Collie Eye Anomaly (CEA)
Choroidal Hypoplasia (CH)
- Also known as Choroidal Hypoplasia (CH)
- First discovered in Europe in the middle of the twentieth century
- Disease is present before birth, but eyes are checked at about six to eight weeks of age
- Most commonly found in the U.S. Collies, but also found in Border Collies, Rough and Smooth Collies, and Australian Shepherds
- Disease is caused by abnormal development in the choroid part of the eye
- The most common eye disease in Collies, however other dog breeds can also have it.
- There is no treatment or cure
- This disease affects the choroid of the eye, which is the tissue layer that supplies blood to the retina
- With CEA, the choroid is developed improperly, causing the choroid to be very thin
- Although CEA is relatively asymptomatic, it can lead to detachment of the retina, and even blindness in severe cases
- Retinal detachment occurs in about 4-5% of affected offspring
- Has a "go normal" phenomenon in which CEA can go undetected at a young age
- Autosomal recessive
- Not a sex-linked disorder
- Dr. Gregory Acland did research on CEA at Cornell University in the mid-1990s
- Dr. Acland mostly used Border Collies and Collies for his research
- He discovered that the disease was recessive and was from a single gene mutation
- The mutation that causes CEA is deletion in the 7799 basepair
- This deletion was found on chromosome 37 in the NHEJI gene
- Each animal born from this pairing has a 25% chance of inheritance and 50% of being a carrier by inheriting one copy of the mutation
- Animals that carry one or two copies of the NHEJI gene mutation: Rough Collie 72%, Smooth Collie 62%, Whippet, Longhaired 60%, Shetland Sheepdog 52%, Border Collie 35%, Lancashire Heeler 30%, Nova Scotia Duck Tolling Retriever 18%, Australian Shepherd 15%
- To know for sure if the animal has CEA is through DNA testing using Optigen
As described in the picture above:
- Mating a "normal" parent with another "normal" parent will produce 100% "normal" offspring
- Mating a parent that is a carrier with another parent that is normal will produce 50% normal offspring, and 50% that are carriers
- Mating a parent that is a carrier with another parent that is a carrier will produce offspring in which 25% are "normal", 50% are carriers, and 25% are affected
- Mating an affected parent with a normal parent will produce offspring in which 100% of them are carriers
- Mating an affected parent with a parent that is a carrier will produce offspring in which 50% are carriers and 50% are affected
- Mating an affected parent with another affected parent will produce offspring in which 100% are affected
- It is highly recommended that no breeding occurs with known carriers of the NHEJ1 gene
- Polymerase chain reaction (PCR) testing is done using DNA strands of the mutated gene
- Gel electrophoresis is done where this causes an electric field to be generated, causing the charged molecules to move to the oppositely charged end
- With the known affected alleles now being shown, this allows for selective breeding to occur
- This leads to the possibility of erradication of this disorder
CAE is prevalent in dog breeds including Collies, and other herding breeds. This has been shown to have detrimental affects particularly with breeding these animals. If these specific dog breeds have been proven to be affected and carry this gene mutation, is it even remotely possible that cats can be affected?
2. "Collie Eye Anomaly". Paw Print Genetics. Genetic Veterinary Sciences, Inc., 2003-2014. Web. 16 Apr. 2016.
3. Moll, Kathy. "Understanding Collie Eye Anomaly". Deep River Collies, 2015. Web. 17 Apr. 2016.
4. Sharp, C.A. "Collie Eye Anomaly in Australian Shepherds". Doulbe Helix Network News, 2006. ASHGI. Web. 16 Apr. 2016
5. Unnarsdóttir, Silja. "Collie Eye Anomaly". Morbærhaven, 2011. Print.