OMIA:002124-9796 : Coat colour, albinism, oculocutaneous type VI in Equus caballus (horse)

In other species: Chinese giant salamander

Categories: Pigmentation phene , Vision / eye phene

Links to possible relevant human trait(s) and/or gene(s) in OMIM: 113750 (trait) , 609802 (gene)

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal recessive

Considered a defect: no

Key variant known: yes

Year key variant first reported: 2017

Species-specific name: Tiger-eye or Goat-eye

Species-specific description: Mack et al. (2017): "A unique eye color, called tiger-eye, segregates in the Puerto Rican Paso Fino (PRPF) horse breed and is characterized by a bright yellow, amber, or orange iris."

Inheritance: Mack et al. (2017): "Pedigree analysis identified a simple autosomal recessive mode of inheritance for this trait" (i.e., tiger eye0

Mapping: Mack et al. (2017): "A genome-wide association study (GWAS) with 24 individuals identified a locus on ECA 1 reaching genome-wide significance (Pcorrected = 1.32 × 10-5). This ECA1 locus harbors the candidate gene, Solute Carrier Family 24 (Sodium/Potassium/Calcium Exchanger), Member 5 (SLC24A5), with known roles in pigmentation in humans, mice, and zebrafish. Humans with compound heterozygous mutations in SLC24A5 have oculocutaneous albinism (OCA) type 6 (OCA6) [see MIM hyperlink 113750 above], which is characterized by dilute skin, hair, and eye pigmentation, as well as ocular anomalies."

Markers: Kreuzer et al. (2010) identified six variants within the equine SLC24A5 gene. One of these variants, "an intronic mutation, which is localized 23 bp upstream of exon 5" which they called SME5 (g.13858G>T; ENSECAG00000018641, 12.12.09) was associated with "fading black" in a sample of "31 black horses and 23 fading black horses" from a range of unspecified breeds. {12 Dec 2019: FN thanks Corinne Benavides-Gyger for alerting him to this publication}

Molecular basis: Mack et al. (2017): "Twenty tiger-eye horses were homozygous for a nonsynonymous mutation in exon 2 (p.Phe91Tyr) of SLC24A5 (called here Tiger-eye 1), which is predicted to be deleterious to protein function. Additionally, eight of the remaining 12 tiger-eye horses heterozygous for the p.Phe91Tyr variant were also heterozygous for a 628 bp deletion encompassing all of exon 7 of SLC24A5 (c.875-340_1081+82del), which we will call here the Tiger-eye 2 allele. None of the 122 brown-eyed horses were homozygous for either tiger-eye-associated allele or were compound heterozygotes. Further, neither variant was detected in 196 horses from four related breeds not known to have the tiger-eye phenotype."

Breed: Paso Fino (Horse) (VBO_0001040).
Breeds in which the phene has been documented. (If a likely causal variant has been documented for the phene, see the variant table breeds in which the variant has been reported).

Associated gene:

Symbol Description Species Chr Location OMIA gene details page Other Links
SLC24A5 solute carrier family 24 (sodium/potassium/calcium exchanger), member 5 Equus caballus 1 NC_009144.3 (142739110..142718600) SLC24A5 Homologene, Ensembl , NCBI gene


By default, variants are sorted chronologically by year of publication, to provide a historical perspective. Readers can re-sort on any column by clicking on the column header. Click it again to sort in a descending order. To create a multiple-field sort, hold down Shift while clicking on the second, third etc relevant column headers.

WARNING! Inclusion of a variant in this table does not automatically mean that it should be used for DNA testing. Anyone contemplating the use of any of these variants for DNA testing should examine critically the relevant evidence (especially in breeds other than the breed in which the variant was first described). If it is decided to proceed, the location and orientation of the variant sequence should be checked very carefully.

Since October 2021, OMIA includes a semiautomated lift-over pipeline to facilitate updates of genomic positions to a recent reference genome position. These changes to genomic positions are not always reflected in the ‘acknowledgements’ or ‘verbal description’ fields in this table.

OMIA Variant ID Breed(s) Variant Phenotype Gene Allele Type of Variant Source of Genetic Variant Reference Sequence Chr. g. or m. c. or n. p. Verbal Description EVA ID Year Published PubMed ID(s) Acknowledgements
811 Paso Fino (Horse) Tiger eye SLC24A5 Tiger-eye 2 deletion, gross (>20) Naturally occurring variant EquCab3.0 1 NC_009144.3:g.143129074_143129702del published as a 628bp deletion: chr1:141660611–141661239; ENSECAT00000019866.1:c.875-340_1081 + 82del 2017 28655738
810 Paso Fino (Horse) Tiger eye SLC24A5 Tiger-eye 1 missense Naturally occurring variant EquCab3.0 1 NC_009144.3:g.143145865A>T XM_023618043.1:c.272A>T XP_023473811.1:p.(F91Y) rs5334475205 2017 28655738 Variant coordinates obtained from or confirmed by EBI's Some Effect Predictor (VEP) tool

Cite this entry

Nicholas, F. W., Tammen, I., & Sydney Informatics Hub. (2019). OMIA:002124-9796: Online Mendelian Inheritance in Animals (OMIA) [dataset].


Note: the references are listed in reverse chronological order (from the most recent year to the earliest year), and alphabetically by first author within a year.

2017 Mack, M., Kowalski, E., Grahn, R., Bras, D., Penedo, M.C.T., Bellone, R. :
Two variants in SLC24A5 are associated with "Tiger-Eye" iris pigmentation in Puerto Rican Paso Fino horses. G3 (Bethesda) 7:2799-2806, 2017. Pubmed reference: 28655738. DOI: 10.1534/g3.117.043786.
2012 Kowalski, E., Staiger, E., Brooks, S., Bellone, R. :
A genome-wide association study identifies “tiger” eye color variation locus on ECA1 in Puerto Rican Paso Fino horses Proceedings of the 33rd Conference of the International Society of Animal Genetics :Abstract 3003, 2012.
2011 Kowalski, E.J.A., Bellone, R.R. :
Investigation of HERC2 and OCA2 SNP for iris color variation in puerto rican paso fino horses Journal of Equine Veterinary Science 31:319, 2011. DOI: 10.1016/j.jevs.2011.03.154.
2010 Kreuzer, S., Reissmann, M., Brockmann, G.A. :
A mutation in the equine SLC24A5 gene is associated with a dilution of black horses. Proceedings of the 9th World Congress on Genetics Applied to Livestock Production Leipzig (Germany). August 1-6. Horse Breeding:Poster 0516, 2010.

Edit History

  • Created by Frank Nicholas on 02 Sep 2017
  • Changed by Frank Nicholas on 02 Sep 2017
  • Changed by Frank Nicholas on 12 Dec 2019