Mixed Breed — Retinal atrophy, progressive, X-linked, type 2 (hereditary; OMIA-verified breed predisposition)

--- license: permission_granted topic_id: companion_breed_health_mixed_breed_omia2992_dog category: companion-breed-health title: "Mixed Breed — Retinal atrophy, progressive, X-linked, type 2 (hereditary; OMIA-verified breed predisposition)" lang: en source: "OMIA (Online Mendelian Inheritance in Animals, University of Sydney) breed-specific hereditary-disorder record, saved verbatim to source_file; C1 substring-verified. Pulled 2026-08-02 from local OMIA database dump." source_file: pdf-raw/breed-health/mixed_breed_omia2992_2992.txt date_parsed: 2026-08-02 tokens_estimated: 416 verification: method: substring_match claims: 6 passed: 6 date: 2026-08-02 recovered: false path: companion-breed-health/companion_breed_health_mixed_breed_omia2992_dog/01_companion_breed_health_mixed_breed_omia2992_dog.md source_document: "OMIA — Online Mendelian Inheritance in Animals (University of Sydney)" citation: authority: "OMIA — Online Mendelian Inheritance in Animals (University of Sydney)" title: "Mixed Breed — Retinal atrophy, progressive, X-linked, type 2 (hereditary; OMIA-verified breed predisposition)" url: "https://omia.org/OMIA001518/9615/" retrieved: "2026-08-02" ref: "OMIA breed-specific hereditary-disorder records (omia.org), derived from local OMIA database dump; dataset: https://doi.org/10.25910/2AMR-PV70" doc_type: "academic animal-genetics database (breed-specific disorder entries)" needs_review: false

Mixed Breed — Retinal atrophy, progressive, X-linked, type 2 (hereditary; OMIA-verified breed predisposition)

Source: first-hand OMIA (University of Sydney) breed-specific hereditary-disorder record, saved verbatim to source_file; every claim below is a C1 byte-substring of it.

Claims

• Breed: Mixed Breed (Dog)
• Disorder:
• Mode of inheritance: X-linked
• Summary: The difference between XLPRA1 (a href=../../../../../../OMIA000831/9615/OMIA:000831-9615/a) and XLPRA2 (this entry) 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.
• Clin feat: Beltran et al. (2006): Abnormal development of photoreceptors was recognizable as early as 3.9 weeks of age. Outer segment (OS) misalignment was followed by their disorganization and fragmentation. Reduction in length and broadening of rod and cone inner segments (IS) was next observed, followed by the focal loss of rod and cone IS at later time points. The proportion of dying photoreceptors peaked at approximately 6 to 7 weeks of age and was significantly reduced after 12 weeks. In addition to rod and cone opsin mislocalization, there was early rod neurite sprouting, retraction of rod bipolar cell dendrites, and increased Müller cell reactivity. Later in the course of the disease, changes were also noted in horizontal cells and amacrine cells. As summarised by these authors: XLPRA2 is an early-onset model of XLRP that is morphologically characterized by abnormal photoreceptor maturation followed by progressive rod-cone degeneration and early inner retina remodeling.
• Defect: yes

Associated gene(s)

Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.

• Gene: Entrez Gene ID 403726 (no symbol in OMIA GeneSynonym) — OMIA Phene_Gene
• OMIA molecular-genetics note: 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 "a two-nucleotide deletion (delGA) in 1084–1085" in the canine RPGR gene as a causal mutation for a form of X-linked PRA they cal…

Evidence (references)

Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.

• 2002. Different RPGR exon ORF15 mutations in Canids provide insights into photoreceptor cell degeneration. Hum Mol Genet — PubMed:PMID11978759 — OMIA Phene_Article / Article
• 2010. Transcriptional Profile Analysis of RPGRORF15 Frameshift Mutation Identifies Novel Genes Associated with Retinal Degeneration. Invest Ophthalmol Vis Sci — PubMed:PMID20574030 | DOI:10.1167/iovs.10-5443 — OMIA Phene_Article / Article
• 2006. A frameshift mutation in RPGR exon ORF15 causes photoreceptor degeneration and inner retina remodeling in a model of X-linked retinitis pigmentosa. Invest Ophthalmol Vis Sci — PubMed:PMID16565408 | DOI:10.1167/iovs.05-0845 — OMIA Phene_Article / Article
• 2007. Independent origin and restricted distribution of RPGR deletions causing XLPRA. J Hered — PubMed:PMID17646274 | DOI:10.1093/jhered/esm060 — OMIA Phene_Article / Article
• 2012. Genetic and phenotypic variations of inherited retinal diseases in dogs: the power of within- and across-breed studies. Mamm Genome — PubMed:PMID22065099 | DOI:10.1007/s00335-011-9361-3 — OMIA Phene_Article / Article
• 2012. Gene therapy rescues photoreceptor blindness in dogs and paves the way for treating human X-linked retinitis pigmentosa. Proc Natl Acad Sci U S A — PubMed:PMID22308428 | DOI:10.1073/pnas.1118847109 — OMIA Phene_Article / Article
• 2013. Up-regulation of tumor necrosis factor superfamily genes in early phases of photoreceptor degeneration. PLoS One — PubMed:PMID24367709 | DOI:10.1371/journal.pone.0085408 — OMIA Phene_Article / Article
• 2014. Altered miRNA expression in canine retinas during normal development and in models of retinal degeneration. BMC Genomics — PubMed:PMID24581223 | DOI:10.1186/1471-2164-15-172 — OMIA Phene_Article / Article
• 2017. Involvement of innate immune system in late stages of inherited photoreceptor degeneration. Sci Rep — PubMed:PMID29263354 | DOI:10.1038/s41598-017-18236-7 — OMIA Phene_Article / Article
• 2020. Toxicity and efficacy evaluation of an AAV vector expressing codon-optimized RPGR delivered by subretinal injection in a canine model of X-linked retinitis pigmentosa. Hum Gene Ther — PubMed:PMID31910043 | DOI:10.1089/hum.2019.297 — OMIA Phene_Article / Article
• 2020. Critical decrease in the level of axon guidance receptor ROBO1 in rod synaptic terminals is followed by axon retraction. Invest Ophthalmol Vis Sci — PubMed:PMID32176262 | DOI:10.1167/iovs.61.3.11 — OMIA Phene_Article / Article
• 2020. Impact of gene therapy for canine monogenic diseases on the progress of preclinical studies. J Appl Genet — PubMed:PMID32189222 | DOI:10.1007/s13353-020-00554-8 — OMIA Phene_Article / Article
• (15 additional references in OMIA)

Comparative medicine (human OMIM)

Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.

• OMIM:300029 (type: trait) — OMIA Group_OMIM (via OMIA_ID)
• OMIM:312610 (type: gene) — OMIA Group_OMIM (via OMIA_ID)
• OMIM:304020 (type: trait) — OMIA Group_OMIM (via OMIA_ID)
• OMIM:300834 (type: trait) — OMIA Group_OMIM (via OMIA_ID)
• OMIM:300455 (type: trait) — OMIA Group_OMIM (via OMIA_ID)

verification_derived: method: derived_from_dataset source: "OMIA database dump (omia.xml, local); fields Gene/Variant/Article/OMIM" note: "Structured fields (gene, variant rsID/protein change, PubMed/DOI references, OMIM cross-link) extracted from OMIA dump and presented with first-hand values; not verbatim prose."