Canine Multifocal Retinopathy (CMR1 Dog)
Canine multifocal retinopathy (CMR1) is a disease of the retina in which lesions and defects occur at various sites of the retina. Affected animals show very mild visual impairment; severe cases are rare.
The disease occurs in Mastiff-related breeds such as Dogue de Bordeaux, English Bulldog, American Bulldog, Bullmastiff and Cane Corso Italiano. The inheritance is autosomal recessive.
Symptoms
- Several brownish-pink subretinal spots
- Areas of focal retinal degeneration
- Causes visual impairment only in severe cases
- Mostly normal vision with minor limitations
General Information
- Canine multifocal retinopathy (CMR1) is caused by lesions and defects at various sites of the retina.
- The condition is usually diagnosed at an age of 10-14 weeks and is not progressive.
Breeds affected
Mastiff-related breeds such as Dogue de Bordeaux, English Bulldog, American Bulldog, Bullmastiff, Cane Corso Italiano etc. and Australian Shepherd.
Test Information
This mutation test detects a change of a single base pair (c.73C>T) in the first coding exon of the BEST1 gene (also known as VMD2).
Genotype and Lab Report
Inheritance: autosomal recessive
→ The disease only occurs if both alleles of the gene are affected by the mutation (cmr1/cmr1). Dogs that have only one allele with the causative mutation (N/cmr1) are clinically healthy carriers.
Genotypes:
N/N = genetically normal
The dog has no predisposition for CMR1 and therefore cannot pass it on to its offspring.
N/cmr1 = a carrier
The dog is a clinically healthy carrier. The variation is passed on 50% to the offspring, which are also carriers.
cmr1/cmr1 = affected
The variation is passed on 100% to the offspring.
Recommendations
- Carrier animals can be bred to normal animals (N/cmr1 x N/N). Before using the offspring in breeding, it should be tested whether they are normal or carriers.
- Mating two carrier animals (N/cmr1 x N/cmr1) should be avoided because there is a 25% chance that the offspring will be affected.
- Affected animals (cmr1/cmr1) should be excluded from breeding.
Literature
Donner, J., Kaukonen, M., Anderson, H., Möller, F., Kyöstilä, K., Sankari, S., Hytönen, M., Giger, U., Lohi, H.: Genetic Panel Screening of Nearly 100 Mutations Reveals New Insights into the Breed Distribution of Risk Variants for Canine Hereditary Disorders.PLoS One 11:e0161005, 2016. Pubmed reference: 27525650. DOI: 10.1371/journal.pone.0161005.
Gornik, K.R., Pirie, C.G., Duker, J.S., Boudrieau, R.J.: Canine multifocal retinopathy caused by a BEST1 mutation in a Boerboel.Vet Ophthalmol 17:368-72, 2014. Pubmed reference: 23998685. DOI: 10.1111/vop.12095.
Hoffmann, I., Guziewicz, K.E., Zangerl, B., Aguirre, G.D., Mardin, C.Y.: Canine multifocal retinopathy in the Australian Shepherd: a case report.Vet Ophthalmol 15 Suppl 2:134-8, 2012. Pubmed reference: 22432598. DOI: 10.1111/j.1463-5224.2012.01005.x.
Zangerl, B., Wickström, K., Slavik, J., Lindauer, S.J., Ahonen, S., Schelling, C., Lohi, H., Guziewicz, K.E., Aguirre, G.D.: Assessment of canine BEST1 variations identifies new mutations and establishes an independent bestrophinopathy model (cmr3).Mol Vis 16:2791-804, 2010. Pubmed reference: 21197113.
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 48:1959-67, 2007. Pubmed reference: 17460247. DOI: 10.1167/iovs.06-1374
Further information is available at: Online Mendelian Inheritance in Animals.