Juvenile-onset distal myopathy in Rottweiler dogs

COL6A1 related muscular dystrophy in Landseer dogs: A canine model for Ullrich congenital muscular dystrophy

BACKGROUND

Collagen VI related myopathies are congenital diseases of variable phenotype. The severe phenotype is referred to as Ullrich congenital muscular dystrophy. In this study, we describe analoguos clinical signs and histopathological alterations in Landseer dogs.

MATERIALS

We collected clinical data from two affected dogs and investigated the neuromuscular changes in five dogs from two different litters with immunohistochemistry and immunofluorescence. All affected dogs were homozygous for the p.Glu97* nonsense variant in the COL6A1 gene encoding the alpha-1 chain of collagen VI.

RESULTS

Muscle biopsies revealed alterations similar to those in human patients with Ullrich congenital muscular dystrophy including the virtual absence of collagen VI in skeletal muscles.

CONCLUSIONS

The clinical and pathological characterization of the affected Landseer dogs enhances the value of this animal model for human Ullrich congenital muscular dystrophy.

Protein Expression of Canine and Feline Muscular Dystrophies

Muscular dystrophies in dogs and cats represent a heterogeneous group of inherited, sometimes congenital, but infrequently diagnosed, progressive neuromuscular disorders. A correct identification and characterization of canine and feline muscular dystrophies could increase diagnostic and treatment strategies for veterinary neurologists and could identify useful animal models for the study of human dystrophies. However, in dogs and cats, diagnosis of muscular dystrophies is challenging due to a nonspecific clinical phenotype and pathological lesions, thus is most likely underestimated. We performed immunofluorescence and Western blot techniques using a wide panel of antibodies against proteins involved in human dystrophies (dystrophin mid-rod and carboxyterminal domain, α, β, γ, and δ-sarcoglycan, α-dystroglycan, caveolin-3, emerin, merosin, dysferlin, calpain-3, spectrin epitopes), on 9 canine and 3 feline muscle biopsies characterized by myopathic changes. Dystrophin deficiency was detected in 3 dogs and 2 novel canine muscular dystrophies have been identified, characterized by deficiency of caveolin-3 and calpain-3, respectively. In 2 cats, deficiency of β-SG and carboxyterminal domain of dystrophin in all muscle fibers has been detected. Performing immunofluorescence and Western blot analyses with a wider panel of antibodies allowed a correct identification of muscular dystrophies in dogs and cats and provides a direction for subsequent targeted genetic testing.

A Homozygous RAB3GAP1:c.743delC Mutation in Rottweilers with Neuronal Vacuolation and Spinocerebellar Degeneration

BACKGROUND

A variety of presumed hereditary, neurologic diseases have been reported in young Rottweilers. Overlapping ages of onset and clinical signs have made antemortem diagnosis difficult. One of these diseases, neuronal vacuolation and spinocerebellar degeneration (NVSD) shares clinical and histological features with polyneuropathy with ocular abnormalities and neuronal vacuolation (POANV), a recently described hereditary disease in Black Russian Terriers (BRTs). Dogs with POANV harbor mutations in RAB3GAP1 which codes for a protein involved in membrane trafficking.

HYPOTHESIS

Rottweilers with NVSD will be homozygous for the RAB3GAP1:c.743delC allele associated with POANV in BRTs.

ANIMALS

Eight Rottweilers with NVSD confirmed at necropsy, 128 Rottweilers without early onset neurologic signs, and 468 randomly selected dogs from 169 other breeds.

METHODS

Retrospective case-control study. Dogs were genotyped for the RAB3GAP1:c.743delC allele with an allelic discrimination assay.

RESULTS

All 8 NVSD-affected dogs were homozygous for the RAB3GAP1:c.743delC allele while the 128 NVSD-free Rottweilers were either homozygous for the reference allele (n = 105) or heterozygous (n = 23) and the 468 genotyped dogs from other breeds were all homozygous for the reference allele.

CONCLUSIONS AND CLINICAL IMPORTANCE

The RAB3GAP1:c.743delC mutation is associated with a similar phenotype in Rottweilers and BRTs. Identification of the mutation permits a DNA test that can aid in the diagnosis of NVSD and identify carriers of the trait so that breeders can avoid producing affected dogs. Disruption of membrane trafficking could explain the neuronal vacuolation seen in NVSD and other spongiform encephalopathies.

The paradox of muscle hypertrophy in muscular dystrophy

Mutations in the dystrophin gene cause Duchenne and Becker muscular dystrophy in humans and syndromes in mice, dogs, and cats. Affected humans and dogs have progressive disease that leads primarily to muscle atrophy. Mdx mice progress through an initial phase of muscle hypertrophy followed by atrophy. Cats have persistent muscle hypertrophy. Hypertrophy in humans has been attributed to deposition of fat and connective tissue (pseudohypertrophy). Increased muscle mass (true hypertrophy) has been documented in animal models. Muscle hypertrophy can exaggerate postural instability and joint contractures. Deleterious consequences of muscle hypertrophy should be considered when developing treatments for muscular dystrophy.

Degenerative neurological and neuromuscular disease in young rottweilers

A number of idiopathic degenerative diseases affecting the central nervous system, peripheral nerves and muscles of immature and young adult rottweilers are reported. Tetraparesis or ataxia causing abnormalities in gait and posture are clinical findings common to these conditions. The current knowledge about these syndromes is presented in this review, with an emphasis on the clinical characteristics. Knowledge of these syndromes and a methodical approach to neurological diagnosis can help the veterinarian to identify the underlying disease and establish a prognosis when presented with a tetraparetic or ataxic young rottweiler.

Muscular dystrophies and other inherited myopathies

It is certain that more inherited neuromuscular disorders of dogs and cats will be identified as the ability of practicing veterinarians to recognize disorders of muscle, nerve, and neuromuscular junction improves and newer diagnostic tests become available. Two specific points are critical. Before DNA-based genetic tests and specific therapies can be developed, an accurate description of the problem, clinically and histopathologically, must be performed. This is particularly important for the accuracy of a pedigree analysis, because inclusion of dogs with unrelated problems would alter the interpretation. Second, animals with inherited breed-associated disease should not be bred for generation of companion animals.