Today, horses come in a variety of coat colors, but most lack the camouflaging coat of their ancestors. However, a trace of that legacy remains in horses with the dun pattern, which characterized by pale hair covering most of the body, a dark stripe along the back, and zebra-like stripes on the legs. And recent study results reveal a new mechanism that explains the genetic roots of the dun pattern and uncovers why the pattern does not appear in most domestic horses.

The study is the work of an international team of scientists, led by Texas A&M University Institute for Advanced Study scholar Leif Andersson, PhD, and is the result of a collaboration between groups at Texas A&M University; Uppsala University in Uppsala, Sweden; and the HudsonAlpha Institute of Biotechnology in Huntsville, Alabama.

The dun pattern camouflaged ancient wild horses, protecting them from predators. However, domestic horses, like other domestic animals, have been selected over many generations to appear different from their wild counterparts. As a result of selective breeding, most domestic horses today are not dun and have coat colors that are more intensely pigmentation and uniformly distributed across the body.

“Dun is clearly one of the most interesting coat color variants in domestic animals because it does not just change the color but the color pattern,” Andersson stated. “We were really curious to understand the underlying molecular mechanism of why the dun pigment dilution does not affect all parts of the body.”

Freyja Imsland, a PhD student in Andersson’s group, added, “Unlike the hair of most well-studied mamm