Plant & Animal Genome IX Conference

Workshop: Coat Color
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GENETIC AND MOLECULAR BASIS OF MAMMALIAN PIGMENTATION PATTERNS

¹ Departments of Pediatrics and Genetics, and HHMI, Stanford University School of Medicine, Stanford, CA 94305

² 2MRC Human Genetics Unit, Western General Hospital, Edinburgh, EH4 2XU

Alterations in the expression and/or interaction of the Agouti and Extension genes are thought to explain common pigmentation patterns in many different mammals including black-and-tan in mice and dogs, brindling and dominant black in dogs, and Tabby striping in cats. Recent work from our laboratory has demonstrated that common Agouti pigmentation patterns are explained by a dermal-papilla-specific enhancer and two silencers that interact to restrict postnatal Agouti expression to the midphase of the hair growth cycle or the ventral surface of the body. Transgenic experiments suggest that a Tcf/Lef element is required for these interactions. In dogs, dominant black has been suggested to arise from variation in Agouti while recessive yellow and brindling have been suggested to arise from variation in Extension. Association studies of Mc1r variants demonstrate that recessive yellow as seen in yellow Labradors, Irish Setters, or Golden Retrievers, is likely caused by premature truncation of the Mc1r that removes 12 residues containing a potential palmitoylation site. Ongoing genetic and biochemical studies of Agouti and Mc1r in dog pedigrees segregating brindled and dominant black will determine the genetic and molecular basis for these common phenotypes.