title: Mammalian-Specific Central Myelin Protein Opalin Is Redundant for Normal Myelination: Structural and Behavioral Assessments.
abstract: Opalin, a central nervous system-specific myelin protein phylogenetically unique to mammals, has been suggested to play a role in mammalian-specific myelin. To elucidate the role of Opalin in mammalian myelin, we disrupted the Opalin gene in mice and analyzed the impacts on myelination and behavior. Opalin-knockout (Opalin-/-) mice were born at a Mendelian ratio and had a normal body shape and weight. Interestingly, Opalin-/- mice had no obvious abnormalities in major myelin protein compositions, expression of oligodendrocyte lineage markers, or domain organization of myelinated axons compared with WT mice (Opalin+/+) mice. Electron microscopic observation of the optic nerves did not reveal obvious differences between Opalin+/+ and Opalin-/- mice in terms of fine structures of paranodal loops, transverse bands, and multi-lamellae of myelinated axons. Moreover, sensory reflex, circadian rhythm, and locomotor activity in the home cage, as well as depression-like behavior, in the Opalin-/- mice were indistinguishable from the Opalin+/+ mice. Nevertheless, a subtle but significant impact on exploratory activity became apparent in Opalin-/- mice exposed to a novel environment. These results suggest that Opalin is not critical for central nervous system myelination or basic sensory and motor activities under conventional breeding conditions, although it might be required for fine-tuning of exploratory behavior.
authors.affiliation: Laboratory for Molecular Neurogenesis, RIKEN Brain Science Institute, Wako, Saitama, 351-0198, Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Yoshikawa
authors.affiliation: Laboratory for Molecular Neurogenesis, RIKEN Brain Science Institute, Wako, Saitama, 351-0198, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Sato
authors.affiliation: The Center for Electron Microscopy and Bio-Imaging Research and Department of Physiology, Iwate Medical University, Morioka, Iwate, 020-8505, Japan.
authors.forename: Koujiro
authors.initials: K
authors.lastname: Tohyama
authors.affiliation: Support Unit for Neuromorphological Analysis, RIKEN Brain Science Institute, Wako, Saitama, 351-0198, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Akagi
authors.affiliation: Technology and Development Team for Mouse Phenotype Analysis, RIKEN BioResource Center, Tsukuba, Ibaraki, 305-0074, Japan.
authors.forename: Tamio
authors.initials: T
authors.lastname: Furuse
authors.affiliation: Laboratory for Molecular Neurogenesis, RIKEN Brain Science Institute, Wako, Saitama, 351-0198, Japan.|Advanced Scientific Research Leaders Development Unit, Gunma University, Maebashi, Gunma, 371-8511, Japan.
authors.forename: Tetsushi
authors.initials: T
authors.lastname: Sadakata
authors.affiliation: Laboratory for Behavioral Genetics, RIKEN Brain Science Institute, Wako, Saitama, 351-0198, Japan.
authors.forename: Mika
authors.initials: M
authors.lastname: Tanaka
authors.affiliation: Laboratory for Molecular Neurogenesis, RIKEN Brain Science Institute, Wako, Saitama, 351-0198, Japan.|School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, 192-0392, Japan.
authors.forename: Yo
authors.initials: Y
authors.lastname: Shinoda
authors.affiliation: Support Unit for Neuromorphological Analysis, RIKEN Brain Science Institute, Wako, Saitama, 351-0198, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Hashikawa
authors.affiliation: Laboratory for Behavioral Genetics, RIKEN Brain Science Institute, Wako, Saitama, 351-0198, Japan.
authors.forename: Shigeyoshi
authors.initials: S
authors.lastname: Itohara
authors.affiliation: Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba, 278-8510, Japan.
authors.forename: Yoshitake
authors.initials: Y
authors.lastname: Sano
authors.affiliation: Unite´ Mixte de Recherche 7357, Université de Strasbourg, Strasbourg, 67085, France and Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, Virginia, United States of America.
authors.forename: M Said
authors.initials: MS
authors.lastname: Ghandour
authors.affiliation: Technology and Development Team for Mouse Phenotype Analysis, RIKEN BioResource Center, Tsukuba, Ibaraki, 305-0074, Japan.
authors.forename: Shigeharu
authors.initials: S
authors.lastname: Wakana
authors.affiliation: Laboratory for Molecular Neurogenesis, RIKEN Brain Science Institute, Wako, Saitama, 351-0198, Japan.|Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba, 278-8510, Japan.
authors.forename: Teiichi
authors.identifier: http://orcid.org/0000-0002-9676-1888
authors.initials: T
authors.lastname: Furuichi
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure; D001522:Behavior, Animal; D001835:Body Weight; D001921:Brain / Q000378:metabolism; D002450:Cell Communication; D002454:Cell Differentiation; D005106:Exploratory Behavior; D015151:Immunoblotting; D008322:Mammals / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D009185:Myelin Proteins / Q000172:deficiency / Q000378:metabolism*; D009186:Myelin Sheath / Q000378:metabolism* / Q000648:ultrastructure; D009836:Oligodendroglia / Q000378:metabolism / Q000473:pathology; D009900:Optic Nerve / Q000378:metabolism / Q000648:ultrastructure; D010641:Phenotype; D013045:Species Specificity
chemical_list: D009185:Myelin Proteins; C524019:Opalin protein, mouse