title: Not All Inner Ears are the Same: Otolith Matrix Proteins in the Inner Ear of Sub-Adult Cichlid Fish, Oreochromis Mossambicus, Reveal Insights Into the Biomineralization Process.
abstract: The fish ear stones (otoliths) consist mainly of calcium carbonate and have lower amounts of a proteinous matrix. This matrix consists of macromolecules, which directly control the biomineralization process. We analyzed the composition of this proteinous matrix by mass spectrometry in a shotgun approach. For this purpose, an enhanced protein purification technique was developed that excludes any potential contamination of proteins from body fluids. Using this method we identified eight proteins in the inner ear of Oreochromis mossambicus. These include the common otolith matrix proteins (OMP-1, otolin-1, neuroserpin, SPARC and otoconin), and three proteins (alpha tectorin, otogelin and transferrin) not previously localized to the otoliths. Moreover, we were able to exclude the occurrence of two matrix proteins (starmaker and pre-cerebellin-like protein) known from other fish species. In further analyses, we show that the absence of the OMP starmaker corresponds to calcitic otoliths and that pre-cerebellin-like protein is not present at any stage during the development of the otoliths of the inner ear. This study shows O. mossambicus does not have all of the known otolith proteins indicating that the matrix proteins in the inner ear of fish are not the same across species. Further functional studies of the novel proteins we identified during otolith development are required.
authors.affiliation: Zoological Institute, University of Stuttgart-Hohenheim, Garbenstrasse 30, Stuttgart, 73734, Germany.|Department of Biology, Mount Saint Vincent University, 166 Bedford Highway, Halifax, Nova Scotia, B3M 2J6, Canada.
authors.forename: Jochen
authors.initials: J
authors.lastname: Weigele
authors.affiliation: Department of Biology, Mount Saint Vincent University, 166 Bedford Highway, Halifax, Nova Scotia, B3M 2J6, Canada.
authors.forename: Tamara A
authors.initials: TA
authors.lastname: Franz-Odendaal
authors.affiliation: Zoological Institute, University of Stuttgart-Hohenheim, Garbenstrasse 30, Stuttgart, 73734, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Hilbig
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002853:Chromatography, Liquid / Q000379:methods; D023681:Cichlids / Q000254:growth & development / Q000378:metabolism*; D007758:Ear, Inner / Q000254:growth & development / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D029941:Fish Proteins / Q000378:metabolism*; D007814:Larva / Q000254:growth & development / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning / Q000379:methods; D010037:Otolithic Membrane / Q000254:growth & development / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods
chemical_list: D016326:Extracellular Matrix Proteins; D029941:Fish Proteins; D002118:Calcium
keywords: Mozambique tilapia; development; mass spectrometry; matrix protein; otolith