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Goniodysgenesis and glaucoma in Border Collie (GG)
| Acronym: | GG |
| Gene: | OLFML3 |
| Mutation: | c.590G>A |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Goniodysgenesis and glaucoma in Border Collie (GDD) is a hereditary disorder affecting the eyes. Glaucoma can be divided into two categories, primary and secondary glaucoma. Primary glaucoma is characterized by its onset without any other ocular cause, while secondary glaucoma appears when another cause is present, which triggers glaucoma. Primary open-angle glaucoma is the most common type of canine primary glaucoma. Goniodysgenesis, also known as mesodermal dysgenesis, is an abnormality of the anterior chamber of the eye, and it has been associated with glaucoma and blindness. Goniodysgenesis and early-onset glaucoma have been documented for the first time in Australia in the late 1990s and afterward have been found also in Europe and the USA. It is particularly commonly diagnosed in some Border collie lineages; in the conducted study, 10.8% of Border collies were reported to have moderate or severe pectinate ligament dysplasia, alteration in eye structure responsible for proper humor drainage.
The fluid inside of the eye is called aqueous humor. It is produced behind the iris, in the ciliary body. This fluid flows through the eye and drains from the eye, maintaining normal eye pressure. The drain network in the eye is called the drainage angle or drainage canal. The inadequate outflow of aqueous humor causes a build-up of pressure, and consequently, glaucoma. Prolonged intraocular pressure results in damage to optic nerves, whose damage is irreversible. Glaucoma can be preceded by goniodysgenesis, which is a developmental abnormality of the eye characterized by narrowing or closure of the iridocorneal angle through which the aqueous humor drains. Symptoms of goniodysgenesis and primary glaucoma include severe pain, sensitivity to light (photophobia), winking spasms (blepharospasm), startling when the dog’s head is touched, watery, red eyes with dilated pupils, and behavioral change, such as hiding, refusal to eat.
Goniodysgenesis and glaucoma in Border Collie are caused by a missense mutation in the OLFML3 gene, which is expressed in tissues of the eye, such as the lens, iris, sclera, and trabecular meshwork. OLFML3 stands for olfactomedin-like 3 protein, an extracellular matrix protein associated with the formation of tissue needed for the formation of the proper drainage channels. Goniodysgenesis and glaucoma in Border Collie are inherited in an autosomal recessive pattern. A cat carrying one copy of the mutated gene is heterozygous and will not show the PCG symptoms. When mating two carriers (heterozygotes) at conception each kitten has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
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:
Carys A Pugh, Lindsay L Farrell, Ailsa J Carlisle, Stephen J Bush, Violeta Trejo-Reveles, Oswald Matika, Arne de Kloet, Caitlin Walsh, Stephen C Bishop, James GD Prendergast, Jeffrey J Schoenebeck, Joe Rainger, Kim M Summers: Arginine to glutamine mutation in olfactomedin-like 3 (OLFML3) is a candidate for severe goniodysgenesis and glaucoma in the Border Collie dog breed. doi: https://doi.org/10.1101/321406
Gelatt KN, (2004.): Prevalence of the breed-related glaucomas in pure-bred dogs in North America. Vet Ophthalmol. 2004;7:97–111.