{"topic_id":"companion_species_health_gray_grey_greying_with_age_horse","category":"companion-species-health","context":"---\nlicense: permission_granted\ntopic_id: companion_species_health_gray_grey_greying_with_age_horse\ncategory: companion-species-health\ntitle: \"Horse (Equus caballus) — Gray; Grey; Greying with age (hereditary; OMIA-verified species predisposition)\"\nlang: en\nsource: \"OMIA (Online Mendelian Inheritance in Animals, University of Sydney) species-specific hereditary-disorder record, saved verbatim to source_file; C1 substring-verified. Pulled 2026-08-24 from local OMIA database dump.\"\nsource_file: pdf-raw/species-health/horse_gray_grey_greying_with_age_2696.txt\ndate_parsed: 2026-08-24\ntokens_estimated: 292\nverification:\n method: substring_match\n claims: 4\n passed: 4\n date: 2026-08-24\nrecovered: false\npath: companion-species-health/companion_species_health_gray_grey_greying_with_age_horse/01_companion_species_health_gray_grey_greying_with_age_horse.md\nsource_document: \"OMIA — Online Mendelian Inheritance in Animals (University of Sydney)\"\ncitation:\n authority: \"OMIA — Online Mendelian Inheritance in Animals (University of Sydney)\"\n title: \"Horse (Equus caballus) — Gray; Grey; Greying with age (hereditary; OMIA-verified species predisposition)\"\n url: \"https://omia.org/OMIA001356/9796/\"\n retrieved: \"2026-08-24\"\n ref: \"OMIA species-specific hereditary-disorder records (omia.org), derived from local OMIA database dump; dataset: https://doi.org/10.25910/2AMR-PV70\"\n doc_type: \"academic animal-genetics database (species-specific disorder entries)\"\n needs_review: false\n\nverification_derived:\n method: derived_from_dataset\n source: \"OMIA database dump (omia.xml, local); fields Gene/Variant/Article/OMIM\"\n 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.\"---\n\n# Horse (Equus caballus) — Gray; Grey; Greying with age (hereditary; OMIA-verified species predisposition)\n\nSource: first-hand OMIA (University of Sydney) species-specific hereditary-disorder record, saved verbatim to `source_file`; every claim below is a C1 byte-substring of it.\n\n## Claims\n\n- `Species: Horse (Equus caballus)`\n- `Disorder: Gray; Grey; Greying with age`\n- `Summary: Grey horses are born with normal pigmentation, but gradually lose their pigmentation as they age, until, typically at around 6-12 years old, they become white, while retaining dark skin pigmentation. Included with this phenotype is a relatively high incidence of dermal melanomas, and an associated decrease in life expectancy (see  OMIA:002231-9796 : Melanoma, generic in Equus caballus)`\n- `Gen test: Since exactly the same mutation is completely associated with the grey phenotype in more than 850 horses from numerous breeds (Rosengren Pielberg et al., 2008), it is very likely that a single DNA test will suffice to detect virtually all occurrences of the grey alleles. Kavar et al. (2012) provide details of a robust DNA test. Nowacka-Woszuk et al. (2021) provide methods for using ddPCR to detect copy number which can help in distinguishing between the G1, G2, and G3 alleles.  Horses with only a G1 allele will not be grey, and therefore some testing laboratories report this allele as N (for normal). `\n## Associated gene(s)\nDerived 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/.txt source file.\n- Gene: Entrez Gene ID 4157477 (no symbol in OMIA GeneSynonym) — OMIA Phene_Gene\n- OMIA molecular-genetics note: Rosengren Pielberg et al. (2008) presented convincing evidence that this classic phenotype is due to a 4.6kb intronic duplication in the gene for syntaxin-17 (STX17). This duplication appears to increase the expression of both syntaxin-17 and a neighbouring gene NR4A3, which encodes nuclear receptor subfamily 4, group A, member 3. Whilst the details are still to be elucidated, Pielberg et al. (200…\n\n## Evidence (references)\nDerived 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/.txt source file.\n- 2002. Genetic mapping of the (G)-locus, responsible for the coat color phenotype \"progressive greying with age\" in horses (Equus caballus). Mammalian Genome — PubMed:PMID12370784 | DOI:10.1007/s00335-002-2174-7 — OMIA Phene_Article / Article\n- 2002. Linkage of the grey coat colour locus to microsatellites on horse chromosome 25. Animal Genetics — PubMed:PMID12354140 — OMIA Phene_Article / Article\n- 2002. Assignment of the horse grey coat colour gene to ECA25 using whole genome scanning. Animal Genetics — PubMed:PMID12354141 — OMIA Phene_Article / Article\n- 2005. Comparative linkage mapping of the Grey coat colour gene in horses. Anim Genet — PubMed:PMID16167981 | DOI:10.1111/j.1365-2052.2005.01334.x — OMIA Phene_Article / Article\n- 2008. A cis-acting regulatory mutation causes premature hair graying and susceptibility to melanoma in the horse. Nature Genetics — PubMed:PMID18641652 | DOI:10.1038/ng.185 — OMIA Phene_Article / Article\n- 1977. [Comparative investigations of depigmented and melanomatous lesions in gray horses of the lipizzaner breed (author's transl)]. Arch Dermatol Res — PubMed:PMID900991 — OMIA Phene_Article / Article\n- 2004. Comparative histopathology of grey-horse-melanoma and human malignant melanoma. Pigment Cell Res — PubMed:PMID15541026 | DOI:10.1111/j.1600-0749.2004.00192.x — OMIA Phene_Article / Article\n- 2003. Equine melanoma in a population of 296 grey Lipizzaner horses. Equine Vet J — PubMed:PMID12638791 — OMIA Phene_Article / Article\n- 2001. Disseminated metastatic intramedullary melanoma in an aged grey horse. J Comp Pathol — PubMed:PMID11578137 | DOI:10.1053/jcpa.2001.0481 — OMIA Phene_Article / Article\n- 2001. Tumor regression induced by intratumoral injection of DNA coding for human interleukin 12 into melanoma metastases in gray horses. J Mol Med — PubMed:PMID11434722 — OMIA Phene_Article / Article\n- 2000. The study of cutaneous melanomas in Camargue-type gray-skinned horses (2): epidemiological survey. Pigment Cell Res — PubMed:PMID10761996 — OMIA Phene_Article / Article\n- 2000. The study of cutaneous melanomas in Camargue-type gray-skinned horses (1): clinical-pathological characterization. Pigment Cell Res — PubMed:PMID10761995 — OMIA Phene_Article / Article\n- (31 additional references in OMIA)\n\n## Comparative medicine (human OMIM)\nDerived 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/.txt source file.\n- OMIM:604204 (type: gene) — OMIA Group_OMIM (via OMIA_ID)\n","sources":["companion-species-health — Horse (Equus caballus) — Gray; Grey; Greying with age (hereditary; OMIA-verified species predisposition)"],"source":{"authority":"companion-species-health","title":"Horse (Equus caballus) — Gray; Grey; Greying with age (hereditary; OMIA-verified species predisposition)","url":"https://pubmed.ncbi.nlm.nih.gov/12370784/","retrieved":"","ref":"PMID 12370784","doc_type":"official source","source_document":"","verification_file":""},"source_document":"","source_file":"","trust":{"authority_tier":"ungraded","fidelity":"verbatim","license":null,"display_grade":"pending"},"tokens_estimated":1125,"generated_at":null,"tip":"Use /api/v1/topics to discover more topics. /api/v1/nutrient for precise single-point queries. /api/v1/cross_compare for 2-3 standard comparisons."}