Search keywords: 'otolith matrix protein' Search Date 1/16/07

Some abstracts of interest:

• Protoplasma. 2006 Dec;229(2-4):205-8. Epub 2006 Dec 16. On the role of the central nervous system in regulating the mineralisation of inner-ear otoliths of fish.

Anken RH.

Zoological Institute, University of Hohenheim, Stuttgart, anken@uni-hohenheim.de.

Stato- or otoliths are calcified structures in the organ of balance and equilibrium of vertebrates, the inner ear, where they enhance its sensitivity to gravity. The compact otoliths of fish are composed of the calcium carbonate polymorph aragonite and a small fraction of organic molecules. The latter form a protein skeleton which determines the morphology of an otolith as well as its crystal lattice structure. This short review addresses findings according to which the brain obviously plays a prominent role in regulating the mineralisation of fish otoliths and depends on the gravity vector. Overall, otolith mineralisation has thus been identified to be a unique, neuronally guided biomineralisation process. The following is a hypothetical model for regulation of calcification by efferent vestibular neurons: (1) release of calcium at tight junctions in the macular epithelia, (2) macular carbonic anhydrase activity (which in turn is responsible for carbonate deposition), (3) chemical composition of matrix proteins. The rationale and evidence that support this model are discussed.

PMID: 17180502 [PubMed - in process]

• Brain Res. 2006 May 26;1091(1):58-74. Epub 2006 Mar 9. Mixing model systems: using zebrafish and mouse inner ear mutants and other organ systems to unravel the mystery of otoconial development.

Hughes I, Thalmann I, Thalmann R, Ornitz DM.

Department of Molecular Biology and Pharmacology, Rm. 3902 South Building (Campus Box 8103), Washington University in St. Louis, School of Medicine, 660 S. Euclid Ave, St. Louis, MO 63110, USA.

Human vestibular dysfunction is an increasing clinical problem. Degeneration or displacement of otoconia is a significant etiology of age-related balance disorders and Benign Positional Vertigo (BPV). In addition, commonly used antibiotics, such as aminoglycoside antibiotics, can lead to disruption of otoconial structure and function. Despite such clinical significance, relatively little information has been compiled about the development and maintenance of otoconia in humans. Recent studies in model organisms and other mammalian organ systems have revealed some of the proteins and processes required for the normal biomineralization of otoconia and otoliths in the inner ear of vertebrates. Orchestration of extracellular biomineralization requires bringing together ionic and proteinaceous components in time and space. Coordination of these events requires the normal formation of the otocyst and sensory maculae, specific secretion and localization of extracellular matrix proteins, as well as tight regulation of the endolymph ionic environment. Disruption of any of these processes can lead to the formation of abnormally shaped, or ectopic, otoconia, or otoconial agenesis. We propose that normal generation of otoconia requires a complex temporal and spatial control of developmental and biochemical events. In this review, we suggest a new hypothetical model for normal otoconial and otolith formation based on matrix vesicle mineralization in bone which we believe to be supported by information from existing mutants, morphants, and biochemical studies.

PMID: 16529728 [PubMed - indexed for MEDLINE]

*Mech Dev. 2005 Jun;122(6):791-803. Otolith matrix proteins OMP-1 and Otolin-1 are necessary for normal otolith growth and their correct anchoring onto the sensory maculae.

Murayama E, Herbomel P, Kawakami A, Takeda H, Nagasawa H.

Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, 113-8657 Tokyo, Japan. emur@pasteur.fr

Fish otoliths are highly calcified concretions deposited in the inner ear and serve as a part of the hearing and balance systems. They consist mainly of calcium carbonate and a small amount of organic matrix. The latter component is considered to play important roles in otolith formation. Previously, we identified two major otolith matrix proteins, OMP-1 (otolith matrix protein-1) and Otolin-1, from salmonid species. To assess the function of these proteins in otolith formation, we performed antisense morpholino oligonucleotide (MO)-mediated knockdown of omp-1 and otolin-1 in zebrafish embryos. We first identified zebrafish cDNA homologs of omp-1 (zomp-1) and otolin-1 (zotolin-1). Whole-mount in situ hybridization then revealed that the expression of both zomp-1 and zotolin-1 mRNAs is restricted to the otic vesicles. zomp-1 mRNA was expressed from the 14-somite stage in the otic placode, but the zOMP-1 protein was detected only from 26-somite stage onwards. In contrast, zotolin-1 mRNA expression became clear around 72 hpf. MOs designed to inhibit zomp-1 and zotolin-1 mRNA translation, respectively, were injected into 1-2 cell stage embryos. zomp-1 MO caused a reduction in otolith size and an absence of zOtolin-1 deposition, while zotolin-1 MO caused a fusion of the two otoliths, and an increased instability of otoliths after fixation. We conclude that zOMP-1 is required for normal otolith growth and deposition of zOtolin-1 in the otolith, while zOtolin-1, a collagenous protein, is involved in the correct arrangement of the otoliths onto the sensory epithelium of the inner ear and probably in stabilization of the otolith matrix.

PMID: 15905077 [PubMed - indexed for MEDLINE]

*Dev Biol. 2004 Dec 15;276(2):391-402. Otopetrin 1 is required for otolith formation in the zebrafish Danio rerio.

Hughes I, Blasiole B, Huss D, Warchol ME, Rath NP, Hurle B, Ignatova E, Dickman JD, Thalmann R, Levenson R, Ornitz DM.

Department of Molecular Biology and Pharmacology, Washington University Medical School, 660 South Euclid Avenue, St. Louis, MO 63110, USA.

Orientation with respect to gravity is essential for the survival of complex organisms. The gravity receptor is one of the phylogenetically oldest sensory systems, and special adaptations that enhance sensitivity to gravity are highly conserved. The fish inner ear contains three large extracellular biomineral particles, otoliths, which have evolved to transduce the force of gravity into neuronal signals. Mammalian ears contain thousands of small particles called otoconia that serve a similar function. Loss or displacement of these structures can be lethal for fish and is responsible for benign paroxysmal positional vertigo (BPPV) in humans. The distinct morphologies of otoconial particles and otoliths suggest divergent developmental mechanisms. Mutations in a novel gene Otopetrin 1 (Otop1), encoding multi-transmembrane domain protein, result in nonsyndromic otoconial agenesis and a severe balance disorder in mice. Here we show that the zebrafish, Danio rerio, contains a highly conserved gene, otop1, that is essential for otolith formation. Morpholino-mediated knockdown of zebrafish Otop1 leads to otolith agenesis without affecting the sensory epithelium or other structures within the inner ear. Despite lack of otoliths in early development, otolith formation partially recovers in some fish after 2 days. However, the otoliths are malformed, misplaced, lack an organic matrix, and often consist of inorganic calcite crystals. These studies demonstrate that Otop1 has an essential and conserved role in the timing of formation and the size and shape of the developing otolith.

PMID: 15581873 [PubMed - indexed for MEDLINE]

• Histochem Cell Biol. 2004 Feb;121(2):155-66. Epub 2003 Dec 20. Immunohistochemical localization of two otolith matrix proteins in the otolith and inner ear of the rainbow trout, Oncorhynchus mykiss: comparative aspects between the adult inner ear and embryonic otocysts.

Murayama E, Takagi Y, Nagasawa H.

Laboratory of Bioorganic Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, 113-8657 Tokyo, Japan.

The fish otolith consists mainly of calcium carbonate and organic matrices, the latter of which may play important roles in the process of otolith formation. We previously identified two otolith matrix proteins, named otolith matrix protein-1 (OMP-1) and otolin-1, from the rainbow trout, Oncorhynchus mykiss, and the chum salmon, O. keta. In this study, recombinant proteins corresponding to OMP-1 and otolin-1 were synthesized using yeast and bacterial expression systems, respectively, to produce specific antibodies against each protein. Immunohistochemical analysis using these antisera revealed that in the otoliths of adult fish, OMP-1 and otolin-1 were colocalized along the daily rings possibly formed by alternate deposition of calcium carbonate and organic matrices. In the adult inner ear, OMP-1 was produced at most of the saccular epithelium, while otolin-1 was produced at a limited part of cylindrical cells located at the marginal zone of the sensory epithelium. In the embryonic inner ear, these proteins had already existed in the otolith primordia when calcification had commenced. In addition, otolin-1 was localized in the fibrous materials connecting otolith primordia and sensory epithelium at this stage. These results indicate that these proteins are required as essential components for otolith formation and calcification.

PMID: 14689310 [PubMed - indexed for MEDLINE]

*J Exp Biol. 2003 Aug;206(Pt 15):2685-92. Daily variations of endolymph composition: relationship with the otolith calcification process in trout.

Borelli G, Guibbolini ME, Mayer-Gostan N, Priouzeau F, De Pontual H, Allemand D, Puverel S, Tambutte E, Payan P.

Laboratoire Reponse des Organismes aux Stress Environnementaux, UMR INRA-UNSA 1112, Universite de Nice-Sophia Antipolis, Faculte des Sciences, BP 71, 06108 Nice Cedex 2, France.

Ionic and organic parameters of the otolith calcification process in the trout Oncorhynchus mykiss were analysed in plasma and endolymph over the day:night cycle. Plasma pH remained constant and total CO(2) concentration was significantly lower (by 21%) during the day than at night. Calcifying parameters (total CO(2), total calcium concentration) were measured in the proximal and distal endolymphs and were unchanged in the latter during the day:night cycle, but fluctuated in the former. Non-collagenous protein and collagen concentrations in endolymph were higher (1.5- and 10-fold, respectively) during the day than at night. As there was no change in total calcium concentration, we propose that Ca(2+) increases during the dark period and was maximal by the end of the night when the total CO(2) concentration has also increased (by 14%). Measurements of endolymph pH in situ revealed significant differences between samples from proximal and distal endolymph (7.38 and 7.87, respectively), but no variation between values obtained during the day and at night. Thus, the saturation state of aragonite (Sa) in the proximal endolymph should fluctuate around unity during the day:night cycle, and CaCO? (3) precipitation should occur when supersaturation is reached. The electrophoretic pattern of proximal endolymph showed variations in both major and minor components. Immunoblotting of endolymph, using a rabbit antiserum raised against the otolith soluble organic matrix revealed an increase in the expression of two proteins (65 kDa and 75 kDa) during the day period. We propose that organic matrix and calcium carbonate deposition on the otolith vary antiphasically: organic matrix deposition begins by the end of the day period, when the concentration of organic precursors is maximal in the endolymph, whereas CaCO? (3) precipitation starts once the solubility of CaCO? (3) is exceeded.

PMID: 12819274 [PubMed - indexed for MEDLINE]

*Comp Biochem Physiol A Mol Integr Physiol. 2003 Mar;134(3):551-61. Composition and properties of the soluble organic matrix of the otolith of a marine fish: Gadus morhua Linne, 1758 (Teleostei, Gadidae).

Dauphin Y, Dufour E.

UMR 8616, Laboratoire de Paleontologie, bat. 504, Universite Paris Sud, 91405 Cedex, Orsay, France. dauphin@geophy.geol.u-psud.fr

The soluble matrix of the sagittal otolith of the cod Gadus morhua was analyzed using UV and IR spectroscopy, liquid chromatography and electrophoresis. This matrix is a complex mixture of proteins and glycoproteins, with a large range of molecular weights. High weights (>1000 kDa) are shown for the first time in water-soluble matrix of otolith. However, the 2D denaturing electrophoresis and large range of sorting used in high performance liquid chromatography columns do not separate the soluble matrix to well-defined molecular weights. The IR data indicate that several conformations are present and the main part of the sugars is not sulfated. Additionally, electrophoresis data show that the acidity of the sugar components is higher than that of the proteins. Despite the relative scarcity of literature data, our study of G. morhua suggests that the chemical composition of otolith soluble organic matrix may differ among species.

PMID: 12600664 [PubMed - indexed for MEDLINE]

*Anat Rec. 1999 Mar;254(3):322-9. Characterization of ootolith soluble-matrix producing cells in the saccular epithelium of rainbow trout (Oncorhynchus mykiss) inner ear.

Takagi Y, Takahashi A.

Otsuchi Marine Research Center, Ocean Research Institute, University of Tokyo, Otsuchi, Iwate, Japan. takagi@wakame.ori.u-tokyo.ac.jp

Although the organic matrix may play an important role in the growth of teleost otoliths, cellular contributions to the production of the organic matrix have been studied in only a small number of teleost species with limited methods, and are still poorly understood. In order to characterize saccular epithelial cells which produce otolith matrix, antiserum was raised against an EDTA-soluble fraction of otolith matrix (otolith soluble-matrix, OSM) of the rainbow trout. The components in the OSM and in the endolymph were characterized by immunoblotting. The saccular epithelium was immunohistochemically stained with the antiserum and the ultrastructure of OSM immunoreactive cells was studied. By immunoblotting, multiple components (> 94.0 kDa [smeared] and 43.0 kDa) in the OSM reacted with the antiserum, whereas only one band (> 94.0 kDa) was detected in the endolymph. Under immunohistochemical staining, reactions to the antiserum were observed in columnar cells lined at the most peripheral region of the sensory epithelium, transitional epithelial cells, and squamous epithelial cells. Electron microscopic observations revealed that all three types of cells were equipped with extended rough endoplasmic reticulum and prominent Golgi apparatus, suggesting the active production of organic material(s). Dilations of translucent vesicles, apocrine-like extrusions of cytoplasm, and vesicles containing many minute globules were frequently associated with the apical surface of these cells. Some ruptured vesicles were observed, releasing their contents into the endolymphatic space. The present study identified columnar cells lining the most peripheral region of the sensory epithelium, transitional epithelial cells, and squamous epithelial cells as the OSM-producing cells. We suggest that the OSM components are secreted and dissolved into the endolymph and subsequently deposited onto the otolith.

PMID: 10096663 [PubMed - indexed for MEDLINE]

*Science. 1995 Feb 17;267(5200):1031-4. Molecular cloning and characterization of an inner ear-specific structural protein.

Davis JG, Oberholtzer JC, Burns FR, Greene MI.

Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104.

Molecular biological studies of the mammalian inner ear have been limited by the relatively small size of the sensory endorgans contained within. The saccular otolithic organ in teleostian fish is structurally similar to its mammalian counterpart but can contain an order of magnitude more sensory cells. The prospect of the evolutionary conservation of proteins utilized in the vertebrate inner ear and the relative abundance of teleostian saccular sensory tissue made this an attractive system for molecular biological studies. A complementary DNA obtained by differential screening of a saccular complementary DNA library was identified that encodes an inner ear-specific collagen molecule.

PMID: 7863331 [PubMed - indexed for MEDLINE]

-- DaniPershouse - 22 Jan 2007