Endogenous Retrovirus Insertion in KIT Determines White Spotting in Cats

This study identified the molecular cause of the dominant white and white-spotting coat patterns in domestic cats, mapping both to the KIT gene that governs the migration of pigment-cell precursors during development. The authors found that an endogenous retrovirus inserted into a regulatory region of KIT disrupts pigment-cell migration, and that the amount of white correlates with the copy number and expression of the inserted element. The work explained the spectrum from a few white toes to an entirely white coat as variation in a single regulatory mechanism, illustrating how a mobile genetic element can generate heritable coat variation that breeders have long selected.