To identify factors that control coat color in Akita-inu dogs, we sequenced all the exons of the
melanocortin 1 receptor (MC1R), β
-defensin103 (CBD103) and
agouti signaling protein (ASIP) genes of dogs with four distinct coat colors, namely, brindle, sesame, red and white. Then we examined correlations among specific alleles and coat color. In the case of the
MC1R gene, all white dogs were homozygous for a nonsense mutation, R306ter, while brindle, sesame, and red dogs had at least one R306 allele. In the case of the
CBD103 gene, all brindle dogs were heterozygous for the G23del mutation (deletion of codon 23, encoding glycine), while all sesame and red dogs were homozygous for G23. In the case of the
ASIP gene, all dogs, regardless of coat color, had at least one S82 H83 allele. A missense mutation in the
ASIP gene, P87L, was identified for the first time in some Akita-inu dogs but was not associated with any specific coloration. Our results indicate that the 2 key mutations, R306ter in the
MC1R gene and G23del in the
CBD103 gene, are associated with the phenotypic discriminations among brindle, red/sesame, and white coats, while no mutation that might potentially be associated with the discrimination of a sesame coat from a red coat is present in the coding sequences of these three genes.
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