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Phenotype: Symptomatic onset of mucopolysaccharidosis VII occurs early and is progressive, with affected pups showing skeletal abnormalities, retarded development, excessively lax joints, and difficulty standing and walking.
Mode of Inheritance: Autosomal recessive
Alleles:N = Normal, MPS7bt = Mucopolysaccharidosis VII (Brazilian Terrier variant)
Breeds appropriate for testing: Brazilian Terrier
Explanation of Results:
- Dogs with N/N genotype will not have mucopolysaccharidosis VII and cannot transmit this variant to their offspring.
- Dogs with N/MPS7bt genotype will not have mucopolysaccharidosis VII, but are carriers. They will transmit this variant to 50% of their offspring. Matings between two carriers are predicted to produce 25% mucopolysaccharidosis VII-affected puppies.
- Dogs with MPS7bt/MPS7bt genotype will have mucopolysaccharidosis VII, a disabling, progressive condition.
Results of this test can be submitted to the OFA (Orthopedic Foundation for Animals)
Brazilian Terrier Health Panel
$105 per animal
Mucopolysaccharidosis VII (MPS VII) is a lysosomal storage disease characterized by accumulation of glycosaminoglycans (amino sugars) within cells. Glycosaminoglycans are found in cells involved with development of bone, cartilage, tendons, corneas, skin and connective tissue, and in fluid that lubricates joints. Under normal conditions of cell metabolism, these amino sugars are broken down into simpler sugars by the beta-glucuronidase enzyme encoded by the gene β- glucuronidase (GUSB). Mutations in the GUSB gene disrupt production or activity of this enzyme leading to an accumulation of amino sugars that causes permanent cell damage.
MPS VII disease has an early onset and is progressive. By one month of age, affected pups typically show shortened broad faces, low-set ears, and broad chests relative to unaffected littermates. By two months of age, corneal clouding is observed and differential development is apparent with affected dogs being roughly half the size of unaffected siblings. As the disease progresses, standing becomes difficult and joints become swollen and are easily dislocated. Additional clinical signs include cardiac abnormalities, tracheal narrowing, and glycosaminoglycans in the urine.
Two independent, breed-specific mutations in the GUSB gene result in MPS VII disease: c.866C>T in Brazilian Terriers (reported as MPS7bt) and c.497G>A in German Shepherd Dogs (reported as MPS7gs). In both cases, the disease is inherited in an autosomal recessive fashion, which means that males and females are equally affected and that two copies of the defective gene are needed to cause MPSVII. Dogs with one normal and one affected gene (carriers) are normal and show no signs of the disease.
Genetic testing for MPS VII assists clinicians with diagnosis of MPS VII and helps breeders identify carriers among breeding stock to avoid producing affected dogs. Matings between carriers are expected to produce 25% of affected puppies.