Created at the VGL Tiger Eye

Quick Summary

Tiger eye is a dilute iris color characterized by a yellow, amber, or bright orange color.

Yellow tiger-eye phenotype on left, dark brown wild type phenotype on right
Yellow tiger eye iris (left); Dark brown wild type iris (right). Image credit: Mack et al. (2017)

Phenotype: Tiger eye is a dilute iris color characterized by a yellow, amber, or bright orange color.

Mode of Inheritance: Autosomal recessive

Alleles: N = Normal or not dilute, TE1 = Tiger eye 1 variant, TE2 = Tiger eye 2 variant

Breeds appropriate for testing: Puerto Rican Paso Fino

Explanation of Results:

  • Horses with N/N genotype will not have tiger eye and cannot transmit a tiger eye variant to their offspring.
  • Horses with N/TE1 or N/TE2 genotype will not have tiger eye, but are carriers. They may transmit a tiger eye variant to 50% of their offspring. Matings between two carriers of a tiger eye variant will result in a 25% chance of producing a foal with tiger eye.
  • Horses with TE1/TE1, TE2/TE2, or TE1/TE2 genotype are expected to display a lighter eye color, and will transmit a tiger eye variant to all of their offspring.
Price

$40 one test per animal

Additional Details

Closeup of yellow eye of horse homozygous for Tiger Eye 1 mutation and horse that is compound heterozygous for Tiger Eye 1 and Tiger Eye 2
Top: Horse homozygous for the Tiger eye 1 variant (TE1/TE1 genotype). Bottom: Horse that is compound heterozygous for the Tiger eye 1 and Tiger eye 2 variants (TE1/TE2 genotype). Image credit: Dr. Dineli Bras

Tiger eye is a dilute iris color found in Puerto Rican Paso Fino Horses. In contrast to the brown-colored eyes of most horses, “tiger eye” is characterized by a yellow, amber, or bright orange color. Researchers at the Veterinary Genetics Laboratory investigated the genetic basis of this phenotype and identified two variants in the gene SLC24A5 responsible for tiger eye, named Tiger eye 1 (TE1), in exon 2, and Tiger eye 2 (TE2), in exon 7. The tiger eye phenotype is inherited as a recessive trait. Horses with tiger eye are most frequently homozygous (two copies) for the TE1 variant (TE1/TE1). Some tiger eye horses are compound heterozygous (one copy each) for both variants (TE1/TE2). Horses with the genotype (TE2/TE2) are rare; the one documented case had a very light yellow/blue iris color. Brown-eyed horses can carry one copy of either TE1 or TE2 but they will also have one copy of the normal gene. Unlike the iris color dilution associated with the cream and champagne mutations, there does not appear to be a connection between tiger eye and dilute coat pigmentation. The tiger eye phenotype has been seen on all three non-dilute base coat colors (black, bay, and chestnut) and in both males and females. While to date TE1 and TE2 have only been detected in Puerto Rican Paso Finos, it is possible that these variants may explain lighter eye color in closely related breeds.

Testing for these tiger eye variants allows breeders to identify carriers of tiger eye. Since brown-eyed horses can carry either TE1 or TE2, owners breeding for or against this unique eye color can use this diagnostic tool to inform mating decisions.

Turnaround Time
2-6 business days
Type of Sample

Species

Breed

Type of Test

Results Reported As
Test Result Tiger Eye
N/N No copies of the tiger eye variants.
N/TE1 Carrier of the tiger eye 1 variant.
TE1/TE1 2 copies of the tiger eye 1 variant, horse should display a lighter eye color.
N/TE2 Carrier of the tiger eye 2 variant.
TE2/TE2 2 copies of the tiger eye 2 variant, horse should display a lighter eye color.
TE1/TE2 1 copy of the tiger eye 1 variant and 1 copy of the tiger eye 2 variant, horse should display a lighter eye color.
References

Kowalski, E. J. A., & Bellone, R. R. (2011). Investigation of HERC2 and OCA2 SNP for iris color variation in Puerto Rican Paso Fino horses. Journal of Equine Veterinary Science, 31(5):319.

Mack, M., Kowalski, E., Grahn, R., Bras, D., Penedo, M. C., & Bellone, R. (2017). Two Variants in SLC24A5 Are Associated with “Tiger-Eye” Iris Pigmentation in Puerto Rican Paso Fino Horses. G3: Genes|Genomes|Genetics, 7(8), 2799-2806. doi: 10.1534/g3.117.043786