Goniodysgenesis and glaucoma in Border Collie
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 has been documented for the first time in Australia in the late 1990s and afterwards have been found also in Europe and the USA. It is particularly commonly diagnosed in some Border collie lineages; in conducted study, 10.8% of Border collies were reported to have moderate or severe pectinate ligament dysplasia, alteration in eye structure responsible for proper humour drainage.
Characteristics and symptoms
Fluid inside of the eye is called aqueous humour. It is produced behind the iris, in the ciliary body. This fluid flows through the eye and drains from the eye, maintaining the normal eye pressure. The drain network in the eye is called the drainage angle or drainage canals. Inadequate outflow of aqueous humour causes build-up of pressure, and consequently, glaucoma. Prolonged intraocular pressure results in damage of optic nerves, whose damage is irreversible. Glaucoma can be preceded by goniodysgenesis, which is a developmental abnormality of the eye characterised by narrowing or closure of the iridocorneal angle through which the aqueous humour drains.
Symptoms of goniodysgenesis and primary glaucoma include severe pain, sensitivity to light (photophobia), winking spasms (blepharospasm), startling when dog’s head is touched, watery, red eyes with dilated pupils, and behavioural change, such as hiding, refusal to eat.
Goniodysgenesis and glaucoma in Border Collie is caused by a missense mutation in the OLFML3 gene, which is expressed in tissues of the eye, such as 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 formation of the proper drainage channels.
Goniodysgenesis and glaucoma in Border Collie is 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.
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