title: Quantitative Analysis of Aquaporin Expression Levels during the Development and Maturation of the Inner Ear.
abstract: Aquaporins (AQPs) are a family of small membrane proteins that transport water molecules across the plasma membrane along the osmotic gradient. Mammals express 13 subtypes of AQPs, including the recently reported "subcellular AQPs", AQP11 and 12. Each organ expresses specific subsets of AQP subtypes, and in the inner ear, AQPs are essential for the establishment and maintenance of two distinct fluids, endolymph and perilymph. To evaluate the contribution of AQPs during the establishment of inner ear function, we used quantitative reverse transcription polymerase chain reaction to quantify the expression levels of all known AQPs during the entire development and maturation of the inner ear. Using systematic and longitudinal quantification, we found that AQP11 was majorly and constantly expressed in the inner ear, and that the expression levels of several AQPs follow characteristic longitudinal patterns: increasing (Aqp0, 1, and 9), decreasing (Aqp6, 8, and 12), and peak of expression on E18 (Aqp2, 5, and 7). In particular, the expression level of Aqp9 increased by 70-fold during P3-P21. We also performed in situ hybridization of Aqp11, and determined the unique localization of Aqp11 in the outer hair cells. Immunohistochemistry of AQP9 revealed its localization in the supporting cells inside the organ of Corti, and in the root cells. The emergence of AQP9 expression in these cells was during P3-P21, which was coincident with the marked increase of its expression level. Combining these quantification and localization data, we discuss the possible contributions of these AQPs to inner ear function.
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Kyoto, Japan.
authors.forename: Takushi
authors.initials: T
authors.lastname: Miyoshi
authors.affiliation: Department of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Neyagawa, 572-0074, Osaka, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Yamaguchi
authors.affiliation: Department of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Neyagawa, 572-0074, Osaka, Japan.
authors.forename: Kiyokazu
authors.initials: K
authors.lastname: Ogita
authors.affiliation: Department of Medical Physiology, Meiji Pharmaceutical University, Kiyose, 204-0004, Tokyo, Japan.
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Department of Medical Physiology, Meiji Pharmaceutical University, Kiyose, 204-0004, Tokyo, Japan.
authors.forename: Ken-Ichi
authors.initials: KI
authors.lastname: Ishibashi
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Kochi Medical School, Nangoku, 783-0043, Kochi, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ito
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Kochi Medical School, Nangoku, 783-0043, Kochi, Japan.
authors.forename: Taisuke
authors.initials: T
authors.lastname: Kobayashi
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Kyoto, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Nakagawa
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Kyoto, Japan.|Shiga Medical Center Research Institute, Moriyama, 524-0022, Shiga, Japan.
authors.forename: Juichi
authors.initials: J
authors.lastname: Ito
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Kyoto, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Omori
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Kyoto, Japan. yamamoto@ent.kuhp.kyoto-u.ac.jp.
authors.forename: Norio
authors.identifier: http://orcid.org/0000-0001-8924-0710
authors.initials: N
authors.lastname: Yamamoto
mesh_terms: D000818:Animals; D020346:Aquaporins / Q000378:metabolism*; D007758:Ear, Inner / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D008810:Mice, Inbred C57BL
chemical_list: D020346:Aquaporins
keywords: aquaporin; development; inner ear; qRT-PCR