Gene or region: MITF
Reference allele: T (N)
Mutant allele: C (M)
Affected Breeds: Franches-Montagnes
Research Confidence: High confidence, mutations in MITF have been well-documented to cause white spotting in both the horse and other species
The macchiato coat color was documented in a single Franches-Montagnes stallion. He displayed a dilute coat color, blue eyes, extended face and leg markings, and white on the body. He was also noted as being completely deaf and had low progressive sperm motility. As a result, he is unlikely to pass along this variant, and thus will likely be the only macchiato horse to exist.
MITF is a transcription factor that serves to activate several key genes involved in the development of pigmentation. Mutations in both the horse and in other species have led to white spotting, deafness, and sterility. The M mutation alters an amino acid in the protein, which leads to a sharp reduction in MITF's DNA binding ability.
Hauswirth R et al., “Mutations in MITF and PAX3 cause "splashed white" and other white spotting phenotypes in horses.” (2012) PLoS Genet. 8: e1002653.
One of a Kind - Macchiato
Photo from Hauswirth et al. 2012