title: A simple repeat polymorphism in the MITF-M promoter is a key regulator of white spotting in dogs.
abstract: The white spotting locus (S) in dogs is colocalized with the MITF (microphtalmia-associated transcription factor) gene. The phenotypic effects of the four S alleles range from solid colour (S) to extreme white spotting (s(w)). We have investigated four candidate mutations associated with the s(w) allele, a SINE insertion, a SNP at a conserved site and a simple repeat polymorphism all associated with the MITF-M promoter as well as a 12 base pair deletion in exon 1B. The variants associated with white spotting at all four loci were also found among wolves and we conclude that none of these could be a sole causal mutation, at least not for extreme white spotting. We propose that the three canine white spotting alleles are not caused by three independent mutations but represent haplotype effects due to different combinations of causal polymorphisms. The simple repeat polymorphism showed extensive diversity both in dogs and wolves, and allele-sharing was common between wolves and white spotted dogs but was non-existent between solid and spotted dogs as well as between wolves and solid dogs. This finding was unexpected as Solid is assumed to be the wild-type allele. The data indicate that the simple repeat polymorphism has been a target for selection during dog domestication and breed formation. We also evaluated the significance of the three MITF-M associated polymorphisms with a Luciferase assay, and found conclusive evidence that the simple repeat polymorphism affects promoter activity. Three alleles associated with white spotting gave consistently lower promoter activity compared with the allele associated with solid colour. We propose that the simple repeat polymorphism affects cooperativity between transcription factors binding on either flanking sides of the repeat. Thus, both genetic and functional evidence show that the simple repeat polymorphism is a key regulator of white spotting in dogs.
authors.affiliation: Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Izabella
authors.initials: I
authors.lastname: Baranowska Körberg
authors.affiliation: Science for Life Laboratory Uppsala, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Sundström
authors.affiliation: Science for Life Laboratory Uppsala, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Jennifer R S
authors.initials: JR
authors.lastname: Meadows
authors.affiliation: Science for Life Laboratory Uppsala, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Gerli
authors.initials: G
authors.lastname: Rosengren Pielberg
authors.affiliation: Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Ulla
authors.initials: U
authors.lastname: Gustafson
authors.affiliation: Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Åke
authors.initials: Å
authors.lastname: Hedhammar
authors.affiliation: Broad Institute of Harvard and MIT, Cambridge, Massachusetts, United States of America; FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts, United States of America.
authors.forename: Elinor K
authors.initials: EK
authors.lastname: Karlsson
authors.affiliation: Science for Life Laboratory Uppsala, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden; School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Seddon
authors.affiliation: Department of Pathology and Wildlife Disease, National Veterinary Institute (SVA), Uppsala, Sweden.
authors.forename: Arne
authors.initials: A
authors.lastname: Söderberg
authors.affiliation: Conservation and Evolutionary Genetics Group, Estación Biológica de Doñana (EBD-CSIC), Seville, Spain.
authors.forename: Carles
authors.initials: C
authors.lastname: Vilà
authors.affiliation: Broad Institute of Harvard and MIT, Cambridge, Massachusetts, United States of America.
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Grimsö Wildlife Research Station, Department of Ecology, Swedish University of Agricultural Sciences, Riddarhyttan, Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Åkesson
authors.affiliation: Science for Life Laboratory Uppsala, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden; Broad Institute of Harvard and MIT, Cambridge, Massachusetts, United States of America.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Lindblad-Toh
authors.affiliation: Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Göran
authors.initials: G
authors.lastname: Andersson
authors.affiliation: Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden; Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden; Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America.
authors.forename: Leif
authors.initials: L
authors.lastname: Andersson
mesh_terms: D000483:Alleles; D000818:Animals; D002170:Canada; D004285:Dogs / Q000235:genetics*; D005060:Europe; D005787:Gene Frequency; D014644:Genetic Variation; D005838:Genotype; D006200:Hair Color; D006239:Haplotypes; D051739:Microphthalmia-Associated Transcription Factor / Q000235:genetics*; D018895:Microsatellite Repeats; D016254:Mutagenesis, Insertional; D010641:Phenotype; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D040641:Quantitative Trait Loci; D019655:Quantitative Trait, Heritable; D015533:Transcriptional Activation; D019596:Wolves / Q000235:genetics
chemical_list: D051739:Microphthalmia-Associated Transcription Factor