title: Origin of agouti-melanistic polymorphism in Wild Black Rats (Rattus rattus) inferred from Mc1r gene sequences.
abstract: We examined nucleotide changes that underlie coat color variation in Black Rats (the Rattus rattus species complex), which show polymorphism in dorsal fur color, including either grayish brown (agouti) or black (melanistic) forms. We examined the full coding sequence of a gene known to produce melanism in other vertebrates-melanocortin-1-receptor gene Mc1r (954 bp) -using samples of both R. rattus (with 2n = 38) and its close relative Asian Black Rat (R. tanezumi; 2n = 42). We used 61 specimens from Japan with karyotype-known individuals and four samples from Pakistan. We found 11 allele sequences and constructed a network tree that shows two distinct clusters, with allelic segregation according to karyotype and by inference, representing the two species. We found that a nucleotide substitution from G to A at site 280, producing an amino acid change from glutamic acid to lysine, was associated with the dominant trait of the melanistic form of the coat color in R. rattus. Notably, the derived SNP 280A was found in a single allele, with the ancestral SNP 280G present in seven alleles. By contrast, all three alleles for R. tanezumi retain the ancestral SNP 280G. These results suggest a possible recent origin of melanism in R. rattus.
authors.affiliation: Division of Bioscience, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kambe
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Tanikawa
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Matsumoto
authors.forename: Morihiko
authors.initials: M
authors.lastname: Tomozawa
authors.forename: Ken P
authors.initials: KP
authors.lastname: Aplin
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Suzuki
mesh_terms: D054366:Agouti Signaling Protein / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D000835:Animals, Wild; D010858:Pigmentation / Q000235:genetics; D010860:Pigments, Biological / Q000235:genetics*; D011110:Polymorphism, Genetic; D051381:Rats / Q000235:genetics* / Q000502:physiology; D044102:Receptor, Melanocortin, Type 1 / Q000235:genetics* / Q000378:metabolism; D013045:Species Specificity
chemical_list: D054366:Agouti Signaling Protein; C515184:Asip protein, rat; D010860:Pigments, Biological; D044102:Receptor, Melanocortin, Type 1