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Hereditary Cataract (HC) Terrier Type
| Acronym: | HC, PHC |
| Gene: | HSF4 |
| Mutation: | c.971_972insC |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Primary hereditary cataract (HC) is one of the most common genetic disorders in purebred dogs, affecting approximately 100 breeds and representing a leading cause of blindness in dogs. A recessive form of HC in Staffordshire Bull Terriers and French Bulldogs and juvenile hereditary cataract Terrier type in Boston Terriers is caused by a single nucleotide insertion in the HSF4 gene, encoding for a heat shock transcription factor that regulates the expression of heat shock proteins in response to different stresses, such as oxidants, heavy metals, elevated temperatures, and bacterial and viral infections.
HC in mentioned breeds is bilateral, symmetrical in the two eyes, and progressive until total with resultant blindness. It appears at a few weeks to months in age, progressing to total by 2 to 4 years of age. Affected dogs are homozygous for the mutation. The occurrence of hereditary cataract Terrier type in the Boston Terrier is 11.11%.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Mellersh, C.S., Pettitt, L., Forman, O.P., Vaudin, M., and Barnett, K.C. (2006). Identification of mutations in HSF4 in dogs of three different breeds with hereditary cataracts. Veterinary Ophthalmology 9, 369–378.
Mellersh, C.S., Graves, K.T., McLaughlin, B., Ennis, R.B., Pettitt, L., Vaudin, M., and Barnett, K.C. (2007). Mutation in HSF4 associated with early but not late-onset hereditary cataract in the Boston Terrier. Journal of Heredity 98, 531–533.