American Trotter (Horse) — Night blindness, congenital stationary, GRM6-related (hereditary; OMIA-verified breed predisposition)

--- license: permission_granted topic_id: companion_breed_health_american_trotter_horse_omia5331_horse category: companion-breed-health title: "American Trotter (Horse) — Night blindness, congenital stationary, GRM6-related (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 2026-08-23 from local OMIA database dump." source_file: pdf-raw/breed-health/american_trotter_horse_omia5331_5331.txt date_parsed: 2026-08-23 tokens_estimated: 348 verification: method: substring_match claims: 5 passed: 5 date: 2026-08-23 recovered: false path: companion-breed-health/companion_breed_health_american_trotter_horse_omia5331_horse/01_companion_breed_health_american_trotter_horse_omia5331_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: "American Trotter (Horse) — Night blindness, congenital stationary, GRM6-related (hereditary; OMIA-verified breed predisposition)" url: "https://omia.org/OMIA002692/9796/" retrieved: "2026-08-23" 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

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."---

American Trotter (Horse) — Night blindness, congenital stationary, GRM6-related (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: American Trotter (Horse)
Disorder:
Summary: Hack et al. (2021) reported a Tennessee Walking Horse with congenital stationary night blindness (CSNB) that did not have a the TRPM1 variant known to cause CSNB in horses (see OMIA:001341-9796 : Night blindness, congenital stationary, TRPM1-related in Equus caballus). Esdaile et al. (2024) provides additional evidence that GRM6 c.533Cgt;T homozygosity is likely causal to CSNB in Tennessee Walking Horses, Standardbreds, and Missouri Fox Trotting Horses.
Defect: yes
Prevalence: Hack et al. (2021): This variant [GRM6 c.533Cgt;T] was not detected in 273 horses from three additional breeds. The estimated allele frequency in Tennessee Walking Horses is 10%. Esdaile et al. (2024): The CSNB2 allele was present in nine breeds [American Quarter Horse, Racking Horse, Rocky Mountain Horse, American Saddlebred, Spotted Saddle Horse, Standardbred (pacer), Miniature Horse, Missouri Fox Trotting Horse, Morgan], ranging in frequency from 0.0010 in American Quarter Horses (n = 486) to 0.17 in pacing Standardbreds (n = 110 ...). The CSNB2 allele was not detected in trotting Standardbreds (n = 70), Thoroughbreds (n = 1787), Hackney Horses (n = 47), Hackney Ponies (n = 44), and Shetland Ponies (n = 99 ...).

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 388955788 (no symbol in OMIA GeneSynonym) — OMIA Phene_Gene
OMIA molecular-genetics note: Hack et al. (2021): "WGS [whole genome sequencing] analysis identified a missense mutation in metabotropic glutamate receptor 6 (GRM6) (c.533C>T p.Thr178Met)."

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.

2021. Whole-genome sequencing identifies missense mutation in GRM6 as the likely cause of congenital stationary night blindness in a Tennessee Walking Horse. Equine Vet J — PubMed:PMID32654228 | DOI:10.1111/evj.13318 — OMIA Phene_Article / Article
2024. Additional evidence supports GRM6 p.Thr178Met as a cause of congenital stationary night blindness in three horse breeds. Vet Ophthalmol — PubMed:PMID37815029 | DOI:10.1111/vop.13151 — OMIA Phene_Article / Article
2024. Consensus guidelines for nomenclature of companion animal inherited retinal disorders. Vet Ophthalmol — PubMed:PMID38334230 | DOI:10.1111/vop.13185 — OMIA Phene_Article / Article

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:604096 (type: gene) — OMIA Group_OMIM (via OMIA_ID)
OMIM:257270 (type: trait) — OMIA Group_OMIM (via OMIA_ID)

American Trotter (Horse) — Night blindness, congenital stationary, GRM6-related (hereditary; OMIA-verified breed predisposition)