Hereditary Cataracts (HC)
Early onset cataracts, Juvenile cataracts, HC, HSF4, JC
Cataracts are a clouding of the lens of the eye caused by a breakdown of tissue. This generally results in an inability to see clearly and can cause total blindness. Mutations in the HSF4 gene can lead to a hereditary version of cataracts in several breeds of dogs. One HSF4 mutation causes the recessive form of HC 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 HC, which typically occurs between 12 months and 3 years of age in Staffordshire’s, and between 2-3 years in Boston Terriers. Boston Terriers can also be afflicted by late-onset HC; however, the HSF4 gene mutation is not responsible for that particular form of cataracts.
A different mutation in the HSF4 gene is responsible for HC 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 an Australian Shepherd to the disease, however, incomplete penetrance means that a dog that has this mutation will not always develop HC.
It is important to note 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, but not necessarily attributed to the HSF4 mutations.
Reading Your Results
Terrier/Bulldog Type:
A. (CLEAR/NORMAL):
These dogs have two copies of the normal gene and will neither develop HSF4-Hereditary Cataracts nor pass this mutation to their offspring.
B. (CARRIER/NOT AFFECTED):
These dogs have one copy of the normal gene and one copy of the mutation associated with this disease. They will not develop HSF4-Hereditary Cataracts but will, if bred, pass the mutation to 50% of its offspring, on average.
C. (AT RISK/AFFECTED):
These dogs have two copies of the mutation associated with HSF4-Hereditary Cataracts which will likely result in cataract formation, the inability to see clearly, and potential blindness.
Australian Shepherd Type:
A. (CLEAR/NORMAL):
These dogs have two copies of the normal gene and will neither develop HSF4-Hereditary Cataracts nor pass this mutation to their offspring.
B. (CARRIER/AT RISK):
These dogs have one copy of the normal gene and one copy of the mutation associated with this disease. They will likely develop HSF4-Hereditary Cataracts and will, if bred, pass the mutation to 50% of its offspring, on average.
C. (AT RISK/AFFECTED):
These dogs have two copies of the mutation associated with HSF4-Hereditary Cataracts which will likely result in cataract formation, the inability to see clearly, and potential blindness.
Additional Details
Inheritances
Terrier/Bulldog Type: Autosomal Recessive
Australian Shepherd Type: Autosomal Dominant With Incomplete Penetrance
Affected gene
HSF4
Chromosome
Ch. 5
Mutation
Terrier/Bulldog Type: C.971_972insC (CanFam3.1) Single Bp Insertion (Del C)
Australian Shepherd Type: C.971delC (CanFam3.1) Single Bp Deletion (Del C)
Publication:
Terrier/Bulldog Type: Mellersh CS, Graves KT, McLaughlin B, Ennis RB, Pettitt L, Vaudin M, Barnett KC. Mutation in HSF4 is associated with early but not late-onset hereditary cataracts in the Boston Terrier. J Hered. 2007;98(5):531-3. [PubMed: 17611257].
Australian Shepherd Type: Mellersh CS, McLaughlin B, Ahonen S, Pettitt L, Lohi H, Barnett KC. Mutation in HSF4 is associated with hereditary cataracts in the Australian Shepherd. Vet Ophthalmol. 2009 Nov-Dec; 12(6):372-8. [PubMed: 19883468]
