UC Davis School of Veterinary Medicine Veterinary Genetics Laboratory

Canine Multifocal Retinopathy2 (CMR2)

Canine Multifocal Retinopathy 2 (CMR2) in an inherited eye disease caused by a mutation (c.482G>A) in the Bestrophin 1 gene that disrupts protein function. Affected dogs typically present with multiple, discrete circular areas of retinal detachment around 15 weeks of age. Fluid accumulates under the detached retina resulting in gray, tan, orange or pink “blisters” in the eye. Progression of retinal changes is slow, ceases by 1 year of age and does not lead to blindness. In some cases, the blisters appear to heal as the dog ages although vision loss has been reported. The disease is inherited in an autosomal recessive fashion thus two copies of the CMR2 mutation must be present to cause the disease. Breeding two carriers is predicted to produce 25% affected pups.

Canine Multifocal Retinopathy3 (CMR3)

Canine Multifocal Retinopathy 3 (CMR3) is an inherited eye disease caused by a deletion (C1388del) in the Bestrophin 1 gene that results in incomplete protein formation. Affected dogs typically present with multiple, discrete circular areas of retinal detachment between 9 and 24 months of age. Fluid accumulates under the detached retina resulting in gray, tan, orange or pink “blisters” in the eye. Progression of retinal changes is usually slow and does not lead to blindness. In some cases the blisters appear to heal as the dog ages but vision loss has been reported. The disease is inherited in an autosomal recessive fashion thus two copies a must be present to cause the disease. Breeding two carriers is predicted to produce 25% affected pups.

The VGL offers a genetic test for CMR2 and CMR3 mutations. Genetic screening helps breeders establish the genetic status of breeding stock and select mating pairs appropriately in order to reduce the risk of producing affected offspring. CMR2 and CMR3 mutations have different breed origins and distributions and thus test selection needs to be breed-appropriate.

Testing is recommended for:

CMR2: Coton de Tulear

CMR3: Finnish Lapphund, Lapponian Herder, Swedish Lapphund

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Allow 5-10 business days for results.

Results reported as:

N/N

Normal - no copies of the CMR2 mutation

N/CMR2

Carrier - 1 copy of the CMR2 mutation; dog is normal

CMR2/CMR2

Affected - 2 copies of the CMR2 mutation; dog will develop multifocal retinopathy

 

N/N

Normal - no copies of the CMR3 mutation

N/CMR3

Carrier - 1 copy of the CMR3 mutation; dog is normal

CMR3/CMR3

Affected - 2 copies of the CMR3 mutation; dog will develop multifocal retinopathy

References:

Guziewicz KE, Zangerl B, Lindauer SJ, Mullins RF, Sandmeyer LS, Grahn BH, Stone EM, Acland GM, Aguirre GD. Bestrophin gene mutations cause canine multifocal retinopathy: a novel animal model for best disease. Invest Ophthalmol Vis Sci. 2007 May; 48(5):1959-67. [PubMed: 17460247]

Zangerl B, Wickström K, Slavik J, Lindauer SJ, Ahonen S, Schelling C, Lohi H, Guziewicz KE, Aguirre GD. Assessment of canine BEST1 variations identifies new mutations and establishes an independent bestrophinopathy model (cmr3). Mol Vis. 2010 Dec 16; 16:2791-804. [PubMed: 21197113]

 
Veterinary Genetics Laboratory, Tel 530-752-2211, Email VGL