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

Background- The melanocortin1 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 954bp, the same as for wild-type raccoon dogs and domestic dogs. By comparing the gene with that in the wild-type raccoon dog, a 2bp deletion was detected in the 5′-untranslated region, positioned 152bp 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.