Genetics and characteristics
POAG Petit Basset Griffon Vendeen Type is an inherited ocular neuropathy caused by a mutation in the ADAMTS17 gene. POAG stands for ”primary open-angle glaucoma” a specific form of the disorder that is part of a wide group of disorders generally known as glaucoma. Glaucoma can be divided into two different forms of the disorder, 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. Except in Petit Basset Griffon Vendeen breed, POAG has been identified also in other dog breeds: Shar Pei, Beagle, Norwegian Elkhound, Basset Hound, and Basset Fauve de Bretagne.
The first case of POAG Petit Basset Griffon Vendeen Type was recorded in the United Kingdom in 1996. First symptoms usually start to develop between 3 to4 years of age, equally in both sexes. The disorder is characterized by elevated intraocular pressure and lens subluxation. The pectinate ligament abnormality and the closure of the iridocorneal angle do not appear until the late stages of the disease, followed by retinal degeneration and a cupping deformation of the optic papilla. The disorder is usually painless, which results in a late diagnosis of the disorder, most commonly when the onset of vision loss occurs.
POAG Petit Basset Griffon Vendeen Type is caused by inversion mutation within the ADAMTS17 gene. The disorder is inherited as an autosomal recessive disorder. Healthy parents of an affected dog are obligate heterozygotes and therefore carry one mutant allele. Heterozygotes are carriers and show no symptoms. At conception, each cub 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:
Forman, O. P., Pettitt, L., Komaromy, A. M., Bedford, P., Mellersh, C. (2015) A Novel Genome-Wide Association Study Approach Using Genotyping by Exome Sequencing Leads to the Identification of a Primary Open Angle Glaucoma Associated Inversion Disrupting ADAMTS17. PloS ONE 10(12): e0143546. doi: 10.1371/journal.pone.0143546.