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July 10th 2017
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Canine Multifocal Retinopathy Type 2 (CMR2)

Description:

Canine Multifocal Retinopathy (CMR) is a hereditary disease caused by mutation G482A in exon 5 affecting Great Pyrenees, English Mastiffs, Bullmastiffs, Coton de Tulear and related breeds.


CMR can cause of range of symptoms from minor retinal folding to detached retinas and is very similar to Best Macular Dystrophy disease (BMD) in humans. Both BMD and CMR are retinal disorders caused by a mutation in VMD2 gene (Vitelliform Macular Dystrophy 2 Gene). VMD2 gene is responsible for coding a protein called bestrophin which is responsible for correct formation of pigment epithelium in retina. Mutations in VMAD2 gene cause pigment epithelium atrophy and potential reduction of sight.

 

In affected puppies, symptoms of CMR disease usually begin before 4 months of age. Rose-grey coloured lesions of different sizes and shapes occur in both eyes. Total blindness usually develops as the dog matures.


Canine Multifocal Retinopathy type 1 is a recessive disorder, meaning that the dog must have two copies (CMR2/CMR2) of the defective gene to suffer from the disease. Because CMR is a recessive disorder, an animal can also be a carrier (CMR2/n) of this disease, meaning it carries one copy of the mutation, but does not display any symptoms. A carrier dog can pass on this mutation to their offspring 50% of the time. If two carrier dogs are bred, there is a 25% chance of having affected (CMR2/CMR2) offspring.

Sample Type:

Animal Genetics accepts buccal swab, blood, and dewclaw samples for testing. Sample collection kits are available and can be ordered at Canine Test Now.

Test Is Relevant To the Following Breeds:

There are two types of CMR: CMR Type 1 and CMR Type 2. Which type you should test for depends on the breed:

 

Type 1: Great Pyrenees, English Mastiffs, Bullmastiffs, Australian Shepherds, Dogue de Bordeaux, English Bulldogs, American Bulldogs, Perro de Presa Canario, and Cane Corsos

 

Type 2: Coton de Tulears

Results:

Animal Genetics UK offers DNA testing for Canine Multifocal Retinopathy Type 2. The genetic test verifies the presence of the recessive mutation and presents results as one of the following:

CMR2/CMR2 Affected The dog carries two copies of the mutant gene and is homozygous for CMR2. This dog will be affected and will always pass on a copy of the mutated gene to its offspring.
CMR2/n Carrier Both the normal and mutant copies of the gene detected. Dog is a carrier for the CMR2 mutation and can pass on a copy of the defective gene to its offspring 50% of the time.
n/n Clear Dog tested negative for the gene mutation that causes CMR2 and will not pass on the defective gene to its offspring.