A genome-wide scan study identifies a single nucleotide substitution in ASIP associated with white versus non-white coat-colour variation in sheep (Ovis aries)

Abstract

In sheep, coat colour (and pattern) is one of the important traits of great biological, economic and social importance. However, the genetics of sheep coat colour has not yet been fully clarified. We conducted a genome-wide association study of sheep coat colours by genotyping 47 303 single-nucleotide polymorphisms (SNPs) in the Finnsheep population in Finland. We identified 35 SNPs associated with all the coat colours studied, which cover genomic regions encompassing three known pigmentation genes (TYRP1, ASIP and MITF) in sheep. Eighteen of these associations were confirmed in further tests between white versus non-white individuals, but none of the 35 associations were significant in the analysis of only non-white colours. Across the tests, the s66432.1 in ASIP showed significant association (P ¼ 4.2 Â 10 À11 for all the colours; P ¼ 2.3 Â 10 À11 for white versus non-white colours) with the variation in coat colours and strong linkage disequilibrium with other significant variants surrounding the ASIP gene. The signals detected around the ASIP gene were explained by differences in white versus non-white alleles. Further, a genome scan for selection for white coat pigmentation identified a strong and striking selection signal spanning ASIP. Our study identified the main candidate gene for the coat colour variation between white and non-white as ASIP, an autosomal gene that has been directly implicated in the pathway regulating melanogenesis. Together with ASIP, the two other newly identified genes (TYRP1 and MITF) in the Finnsheep, bordering associated SNPs, represent a new resource for enriching sheep coat-colour genetics and breeding.

Application of genomic data to assist a community-based breeding program: A preliminary study of coat color genetics in Morada Nova sheep

“…Most studies to identify mutations affecting coat colour in sheep have focused on differences between white and black animals (Li et al, 2014;Kijas et al, 2013;Hepp et al, 2012;Fontanesi et al, 2011). This is one of the first studies to evaluate the segregation of coat colour genes controlling the red colour in sheep, in addition to Fontanesi et al (2010) to organize a breeding program for the breed.…”

Genetic background of coat colour in sheep

“…The microarray study conducted on Finnsheep (Li et al, 2014) indicates a significance effect of SNP s66432.1 in ASIP on white/non-white-coloured wool. The homozygotes (A/A) are found in 96 % of white-coloured Finnsheep, whereas they are found in only 2 % of black animals in the non-white Finnsheep.…”

“…In addition to Extension and agouti loci, the best-known colour genes in the sheep genome are the tyrosinaserelated protein 1 (TYRP1), the v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homologue (KIT), and the microphthalmia-associated transcription factor (MITF) (García-Gámez et al, 2011;Kijas et al, 2012;Li et al, 2014).…”

Cloning and identification of the ASIP gene in Chinese raccoon dog (Nyctereutes procyonoides procyonoides)

“…The ASIP gene encodes the agouti signaling protein, which is involved in the switch from eumelanin to pheomelanin synthesis in melanocytes. Mutations or polymorphisms in the ASIP gene have been implicated in coat color phenotype in a variety of animals including mice (Vrieling et al, 1994;Hustad et al, 1995), pigs (Drögemüller et al, 2006), sheep (Norris andWhan, 2008;Li et al, 2014), goats (Badaoui et al, 2011), horses (Rieder et al, 2001), rabbits (Fontanesi et al, 2010), red foxes (Våge et al, 1997), and dogs (Dreger and Schmutz, 2011;Ciampolini et al, 2013).…”