title: Identification of a feather β-keratin gene exclusively expressed in pennaceous barbule cells of contour feathers in chicken.
abstract: Feathers are elaborate skin appendages shared by birds and theropod dinosaurs that have hierarchical branching of the rachis, barbs, and barbules. Feather filaments consist of β-keratins encoded by multiple genes, most of which are located in tandem arrays on chromosomes 2, 25, and 27 in chicken. The expansion of the genes is thought to have contributed to feather evolution; however, it is unclear how the individual genes are involved in feather formation. The aim of the present study was to identify feather keratin genes involved in the formation of barbules. Using a combination of microarray analysis, reverse-transcription polymerase chain reaction, and in situ hybridization, we found an uncharacterized keratin gene on chromosome 7 that was expressed specifically in barbule cells in regenerating chicken feathers. We have named the gene barbule specific keratin 1 (BlSK1). The BlSK1 gene structure was similar to the gene structure of previously characterized feather keratin genes, and consisted of a non-coding leader exon, an intron, and an exon with an open reading frame (ORF). The ORF was predicted to encode a 98 aa long protein, which shared 59% identity with feather keratin B. Orthologs of BlSK1 were found in the genomes of other avian species, including turkey, duck, zebra finch, and flycatcher, in regions that shared synteny with chromosome 7 of chicken. Interestingly, BlSK1 was expressed in feather follicles that generated pennaceous barbules but not in follicles that generated plumulaceous barbules. These results suggested that the composition of feather keratins probably varies depending on the structure of the feather filaments and, that individual feather keratin genes may be involved in building different portions and/or types of feathers in chicken.
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kitaku, Okayama 700-8530, Japan.
authors.forename: Kinue
authors.initials: K
authors.lastname: Kowata
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kitaku, Okayama 700-8530, Japan.
authors.forename: Minori
authors.initials: M
authors.lastname: Nakaoka
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kitaku, Okayama 700-8530, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Nishio
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kitaku, Okayama 700-8530, Japan.
authors.forename: Ayaka
authors.initials: A
authors.lastname: Fukao
authors.affiliation: Research Core for Interdisciplinary Sciences, Okayama University, 3-1-1 Tsushimanaka, Kitaku, Okayama 700-8530, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Satoh
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kitaku, Okayama 700-8530, Japan.
authors.forename: Maho
authors.initials: M
authors.lastname: Ogoshi
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kitaku, Okayama 700-8530, Japan.
authors.forename: Sumio
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima 739-8528, Japan.
authors.forename: Masaoki
authors.initials: M
authors.lastname: Tsudzuki
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kitaku, Okayama 700-8530, Japan. Electronic address: stakeuch@cc.okayama-u.ac.jp.
authors.forename: Sakae
authors.initials: S
authors.lastname: Takeuchi
mesh_terms: D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002645:Chickens / Q000235:genetics*; D004958:Estradiol / Q000494:pharmacology; D005241:Feathers / Q000166:cytology* / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D016366:Open Reading Frames / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D016415:Sequence Alignment; D053800:beta-Keratins / Q000235:genetics*
chemical_list: D012333:RNA, Messenger; D053800:beta-Keratins; D004958:Estradiol
keywords: Birds; Evolution; Feather filaments; Gene expression; Microarray