Collie Eye Anomaly (CEA)

Gene: NHEJ1

Transmission: Autosomal, recessive (variable penetration)

For an autosomal recessive genetic disease an animal must have two copies of the mutation in question to be at risk of developing the disease.  Both parents of an affected animal must be carriers of at least one copy of the mutation.  Animals that have only one copy of the mutation are not at risk of developing the disease but are carrier animals that can pass the mutation on to future generations.

Mutation: Deletion, NHEJ1 7; 6Kb del., intron4-5

Breeds: Australian Shepherd, Bearded Collie, Border Collie, Boykin Spaniel, Collie, English Shepherd, Hokkaido Dog, Lancashire Heeler, Long-Haired Whippet, Miniature American Shepherd, Miniature Australian Shepherd, Nova Scotia Duck Tolling, Rough Collie, Shetland Sheepdog, Silken Windhound, Smooth Collie, Whippet

Age of onset of symptoms: Young age

Colley eye anomaly, also known as choroidal hypoplasia, is a developmental eye disease that affects the choroid, the layer responsible for the blood supply to the retina of the eye.  Affected animals have a thinner choroid than normal.  In mild cases, no vision problems result, while in severe cases retinal detachment, and intraocular haemorrhage can lead to blindness. The degree of severity of this condition varies from one individual to another and is unfortunately not predictable, thus mildly affected parents can give birth to severely afflicted puppies.

References:

Lowe JK et al. (2003) Linkage mapping of the primary disease locus for collie eye anomaly. Genomics 82(1):86-95. [pubmed12809679]

Parker HG, Kukekova AV et al. (2007). Breed relationships facilitate fine-mapping studies: A 7.8-kb deletion cosegregates with Collie eye anomaly across multiple dog breeds. Genome Research 17:1562-1571. [pubmed/17916641]

Mizukami K, Yabuki A, Endoh D et al. (2014) Investigation of parallel and simultaneous selection for collie eye anomaly and ivermectin toxicosis. Bet Rec 175:174. [pubmed/24939474]