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Congenital stationary night blindness (CSNB) - Beagle type
| Acronym: | CSNB |
| Gene: | LRIT3 |
| Mutation: | c.763del |
| Inheritance: | Autosomal Recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Congenital stationary night blindness (CSNB) is a genetic sight disease that affects a lot of animals and it has been recently described in dogs too. The first disease causative variant associated with CSNB in the dog was reported in Beagle dogs. This still incurable disease causes non-progressive retinal dystrophies that manifest as dark or dim-light vision impairment in affected dogs starting from birth. Vision impairment is usually a consequence of defects in retinoid metabolism in the retinal pigment epithelium (RPE), defects in photoreceptor transduction, or signal transmission through other types of eye cells. This type of CSNB found in Beagles is caused by a 1 bp deletion in the LRIT3 gene that gives a rise to a truncated protein with an important role in the synapse formation and synaptic transmission between cone photoreceptor cells and retinal bipolar cells.
CSNB in Beagle dogs is inherited as an autosomal recessive trait meaning two copies of the mutated gene are required for the diseases to develop. That means Beagles with only one copy of the gene will not develop the disease but can act as carriers of the mutation. Since currently there is no cure for the disease, early genetic testing can help identify affected dogs that carry the mutation and prevent their further breeding by proper selection of 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:
Oh, A., Loew, E. R., Foster, M. L., Davidson, M. G., English, R. V., Gervais, K. J., Herring, I. P., Mowat, F. M. (2018). Phenotypic characterization of complete CSNB in the inbred research beagle: how common is CSNB in research and companion dogs?. Documenta ophthalmologica. Advances in ophthalmology, 137(2), 87–101. https://doi.org/10.1007/s10633-018-9653-y
Das, R. G., Becker, D., Jagannathan, V., Goldstein, O., Santana, E., Carlin, K., Sudharsan, R., Leeb, T., Nishizawa, Y., Kondo, M., Aguirre, G. D., Miyadera, K. (2019). Genome-wide association study and whole-genome sequencing identify a deletion in LRIT3 associated with canine congenital stationary night blindness. Scientific reports, 9(1), 14166. https://doi.org/10.1038/s41598-019-50573-7