Altered expression of melanocortin-1 receptor (MC1R) in a yellow-coloured wild raccoon dog (Nyctereutes procyonoides).

Abstract

BACKGROUND: The melanocortin 1 receptor (MC1R) gene plays a key role in determining coat colour in mammals by controlling the proportion of eumelanin and pheomelanin granules. Wild raccoon dogs have a mixed coat colour, with black to brown and grey hairs. HYPOTHESIS/OBJECTIVES: The study was performed to identify the cause of the variant yellow coat colour in a wild raccoon dog. ANIMALS: A wild raccoon dog that showed coat colour change to yellow and four wild-type raccoon dogs that showed normal coat colour were included. METHODS: To identify the cause of the variant yellow coat colour, we examined the sequence of the MC1R gene and its expression at the mRNA and protein levels. RESULTS: The coding region of the MC1R gene of this raccoon dog comprised 954 bp, the same as for wild-type raccoon dogs and domestic dogs. By comparing the gene with that in the wild-type raccoon dog, a 2 bp deletion was detected in the 5'-untranslated region, positioned 152 bp upstream of the start codon. However, there was no significant difference in the mRNA expression level. The yellow raccoon dog revealed a significantly decreased MC1R protein level compared with the wild-type raccoon dogs, indicating an increase in pheomelanin synthesis. CONCLUSIONS AND CLINICAL IMPORTANCE: These results suggest that the variant coat colour in the yellow raccoon dog was associated with decreased MC1R function.