Variants in CLCN1 and PDE4C Associated with Muscle Hypertrophy, Dysphagia, and Gait Abnormalities in Young French Bulldogs.

(1) Background: Muscle hypertrophy, swallowing disorders, and gait abnormalities are clinical signs common to many muscle diseases, including muscular dystrophies, non-dystrophic myotonias, genetic myopathies associated with deficiency of myostatin, and acquired inflammatory myopathies. Here, we investigated underlying causes of this triad of clinical signs in four young French bulldogs via muscle histopathology coupled with whole genome and Sanger sequencing. (2) Methods: Dogs were evaluated by veterinary clinical internists and neurologists, and biopsies were obtained for histopathological diagnosis. DNA was submitted for whole genome sequencing, followed by bioinformatics evaluation and confirmation of variants via Sanger sequencing in two cases. (3) Results: Two novel variants were identified. The first, found in two related French bulldogs, was a homozygous variant in the chloride channel gene CLCN1 known to cause non-dystrophic congenital myotonia, and the second, found in an unrelated French bulldog, was a heterozygous variant in the cAMP phosphodiesterase gene PDE4C, which is the major phosphodiesterase expressed in skeletal muscle and may play a role in decreasing muscle atrophy. An underlying molecular basis in one other case has not yet been identified. (4) Conclusions: Here, we identified two novel variants, one in the CLCN1 and one in the PDE4C gene, associated with clinical signs of muscle hypertrophy, dysphagia, and gait abnormalities, and we suggested other bases of these phenotypes in French bulldogs that are yet to be discovered. Identification of genes and deleterious variants associated with these clinical signs may assist breeders in improving the overall health of this very popular breed and may lead to the identification of new therapies to reverse muscle atrophy in people and animals with neuromuscular diseases.

NDUFS7 variant in dogs with Leigh syndrome and its functional validation in a Drosophila melanogaster model.

Two Jack-Russell Terrier × Chihuahua mixed-breed littermates with Leigh syndrome were investigated. The dogs presented with progressive ataxia, dystonia, and increased lactate levels. Brain MRI showed characteristic bilateral symmetrical T2 hyperintense lesions, histologically representing encephalomalacia. Muscle histopathology revealed accumulation of mitochondria. Whole genome sequencing identified a missense variant in a gene associated with human Leigh syndrome, NDUFS7:c.535G > A or p.(Val179Met). The genotypes at the variant co-segregated with the phenotype in the investigated litter as expected for a monogenic autosomal recessive mode of inheritance. We investigated the functional consequences of the missense variant in a Drosophila melanogaster model by expressing recombinant wildtype or mutant canine NDUFS7 in a ubiquitous knockdown model of the fly ortholog ND-20. Neither of the investigated overexpression lines completely rescued the lethality upon knockdown of the endogenous ND-20. However, a partial rescue was found upon overexpression of wildtype NDUFS7, where pupal lethality was moved to later developmental stages, which was not seen upon canine mutant overexpression, thus providing additional evidence for the pathogenicity of the identified variant. Our results show the potential of the fruit fly as a model for canine disease allele validation and establish NDUFS7:p.(Val179Met) as causative variant for the investigated canine Leigh syndrome.

Precision medicine using whole genome sequencing identifies a novel dystrophin (DMD) variant for X-linked muscular dystrophy in a cat.

BACKGROUND: Muscular dystrophies (MDs) are a large, heterogeneous group of degenerative muscle diseases. X-linked dystrophin-deficient MD in cats is the first genetically characterized cat model for a human disease and a few novel forms have been identified. HYPOTHESIS/OBJECTIVES: Muscular dystrophy was suspected in a young male domestic shorthair cat. Clinical, molecular, and genetic techniques could provide a definitive diagnosis. ANIMALS: A 1-year-old male domestic shorthair cat presented for progressive difficulty walking, macroglossia and dysphagia beginning at 6 months of age. The tongue was thickened, protruded with constant ptyalism, and thickening and rigidity of the neck and shoulders were observed. METHODS: A complete neurological examination, baseline laboratory evaluation and biopsies of the trapezius muscle were performed with owner consent. Indirect immunofluorescence staining of muscle cryosections was performed using several monoclonal and polyclonal antibodies against dystrophy-associated proteins. DNA was isolated for genomic analyses by whole genome sequencing and comparison to DNA variants in the 99 Lives Cat Genome Sequencing dataset. RESULTS AND CLINICAL IMPORTANCE: Aspartate aminotransferase (687 IU/L) and creatine kinase (24 830 IU/L) activities were increased and mild hypokalemia (3.7 mmol/L) was present. Biopsy samples from the trapezius muscle confirmed a degenerative and regenerative myopathy and protein alterations identified by immunohistochemistry resulted in a diagnosis of a in dystrophin-deficient form of X-linked MD. A stop gain variant (c.4849C>T; p.Gln1617Ter) dystrophin was identified by genome sequencing. Precision/genomic medicine efforts for the domestic cat and in veterinary medicine support disease variant and animal model discovery and provide opportunities for targeted treatments for companion animals.

Combination HSCT and intravenous AAV-mediated gene therapy in a canine model proves pivotal for translation of Krabbe disease therapy.

Hematopoietic stem cell transplantation (HSCT) is the only approved treatment for presymptomatic infantile globoid cell leukodystrophy (GLD [Krabbe disease]). However, correction of disease is not complete, and outcomes remain poor. Herein we evaluated HSCT, intravenous (IV) adeno-associated virus rh10 vector (AAVrh10) gene therapy, and combination HSCT + IV AAVrh10 in the canine model of GLD. While HSCT alone resulted in no increase in survival as compared with untreated GLD dogs (∼16 weeks of age), combination HSCT + IV AAVrh10 at a dose of 4E13 genome copies (gc)/kg resulted in delayed disease progression and increased survival beyond 1 year of age. A 5-fold increase in AAVrh10 dose to 2E14 gc/kg, in combination with HSCT, normalized neurological dysfunction up to 2 years of age. IV AAVrh10 alone resulted in an average survival to 41.2 weeks of age. In the peripheral nervous system, IV AAVrh10 alone or in addition to HSCT normalized nerve conduction velocity, improved ultrastructure, and normalized GALC enzyme activity and psychosine concentration. In the central nervous system, only combination therapy at the highest dose was able to restore galactosylceramidase activity and psychosine concentrations to within the normal range. These data have now guided clinical translation of systemic AAV gene therapy as an addition to HSCT (NCT04693598, NCT05739643).

Novel COL6A3 frameshift variant in American Staffordshire Terrier dogs with Ullrich-like congenital muscular dystrophy.

Two (male and female) 10-month-old American Staffordshire Terrier littermates presented for progressive weakness, joint contracture, and distal limb joint hyperlaxity beginning around 6 months of age. Neurological examination, serum creatine kinase activity, infectious disease titers, cerebrospinal fluid analysis, and electrodiagnostic testing were performed. Muscle biopsies were collected for histopathology and immunofluorescence staining for localization of dystrophy associated proteins. Whole-genome sequencing (WGS) was performed on 1 affected dog. Variants were compared to a database of 671 unaffected dogs of multiple breeds. Histopathology confirmed a dystrophic phenotype and immunofluorescence staining of muscle cryosections revealed an absence of staining for collagen-6. WGS identified a homozygous 1 bp deletion in the COL6A3 gene, unique to the first affected dog. Sanger sequencing confirmed the homozygous presence of the frameshift variant in both affected dogs. This report describes the clinical features and most likely genetic basis of an Ullrich-like recessively inherited form of congenital muscular dystrophy in American Staffordshire Terriers.

A SACS deletion variant in Great Pyrenees dogs causes autosomal recessive neuronal degeneration.

ARSACS (autosomal recessive spastic ataxia of Charlevoix-Saguenay) is a human neurological disorder characterized by progressive cerebellar ataxia and peripheral neuropathy. A recently recognized disorder in Great Pyrenees dogs is similarly characterized by widespread central nervous system degeneration leading to progressive cerebellar ataxia and spasticity, combined with peripheral neuropathy. Onset of clinical signs occurred in puppies as young as 4 months of age, with slow progression over several years. A multi-generation pedigree suggested an autosomal recessive mode of inheritance. Histopathology revealed consistent cerebellar Purkinje cell degeneration, neuronal degeneration in brainstem nuclei, widespread spinal cord white matter degeneration, ganglion cell degeneration, inappropriately thin myelin sheaths or fully demyelinated peripheral nerve fibers, and normal or only mild patterns of denervation atrophy in skeletal muscles. Genome-wide single nucleotide polymorphism (SNP) genotype data was collected from 6 cases and 26 controls, where homozygosity mapping identified a 3.3 Mb region on CFA25 in which all cases were homozygous and all controls were either heterozygous or homozygous for alternate haplotypes. This region tagged the SACS gene where variants are known to cause ARSACS. Sanger sequencing of SACS in affected dogs identified a 4 bp deletion that causes a frame shift and truncates 343 amino acids from the C terminus of the encoded sacsin protein (p.Val4244AlafsTer32). Our clinical and histopathological descriptions of this canine disorder contribute to the description of human ARSACS and represents the first naturally occurring large animal model of this disorder.

Current Classification of Canine Muscular Dystrophies and Identification of New Variants.

The spectrum of canine muscular dystrophies has rapidly grown with the recent identification of several more affected breeds and associated mutations. Defects include those in genes and protein products associated with the sarcolemma (dystrophin deficient X-linked muscular dystrophy and sarcoglycan-deficient limb-girdle muscular dystrophy) and with the extracellular matrix (collagen 6, laminin α2, and α-dystroglycan-deficient congenital muscular dystrophies). With the increasing application of whole genome sequencing and whole exome sequencing, the clinical and pathological spectra associated with specific neuromuscular genetic defects are constantly evolving. In this report, we provide a brief overview of the current status of gene defects reported in canine muscular dystrophies. We also report the causative mutations for novel forms of X-linked muscular dystrophy in Brittany spaniels and in a French bulldog.

Canine models of Charcot-Marie-Tooth: MTMR2, MPZ, and SH3TC2 variants in golden retrievers with congenital hypomyelinating polyneuropathy.

Congenital hypomyelinating polyneuropathy (HPN) restricted to the peripheral nervous system was reported in 1989 in two Golden Retriever (GR) littermates. Recently, four additional cases of congenital HPN in young, unrelated GRs were diagnosed via neurological examination, electrodiagnostic evaluation, and peripheral nerve pathology. Whole-genome sequencing was performed on all four GRs, and variants from each dog were compared to variants found across >1,000 other dogs, all presumably unaffected with HPN. Likely causative variants were identified for each HPN-affected GR. Two cases shared a homozygous splice donor site variant in MTMR2, with a stop codon introduced within six codons following the inclusion of the intron. One case had a heterozygous MPZ isoleucine to threonine substitution. The last case had a homozygous SH3TC2 nonsense variant predicted to truncate approximately one-half of the protein. Haplotype analysis using 524 GR established the novelty of the identified variants. Each variant occurs within genes that are associated with the human Charcot-Marie-Tooth (CMT) group of heterogeneous diseases, affecting the peripheral nervous system. Testing a large GR population (n = >200) did not identify any dogs with these variants. Although these variants are rare within the general GR population, breeders should be cautious to avoid propagating these alleles.

An Inflammatory Myopathy in the Dutch Kooiker Dog.

The Dutch Kooiker dog (het Nederlandse Kooikerhondje) is one of nine Dutch dog breeds. As of 1960, a number of heritable diseases have been noted in this breed. One is an inflammatory myopathy that emerged in 1972, with numbers of affected dogs gradually increasing during the last few decades. The objective of this paper is to describe clinical signs, laboratory results, electromyography and histopathology of the muscle biopsies of the affected dogs. Method: Both retrospectively as well as prospectively affected Kooiker dogs were identified and categorized using a Tiered level of Confidence. Results: In total, 160 Kooiker dogs-40 Tier I, 33 Tier II and 87 Tier III-were included. Clinical signs were (1) locomotory problems, such as inability to walk long distances, difficulty getting up, stiff gait, walking on eggshells; (2) dysphagia signs such as drooling, difficulty eating and/or drinking; or (3) combinations of locomotory and dysphagia signs. CK activities were elevated in all except for one dog. Histopathology revealed a predominant lymphohistiocytic myositis with a usually low and variable number of eosinophils, neutrophils and plasma cells. It is concluded that, within this breed, a most likely heritable inflammatory myopathy occurs. Further studies are needed to classify this inflammatory myopathy, discuss its treatment, and unravel the genetic cause of this disease to eradicate it from this population.

A Nonsense Variant in the DMD Gene Causes X-Linked Muscular Dystrophy in the Maine Coon Cat.

(1) Feline dystrophin-deficient muscular dystrophy (ddMD) is a fatal disease characterized by progressive weakness and degeneration of skeletal muscles and is caused by variants in the DMD gene. To date, only two feline causal variants have been identified. This study reports two cases of male Maine coon siblings that presented with muscular hypertrophy, growth retardation, weight loss, and vomiting. (2) Both cats were clinically examined and histopathology and immunofluorescent staining of the affected muscle was performed. DMD mRNA was sequenced to identify putative causal variants. (3) Both cats showed a significant increase in serum creatine kinase activity. Electromyography and histopathological examination of the muscle samples revealed abnormalities consistent with a dystrophic phenotype. Immunohistochemical testing revealed the absence of dystrophin, confirming the diagnosis of dystrophin-deficient muscular dystrophy. mRNA sequencing revealed a nonsense variant in exon 11 of the feline DMD gene, NC_058386.1 (XM_045050794.1): c.1180C > T (p.(Arg394*)), which results in the loss of the majority of the dystrophin protein. Perfect X-linked segregation of the variant was established in the pedigree. (4) ddMD was described for the first time in the Maine coon and the c.1180C>T variant was confirmed as the causal variant.

Dystrophin-Deficient Muscular Dystrophy in Two Male Juvenile Brittanys.

A 6 mo old and a 7 mo old male intact Brittany were presented for progressive exercise intolerance, failure to grow, and dysphagia. Creatine kinase activity was markedly and persistently elevated in both dogs. Based on the neurological examination, clinical signs localized to the neuromuscular system. Electromyography revealed complex repetitive discharges in multiple muscle groups. Immunofluorescence of biopsies confirmed dystrophin-deficient muscular dystrophy. This is the first report describing dystrophin-deficient muscular dystrophy in the Brittany breed. Currently, no specific therapies are available for this form of myopathy. The presence of dystrophin deficiency in the two dogs suggests an inherited myopathy rather than a spontaneous mutation. The location of the dogs in the United States and Japan suggests a wide distribution of this dystrophy and should alert clinicians to the existence of this myopathy in the Brittany breed. A mutation in the DMD gene has not yet been identified.

X-linked myotubular myopathy associated with an MTM1 variant in a Maine coon cat.

OBJECTIVE: Describe the clinical course and diagnostic and genetic findings in a cat with X-linked myotubular myopathy. CASE SUMMARY: A 7-month-old male Maine coon was evaluated for progressively worsening gait abnormalities and generalized weakness. Neurolocalization was to the neuromuscular system. Genetic testing for spinal muscular atrophy (LIX1) was negative. Given the progressive nature and suspected poor long-term prognosis, the owners elected euthanasia. Histopathology of skeletal muscle obtained post-mortem disclosed numerous rounded atrophic or hypotrophic fibers with internal nuclei or central basophilic staining. Using oxidative reactions mediated by cytochrome C oxidase and succinic dehydrogenase, scattered myofibers were observed to have central dark staining structures and a "ring-like" appearance. Given the cat's age and clinical history, a congenital myopathy was considered most likely, with the central nuclei and "ring-like" changes consistent with either centronuclear or myotubular myopathy. Whole genome sequencing identified an underlying missense variant in myotubularin 1 (MTM1), a known candidate gene for X-linked myotubular myopathy. NEW OR UNIQUE INFORMATION PROVIDED: This case is the first report of X-linked myotubular myopathy in a cat with an MTM1 missense mutation. Maine coon cat breeders may consider screening for this variant to prevent production of affected cats and to eradicate the variant from the breeding population.

Glossitis in an older non-corgi dog: Diagnosis and long-term follow-up.

A 9-year-old spayed female 18.8 kg mixed breed boxer dog was referred for evaluation of a 7-month history of difficulty swallowing and prehending food, regurgitation, hypersalivation, and an abnormal dorsiflexion of the tongue. Prior to referral, a barium study was performed, which revealed a mildly dilated esophagus. Treatment with sucralfate, cisapride, and prednisone was initiated. Physical examination revealed bilateral, symmetric atrophy of the temporalis muscles, dorsiflexion of the distal aspect of the tongue with concurrent muscle atrophy, and a reduced gag reflex. Electrodiagnostic examinations revealed spontaneous electrical activity in the muscles of mastication and tongue. Biopsies from the right temporalis, tongue, and biceps femoris muscles were collected. An immune-mediated myositis with fibrosis, scattered CD3, CD4, and CD8+ T-lymphocytes, and upregulation of markers for major histocompatibility antigens were observed in the tongue and temporalis muscles. The dog was treated with a tapering course of prednisone over 2 months and cyclosporine long-term. The dog was maintained on cyclosporine alone for > 2 years and clinical signs remained static, although multiple episodes of aspiration pneumonia occurred. Ultimately, euthanasia was performed due to chronic kidney disease with associated anemia, lethargy, and anorexia.

Glossite chez un chien âgé non-corgi : diagnostic et suivi à long terme. Une chienne boxer de race mixte de 18,8 kg stérilisée âgée de 9 ans a été référée pour l'évaluation d'une histoire de 7 mois de difficulté à avaler et de préhension des aliments, de régurgitation, d'hypersalivation et d'une dorsiflexion anormale de la langue. Avant la référence, un examen baryté a été réalisée et a révélé un oesophage légèrement dilaté. Un traitement par sucralfate, cisapride et prednisone a été initié. L'examen physique a révélé une atrophie bilatérale et symétrique des muscles temporaux, une flexion dorsale de la face distale de la langue avec atrophie musculaire concomitante et un réflexe nauséeux réduit. Les examens électrodiagnostiques ont révélé une activité électrique spontanée dans les muscles de la mastication et de la langue. Des biopsies des muscles temporaux droits, de la langue et du biceps fémoral ont été recueillies. Une myosite à médiation immunitaire avec fibrose, des lymphocytes T CD3, CD4 et CD8+ dispersés et une régulation positive des marqueurs des principaux antigènes d'histocompatibilité ont été observées dans la langue et les muscles temporaux. Le chien a été traité avec une posologie décroissante de prednisone sur 2 mois et de cyclosporine à long terme. Le chien a été maintenu sous cyclosporine seule pendant > 2 ans et les signes cliniques sont restés stables, bien que plusieurs épisodes de pneumonie par aspiration se soient produits. En fin de compte, l'euthanasie a été pratiquée en raison d'une maladie rénale chronique associée à une anémie, une léthargie et une anorexie.(Traduit par Dr Serge Messier).

Tandem duplication within the DMD gene in Labrador retrievers with a mild clinical phenotype.

A form of dystrophinopathy with mild or subclinical neuromuscular signs has been previously reported in a family of Labrador retrievers. Markedly and persistently elevated creatine kinase activity was first noted at 6 months of age. Skeletal muscle biopsies revealed a dystrophic phenotype, with dystrophin non-detectable on western blotting and immunohistochemical staining, and with increased utrophin expression. In this report we demonstrate with western blotting that α-dystroglycan is present at essentially normal levels. Whole genome sequencing has also now revealed an approximately 400kb tandem genomic DNA duplication including exons 2-7 of the DMD gene that was inserted into intron 7 of the wild type gene. Skeletal muscle cDNA from 2 cases contained DMD transcripts as expected from an in-frame properly-spliced exon 2-7 tandem insertion. A similar 5' duplication involving DMD exons 2-7 has been reported in a human family with dilated cardiomyopathy but without skeletal myopathy. This is the 3rd confirmed mutation in the DMD gene in Labrador retrievers.

An EHPB1L1 Nonsense Mutation Associated with Congenital Dyserythropoietic Anemia and Polymyopathy in Labrador Retriever Littermates.

In this report, we describe a novel genetic basis for congenital dyserythropoietic anemia and polymyopathy in Labrador Retriever littermates characterized by incidental detection of marked microcytosis, inappropriate metarubricytosis, pelvic limb weakness and muscle atrophy. A similar syndrome has been described in English Springer Spaniel littermates with an early onset of anemia, megaesophagus, generalized muscle atrophy and cardiomyopathy. Muscle histopathology in both breeds showed distinctive pathological changes consistent with congenital polymyopathy. Using whole genome sequencing and mapping to the CanFam4 (Canis lupus familiaris reference assembly 4), a nonsense variant in the EHBP1L1 gene was identified in a homozygous form in the Labrador Retriever littermates. The mutation produces a premature stop codon that deletes approximately 90% of the protein. This variant was not present in the English Springer Spaniels. Currently, EHPB1L1 is described as critical to actin cytoskeletal organization and apical-directed transport in polarized epithelial cells, and through connections with Rab8 and a BIN1-dynamin complex generates membrane vesicles in the endocytic recycling compartment. Furthermore, EHBP1L1 knockout mice die early and develop severe anemia. The connection of EHBP1L1 to BIN1 and DMN2 functions is particularly interesting due to BIN1 and DMN2 mutations being causative in forms of centronuclear myopathy. This report, along with an independent study conducted by another group, are the first reports of an association of EHBP1L1 mutations with congenital dyserythropoietic anemia and polymyopathy.

Congenital muscular dystrophy in a dog with a LAMA2 gene deletion.

A 2-year-old female spayed dog was presented with a chronic history of short-strided gait and inability to completely open the jaw. Clinical signs were present since the dog was adopted from a humane society at a few months of age. Serum creatine kinase activity was abnormally high. Neurological examination, electromyography, muscle biopsies with immunofluorescent staining, and whole genome sequencing (WGS) were performed. A dystrophic phenotype was identified histologically in muscle biopsies, deficiency of laminin α2 protein was confirmed by immunofluorescent staining, and a deletion in the LAMA2 gene was identified by analysis of the WGS data. Congenital muscular dystrophy associated with a disease variant in LAMA2 was identified.

LAMA2 Nonsense Variant in an Italian Greyhound with Congenital Muscular Dystrophy.

A 4-month-old, male Italian Greyhound with clinical signs of a neuromuscular disease was investigated. The affected dog presented with an abnormal short-strided gait, generalized muscle atrophy, and poor growth since 2-months of age. Serum biochemistry revealed a marked elevation in creatine kinase activity. Electrodiagnostic testing supported a myopathy. Histopathology of muscle biopsies confirmed a dystrophic phenotype with excessive variability in myofiber size, degenerating fibers, and endomysial fibrosis. A heritable form of congenital muscular dystrophy (CMD) was suspected, and a genetic analysis initiated. We sequenced the genome of the affected dog and compared the data to that of 795 control genomes. This search revealed a private homozygous nonsense variant in LAMA2, XM_022419950.1:c.3285G>A, predicted to truncate 65% of the open reading frame of the wild type laminin α2 protein, XP_022275658.1:p.(Trp1095*). Immunofluorescent staining performed on muscle cryosections from the affected dog confirmed the complete absence of laminin α2 in skeletal muscle. LAMA2 loss of function variants were shown to cause severe laminin α2-related CMD in humans, mouse models, and in one previously described dog. Our data together with current knowledge on other species suggest the LAMA2 nonsense variant as cause for the CMD phenotype in the investigated dog.

Clinical presentation, MRI, histopathology and outcome in a cat with immune-mediated masticatory myositis.

CASE SUMMARY: A 4-year-old female spayed domestic shorthair cat was presented with facial swelling, ocular discharge and intermittent bilateral exophthalmos. Haematology revealed mild eosinophilia. Serum biochemistry showed a markedly elevated creatine kinase activity. MRI of the head revealed diffuse and severe changes of the masticatory muscles, including irregular areas compatible with fluid or necrosis within the abnormal muscle tissue. Cytological analysis of the left temporal muscle revealed eosinophilic and macrophagic inflammation. Bacterial and fungal cultures were negative. Serological titres against Toxoplasma gondii were compatible with previous exposure. A canine ELISA against masticatory muscle type IIM fibre proteins was positive at 1:4000 (reference interval <1:100). Histopathological examination of the left temporalis muscle revealed moderately severe and multifocal myositis. A diagnosis of immune-mediated masticatory myositis was made and immunosuppressive therapy was started. The cat initially responded to tapering doses of prednisolone, but subsequent relapses required therapy modulation. At the time of writing, 27 months after the initial diagnosis, the cat was in remission, but was diagnosed with diabetes mellitus, probably secondary to chronic glucocorticoid use. RELEVANCE AND NOVEL INFORMATION: To our knowledge, this is the first case report to describe the MRI appearance of masticatory myositis in a cat and the second to describe the clinical presentation, histopathology, response to treatment and outcome in a cat with this condition.

Muscular dystrophy-dystroglycanopathy in a family of Labrador retrievers with a LARGE1 mutation.

Alpha-dystroglycan (αDG) is a highly glycosylated cell surface protein with a significant role in cell-to-extracellular matrix interactions in muscle. αDG interaction with extracellular ligands relies on the activity of the LARGE1 glycosyltransferase that synthesizes and extends the heteropolysaccharide matriglycan. Abnormalities in αDG glycosylation and formation of matriglycan are the pathogenic mechanisms for the dystroglycanopathies, a group of congenital muscular dystrophies. Muscle biopsies were evaluated from related 6-week-old Labrador retriever puppies with poor suckling, small stature compared to normal litter mates, bow-legged stance and markedly elevated creatine kinase activities. A dystrophic phenotype with marked degeneration and regeneration, multifocal mononuclear cell infiltration and endomysial fibrosis was identified on muscle cryosections. Single nucleotide polymorphism (SNP) array genotyping data on the family members identified three regions of homozygosity in 4 cases relative to 8 controls. Analysis of whole genome sequence data from one of the cases identified a stop codon mutation in the LARGE1 gene that truncates 40% of the protein. Immunofluorescent staining and western blotting demonstrated the absence of matriglycan in skeletal muscle and heart from affected dogs. Compared to control, LARGE enzyme activity was not detected. This is the first report of a dystroglycanopathy in dogs.

Progressive increases in creatine kinase activity in an anorexic cat with necrotising myopathy.

CASE SUMMARY: A 5-year-old castrated male domestic shorthair cat with weight loss and reduced appetite was evaluated for increased and progressively rising creatine kinase (CK) activity. The cat had recently been diagnosed with hepatic lipidosis. Muscle biopsy and histopathology revealed mild myonecrosis and phagocytosis without obvious inflammatory cell infiltrates. Resolution of necrotising myopathy was observed after a short course of anti-inflammatory prednisolone and nutritional supplementation. RELEVANCE AND NOVEL INFORMATION: This is the first report of a necrotising myopathy in a cat associated with progressively increasing CK activity and decreased appetite. Anorexia in cats has been associated with increased CK activity, but an underlying cause of this CK elevation has only been postulated. Here we document muscle necrosis and muscle stiffness in a cat with anorexia.