Canine coat color E locus updates: Identification of a new MC1R variant causing 'sable' coat color in English Cocker Spaniels and a proposed update to the E locus dominance hierarchy.

The coat color phenotype 'sable' occurs in the English Cocker Spaniel dog breed. It closely resembles other canine color patterns known as domino/grizzle/pied (eA allele) and grizzle/domino (eG allele) determined by variants in the melanocortin 1 receptor gene (MC1R; 'extension' or E locus), a key multi‐allele regulator of coat color. We examined genetic variation in MC1R, and found one new non‐synonymous variant, c.250G>A (p.(Asp84Asn)), consistently associated with the English Cocker Spaniel 'sable' phenotype. We propose calling this newly identified allele eH and further show that the eA, eH and eG (previously known as EG) alleles associate with similar phenotypes in dogs impacting genotypes regulated by beta‐defensin 103 gene (CBD103; K locus) and agouti signaling protein gene (ASIP; A locus) in the absence of the EM and E alleles. This suggests that all three alleles are putative reduced‐function variants of the MC1R gene. We propose the revised and updated E locus dominance hierarchy to be EM > E > eA/eH/eG > e1–3. [ABSTRACT FROM AUTHOR]