title: Two Opsin 3-Related Proteins in the Chicken Retina and Brain: A TMT-Type Opsin 3 Is a Blue-Light Sensor in Retinal Horizontal Cells, Hypothalamus, and Cerebellum.
abstract: Opsin family genes encode G protein-coupled seven-transmembrane proteins that bind a retinaldehyde chromophore in photoreception. Here, we sought potential as yet undescribed avian retinal photoreceptors, focusing on Opsin 3 homologs in the chicken. We found two Opsin 3-related genes in the chicken genome: one corresponding to encephalopsin/panopsin (Opn3) in mammals, and the other belonging to the teleost multiple tissue opsin (TMT) 2 group. Bioluminescence imaging and G protein activation assays demonstrated that the chicken TMT opsin (cTMT) functions as a blue light sensor when forced-expressed in mammalian cultured cells. We did not detect evidence of light sensitivity for the chicken Opn3 (cOpn3). In situ hybridization demonstrated expression of cTMT in subsets of differentiating cells in the inner retina and, as development progressed, predominant localization to retinal horizontal cells (HCs). Immunohistochemistry (IHC) revealed cTMT in HCs as well as in small numbers of cells in the ganglion and inner nuclear layers of the post-hatch chicken retina. In contrast, cOpn3-IR cells were found in distinct subsets of cells in the inner nuclear layer. cTMT-IR cells were also found in subsets of cells in the hypothalamus. Finally, we found differential distribution of cOpn3 and cTMT proteins in specific cells of the cerebellum. The present results suggest that a novel TMT-type opsin 3 may function as a photoreceptor in the chicken retina and brain.
authors.affiliation: Department of Cytology and Histology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors.forename: Mutsuko
authors.initials: M
authors.lastname: Kato
authors.affiliation: R&D Group, Olympus Corporation, Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Sugiyama
authors.affiliation: Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan.
authors.forename: Kazumi
authors.initials: K
authors.lastname: Sakai
authors.affiliation: Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yamashita
authors.affiliation: Department of Cytology and Histology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Fujita
authors.affiliation: Department of Cytology and Histology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors.forename: Keita
authors.initials: K
authors.lastname: Sato
authors.affiliation: Department of Life Systems, Institute of Technology and Science, Tokushima University Graduate School, Tokushima, Japan.
authors.forename: Sayuri
authors.initials: S
authors.lastname: Tomonari
authors.affiliation: Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Shichida
authors.affiliation: Department of Cytology and Histology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors.forename: Hideyo
authors.initials: H
authors.lastname: Ohuchi
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism; D002645:Chickens; D005091:Exons; D015870:Gene Expression; D023281:Genomics; D007031:Hypothalamus / Q000166:cytology / Q000378:metabolism; D007438:Introns; D008027:Light; D005810:Multigene Family; D010802:Phylogeny; D021381:Protein Transport; D034443:RNA Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000378:metabolism*; D051248:Retinal Horizontal Cells / Q000502:physiology; D017299:Rod Opsins / Q000235:genetics / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D017299:Rod Opsins; D002118:Calcium