The KIT gene is responsible for a multitude of white spotting patterns across many species. One of the latest to be discovered is a de novo mutation (a genetic mutation that neither parent possessed nor transmitted) in the Weimaraner Dog.
Sunset Acres Armor of God "Tank" sire of the example litter
During fetal development cells called melanocytes migrate out from the spinal cord to other areas of the body. These melanocytes produce the pigment that â€œcolorsâ€ the dogs coat and skin. Areas where the melanocytes do not reach during fetal development remain without pigment causing areas of white hair and pink skin. The areas most commonly white in dogs are the last areas that are reached by the melanocytes: the chest, tip of the tail, and the toes. The current theory on white pattern development is that environmental factors in the womb (and perhaps white booster or suppressor genes) can affect melanocytes migration resulting in small white spots in these areas without an actual white pattern mutation. When mutations occur in the genes that control melanocyte migration, large areas of white can result. Recent studies have shown that at least one white pattern is the result of a mutation in the gene microphthalmia-associated transcription factor (MITF). However, this mutation does not account for all the white patterns found in canines and in some dogs the mutation does not follow the expected pattern indicating additional genes at work. (Schmutz et al. 2009)