title: Localization of septin proteins in the mouse cochlea.
abstract: Septins are a family of GTP binding proteins that are well conserved in eukaryotic species except plants. Septins contribute to the lateral compartmentalization of membranes, cortical rigidity, and the regulation of membrane trafficking by associating with membrane lipids, actin, and microtubules. The organ of Corti in the cochlea has pivotal roles in auditory perception and includes two kinds of highly polarized cells, hair and supporting cells, both of which are rich in actin and microtubules. To identify the roles of septins in the cochlea, we analyzed the localization of three septin proteins, septin 4 (SEPT4), septin 5 (SEPT5), and septin 7 (SEPT7) that are abundantly expressed in brain tissues, and also examined auditory functions of Sept4 and Sept5 null mice. SEPT4, SEPT5, and SEPT7 were expressed in inner and outer pillar cells and Deiters' cells but the distribution patterns of each protein in Deiters' cells were different. SEPT4 and SEPT7 were expressed in the phalangeal process where SEPT5 was not detected. In addition to these cells SEPT5 and SEPT7 were co-localized with presynaptic vesicles of efferent nerve terminals. Only SEPT7 was expressed in the cochlea at embryonic stages. Although expression patterns of septin proteins suggested their important roles in the function of the cochlea, both Sept4 and Sept5 null mice had similar auditory functions to their wild type littermates. Immunohistochemical analysis of Sept4 null mice showed that compensatory expression of SEPT5 in the phalangeal process of Deiters' cells may have caused functional compensation of hearing ability in Sept4 null mice.
authors.affiliation: Department of Otolaryngology Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto City, Kyoto 606-8507, Japan.
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Yoshida
authors.forename: Norio
authors.initials: N
authors.lastname: Yamamoto
authors.forename: Makoto
authors.initials: M
authors.lastname: Kinoshita
authors.forename: Noboru
authors.initials: N
authors.lastname: Hiroi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hiramoto
authors.forename: Gina
authors.initials: G
authors.lastname: Kang
authors.forename: William S
authors.initials: WS
authors.lastname: Trimble
authors.forename: Kenji
authors.initials: K
authors.lastname: Tanigaki
authors.forename: Takayuki
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Juichi
authors.initials: J
authors.lastname: Ito
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001306:Auditory Pathways / Q000378:metabolism*; D001309:Auditory Threshold; D003051:Cochlea / Q000196:embryology / Q000378:metabolism*; D016057:Evoked Potentials, Auditory, Brain Stem; D005786:Gene Expression Regulation; D005838:Genotype; D006198:Hair Cells, Auditory / Q000378:metabolism*; D007150:Immunohistochemistry; D007760:Labyrinth Supporting Cells / Q000378:metabolism*; D051379:Mice; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D058112:Septins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: C115474:Sept4 protein, mouse; C491612:Sept5 protein, mouse; C512895:Sept7 protein, mouse; D058112:Septins