Splashed white (SW 5-8)*

Splashed white is a variable white spotting pattern characterized primarily by a large, broad blaze, extensive white markings on legs, variable white spotting on belly, and often blue eyes. Some, but not all, splashed white horses are also deaf. \nIn this test 2 genetic variants are identified which have been named in the order they were discovered: SW5and SW6. All of these mutations cause a similar splashed white phenotype in horses although the amount of white patterning is variable and thought to be controlled by other genes. Some are known, but mostly these additional genes, contributing to the variation in splash white phenotype, are yet to be identified.\n\nSW5 was identified in an American Paint Horse family. It is unknown if SW5 is homozygous lethal and no homozygotes have been reported.\nSW6 was identified in a single family as a de novo (new/recent) mutation. Being a de novo mutation means only this individual, his offspring, and resulting future generations of horses originating with this stallion can have this mutation. \nAt this time, it is not known whether homozygosity for SW6 (two copies of this mutation) is viable. Based on the type of mutation and the role MITF plays in development, it is suspected that SW6/SW6 may be embryonic lethal. However one SW1/SW6 compound heterozygote was identified as part of the VGL study.\nSplashed white mutations are inherited as dominant traits with variable expression, which means that one copy of a SW mutation will produce a white spotting phenotype with variable amount of white. Horses that carry combinations of the splashed white mutations, tobiano, or lethal white overo can display extensive white patterning or their coats maybe entirely white.\nTesting for the splashed white pattern allows breeders to identify which splashed white mutation is present in their horse and can aid in breeding decisions and clinical decisions if deafness is suspected.