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Progressive Retinal Atrophy (PRA4) - Lhasa Apso Type
| Acronym: | PRA4 |
| Gene: | IMPG2 |
| Mutation: | Insercija LINE-1 |
| Inheritance: | Autosomal Recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Progressive retinal atrophy (PRA4) is a genetic eye disorder, which belongs to blinding retinal degenerative diseases. More than 20 genes in dogs have been identified as causes that can lead to retinal defects and progressive vision deprivation, but this type is specific for Lhasa Apso dogs. Like other retinal disorders, PRA4 is characterized by degeneration of retinal photoreceptor cells, progressive loss of vision, retinal thinning, and atrophy of the optic nerve head. The cause of the disorder is a long interspersed element-1 (LINE-1) insertion upstream of the IMPG2 gene. IMPG2 belongs to a group of glycosylated proteins called proteoglycans, which bind the large carbohydrates (glycosaminoglycans) in neural tissues. IPM proteins play an important role in recycling photoreceptors and their elements.
This retinal atrophy disorder in Lhasa Apso dogs is inherited as an autosomal recessive trait, requiring two copies of the mutated gene for the disease to develop. Dogs with only one copy of the mutated gene will not develop the disease but may act as carriers and pass the mutation to their offspring. There is no cure for PRA4, and the only way to prevent it is early detection by genetic testing that can help breeders in selecting future mating pairs.
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:
Hitti-Malin, R. J., Burmeister, L. M., Ricketts, S. L., Lewis, T. W., Pettitt, L., Boursnell, M., Schofield, E. C., Sargan, D., Mellersh, C. S. (2020). A LINE-1 insertion situated in the promoter of IMPG2 is associated with autosomal recessive progressive retinal atrophy in Lhasa Apso dogs. BMC genetics, 21(1), 100. https://doi.org/10.1186/s12863-020-00911-w