title: Identification of a melanocyte-specific, microphthalmia-associated transcription factor-dependent regulatory element in the intronic duplication causing hair greying and melanoma in horses.
abstract: Greying with age in horses is an autosomal dominant trait, characterized by hair greying, high incidence of melanoma and vitiligo-like depigmentation. Previous studies have revealed that the causative mutation for this phenotype is a 4.6-kb intronic duplication in STX17 (Syntaxin 17). By using reporter constructs in transgenic zebrafish, we show that a construct containing two copies of the duplicated sequence acts as a strong enhancer in neural crest cells and has subsequent melanophore-specific activity during zebrafish embryonic development whereas a single copy of the duplicated sequence acts as a weak enhancer, consistent with the phenotypic manifestation of the mutation in horses. We further used luciferase assays to investigate regulatory regions in the duplication, to reveal tissue-specific activities of these elements. One region upregulated the reporter gene expression in a melanocyte-specific manner and contained two microphthalmia-associated transcription factor (MITF) binding sites, essential for the activity. Microphthalmia-associated transcription factor regulates melanocyte development, and these binding sites are outstanding candidates for mediating the melanocyte-specific activity of the element. These results provide strong support for the causative nature of the duplication and constitute an explanation for the melanocyte-specific effects of the Grey allele.
authors: Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors: Elisabeth
authors: E
authors: Sundström
authors: Anna Z
authors: AZ
authors: Komisarczuk
authors: Lin
authors: L
authors: Jiang
authors: Anna
authors: A
authors: Golovko
authors: Pavla
authors: P
authors: Navratilova
authors: Silke
authors: S
authors: Rinkwitz
authors: Thomas S
authors: TS
authors: Becker
authors: Leif
authors: L
authors: Andersson
mesh_terms: D000375:Aging / Q000235:genetics; D000818:Animals; D030801:Animals, Genetically Modified; D001665:Binding Sites; D004742:Enhancer Elements, Genetic; D018628:Gene Dosage; D020440:Gene Duplication; D018507:Gene Expression Regulation, Developmental; D005799:Genes, Dominant; D017930:Genes, Reporter; D006200:Hair Color / Q000235:genetics*; D006734:Horse Diseases / Q000235:genetics*; D006736:Horses / Q000235:genetics*; D006801:Humans; D007438:Introns / Q000235:genetics*; D008322:Mammals; D008544:Melanocytes / Q000378:metabolism*; D008545:Melanoma / Q000235:genetics / Q000662:veterinary*; D008547:Melanophores / Q000378:metabolism; D051739:Microphthalmia-Associated Transcription Factor / Q000378:metabolism*; D009432:Neural Crest / Q000166:cytology; D010641:Phenotype; D050765:Qa-SNARE Proteins / Q000235:genetics* / Q000502:physiology; D012878:Skin Neoplasms / Q000235:genetics / Q000662:veterinary*; D013045:Species Specificity; D015027:Zebrafish
chemical_list: D051739:Microphthalmia-Associated Transcription Factor; D050765:Qa-SNARE Proteins