Quick Summary
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Phenotype: Cataracts may start forming after 2 years of age and show variable rate of progression and vision impairment. The HC mutation in Australian Shepherds is mostly associated with bilateral posterior cataracts. Both sexes are equally affected. In general, dogs that have 2 copies of the HC mutation tend to have cataracts of the nuclear type, which progresses more rapidly and results in blindness at an earlier adult age. Dogs that have 1 copy of the HC mutation tend to have posterior polar subcapsular type of cataract that is not progressive and does not interfere with vision. Not all dogs that have the mutation will develop cataracts.
Mode of Inheritance: Autosomal dominant (incomplete penetrance)
Alleles: N = Normal, HC = Hereditary cataract
Breeds appropriate for testing: Australian Shepherd
Explanation of Results:
- Dogs with N/N genotype do not have this hereditary cataract variant and cannot transmit this variant to their offspring. However, cataracts may develop because of other genetic and environmental factors.
- Dogs with N/HC genotype may develop or are at risk to develop hereditary cataracts. They will transmit this hereditary cataract variant to 50% of their offspring, which will also be at risk to develop hereditary cataracts.
- Dogs with HC/HC genotype may develop or are at risk to develop the more severe form of hereditary cataracts that leads to blindness. If bred, dog will transmit this hereditary cataract variant to all of their offspring.
Results of this test can be submitted to the OFA (Orthopedic Foundation for Animals)
Sample Collection
Dog DNA tests are carried out using cells brushed from your dog's cheeks and gums. The preferred cytology brushes are sent to you by mail, or you may provide your own brushes. For accepted alternative brushes, click here
We recommend waiting until puppies are at least three weeks old before testing.
Step-By-Step:
- Make sure the dog has not had anything to eat or drink for at least 1 hour prior to collecting sample.
- When swabbing puppies, isolate each puppy from the mother, littermates and any shared toys for 1 hour prior to swabbing. Puppies should not have nursed or eaten for 1 hour prior to collecting sample.
- If collecting samples from more than one dog, make sure to sample one dog at a time and wash your hands before swabbing another dog.
- Label brush sleeve with name or ID of dog to be sampled.
- Open brush sleeve by arrow and remove one brush by its handle.
- Place bristle head between the dog’s gums and cheek and press lightly on the outside of the cheek while rubbing or rotating the brush back and forth for 15 seconds.
- Wave the brush in the air for 20 seconds to air dry.
- Insert brush back into sleeve.
- Repeat steps 5 - 8 for each unused brush in sleeve on a fresh area of cheek and gums. Make sure to use and return all brushes sent by the VGL. In most cases, it will be 3 brushes per dog. If using interdental gum brushes, please note that the VGL requires 4 brushes per dog and only moderate or wide interdental gum brushes are accepted.
- Do not seal brushes in sleeve.
- Place all samples in an envelope and return to the address provided.
ATTENTION:
- Do not collect saliva/drool – the key to obtaining a good sample is getting cheek cells on the swab
- Do not rub swab on the dog’s tongue or teeth – this will result in poor quality sample
- Do not collect a sample from a puppy that has recently nursed – the mother’s genetic material can rub off on the puppy’s mouth and contaminate the sample
Cataracts are a common cause of blindness in dogs. Cataracts are defined as the clouding (opacity) of the lens of the eye. The lens focuses light on the retina to enable vision. Cataracts can therefore impair vision and, if progressive, they can lead to total blindness. Cataracts can develop in one eye (unilateral) or both (bilateral) as a result of the normal aging process, underlying diseases, injury, or be caused by a genetic defect (primary hereditary cataracts). Primary hereditary cataracts tend to be of the bilateral type. In dogs, mutations in the HSF4 gene are associated with two different forms of cataracts, Juvenile Hereditary Cataract (JHC) and Hereditary Cataract (HC).
Hereditary Cataract (HC) in the Australian Shepherd is associated with a mutation in HSF4 different from the mutation associated with JHC. Cataracts may start forming after 2 years of age and show variable rate of progression and vision impairment. The inheritance of HC in this breed is complex and this mutation is not the sole determinant for development of cataracts. Other unknown genetic and non-genetic factors contribute to cataract development and progression. The HC mutation in Australian Shepherds is mostly associated with bilateral posterior cataracts. Both sexes are equally affected. HC is inherited as a dominant trait with incomplete penetrance, which means that not all dogs that have the mutation will develop cataracts. Dogs that have the HC mutation are 17 times more likely to develop bilateral cataracts compared to dogs that do not have any copies of the mutation. In general, dogs that have 2 copies of the HC mutation tend to have cataracts of the nuclear type, which progresses more rapidly and results in blindness at an earlier adult age. Dogs that have 1 copy of the HC mutation tend to have posterior polar subcapsular type of cataract that is not progressive and does not interfere with vision.
Owners and breeders can benefit from this test by identifying at an early age which dogs have this mutation and are at significant risk for developing HC. Selection of breeding stock that are free (N/N) of this mutation will help reduce incidence of cataract in the breed. Veterinarians can benefit from this test by determining if a clinical cataract case in this breed has a known genetic etiology.
