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Hereditary Cataracts (HC)


Description

Cataracts are a clouding of lens of the eye caused by a breakdown of tissue in the eye. This generally results in an inability to see clearly, and can cause total blindness. In canines, cataracts are often familial; this type is known as Hereditary Cataracts. A mutation in the HSF4 gene causes this type of cataracts in several breeds of dogs. In this case, the dog is typically affected bilaterally, in that both eyes are affected by the cataracts. The cataracts associated with HSF4 also occur in the posterior region of the lens. They usually begin small and grow progressively, though the speed of growth is highly variable. Some cataracts will grow so slowly that the dog's vision remains relatively clear, while others will grow such that the dog will quickly go blind. Corrective surgery is possible, though it is costly and is not always effective.


One HSF4 mutation causes the recessive form of Hereditary Cataracts in Boston Terriers, Staffordshire Bull Terriers, and French Bulldogs. Because it is recessive, a dog must have two copies of this mutation to experience this form of cataracts. This mutation is only responsible for early-onset hereditary cataracts, which typically occur between 12 months and 3 years of age in Staffordshires, and between 2-3 years in Boston Terriers. Boston Terriers can also be afflicted by late-onset hereditary cataracts; however, the HSF4 gene mutation is not responsible for that particular form of cataracts. The causative gene for Late-onset Hereditary Cataracts in Boston Terriers has not been determined at this time.

A separate mutation of the HSF4 gene is responsible for Hereditary Cataracts in Australian Shepherds. This mutation affects Aussies differently, in that the disease is dominant, but not completely penetrant. This means that only one copy of the mutation is necessary to predispose a dog to the disease, however, incomplete penetrance means that a dog that has this mutation will not always develop HC. Research suggests that the mutation makes a dog 12 times more likely to develop posterior bilateral cataracts at some point in their lifetime. It is likely that a secondary gene interaction occurs in the small percentage of dogs possessing the HC mutation but do not develop cataracts, however, this interaction is not yet know.

It should also be noted that not all cataracts are hereditary. Cataracts can also be caused by old age or injury. Also, cataracts that occur in different regions of the lens can also be familial, however, are not attributed to this gene mutation.

HC Testing
Animal Genetics offers DNA testing and detection of the gene mutation responsible for certain forms of Hereditary Cataracts in Australian Shepherds, Boston Terriers, French Bulldogs and Staffordshire Bull Terriers.


Breeds Affected
Australian Shepherds
Boston Terriers
French Bulldogs
Staffordshire Bull Terriers


Cost
$45.00 US per sample


Sample Collection
Collect sample using buccal swabs provided by Animal Genetics. Ensure that the dog has not eaten within a few hours of sample collection. Any food particles can inhibit the test. Rub each of the swabs along the inside of the dog's mouth for 10-15 seconds, and allow the swabs to dry thoroughly. Label the provided envelope with the dog's name, and place the swab inside it. Download and complete a submission form for each sample and send along with payment to Animal Genetics for testing.

 


Results

Results are given using the following symbolic notation:

Staffordshire Bull Terriers, French Bulldogs, Boston Terrier:

HC/HC
AFFECTED: The dog carries two copies of the mutant gene and is homozygous for Hereditary Cataracts. The dog is affected by HSF4-Hereditary Cataracts, and will always pass on a copy of the mutated gene to its offspring.
n/HC
CARRIER: Both the normal and mutant copies of the gene detected. Dog is a carrier for Hereditary Cataracts, and can pass on a copy of the defective gene to any offspring.
n/n
CLEAR: Dog tested negative for the Hereditary Cataract gene mutation, and will not pass on the defective gene to its offspring.


Australian Shepherds
:

HC/HC
AFFECTED: The dog carries two copies of the mutant gene and is homozygous for the HSF4-HC gene mutation. The dog is extremely likely to develop cataracts over his lifetime, and will always pass on the mutation to any offspring.
n/HC
AFFECTED: Both the normal and mutant copies of the gene detected. Dog is heterozygous for the HSF4-HC gene mutation. The dog is extremely likely to develop cataracts over his lifetime, and can pass a copy of the mutation to any offspring.
n/n
CLEAR: Dog tested negative for the Hereditary Cataract gene mutation, and will not pass on the defective gene to its offspring.

 


Animal Genetics, Inc.
1336 Timberlane Rd - Tallahassee, FL 32312
Toll Free: 866-922-6436

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