A SINE Insertion Causes the Black-and-Tan and Saddle Tan Phenotypes in Domestic Dogs.

Agouti Signaling Protein (ASIP) controls the localized expression of red and black pigment in the domestic dog through interaction with other genes, such as Melanocortin 1 Receptor and Beta-Defensin 103. Specific ASIP alleles are necessary for many of the coat color patterns, such as black-and-tan and saddle tan. Mutations in 2 ASIP alleles, ay and a, have previously been identified. Here, we characterize a mutation consisting of a short interspersed nuclear element (SINE) insertion in intron 1 of ASIP that allows for the differentiation of the aw wolf sable and at black-and-tan alleles. The SINE insertion is present in dogs with the at and a alleles but absent from dogs with the aw and ay alleles. Dogs with the saddle tan phenotype were all at/at. Schnauzers were all aw/aw. Genotypes of 201 dogs of 35 breeds suggest that there are only 4 ASIP alleles, as opposed to the 5 or 6 predicted in previous literature. These data demonstrate that the dominance hierarchy of ASIP is ay > aw > at > a. [ABSTRACT FROM PUBLISHER]