Researchers at the Laboratoire de Genetique Biochimique et de Cytogenetique in the Institut National de la Recherche Agronomique (INRA) at the Centre de Recherche de Jouy-en-Josas, France, recently identified the gene that produces the cremello coat color in the horse. The cremello color is a dilution of all basic coat colors, and produces a pale (cream) to an almost white coat in a horse with pink skin and blue eyes (resulting in a blue-eyed cream horse, or BEC). The cremello color has been considered undesirable by certain breed registries, some of which have denied registration to cremello horses. This breakthrough will allow breeders to plan more precise breedings in the hope of producing or avoiding the cremello coat color, and it will also allow breed registries to confirm the genotype (genetic makeup) for coat color of horses being registered.

The three-year study was first published in Genetics, Selection, Evolution. It identified that a mutation in the membrane-associated transport protein (MATP) gene causes the cream coat color; however, it's not precisely known how the mutation works. Scientists were able to zero in on this gene due to known mutations in fish, mice, and humans that cause depigmentation related to a form of albinism. According to Gerard Guerin, PhD, research scientist in charge of horse molecular genetics at INRA, the researchers hypothesize that the MATP gene encodes a transporter protein (which transports nutrients through a membrane) that regulates the production of melanin, or pigments.

According to authors working on the gene in different species, the cream mutation results in a change in the makeup of the transmembrane protein. During this change, the amino acid asparagine is produced instead of aspartic acid. This mutation in animals heterozygous for the cremello gene produces the diluted colors for buckskin on a bay background and palomino on a chestnut background, and the cremello color in the homozygous condition (double mutant).

Guerin; Denis Mariat, PhD, an INRA researcher; and Sead Taourit, a senior scientist, have worked on the genetics of basic coat colors, and became interested in the dilution genes, such as the cremello gene