. Among the compounds, GIF-0854-r and GIF-0890-r were most effective. Their inhibitory effects were also observed in cSOD1 E40K-transfected cells. Additionally, GIF-0890-r effectively inhibited the aggregate formation of human SOD1 G93A, a causative mutation of ALS. GIF-0827-r and GIF-0856-r also effectively inhibited aggregate formation of human prion protein (hPrP). Subsequently, the correlation between their inhibitory effects on cSOD1 and hPrP aggregation was shown, indicating GIF compounds inhibited the aggregate formation of multiple amyloidogenic proteins. Conclusively, the novel oxindole compounds (GIF-0827-r, GIF-0854-r, GIF-0856-r, and GIF-0890-r) are proposed as useful therapeutic candidates for amyloidogenic neurodegenerative disorders.

In vitro evidence of propagation of superoxide dismutase-1 protein aggregation in canine degenerative myelopathy

Canine degenerative myelopathy (DM) is a progressive and fatal neurodegenerative disorder that has been linked to mutations in the superoxide dismutase 1 (SOD1) gene. The accumulation of misfolded protein aggregates in spinal neurons and astrocytes is implicated as an important pathological process in DM; however, the mechanism of protein aggregate formation is largely unknown. In human neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), cell-to-cell propagation of disease-relevant proteins has been demonstrated. Therefore, in this study, propagation of aggregation-forming property of mutant SOD1 protein in DM in vitro was investigated. This study demonstrated that aggregates composed of canine wild type SOD1 protein were increased by co-transfection with canine mutant SOD1 (E40K SOD1), indicating intracellular propagation of SOD1 aggregates. Further, aggregated recombinant SOD1 proteins were released from the cells, taken up by other cells, and induced further aggregate formation of normally folded SOD1 proteins. These results suggest intercellular propagation of SOD1 aggregates. The hypothesis of cell-to-cell propagation of SOD1 aggregates proposed in this study may underly the progressive nature of DM pathology.

Up-regulated spinal microRNAs induce aggregation of superoxide dismutase 1 protein in canine degenerative myelopathy

Canine degenerative myelopathy (DM) is a fatal progressive neurodegenerative disease. Mutations in the superoxide dismutase 1 (SOD1) gene have been shown to be the major risk factor for DM, and it is hypothesized that neural degeneration is caused by a "gain of toxic function" of mutant SOD1. In this study, the spinal cord microRNA (miRNA) profiles of DM-affected dogs were investigated to elucidate the pathomechanisms of DM. Quantification of 277 miRNAs identified three up-regulated miRNAs and 18 down-regulated miRNAs in the spinal cords of DM-affected dogs. Based on gene ontology analysis, the target cluster of up-regulated miRNAs was associated with protein expression or modification and cellular response, and that of down-regulated miRNAs was associated with tissue development. In these clusters, we focused on the mechanism of protein ubiquitination. Polyubiquitination assay demonstrated that canine SOD1 proteins were polyubiquitinated and degraded by proteasomes. Immunohistochemistry of the spinal cords of DM-affected dogs showed that mutant SOD1 aggregations were not ubiquitin immunopositive. Using cultured cells, co-transfection of canine SOD1 and up-regulated miRNA in DM-affected dogs demonstrated that miR-23a, miR-142 and miR-221 significantly increased the proportion of cells with mutant SOD1 aggregation. These results suggested that up-regulated miRNAs in the spinal cords of DM-affected dogs may inhibit ubiquitination of misfolded SOD1 protein and induce mutant SOD1 aggregations, leading to further progression of degenerative processes in the DM pathology.

Up-regulated inflammatory signatures of the spinal cord in canine degenerative myelopathy

Canine degenerative myelopathy (DM) is an adult-onset fatal disease characterized by progressive degeneration of the spinal cord. Affected dogs have homozygous mutations in superoxide dismutase 1, and thus DM is a potential spontaneous animal model of human familial amyotrophic lateral sclerosis (ALS). Neuroinflammation is the pathological hallmark of ALS, whereby proinflammatory cytokines and chemokines are overproduced by activated glial cells such as astrocytes and microglia. However, the detailed pathogenesis of spinal cord degeneration in DM remains unknown. To further characterize the pathological mechanism of DM, we analyzed the caudal cervical cords of ten Pembroke Welsh Corgis pathologically diagnosed with DM by quantitative real-time reverse transcription polymerase chain reaction, immunohistochemistry (IHC), and double immunofluorescence. Compared to control spinal cord tissues, we found significantly enhanced transcriptions of interleukin-1β, tumor necrosis factor-α, CC motif chemokine ligand (CCL) 2 and vascular cell adhesion molecule -1 mRNA in the spinal cords of DM dogs. Moreover, IHC for the class II major histocompatibility complex molecules HLA-DR and CCL2 indicated that the immunopositive areas of activated macrophages/microglia and CCL2 protein were significantly increased in DM, and CCL2 protein was mainly overproduced by astrocytes. Our results suggest a proinflammatory state of the microenvironment in the DM spinal cord in which activated microglia and astrocytes play important roles by secreting a set of cytokines, chemokines, and expressing adhesion molecules.

Canine SOD1 harboring E40K or T18S mutations promotes protein aggregation without reducing the global structural stability

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease associated with aggregation of superoxide dismutase 1 (SOD1) protein. More than 160 mutations in human SOD1 have been identified in familial ALS and extensively characterized in previous studies. Here, we investigated the effects of T18S and E40K mutations on protein aggregation of canine SOD1. These two mutations are exclusively found in canine degenerative myelopathy (an ALS-like neurodegenerative disease in dogs), whose phenotype is unknown at the level of protein folding. Interestingly, the T18S and E40K mutations did not alter far-UV CD spectrum, enzymatic activity, or global structural stability of canine SOD1. However, thioflavin-T assay and transmission electron microscopy analysis revealed that these mutations promote formation of fibrous aggregates, in particular in the Cu²⁺/Zn²⁺-unbound state. These evidence suggested that the T18S and E40K mutations promote protein aggregation through a unique mechanism, possibly involving destabilization of the local structure, reduction of net negative charge, or production of disulfide-linked oligomers.

Species-specific consequences of an E40K missense mutation in superoxide dismutase 1 (SOD1)

A glutamic acid to lysine (E40K) residue substitution in superoxide dismutase 1 (SOD1) is associated with canine degenerative myelopathy: the only naturally occurring large animal model of amyotrophic lateral sclerosis (ALS). The E40 residue is highly conserved across mammals, except the horse, which naturally carries the (dog mutant) K40 residue. Here we hypothesized that in vitro expression of mutant dog SOD1 would recapitulate features of human ALS (ie, SOD1 protein aggregation, reduced cell viability, perturbations in mitochondrial morphology and membrane potential, reduced ATP production, and increased superoxide ion levels); further, we hypothesized that an equivalent equine SOD1 variant would share similar perturbations in vitro, thereby explain horses' susceptibility to certain neurodegenerative diseases. As in human ALS, expression of mutant dog SOD1 was associated with statistically significant increased aggregate formation, raised superoxide levels (ROS), and altered mitochondrial morphology (increased branching (form factor)), when compared to wild-type dog SOD1-expressing cells. Similar deficits were not detected in cells expressing the equivalent horse SOD1 variant. Our data helps explain the ALS-associated cellular phenotype of dogs expressing the mutant SOD1 protein and reveals that species-specific sequence conservation does not necessarily predict pathogenicity. The work improves understanding of the etiopathogenesis of canine degenerative myelopathy.

In vitro evidence consistent with an interaction between wild-type and mutant SOD1 protein associated with canine degenerative myelopathy

Canine degenerative myelopathy (DM) is a progressive neurological disorder that may be considered to be a large animal model for specific forms of the fatal human disease, familial amyotrophic lateral sclerosis (fALS). DM is associated with a c118G>A mutation of the superoxide dismutase 1 (Sod1) gene, and a significant proportion of cases are inherited in an autosomal recessive manner in contrast to the largely, but not exclusively, dominant mode of inheritance in fALS. The consensus view is that these Sod1/SOD1 mutations result in a toxic gain of function but the mechanisms remain unclear. Here we used an in vitro neuroblastoma cell line transfection system to monitor wild-type and mutant forms of SOD1 fusion proteins containing either a Cherry or an enhanced green fluorescent protein (EGFP) tag. These fusion proteins retained SOD1 enzymatic activity on a native gel assay system. We demonstrate that SOD1 aggregate density is significantly higher in DM transfectants compared to wild-type. In addition, we show by co-immunoprecipitation and confocal microscopy, evidence for a potential interaction between wild-type and mutant forms of SOD1 in co-transfected cells. While in vitro studies have shown SOD1 heterodimer formation in fALS models, this is the first report for DM SOD1. Therefore, despite for the majority of cases there is a difference in the mode of inheritance between fALS and DM, a similar interaction between wild-type and mutant SOD1 forms can occur. Clarifying the role of SOD1 in DM may also be of benefit to understanding the role of SOD1 in fALS.

Canine Cognitive Dysfunction and Alzheimer's Disease - Two Facets of the Same Disease?

Neurodegenerative diseases present a major and increasing burden in the societies worldwide. With aging populations, the prevalence of neurodegenerative diseases is increasing, yet there are no effective cures and very few treatment options are available. Alzheimer’s disease is one of the most prevalent neurodegenerative conditions and although the pathology is well studied, the pathogenesis of this debilitating illness is still poorly understood. This is, among other reasons, also due to the lack of good animal models as laboratory rodents do not develop spontaneous neurodegenerative diseases and human Alzheimer’s disease is only partially mimicked by transgenic rodent models. On the other hand, older dogs commonly develop canine cognitive dysfunction, a disease that is similar to Alzheimer’s disease in many aspects. Dogs show cognitive deficits that could be paralleled to human symptoms such as disorientation, memory loss, changes in behavior, and in their brains, beta amyloid plaques are commonly detected both in extracellular space as senile plaques and around the blood vessels. Dogs could be therefore potentially a very good model for studying pathological process and novel treatment options for Alzheimer’s disease. In the present article, we will review the current knowledge about the pathogenesis of canine cognitive dysfunction, its similarities and dissimilarities with Alzheimer’s disease, and developments of novel treatments for these two diseases with a focus on canine cognitive dysfunction.

Plasma microRNA miR-26b as a potential diagnostic biomarker of degenerative myelopathy in Pembroke welsh corgis

BACKGROUND

Degenerative myelopathy (DM) is a progressive neurodegenerative disease frequently found in Pembroke Welsh Corgis (PWCs). Most DM-affected PWCs are homozygous for the mutant superoxide dismutase 1 (SOD1) allele; however, the genetic examination for the SOD1 mutation does not exclusively detect symptomatic dogs. In order to identify novel biomarkers, the plasma microRNA (miRNA) profiles of PWCs with DM were investigated.

RESULTS

Quantification of the plasma levels of 277 miRNAs by an RT-qPCR array identified 11 up-regulated miRNAs and 7 down-regulated miRNAs in DM-affected PWCs from those in wild-type SOD1 PWCs. A pathway analysis identified 3 miRNAs: miR-26b, miR-181a, and miR-196a, which potentially regulate several genes associated with SOD1. In order to validate the diagnostic accuracy of the candidate miRNAs in the aged PWC population, candidate miRNAs in plasma were measured by RT-qPCR and a receiver operating characteristic (ROC) curve analysis was performed. miR-26b had the largest area under the ROC curve for distinguishing DM PWCs from healthy PWCs (sensitivity, 66.7%; specificity, 87.0%). The plasma level of miR-26b was significantly higher in the DM group than in the healthy control group. A positive correlation was observed between increases in the plasma level of miR-26b and disease progression.

CONCLUSIONS

These results suggest that plasma miR-26b is a potential novel diagnostic biomarker of DM.

Protein disulphide isomerase is associated with mutant SOD1 in canine degenerative myelopathy

Canine degenerative myelopathy (DM) is a fatal neurodegenerative disorder prevalent in the canine population. It may represent a unique, naturally occurring disease model for human amyotrophic lateral sclerosis (ALS) because of similar clinical signs and association with superoxide dismutase 1 gene (SOD1) mutations. Misfolded SOD1 aggregates and endoplasmic reticulum (ER) stress are major pathophysiological features associated with ALS. Interestingly, an ER foldase, protein disulphide isomerase (PDI) is upregulated during ALS and it co-localizes with SOD1 inclusions in ALS patient tissues. Furthermore, mutations in the gene encoding PDI were recently associated with ALS. Given the genetic similarity between DM and ALS, we investigated whether ER stress and PDI were associated with DM. Protein extracts from spinal cord tissue of DM-affected dogs bearing a SOD1 mutation were examined for ER stress by western blotting. Immunohistochemical staining was also carried out to examine co-localization between endogenous PDI and SOD1 inclusions in spinal cord tissues of dogs affected with DM. PDI and CHOP, the proapoptotic protein induced during ER stress, were significantly upregulated in DM-affected dogs compared with controls. Furthermore, PDI co-localized with intracellular SOD1 aggregates in DM-affected dogs in all motor neurons examined, indicating that PDI may be a cellular defence mechanism against SOD1 misfolding in DM. Our results imply that ER stress is induced in DM-affected dogs; hence, it is a common pathological mechanism associated with both ALS and DM. The possibility that PDI may be a therapeutic target to inhibit SOD1 aggregation in DM dogs is also raised by this study.

The Role of Glia in Canine Degenerative Myelopathy: Relevance to Human Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive degeneration of motor neurons and grim prognosis. Over the last decade, studies on neurodegenerative diseases pointed on the role of glia in supporting the proper function of neurons. Particularly, oligodendrocytes were shown to be essential through myelin production and supplying axons with energy metabolites via monocarboxylate transporters (MCT). We have used dogs with naturally occurring degenerative myelopathy (DM) which closely resembles features observed in human ALS. We have performed two types of analysis of spinal cord tissue samples: histology and molecular analysis. Histology included samples collected from dogs that succumbed to the DM at different disease stages, which were compared to age-matched controls as well as put in the context of young spinal cords. Molecular analysis was performed on spinal cords with advanced DM and age-matched samples and included real-time PCR analysis of selected gene products related to the function of neurons, oligodendrocytes, myelin, and MCT. Demyelination has been detected in dogs with DM through loss of eriochrome staining and decreased expression of genes related to myelin including MBP, Olig1, and Olig2. The prominent reduction of MCT1 and MCT2 and increased MCT4 expression is indicative of disturbed energy supply to neurons. While Rbfox3 expression was not altered, the ChAT production was negatively affected. DM in dogs reproduces main features of human ALS including loss of motor neurons, dysregulation of energy supply to neurons, and loss of myelin, and as such is an ideal model system for highly translational studies on therapeutic approaches for ALS.

Degenerative myelopathy in the Collie breed: a retrospective immunohistochemical analysis of superoxide dismutase 1 in an affected Rough Collie, and a molecular epidemiological survey of the SOD1: c.118G>A mutation in Japan

Canine degenerative myelopathy (DM) is an adult-onset, progressive neurodegenerative disease that occurs in multiple dog breeds. A DM-associated mutation of the canine superoxide dismutase 1 (SOD1) gene, designated as c.118G>A (p.E40K), has been implicated as one of pathogenetic determinants of the disease in many breeds, but it remains to be determined whether the c.118G>A mutation is responsible for development or progression of DM in Collies. Previously, a Rough Collie was diagnosed clinically and histopathologically as having DM in Japan, suggesting the possibility that the Collie breed may be predisposed to DM due to the high frequency of c.118G>A in Japan. In this study, accumulation and aggregate formation of SOD1 protein were retrospectively demonstrated in the spinal cord of the DM-affected dog by immunohistochemical analysis. Furthermore, a molecular epidemiological survey revealed a high carrier rate (27.6%) and mutant allele frequency (0.138) of c.118G>A in a population of Collies in Japan, suggesting that the Collie breed may be predisposed to DM associated with c.118G>A, and the prevention of DM in Collies in Japan should be addressed through epidemiological and genetic testing strategies.