Collie Eye Anomaly
Affected Genes: NHEJ1
Inheritance: Autosomal Recessive With Variable Expressivity
Variant(canFam6):
chr37:26524447-26532245: 7.8 kb deletion
Breed: Aussiedoodle
Australian Cattle Dog
Australian Kelpie
Australian Koolie
Australian Shepherd
Australian Stumpy Tail Cattle Dog
Australian Working Kelpie
Bearded Collie
Border Collie
Bordoodle
Boykin Spaniel
Collie
English Shepherd
Hokkaido
Koolie
Lancashire Heeler
Longhaired Whippet
Miniature American Shepherd
Miniature Australian Cattle Dog
Miniature Australian Shepherd
Nova Scotia Duck Tolling Retriever
Old-Time Scotch Collie
Rough Collie
Scottish Collie
Shetland Sheepdog
Silken Windhound
Smooth Collie
Toy Australian Shepherd
General Information: Collie Eye Anomaly (CEA), also known as choroidal hypoplasia, is a genetic disorder where the choroid—the eye tissue responsible for nourishing the retina—is underdeveloped. This condition varies in severity; mildly affected dogs may not show any vision problems and their condition can only be detected through specialized veterinary eye exams before the retina matures at around 5 to 12 weeks old. Post this age, changes may be masked by retinal pigmentation, making them appear 'normal'. Severely affected dogs, however, may experience serious complications such as eye malformations, optic nerve colobomas, retinal detachments, or even blindness due to intraocular bleeding. The visual prognosis in severe cases depends significantly on the degree and progression of these complications.
How to Read Your Dog's Test Results for this Genetic Variant:
Two Variants Detected: Dog Likely Affected
One Variant Detected: Dog Unlikely Affected
No Variants Detected: No Effect
Gene / Testing Information: Genetic testing for Collie Eye Anomaly (CEA) targets the NHEJ1 gene, identifying carriers who are at risk of passing this mutation to their offspring. CEA is transmitted as an autosomal recessive trait, requiring two copies of the mutated gene for the phenotype to manifest. Dogs that inherit only one copy of the mutation do not exhibit symptoms but are carriers. Breeding two carriers results in each offspring having a 25% chance of being affected by CEA, and a 50% chance of being a carrier. It is crucial for breeders to use reliable genetic testing to inform breeding decisions and minimize the risk of producing affected pups by avoiding mating two carriers. Genetic testing is also important for reducing the prevalence of this condition in future generations. Since symptoms vary widely and are not strictly predictable based on parental severity, breeding strategies should prioritize genetic health to ensure the well-being of the breed
References:
Brown EA, Thomasy SM, Murphy CJ, Bannasch DL. Genetic analysis of optic nerve head coloboma in the Nova Scotia Duck Tolling Retriever identifies discordance with the NHEJ1 intronic deletion (collie eye anomaly mutation). Vet Ophthalmol. 2017 21(2):144-150.
Lowe JK, Kukekova AV, Kirkness EF, Langlois MC, Aguirre GD, Acland GM, Ostrander EA. Linkage mapping of the primary disease locus for collie eye anomaly. Genomics. 2003 82(1):86-95.
Midshires Bearded Collie Club. [Internet]. Statement on Collie Eye Anomaly in Bearded Collies from the Joint Breed Liaison Committee – December 2013. 21 . Available at http://midshiresbeardedcollieclub.com/Breed-Club-and-Joint-Breed-Liaison-Committee-Releases
Mizukami K, Chang HS, Ota M, Yabuki A, Hossain MA, Rahman MM, Uddin MM, Yamato O. Collie eye anomaly in Hokkaido dogs: case study. Vet Ophthalmol. 2012 Mar;15(2):128-132.
Munyard KA, Sherry CR, Sherry L. A retrospective evaluation of congenital ocular defects in Australian Shepherd dogs in Australia. Vet Ophthalmol. 2007 10(1):19-22.
Parker HG, Kukekova AV, Akey DT, Goldstein O, Kirkness EF, Baysac KC, Mosher DS, Aguirre GD, Acland GM, Ostrander EA. Breed relationships facilitate fine-mapping studies: a 7.8-kb deletion cosegregates with Collie eye anomaly across multiple dog breeds. Genome Res. 2007 17(11):1562-1571.
Walser-Reinhardt L, Hassig M, Spiess B. Schweiz Arch Tierheilkd. Collie Eye Anomaly in Switzerland. 2009 151(12):597-603.