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Horse (Equus caballus) — Gray; Grey; Greying with age (hereditary; OMIA-verified species predisposition)

companion_species_health_gray_grey_greying_with_age_horse

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--- license: permission_granted topic_id: companion_species_health_gray_grey_greying_with_age_horse category: companion-species-health title: "Horse (Equus caballus) — Gray; Grey; Greying with age (hereditary; OMIA-verified species predisposition)" lang: en source: "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." source_file: pdf-raw/species-health/horse_gray_grey_greying_with_age_2696.txt date_parsed: 2026-08-24 tokens_estimated: 292 verification: method: substring_match claims: 4 passed: 4 date: 2026-08-24 recovered: false path: companion-species-health/companion_species_health_gray_grey_greying_with_age_horse/01_companion_species_health_gray_grey_greying_with_age_horse.md source_document: "OMIA — Online Mendelian Inheritance in Animals (University of Sydney)" citation: authority: "OMIA — Online Mendelian Inheritance in Animals (University of Sydney)" title: "Horse (Equus caballus) — Gray; Grey; Greying with age (hereditary; OMIA-verified species predisposition)" url: "https://omia.org/OMIA001356/9796/" retrieved: "2026-08-24" ref: "OMIA species-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 (species-specific disorder entries)" needs_review: false

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."---

Horse (Equus caballus) — Gray; Grey; Greying with age (hereditary; OMIA-verified species predisposition)

Source: 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.

Claims

  • Species: Horse (Equus caballus)
  • Disorder: Gray; Grey; Greying with age
  • 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)
  • 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). 

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 4157477 (no symbol in OMIA GeneSynonym) — OMIA Phene_Gene
  • 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…

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. 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
  • 2002. Linkage of the grey coat colour locus to microsatellites on horse chromosome 25. Animal Genetics — PubMed:PMID12354140 — OMIA Phene_Article / Article
  • 2002. Assignment of the horse grey coat colour gene to ECA25 using whole genome scanning. Animal Genetics — PubMed:PMID12354141 — OMIA Phene_Article / Article
  • 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
  • 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
  • 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
  • 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
  • 2003. Equine melanoma in a population of 296 grey Lipizzaner horses. Equine Vet J — PubMed:PMID12638791 — OMIA Phene_Article / Article
  • 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
  • 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
  • 2000. The study of cutaneous melanomas in Camargue-type gray-skinned horses (2): epidemiological survey. Pigment Cell Res — PubMed:PMID10761996 — OMIA Phene_Article / Article
  • 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
  • (31 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:604204 (type: gene) — OMIA Group_OMIM (via OMIA_ID)

Sources

Horse (Equus caballus) — Gray; Grey; Greying with age (hereditary; OMIA-verified species predisposition)
companion-species-healthPMID 12370784

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