Problems with balance are a leading cause of death and injury in elderly populations. Despite the prevalence of this problem little is known about the molecular mechanisms regulating vestibular development and pathology. Well characterized mouse mutants and techniques for sequencing small amounts of protein provide a means to clone genes that are expressed in the vestibular system. In turn allowing a biochemical and genetic analysis and an understanding of the molecular mechanisms underlying vestibular pathophysiology. We have characterized a mouse mutant (tilted) that is missing vestibular otoconia but that has an apparently normal sensory epithelium. We have also cloned the major matrix protein of mammalian otoconia, otoconin-90 (OC90), and showed that it is expressed in non-sensory vestibular epithelium during development in both control and tilted mice. We hypothesize that the mutation in the tilted mouse results in a missing or defective protein that is involved in the biosynthesis or structure of otoconia, or that is involved in the regulation of expression of other vestibular genes. Other otoconins may therefore also be missing, misexpressed or incorrectly modified secondary to the tilted mutation. We are using the tilted mouse mutant to facilitate the identification of genes responsible for otoconial biosynthesis. In this proposal we will: 1) Identify the mutant gene responsible for the tilted phenotype by positional cloning. 2) Identify and clone protein constituents of the otoconial complex. 3) Determine the spatial and developmental expression of the Oc90 gene and protein in wild type, tilted and head tilt mice (Testing the hypothesis that glycosylation or processing of OC90 is altered in these mouse mutants). The unprecedented structural features and the unexpected expression pattern of Oc90 has provided valuable insights into the mechanisms of otoconial formation and provide us with molecular and biochemical tools to elucidate unresolved areas of otoconial biology and pathophysiology, including turnover of otoconia and their organic and inorganic phases, degeneration, repair and regeneration. Human otoconia are subject to aging, drug and disease related pathology. In combination with age-related degeneration of sensory cells, these dysfunctions contribute significantly to the susceptibility of aged individuals to falling. In postmenopausal women this danger is compounded by osteoporosis, with the sequela of bone fracture. In 1991 medical care for treating individuals with balance related disorders cost 1 billion dollars per year.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC002236-09
Application #
6603475
Study Section
Special Emphasis Panel (ZRG1-IFCN-6 (01))
Program Officer
Platt, Christopher
Project Start
1995-01-01
Project End
2004-07-20
Budget Start
2003-07-01
Budget End
2004-07-20
Support Year
9
Fiscal Year
2003
Total Cost
$368,247
Indirect Cost
Name
Washington University
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
068552207
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
Hurle, Belen; Marques-Bonet, Tomas; Antonacci, Francesca et al. (2011) Lineage-specific evolution of the vertebrate Otopetrin gene family revealed by comparative genomic analyses. BMC Evol Biol 11:23
Kim, Euysoo; Hyrc, Krzysztof L; Speck, Judith et al. (2011) Missense mutations in Otopetrin 1 affect subcellular localization and inhibition of purinergic signaling in vestibular supporting cells. Mol Cell Neurosci 46:655-61
Lu, Wenfu; Zhou, Dan; Freeman, John J et al. (2010) In vitro effects of recombinant otoconin 90 upon calcite crystal growth. Significance of tertiary structure. Hear Res 268:172-83
Kim, Euysoo; Hyrc, Krzysztof L; Speck, Judith et al. (2010) Regulation of cellular calcium in vestibular supporting cells by otopetrin 1. J Neurophysiol 104:3439-50
Hughes, Inna; Binkley, Jonathan; Hurle, Belen et al. (2008) Identification of the Otopetrin Domain, a conserved domain in vertebrate otopetrins and invertebrate otopetrin-like family members. BMC Evol Biol 8:41
Hughes, Inna; Saito, Mitsuyoshi; Schlesinger, Paul H et al. (2007) Otopetrin 1 activation by purinergic nucleotides regulates intracellular calcium. Proc Natl Acad Sci U S A 104:12023-8
Thalmann, Isolde; Hughes, Inna; Tong, Benton D et al. (2006) Microscale analysis of proteins in inner ear tissues and fluids with emphasis on endolymphatic sac, otoconia, and organ of Corti. Electrophoresis 27:1598-608
Hughes, Inna; Thalmann, Isolde; Thalmann, Ruediger et al. (2006) Mixing model systems: using zebrafish and mouse inner ear mutants and other organ systems to unravel the mystery of otoconial development. Brain Res 1091:58-74
Hughes, Inna; Blasiole, Brian; Huss, David et al. (2004) Otopetrin 1 is required for otolith formation in the zebrafish Danio rerio. Dev Biol 276:391-402
Ignatova, Elena G; Thalmann, Isolde; Xu, Baogang et al. (2004) Molecular mechanisms underlying ectopic otoconia-like particles in the endolymphatic sac of embryonic mice. Hear Res 194:65-72

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