The genetic basis of melanism in the gray squirrel (Sciurus carolinensis).
The black squirrel is a melanic variant of the gray squirrel (Sciurus carolinensis). We found 3 coat color variants in the gray squirrel: the wild-type gray, a jet-black, and a brown-black phenotype. These 3 morphs are due to varying distributions of eumelanin and phaeomelanin pigment in hairs. The melanocortin 1 receptor (MC1R) plays a central role in regulating eumelanin and phaeomelanin production. We sequenced the MC1R gene for all 3 coat color phenotypes and found a 24 base-pair deletion. The gray phenotype was homozygous for the wild-type allele E(+), the jet-black phenotype was homozygous for the MC1R-Delta24 allele E(B), and the brown-black phenotype was heterozygous for the E(+) and E(B) alleles. We conclude that melanism in gray squirrels is associated with the MC1R-Delta24 E(B) allele at amino acid positions 87-94 and that this allele is incompletely dominant to the wild-type allele. We predict that the MC1R-Delta24 E(B) allele encodes a constitutively active or hyperactive receptor.
McRobie
Helen
H
Department of Life Sciences, Anglia Ruskin University, Cambridge, UK. helen.mcrobie@anglia.ac.uk
Thomas
Alison
A
Kelly
Jo
J
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D006197:Hair / Q000378:metabolism / Q000502:physiology*; D008548:Melanosis / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010641:Phenotype; D044102:Receptor, Melanocortin, Type 1 / Q000235:genetics* / Q000378:metabolism; D012589:Sciuridae / Q000235:genetics* / Q000502:physiology; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion / Q000235:genetics*
D017931:DNA Primers; D044102:Receptor, Melanocortin, Type 1