Abstract :
Sequence of the melanocortin 1 receptor (MC1R) gene (the Extension locus) was obtained
from a panel of 73 animals belonging to 9 Italian sheep breeds or populations (Appenninica,
Bergamasca, Comisana, Cornigliese-like, Delle Langhe, Massese, Merinizzata Italiana, Sarda
and Valle del Belice) with different coat colours. Evaluation of the identified polymorphisms
on this phenotype was reported with in silico predictions and comparative approaches
within and across breeds and across species. Five novel single nucleotide polymorphisms
(SNPs), organized in three haplotypes, were detected. Another haplotype, including the
two missense mutations already described for the ED allele, was identified in few Massese
sheep. One SNP (c.199C > T) caused a predicted amino acid substitution (p.R67C) in a highly
conserved position of the first intracellular loop of the MC1R protein. The same substitution
causes recessive pheomelanism in other species. We propose that the p.67C allele represents
the recessive e allele at the ovine Extension series that was, so far, not completely
recognized in sheep by classical genetic studies. This polymorphism was analysed in a total
of 388 sheep of the 9 investigated breeds. The p.67C allele was identified only in the Valle
del Belice breed (allele frequency of 21.3% in 176 analysed animals of this breed) in which
the presence of epistatic white-determining loci might mask, at least in part, its effects.
Confirming the effect of this novel allele on coat colour will lead to new perspectives on
the composition of specialized coloured sheep lines.
