title: Developmental expression of otoconin-22 in the bullfrog endolymphatic sac and inner ear.
abstract: In amphibians, calcium carbonate crystals are present in the endolymphatic sac and the inner ear. The formation of these crystals is considered to be facilitated by a protein called otoconin-22. We examined the spatial and temporal expression of otoconin-22 during the development of the bullfrog (Rana catesbeiana) using RT-PCR, in situ hybridization (ISH), and immunofluorescence techniques. By RT-PCR, otoconin-22 mRNA was first detected in embryos at Shumway stage 20, and this expression pattern continues in late stages. The first otoconin-22 mRNA-positive reaction was detected in stage 22 embryos in the placode of the endolymphatic sac. Otoconin-22 protein was observed in the epithelial cells of the endolymphatic sac at stage 24. On the other hand, a whole-mount ISH technique showed the first expression of otoconin-22 mRNA in the inner ear, in addition to the endolymphatic sac, at the mid-phase of Shumway stage 25. We discuss the role of otoconin-22 in the formation of calcium carbonate crystals in the endolymphatic sac and inner ear.
authors.affiliation: Department of Biology, Faculty of Science, Shizuoka University, Shizuoka, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Yaoi
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Onda
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Hidaka
authors.forename: Shinya
authors.initials: S
authors.lastname: Yajima
authors.forename: Masakazu
authors.initials: M
authors.lastname: Suzuki
authors.forename: Shigeyasu
authors.initials: S
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins; D007758:Ear, Inner / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D004712:Endolymphatic Sac / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006023:Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D017403:In Situ Hybridization; D012333:RNA, Messenger / Q000096:biosynthesis; D011892:Rana catesbeiana; D020133:Reverse Transcriptase Polymerase Chain Reaction; D029867:Xenopus Proteins
chemical_list: D002135:Calcium-Binding Proteins; D006023:Glycoproteins; D012333:RNA, Messenger; D029867:Xenopus Proteins; C081347:otocinin-22 protein, Xenopus