TY - JOUR
T1 - Osteopontin is not critical for otoconia formation or balance function
AU - Zhao, Xing
AU - Jones, Sherri M.
AU - Thoreson, Wallace B.
AU - Lundberg, Yunxia Wang
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2008/6
Y1 - 2008/6
N2 - Unlike the structural and mechanical role of bone crystals, the inertial mass of otoconia crystals provides a shearing force to stimulate the mechanoreceptors of the utricle and saccule (the gravity receptor organ) under the stimuli of linear motion. It is not clear whether otoconia, composed primarily of CaCO3 and glycoproteins, go through similar calcification processes as bone. We have recently shown that otoconin-90 (Oc90) regulates the growth of otoconia crystals as osteopontin does bone crystals. Here, we analyzed the role of this non-collagenous bone matrix protein, osteopontin, in otoconia formation and balance function utilizing its knockout mice, whose inner ear phenotype has not been examined. Despite the presence of the protein in wild-type otoconia and vestibular hair cells, morphological, ultrastructural, and protein and calcium composition analyses of osteopontin null otoconia show that the protein is not needed for crystal formation, and no evidence of compensatory protein deposition is found. Employment of a wide spectrum of balance behavioral tests demonstrates that the protein is not critical for balance function either, which is confirmed by the normal function of the gravity receptor organ directly measured with linear vestibular-evoked potentials (VsEPs). When compared with findings on other otoconins, the data manifest a hierarchy of importance of proteins in crystallization and indicate mechanistic similarities and differences between bone and otoconia calcification.
AB - Unlike the structural and mechanical role of bone crystals, the inertial mass of otoconia crystals provides a shearing force to stimulate the mechanoreceptors of the utricle and saccule (the gravity receptor organ) under the stimuli of linear motion. It is not clear whether otoconia, composed primarily of CaCO3 and glycoproteins, go through similar calcification processes as bone. We have recently shown that otoconin-90 (Oc90) regulates the growth of otoconia crystals as osteopontin does bone crystals. Here, we analyzed the role of this non-collagenous bone matrix protein, osteopontin, in otoconia formation and balance function utilizing its knockout mice, whose inner ear phenotype has not been examined. Despite the presence of the protein in wild-type otoconia and vestibular hair cells, morphological, ultrastructural, and protein and calcium composition analyses of osteopontin null otoconia show that the protein is not needed for crystal formation, and no evidence of compensatory protein deposition is found. Employment of a wide spectrum of balance behavioral tests demonstrates that the protein is not critical for balance function either, which is confirmed by the normal function of the gravity receptor organ directly measured with linear vestibular-evoked potentials (VsEPs). When compared with findings on other otoconins, the data manifest a hierarchy of importance of proteins in crystallization and indicate mechanistic similarities and differences between bone and otoconia calcification.
KW - Balance behaviors
KW - Bone
KW - Calcification
KW - Vestibular-evoked potentials
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U2 - 10.1007/s10162-008-0117-z
DO - 10.1007/s10162-008-0117-z
M3 - Article
C2 - 18459000
AN - SCOPUS:44449136661
VL - 9
SP - 191
EP - 201
JO - JARO - Journal of the Association for Research in Otolaryngology
JF - JARO - Journal of the Association for Research in Otolaryngology
SN - 1525-3961
IS - 2
ER -