Identification of a melanocyte-specific, microphthalmia-associated transcription factor-dependent regulatory element in the intronic duplication causing hair greying and melanoma in horses

• 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.

Subject headings

LANTBRUKSVETENSKAPER  -- Bioteknologi med applikationer på växter och djur -- Genetik och förädling inom lantbruksvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agricultural Biotechnology -- Genetics and Breeding in Agricultural Sciences (hsv//eng)

Keyword

melanoma

hair greying

horses

zebrafish

STX17

NR4A3

microphthalmia-associated transcription factor

Publication and Content Type

ref (subject category)

art (subject category)