Cataract’s reign of terrier overthrown!

Cataracts are a major cause of blindness for dogs, particularly in purebred breeds. They occur when the transparent lens tissue of the eye becomes opaque, reducing the lens’ ability to focus light onto the retina, which is vital for clear vision. It was recently discovered that HSF4, a gene related to cataracts in humans, is also associated with hereditary cataracts in dogs. A single nucleotide insertion in exon 9 of the canine HSF4 gene alters the transcript reading frame, causing an early stop codon, which results in a shortened, incorrect protein. Thus, a cataract forms.

This discovery arose in a study focussing on Staffordshire Bull Terriers, a breed in which the mutation causes hereditary cataracts. The gene mutation was also found to be autosomal and have recessive inheritance. Another study found the HSF4 mutation causes early-onset hereditary cataract (EHC) in Boston Terriers, but has no association with late-onset hereditary cataract, which also occurs in Boston Terriers. Yet another study discovered the HSF4 mutation is not related to cataracts of the Dachshund or Entlebucher Mountain Dog. Knowledge of HSF4 mutation is continually refined in this fashion.

Discovery of which types of cataract are caused by HSF4 mutation has allowed the development of diagnostic tests to find if a dog is affected, or a carrier of the mutation. Breeders may now use these tests to select against dogs with the mutation and therefore eliminate HSF4 mutation related cataracts from affected dog breeds, freeing terriers from the terror of cataracts.

Lauren Byrne

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Primary References:

Mellersh, C.S., Pettitt, L., Forman, O.P., Vaudin, M., Barnett, K.C., 2006. Identification of mutations in HSF4 in dogs of three different breeds with hereditary cataracts. Veterinary Ophthalmology 9, 369-378.

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Mellersh, C.S., Graves, K.T., McLaughlin, B., Ennis, R.B., Pettitt, L., Vaudin, M., 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.

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Müller, C., Wöhlke, A., Distl, O., 2008. Evaluation of canine heat shock transcription factor 4 (HSF4) as a candidate gene for primary cataracts in the Dachshund and the Entlebucher Mountain Dog. Veterinary Ophthalmology 11, 34-37.

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Secondary Reference:

Wolfer, J.C. Cataract Surgery. Islington Animal Clinic.

http://www.animaleyeclinic.ca/cataracts.htm.

Accessed 26 May 2008.

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