title: Modified protein expression in the tectorial membrane of the cochlea reveals roles for the striated sheet matrix.
abstract: The tectorial membrane (TM) of the mammalian cochlea is a complex extracellular matrix which, in response to acoustic stimulation, displaces the hair bundles of outer hair cells (OHCs), thereby initiating sensory transduction and amplification. Here, using TM segments from the basal, high-frequency region of the cochleae of genetically modified mice (including models of human hereditary deafness) with missing or modified TM proteins, we demonstrate that frequency-dependent stiffening is associated with the striated sheet matrix (SSM). Frequency-dependent stiffening largely disappeared in all three TM mutations studied where the SSM was absent either entirely or at least from the stiffest part of the TM overlying the OHCs. In all three TM mutations, dissipation of energy is decreased at low (<8 kHz) and increased at high (>8 kHz) stimulus frequencies. The SSM is composed of polypeptides carrying fixed charges, and electrostatic interaction between them may account for frequency-dependent stiffness changes in the material properties of the TM. Through comparison with previous in vivo measurements, it is proposed that implementation of frequency-dependent stiffening of the TM in the OHC attachment region facilitates interaction among tones, backward transmission of energy, and amplification in the cochlea.
authors.affiliation: School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, United Kingdom.
authors.forename: Gareth P
authors.initials: GP
authors.lastname: Jones
authors.affiliation: Institute of Sound and Vibration Research, University of Southampton, Southampton, United Kingdom.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Elliott
authors.affiliation: School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, United Kingdom. Electronic address: i.russell@brighton.ac.uk.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Russell
authors.affiliation: School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, United Kingdom. Electronic address: a.lukashkin@brighton.ac.uk.
authors.forename: Andrei N
authors.initials: AN
authors.lastname: Lukashkin
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000818:Animals; D003638:Deafness / Q000503:physiopathology; D004195:Disease Models, Animal; D004548:Elasticity; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism*; D058851:GPI-Linked Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D009154:Mutation; D013680:Tectorial Membrane / Q000502:physiology*; D046509:Tissue Culture Techniques; D014732:Vibration
chemical_list: D016326:Extracellular Matrix Proteins; D058851:GPI-Linked Proteins; D008565:Membrane Proteins; C486746:Otoa protein, mouse; C105350:Tecta protein, mouse; C512625:beta-tectorin, mouse