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Cone Rod Dystrophy in Dachshund     NPHP4-CORD Test       Code 307

Test Pricing

For Breeds: Miniature Wirehaired Dachshund and Standard Wirehaired Dachshund

Clinical signs/disease description:
An  early onset form of retinal degeneration in Miniature and Standard Wirehaired Dachshunds is characterized by the initial loss of cones, the cells in the retina that are responsible for vision in bright light/daylight, followed by degeneration of rods, the retinal cells that operate during night vision. This sequence of events is reflected in the name of the disorder: cone-rod dystrophy, or CORD. Age of onset of the initial day blindness in affected dogs varies from 10 months to 3 years of age. The retinal degeneration progresses quickly and usually results in complete blindness within 6 years [1].

NPHP4-CORD mutation test:
A small deletion in the nephroretinin NPHP4 gene has been identified that is associated with the cone-rod dystrophy in Standard Wirehaired Dachshund [2] and in the closely related breed, the Miniature Wirehaired Dachshund. This form of retinal degeneration is inherited in an autosomal recessive mode, meaning that dogs of both sexes are equally affected when they inherit two copies of the NPHP4 mutation, one from each parent. 

The DNA-based NPHP4-CORD test allows one to determine the genotype of a tested dog as being:

NORMAL - the dog has two copies of the normal NPHP4 gene and will not develop cone-rod dystrophy caused by the NPHP4-CORD mutation.

CARRIER - the dog has one copy of the normal gene and one copy of the NPHP4 mutation. The dog will not develop clinical signs of cone-rod dystrophy but it will transmit the NPHP4 muation to about 50% of its progeny.

AFFECTED - the dog has two copies of the NPHP4 mutation in and is expected to develop the early-onset cone-rod dystrophy (CORD) caused by this mutation.

Testing/Breeding Recommendations:
The great value of the DNA test is that it allows detection of carriers of one copy of the mutation. These dogs do not show clinical signs of the disease but they can pass the mutation on to their offspring. In order to avoid producing CORD-affected offspring, carriers of the mutation should never be bred to other carriers or to CORD-affected dogs (see chart below).

Expected results for breeding strategies using the
NPHP4-CORD test

Parent 1
Genotype

Parent 2 Genotype

Normal/Clear

Carrier

Affected

Normal/Clear

All = Normal/Clear

1/2 = Normal/Clear
1/2 = Carrier

All = Carrier

Carrier

1/2 = 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

This table highlights in yellow the breedings that will NOT produce CORD-affected pups. These breedings include at least one parent proven "Normal/Clear" by the OptiGen NPHP4-CORD test. All other combinations are at risk of producing affected pups.

References:

1. Ropstad EO, Bjerkas E, Narfstrom K, 2007. Clinical findings in early onset cone-rod dystrophy in the standard wirehaired dachshund. Vet Ophthalmol. 10(2):69-75.

2. Wiik AC, Wade C, Biagi T, Ropstad EO, Bjerkas E, Lindblad-Toh K, Lingaas F. 2008. A deletion in nephronophthisis 4 (NPHP4) is associated with recessive cone-rod dystrophy in standard wirehaired dachshund. Genome Res. 18(9):1415-21.

 


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OptiGen®, LLC · Cornell Business & Technology Park · 767 Warren Road, Suite 300 · Ithaca, New York 14850
Tel: 607 257 0301 · Fax: 607 257 0353 · email: genetest@optigen.com or optigen@clarityconnect.com
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