Altered expression of melanocortin-1 receptor (MC1R) in a yellow-coloured wild raccoon dog (Nyctereutes procyonoides) Jae-Ik Han*, Hyun Yang†, Eui-Bae Jung† and Ki-Jeong Na* Laboratories of *Veterinary Laboratory Medicine and †Veterinary Biochemistry and Molecular Biology, College of Veterinary Medicine, Chungbuk National University, Cheongju 361-763, South Korea Correspondence: Jae-Ik Han, Laboratory of Veterinary Laboratory Medicine, College of Veterinary Medicine, Chungbuk National University, Cheongju 361-763, South Korea. E-mail: jaeikhan@gmail.com 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 col- our, 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. Introduction In mammals, coat colour is mainly determined by the proportion of eumelanin (a brown or black pigment) and pheomelanin (a red or yellow pigment) during the synthe- sis of melanin granules. 1 In melanocytes, the switch between the synthesis of eumelanin and pheomelanin is controlled by two genes, the melanocortin 1 receptor (MC1R) and agouti genes, which encode a 7-transmem- brane domain receptor and its extracellular ligand, respec- tively. 2 Stimulation of MC1R by a-melanocyte-stimulating hormone (a-MSH) and other pro-opiomelanocortin pep- tides leads to enhanced adenylate cyclase activity and increased cAMP concentration, resulting in exclusive production of eumelanin. In contrast, agouti, a paracrine signalling molecule secreted by specialized mesenchymal cells adjacent to hair follicle melanocytes, inhibits MC1R signalling. 3,4 Thus, a gain-of-function mutation of MC1R results in a brown to black coat colour, whereas a loss-of- function mutation of MC1R or gain-of-function mutation of agouti causes a red to yellow coat colour. In general, MC1R is epistatic to agouti. Tyrosinase-related protein 1 stimulates the synthesis of black pigments during eumel- anin synthesis, while the variation of the colour shade from red to bright yellow is determined by the proportion of red pheomelanin pigment. 5 Raccoon dogs (Nyctereutes procyonoides) are the most common wild canids in East Asia. 6 Although the raccoon dog resembles the North American raccoon (Procyon lotor), it is more closely related to domestic dogs. Its coat colour is characterized by a combination of black to brown and grey hairs. There is no informa- tion about their coat colour variation and the related genotypic variation. In this study, we examined a wild raccoon dog with a yellow coat. As MC1R controls which melanin granules are synthesized, we hypothesized that the variant yellow coat colour was due to loss of function in the MC1R gene and ⁄ or MC1R protein. We therefore sequenced and com- pared the MC1R gene between wild-type raccoon dogs and the yellow raccoon dog. We also examined mRNA and protein expression levels of MC1R to confirm the cause of colour variation in the yellow raccoon dog. Accepted 5 January 2012 Sources of Funding: This work was supported by the Basic Sci- ence Research Program through the National Research Founda- tion of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0024447). Conflict of Interest: No conflicts of interest have been declared. ª 2012 The Authors. Veterinary Dermatology ª 2012 ESVD and ACVD, Veterinary Dermatology, 23, 187–e37. 187 DOI: 10.1111/j.1365-3164.2012.01036.x