Localization of septin proteins in the mouse cochlea

• Published in: Hearing research 2012-07, Vol.289 (1-2), p.40-51
• Main Authors: Yoshida, Atsuhiro, Yamamoto, Norio, Kinoshita, Makoto, Hiroi, Noboru, Hiramoto, Takeshi, Kang, Gina, Trimble, William S., Tanigaki, Kenji, Nakagawa, Takayuki, Ito, Juichi
• Format: Article
• Language: English
• Subjects: Acoustic Stimulation; Actin; Animals; Auditory Pathways - metabolism; Auditory perception; Auditory system; Auditory Threshold; Brain; Cochlea; Cochlea - embryology; Cochlea - metabolism; Cortex; Embryos; Evoked Potentials, Auditory, Brain Stem; Gene Expression Regulation; Genotype; GTP-binding protein; Hair Cells, Auditory - metabolism; Hearing; Immunohistochemistry; Labyrinth Supporting Cells - metabolism; Lipids; membrane trafficking; Mice; Mice, Inbred ICR; Mice, Knockout; Microtubules; Nerve endings; Organ of Corti; Phenotype; Reverse Transcriptase Polymerase Chain Reaction; Septin; Septins - deficiency; Septins - genetics; Septins - metabolism; Vesicles
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/j.heares.2012.04.015

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. [Display omitted] ► SEPT4, SEPT5, and SEPT7 were expressed in pillar and Deiters' cells in the cochlea. ► SEPT5 and SEPT7 co-localized with synaptic vesicles of the cochlear efferent nerves. ► SEPT4 and SEPT7 were expressed in the phalangeal processes of Deiters' cells. ► SEPT7 was expressed in the embryonic cochlear epithelia at least from E13.5. ► Hearing of Sept4 or Sept5 null mice was normal due to compensation by other septins.