![]() ![]() The guard hairs in these cats display a silver base, with lengthened black tips, as compared with hairs in silver cats ( Vella et al. A striking silver phenotype in the cat is “smoke,” which stems from the effect of silver on a nonagouti (melanistic, i.e., black) background. Further, hairs in silver domestic cats display a silver (near colorless) base, with normal (including eumelanic, depending on other loci) pigmentation observed in the hair tips ( Figure 2). 2003), is nearly white or colorless in silver cats. ![]() The characteristic “yellowish-orange” agouti band seen in wild-type cats, resulting from a shift in eumelanin to pheomelanin production ( Eizirik et al. In the domestic cat, mutations at the Inhibitor or SILVER locus suppress the development of pigment in the hair, but in contrast to other mammalian silver variants, there is an apparently greater influence on the production of pheomelanin than eumelanin pigment ( Vella et al. The cat displays additional color morphs, which have not yet been mapped or characterized, including a silver pelage variant ( Figure 1), which is due to the autosomal dominant action of what has been termed the “Inhibitor” locus ( Vella et al. 2007), and orange ( Schmidt-Küntzel et al. 2006), Siamese, and Burmese phenotypes, albino ( Lyons et al. 2003), brown, and cinnamon ( Schmidt-Küntzel et al. 2007), and an interactive web browser ( Pontius and O'Brien 2007), several of the genes underlying this phenotypic variation have been mapped and/or characterized at a molecular genetic level, including black ( Eizirik et al. 2009), a 1.9× whole-genome sequence draft ( Pontius et al. With the development of genomic resources in the domestic cat, including comprehensive genetic and radiation hybrid maps ( Menotti-Raymond et al. ![]() (This figure appears in color in the online version of Journal of Heredity.) Images of a wild cat (right), Felis silvestris lybica, and the silver male Ocicat used in the generation of Pedigree Two. This development of pelage polymorphism has been observed in most mammals which have experienced domestication, partly as a consequence of release from purifying selection in natural populations but also due to intense artificial selection in favor of color morphs or patterns that were pleasing to humans ( Zeuner 1963 Trut 1999). Since domestication, a wide range of coat color and pattern variants have arisen in the domestic cat, which have not been reported in the wild cat, including a variety of coat colors, distinctive hair phenotypes, as well as coat patterns (stripes, spots, and blotches, including the unpatterned coat of the “ticked tabby”). This wild progenitor of the domestic cat, Felis silvestris lybica, the African wild cat, is difficult to distinguish today from a common domestic tabby cat with mackerel stripes set against a wild-type agouti coat background ( Figure 1). 2007), likely as a consequence of the development of the first villages and the storage of wild grain stocks which attracted an abundant source of rodents. 2004) in the Middle East ( Driscoll et al. It is estimated that the cat was domesticated approximately 10 000 years ago ( Vigne et al. The mapping of a novel locus for SILVER offers much promise in identifying a gene that may help elucidate aspects of pheomelanogenesis, a pathway that has been very elusive, and illustrates the promise of the cat genome project in increasing our understanding of basic biological processes of general relevance for mammals. In the domestic cat, mutations at the SILVER locus suppress the development of pigment in the hair, but in contrast to other mammalian silver variants, there is an apparently greater influence on the production of pheomelanin than eumelanin pigment. Linkage mapping defined a genomic region for SILVER as a 3.3-Mb region, (95.87–99.21 Mb) on chromosome D2, (peak logarithm of the odds = 10.5, θ = 0), which displays conserved synteny to a genomic interval between 118.58 and 121.85 Mb on chromosome 10 in the human genome. A demonstrated lack of linkage to SILV, the strong candidate gene for silver, led to the initiation of a genome scan utilizing 2 pedigrees segregating for silver coat color. The SILVER locus has been mapped in the domestic cat, identifying a unique genomic location distinct from that of any known reported gene associated with silver or hypopigmentation in mammals. ![]()
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