Two new equine color genes—Splash White 5 and Sunshine dilution—were recently identified by researchers; APHA partner lab Etalon Diagnostics assisted in the discovery.
Splash White 5 was identified in a group of related French Paint Horses—these horses, a stallion and seven of his daughters, had white spotting that resembled existing Splash White patterns, but they tested negative for the four existing alleles that create those coat patterns as well as other white spotting patterns. Whole genome sequencing helped identify a new Splash White spotting pattern in these horses, created as a result of a genetic deletion of the MITF gene—the MITF gene is the same location where two other Splash White spotting patterns (Splash White 1 and Splash White 3) reside. The research, led by J. Henkel of the University of Bern (Switzerland) Institute of Genetics, was published in the April 2019 issue of Animal Genetics—read the study’s abstract and full-text online. Since then, Splash White 5 has been identified in U.S.-based Paint Horses, as well.
A second study, also published via Animal Genetics in April 2019, identified a variant in the SLC45A2 gene—nicknamed “Sunshine”—that produces a cream/pearl-like effect. The Cream and Pearl coat colors are variants of the same SLC45A2 gene. Cream dilutes red pigment when one copy is present (palomino, buckskin) and dilutes both red and black pigment when two copies are present (cremello, perlino, smoky cream). Pearl has little effect when only one copy is present, but can create a pseudo-double dilute effect when two copies are present or when Pearl combines with a Cream gene. Sunshine acts similarly to Pearl, creating a pseudo-double dilute effect when paired with a heterozygous Cream gene; the Sunshine variant was discovered in a Standardbred-Tennessee Walker cross, and its presence in other breeds is yet to be determined. Read the study’s abstract and full-text online; lead researcher for this study was H.M. Holl of the University of Florida Department of Animal Sciences.
The Etalon mini-panel does not currently include testing for Splash White 5 or the Sunshine dilution; the company is evaluating how best to offer testing to consumers and will release details when available.