title: Gene duplication of endothelin 3 is closely correlated with the hyperpigmentation of the internal organs (Fibromelanosis) in silky chickens.
abstract: During early development in vertebrates, pluripotent cells are generated from the neural crest and migrate according to their presumptive fate. In birds and mammals, one of the progeny cells, melanoblasts, generally migrate through a dorsolateral route of the trunk region and differentiate to melanocytes. However, Silky is an exceptional chicken in which numerous melanoblasts travel via a ventral pathway and disperse into internal organs. Finally, these ectopic melanocytes induce heavy dermal and visceral melanization known as Fibromelanosis (Fm). To identify the genetic basis of this phenotype, we confirmed the mode of inheritance of Fm as autosomal dominant and then performed linkage analysis with microsatellite markers and sequence-tagged site markers. Using 85 backcross progeny from crossing Black Minorca chickens (BM-C) with F(1) individuals between White Silky (WS) and BM-C Fm was located on 10.2-11.7 Mb of chicken chromosome 20. In addition, we noticed a DNA marker that all Silky chickens and the F(1) individuals showed heterozygous genotyping patterns, suggesting gene duplication in the Fm region. By quantitative real-time PCR assay, Silky line-specific gene duplication was detected as an ~130-kb interval. It contained five genes including endothelin 3 (EDN3), which encoded a potent mitogen for melanoblasts/melanocytes. EDN3 with another three of these duplicated genes in Silky chickens expressed almost twofold of those in BM-C. Present results strongly suggest that the increase of the expression levels resulting from the gene duplication in the Fm region is the trigger of hypermelanization in internal organs of Silky chickens.
authors.affiliation: Department of Biology, Keio University, Yokohama 223-8521, Japan.
authors.forename: Ai
authors.initials: A
authors.lastname: Shinomiya
authors.forename: Yasunari
authors.initials: Y
authors.lastname: Kayashima
authors.forename: Keiji
authors.initials: K
authors.lastname: Kinoshita
authors.forename: Makoto
authors.initials: M
authors.lastname: Mizutani
authors.forename: Takao
authors.initials: T
authors.lastname: Namikawa
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Matsuda
authors.forename: Toyoko
authors.initials: T
authors.lastname: Akiyama
mesh_terms: D000818:Animals; D002645:Chickens / Q000235:genetics*; D002874:Chromosome Mapping; D002875:Chromosomes; D003433:Crosses, Genetic; D056915:DNA Copy Number Variations; D019334:Endothelin-3 / Q000235:genetics*; D005260:Female; D020440:Gene Duplication; D015870:Gene Expression; D008040:Genetic Linkage; D008297:Male; D018895:Microsatellite Repeats; D010641:Phenotype; D010858:Pigmentation / Q000235:genetics*; D014781:Viscera / Q000033:anatomy & histology / Q000378:metabolism
chemical_list: D019334:Endothelin-3