Pigmentation phenotypes of variant extension locus alleles result from point mutations that alter MSH receptor function.

Bibliographic Collection: 
MOCA Reference, APE
Publication Type: Journal Article
Authors: Robbins, L S; Nadeau, J H; Johnson, K R; Kelly, M A; Roselli-Rehfuss, L; Baack, E; Mountjoy, K G; Cone, R D
Year of Publication: 1993
Journal: Cell
Volume: 72
Issue: 6
Pagination: 827-34
Date Published: 03/1993
Publication Language: eng
ISSN: 0092-8674
Keywords: Alleles, Amino Acid Sequence, Animals, Base Sequence, Chromosome Mapping, Frameshift Mutation, Melanocyte-Stimulating Hormones, Membrane Glycoproteins, Mice, Molecular Sequence Data, Oligodeoxyribonucleotides, Phenotype, pigmentation, Point Mutation, Polymerase Chain Reaction, Receptors, Pituitary Hormone

Coat colors in the chestnut horse, the yellow Labrador retriever, the red fox, and one type of yellow mouse are due to recessive alleles at the extension locus. Similarly, dominant alleles at this locus are often responsible for dark coat colors in mammals, such as the melanic form of the leopard, Panthera pardus. We show here that the murine extension locus encodes the melanocyte-stimulating hormone (MSH) receptor. In mice, the recessive yellow allele (e) results from a frameshift that produces a prematurely terminated, nonfunctioning receptor. The sombre (Eso and Eso-3J) and tobacco darkening (Etob) alleles, which both have dominant melanizing effects, results from point mutations that produce hyperactive MSH receptors. The Eso-3J receptor is constitutively activated, while the Etob receptor remains hormone responsive and produces a greater activation of its effector, adenylyl cyclase, than does the wild-type allele.

Alternate Journal: Cell