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Canine Mendelian disease record

X-Linked Progressive Retinal Atrophy 1 (XLPRA1)

X-Linked Progressive Retinal Atrophy 1 (XLPRA1). X-linked (OMIA); X-linked recessive (Donner 2023). Observed in 1 of 266 breeds tested in the Sniff Atlas, with measured allele frequencies drawn from 242,664 dogs (Donner 2023). Whether a dog carrying this variant is at risk depends on the disease’s inheritance pattern; outcome also depends on penetrance, modifiers, and environment. The frequencies below describe variant prevalence, not confirmed disease incidence.

OMIA identifier
OMIA:000831-9615
X-linked (OMIA); X-linked recessive (Donner 2023)
Source dataset
Sniff Atlas v1.0.2 / DOI
The human connection

A model of human macular degeneration, X-linked atrophic

In dogs this condition is linked to the RPGR gene. In people, changes in the same gene cause macular degeneration, X-linked atrophic. This canine condition is studied as a natural model of macular degeneration, X-linked atrophic in people; it is not the same as that human diagnosis. Studying dogs can move medicine forward for everyone; the canine disease remains the subject.

MONDO:0010443 OMIM 300029OMIM 300455

Mapped from OMIA via the human disease's OMIM entry to the Mondo Disease Ontology (Monarch Initiative, CC-BY 4.0). Closely related human conditions exist for this gene. Sniff renders this as a model-of link; the canine disease remains the subject of this page.

About this disease

From OMIA's curated record

Documented in OMIA (Online Mendelian Inheritance in Animals). This describes the disease as recorded in the published literature, not a prediction for any individual dog. As of 2026-08-27.

Summary

The difference between XLPRA1 (this entry) and XLPRA2 (OMIA:001518-9615) is summarised by Appelbaum et al. (2020) as "XLPRA1-affected dogs have normal PR morphogenesis, after which progressive rod–cone degeneration develops in the peripheral retina, gradually advancing toward the optic disc. . . . The phenotype associated with XLPRA2 is very severe and manifests during early retinal development."

Molecular genetics

Based on a comparative positional cloning approach (the canine disorder maps to a location on the canine X chromosome that is homologous with the location of the same disorder (RP3) in humans, which is due to mutations in the RPGR gene), Zhang et al. (2002) identified a "five-nucleotide deletion (delGAGAA) between 1028 and 1032" (omia.variant:480) in the canine RPGR gene as a causal mutation for a form of X-linked PRA they call XPRA1. The authors also noted that "The XLPRA1 mutation causes a frameshift and immediate premature stop; the truncated protein is missing 230 C-terminal amino acids, causing a slight decrease in the isoelectric point (3.89 versus 4.01 in normal). By mutation scanning, we also found the same five-nucleotide deletion in the Samoyed breed with a clinically similar X-linked retinal degeneration (data not shown)". Kropatsch et al. (2016): "Whole exome sequencing in two PRA-affected Weimaraner dogs identified a large deletion [maximum size 5,006 bp, omia.variant:688] comprising the first four exons of the X-linked retinitis pigmentosa GTPase regulator (RPGR) gene".  
Xie et al. (2025) "generated a stably inherited RPGR-knockout beagle model of XLRP in one-step via CRISPR/Cas9 gene editing tool with multiple gRNAs and zygote microinjection technology. ... The F0-male harbored a single allele, with a ∼4.6 kb deletion from exon 4 to exon 5 (c.3691_8311del) and a 2 bp deletion in exon 6 (c.8789_8790del) ... . The F0-female carried three alleles, first allele (detected as 1/34 clones) with a ∼1.8 kb deletion from exon 4 to exon 5 (c.3691_5485del) and a 1 bp deletion in exon 6 (c.8788del), second allele (detected as 13/34 clones) with a ∼0.9 kb deletion within exon 4 (c.3408_4327del) and a ∼3.3 kb deletion from exon 5 to exon 6 (c.5488_8849del), and third allele (detected as 20/34 clones) with a ∼5.0 kb deletion from exon 4 to exon 6 (c.3691_8789del) ... ." This study involves gene edited or genetically modified organisms (GMO).

Pathology

As summarised by Zeiss et al. (1999): " The earliest lesion detectable by electron microscopy was vesiculation of rod discs, followed by disruption of outer segments and death of rods. Loss of cones and progressive atrophy of inner retinal layers followed. Lesions were most severe in the peripheral retina and advanced toward the optic disc with disease progression. Significant variation in disease severity was present in males despite the presence of the same disease allele in all affected dogs." As concluded by the same authors: "X-linked retinal degeneration is characterized by initial degeneration of rod photoreceptors, followed by loss of cones and progressive atrophy of the inner retina. Carrier females display a phenotype consistent with random X-chromosome inactivation. Variation in genetic background may alter expression of the disease allele in affected animals, thus accounting for variation in phenotypic expression of the disease."

Human analog

OMIA links this condition to its human counterpart in OMIM (Mendelian Inheritance in Man), the place to read across to the deeper human literature for the same biology.

Disease · OMIM 300029 Disease · OMIM 300455 Disease · OMIM 300834 Disease · OMIM 304020 Gene · OMIM 312610

Source: OMIA (Nicholas, Tammen & the Sydney Informatics Hub), entry OMIA:000831-9615, doi:10.25910/2AMR-PV70 (CC-BY 4.0).

OMIA curates the disease definition, the clinical description and the reference list. The cross-species disease identity is Monarch's. Sniff renders these and adds the breed-level frequencies, the plain-language summary, and a stated reason wherever a number is missing.

The evidence

Published references

The peer-reviewed papers behind this disease, curated by OMIA. Starred entries are OMIA-designated landmark papers. Showing 6 of 28.

References curated by OMIA (Nicholas, Tammen & the Sydney Informatics Hub), doi:10.25910/2AMR-PV70 (CC-BY 4.0). Full list at the OMIA entry.

Your breed

See what X-Linked Progressive Retinal Atrophy 1 (XLPRA1) looks like in your dog's breed.
Allele frequency by breed

Top 1 well-sampled breeds (n ≥ 50)

Maximum per breed across variants in the Donner 2023 cohort, with . The list below is split into well-sampled breeds (n ≥ 50 tested) and small-sample breeds (n < 50, where the Wilson CI typically spans more than 20 percentage points and frequencies should not be compared directly to the well-sampled entries). Frequencies are population-level, not per-litter or per-line.

0%1%2%
Siberian Husky<0.1% · n 9,035
n = 9,035 dogs · Donner et al. 2023 carrier-screening cohort · Sniff Atlas
n counts the dogs in the breeds charted here; the page total above counts every breed screened. Each bar is one well-sampled breed; the whisker is its Wilson 95% CI, and fainter bars have wider intervals. Frequencies are population-level, not per-litter. Carrier status for X-Linked Progressive Retinal Atrophy 1 (XLPRA1) is measured; phenotype outcome depends on penetrance and modifiers.
▸ Full table with Wilson 95% confidence intervals
Breed Allele frequency n tested
Siberian Husky <0.1% 9,035

265 additional breeds in the Donner 2023 cohort were tested but showed no variant copies.

Penetrance

From genotype to phenotype

Whether carrying this variant means a dog is at risk depends on the inheritance pattern. Penetrance is the fraction of at-risk dogs that develop the phenotype. The Donner 2023 S4 table tracks this for 1 variant(s) underlying this disease in the cohort.

At-risk dogs evaluated
1
Phenotype confirmed
0
Penetrance range
not yet quantifiable

Fewer than 20 at-risk dogs evaluated; too few to state a penetrance figure.

Predicted disease relevance at the per-dog level is UNPROVEN. The allele frequency is measured; phenotype outcome is governed by penetrance, environment, and modifier loci. Consult a veterinarian for clinical interpretation.

How to cite this record

Citations

If you use this record in published work, cite the Sniff Atlas (the published dataset that carries the breed-level allele frequencies) and the upstream sources:

  • Sniff Atlas v1.0.2 for the per-breed allele frequencies:

    Gehring, M. (2026). Sniff Atlas v1.0.2. Zenodo. https://doi.org/10.5281/zenodo.20566358. CC-BY 4.0.

  • OMIA for the disease definition, inheritance, and gene assignment:

    Nicholas, F. W., & Tammen, I. (2024). OMIA. Sydney Informatics Hub, The University of Sydney. https://doi.org/10.25910/2AMR-PV70. Entry: OMIA:000831-9615.

  • Donner et al. 2023 for the breed × variant allele-frequency cohort:

    Donner, J., Freyer, J., Davison, S., Anderson, H., Blades, M., Honkanen, L., et al. (2023). Genetic prevalence and clinical relevance of canine Mendelian disease variants in over one million dogs. PLOS Genetics, 19(2), e1010651. https://doi.org/10.1371/journal.pgen.1010651.

Full citation formats (BibTeX, RIS, CITATION.cff) at sniff.world/cite.

Related

Related

Last updated
Sources: Sniff Atlas v1.0.2 · OMIA OMIA:000831-9615 · Donner et al. 2023