Gene Structure and Sequence Polymorphism of the Coat Color Gene, Mc1r, in the Black-Bellied Vole (Eothenomys melanogaster).

Yung-Chih Lai, Shiao-Wei Huang, and Hon-Tsen Yu (2016) Color polymorphism is a long-standing issue in ecological and evolutionary biology. The black-bellied vole (Eothenomys melanogaster) with complete melanic and brown forms provides an outstanding opportunity to study the genetic polymorphism underpinning color variation. Mutations in the coding region of melanocortin 1 receptor (Mc1r) have been shown to cause color variation in a wide range of species. However, the contribution to color variation produced by the Mc1r regulatory regions have rarely been studied in wild animals. To this end, the Mc1r promoter sequence in black-bellied voles was cloned and characterized in this study. At least 11 distinct transcription initiation sites were identified using 5'-RACE. Furthermore, a candidate core promoter region in the upstream GC-rich sequence was identified based on key transcription factor binding motifs. The black-bellied vole Mc1r coding region was conserved with that found in the house mouse and demonstrated characteristics that are consistent with the structure of a G-protein coupled receptor, e.g. seven transmembrane domains. We found a negative association between coat color variations and polymorphisms of either regulatory or coding regions. This implies that Mc1r might reflect geographic cline rather than adaptive evolution. Although we found a negative association, the extra information we obtained in the Mc1r promoter of the black-bellied vole can be beneficial to other studies in exploring the association between regulatory mutations and adaptive phenotypes in wild animals.