What’s Behind Horses’ White Spots?

Researchers have found yet another genetic variation responsible for yet-unexplained white spotting.

White spotting seems to have several genetic causes, and current knowledge doesn’t yet allow us to link the kind of spotting to the genetic variation. | Photo: iStock
The science behind white coat coloring isn’t black and white. Yes, genome research has shown us that certain genes and mutations are responsible for white coats and spotting patterns. But those findings don’t explain all our horses’ white body marks—only most of them.

Swiss researchers have taken another step toward unraveling the mystery of the white body hair in horses. In their new whole-genome study, they’ve found yet another variation responsible for yet-unexplained white spotting, one they’ve named W22.

“By now, research from many groups, including our own, has shown that ‘white spotting phenotypes’ in horses are quite heterogeneous,” said Tosso Leeb, PhD, professor at the University of Bern Institute of Genetics, in Switzerland. “This means there is a large number of different genetic variants that leads to horses with nonpigmented body parts. Our research has just uncovered yet one more.”

Leeb’s group sequenced the whole genome of a horse with white spotting patterns that could not be explained by any current genomic testing. They found a variation—a deletion of nearly 2,000 base pairs—in the KIT gene. That gene is the site where other white-pattern variations occur, Leeb said. But his group was the first to discover the existence of the W22 variation, which causes a part of the gene to simply not

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Passionate about horses and science from the time she was riding her first Shetland Pony in Texas, Christa Lesté-Lasserre writes about scientific research that contributes to a better understanding of all equids. After undergrad studies in science, journalism, and literature, she received a master’s degree in creative writing. Now based in France, she aims to present the most fascinating aspect of equine science: the story it creates. Follow Lesté-Lasserre on Twitter @christalestelas.

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