Lightning Strikes Twice: W15/W15 Foal CONFIRMED

Meet Akhrobella, an Arabian filly with an extremely rare genotype: 2 copies of Dominant White 15! Found only once before by Etalon Diagnostics researchers, this discovery confirms Etalon's original finding: that 2 copies of W15 is possible in a [very adorable] live foal. She sure knows how to show off her genes, just take a look at her beautiful white coat and spotting.

Due to the fact that only a very small number of horses are carriers of the W15 gene and testing for its presence is currently only offered here at Etalon, the implications of homozygous W15 were (and are still, to some degree) unknown. It was originally presumed that homozygous W15 was lethal.

In 2015, Etalon researchers made the first discovery of a horse with two copies of W15. This unusual genotype was found in a filly named Angel Khake "Wendy", sired by Khartoon Khlassic. Just prior to Etalon's discovery announcement, the filly tragically passed away at the age of 3 months from a condition known as White Muscle Disease. Although White Muscle Disease results from selenium deficiency during gestation, the filly's death triggered a wave of false information on social media from those attempting to link her death to her color genetics. The owners and breeders of the original filly demonstrated incredible responsibility in genetically testing her, asking questions, and obtaining a full necropsy and veterinary analysis report to assess the actual cause of her death. The unequivocal cause stated in the veterinary and necropsy report is White Muscle Disease due to selenium deficiency unrelated to any known genetic coat color variants. In keeping with the Etalon mission, we are stepping out once again to further provide facts, real science and educational opportunities for those who wish to actively learn and grow. Learn more about selenium in the equine diet here.

Here she is, a healthy foal in 2021 with 2 copies of W15. We are excited to watch what she becomes as she grows older. Scientifically speaking, she is only the second horse ever documented with 2 copies of this gene... n of 2 does not a complete scientific study make! Thank you especially to Akhrobella's humans - it is so important for owners and breeders to share these kinds of experiences so that we may all learn. It takes incredible courage. More exciting horse discoveries to come!

W15 is a Dominant White mutation found in Arabians, and is a missense mutation on exon 10 (KIT). A comparison of the gene sequences can be seen here (fig on the right) with the "normal" or "wild type" on the top and the homozygous W15/W15 on the bottom. The founder is thought to be an Arabian stallion, Khartoon Khlassic, born in 1996. Horses heterozygous for W15 tend to be partially white, while the 2 known homozygotes are nearly fully white.