The PMEL gene and merle (dapple) in the dachshund: cryptic, hidden, and mosaic variants demonstrate the need for genetic testing prior to breeding.

One of the most unique coat color patterns in the domestic dog is merle (also known as dapple in the dachshund breed), characterized by patches of normal pigmentation surrounded by diluted eumelanin pigment. In dogs, this striking variegated pattern is caused by an insertion of a SINE element into the PMEL gene. Differences in the length of the SINE insertion [due to a variable-length poly(A)-tail] has been associated with variation in the merle coat color and patterning.

The PMEL Gene and Merle in the Domestic Dog: A Continuum of Insertion Lengths Leads to a Spectrum of Coat Color Variations in Australian Shepherds and Related Breeds.

Merle is a distinct coat color and pattern found in numerous species, including the domestic dog, characterized by patches of diluted eumelanin (black pigment) interspersed among areas of normal pigmentation. In dogs, this variegated pattern is caused by an insertion of a SINE element into the canine PMEL gene. Although variation in the length of the SINE insertion - due to a variable-length poly(A) tail - has been observed to be associated with variation in merle coat color and patterning, no systematic evaluation of this correlation has been conducted and published in the scientific literature.