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Achromatopsia type 2 in Labrador Retrievers     ACHM2-LR Test     Code 202

For breeds: Australian Cobberdog, Labrador Retrievers (& Labrador crosses e.g. Labradoodles)

A collaborative research effort by a team of investigators at the University of Pennsylvania, veterinary ophthalmologist Dr. Chris Dixon and the OptiGen Research Program , has led to the discovery of a novel mutation in the CNGA3 gene that causes Day Blindness in the Labrador Retriever (1). This condition, also known as Achromatopsia , or color blindness, is characterized by cone photoreceptor dysfunction, severely reduced visual acuity or complete vision loss during daylight hours, and photophobia.  The disease is present at birth (i.e. it is congenital) and is manifested clinically when dogs are approximately 8-10 weeks of age.   

The mutation identified in the Labrador Retriever breed is analogous to the mutation in the CNGA3 gene that causes Achromatopsia type 2 (ACHM2) disease with a similar clinical representation in humans. The mutation has been also found in several related breeds and crosses for which the ACHM2-LR test is currently offered by OptiGen.

Note: A different mutation in the same CNGA3 gene causes a similar form of day blindness/achromatopsia in German Shepherds (1). OptiGen offers a different, breed-specific ACHM2-GS test for achromatopsia in German Shepherds. 


Testing/Breeding strategies:

Achromatopsia type 2-LR is inherited as an autosomal recessive trait, which means that only dogs that have inherited two copies of the CNGA3 mutation (one from each parent) will develop this form of ACHM. Carriers of one copy of the mutation will not develop the disease. In order to avoid producing affected offspring, at least one parent of any litter should be DNA tested and shown to be Normal/Clear of the mutation.

Expected results for breeding strategies using the
mutation test for ACHM2-LR
Parent 1
Genotype
Parent 2 Genotype
Normal/ClearCarrierAffected
Normal/ClearAll = Normal/Clear1/2 = Normal/Clear
1/2 = Carrier
All = Carrier
Carrier1/2 = Normal
1/2 = Carrier
1/4 = Normal/Clear
1/2 = Carrier
1/4 = Affected
1/2 = Carrier
1/2 = Affected
Affected All = Carrier
1/2 = Carrier
1/2 = Affected
All = Affected

References:

1.Tanaka N., Dutrow EV, Miyadera K, Delemotte L, MacDermaid CM, Reinstein SL, et al. (2015) Canine CNGA3 Gene Mutations Provide Novel Insights into Human Achromatopsia-Associated Channelopathies and Treatment. PLoS ONE 10(9): 30138943


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