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

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.