title: Tectorins crosslink type II collagen fibrils and connect the tectorial membrane to the spiral limbus.
abstract: All inner ear organs possess extracellular matrix appendices over the sensory epithelia that are crucial for their proper function. The tectorial membrane (TM) is a gelatinous acellular membrane located above the hearing sensory epithelium and is composed mostly of type II collagen, and α and β tectorins. TM molecules self-assemble in the endolymph fluid environment, interacting medially with the spiral limbus and distally with the outer hair cell stereocilia. Here, we used immunogold labeling in freeze-substituted mouse cochleae to assess the fine localization of both tectorins in distinct TM regions. We observed that the TM adheres to the spiral limbus through a dense thin matrix enriched in α- and β-tectorin, both likely bound to the membranes of interdental cells. Freeze-etching images revealed that type II collagen fibrils were crosslinked by short thin filaments (4±1.5nm, width), resembling another collagen type protein, or chains of globular elements (15±3.2nm, diameter). Gold-particles for both tectorins also localized adjacent to the type II collagen fibrils, suggesting that these globules might be composed essentially of α- and β-tectorins. Finally, the presence of gold-particles at the TM lower side suggests that the outer hair cell stereocilia membrane has a molecular partner to tectorins, probably stereocilin, allowing the physical connection between the TM and the organ of Corti.
authors.affiliation: Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA; Present address: Laboratory of Biomineralization, Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21941-902, Brazil. Electronic address: andrade@histo.ufrj.br.
authors.forename: Leonardo R
authors.initials: LR
authors.lastname: Andrade
authors.affiliation: Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA; Present address: Department of Community Dentistry and Behavioral Science, University of Florida College of Dentistry, Gainesville, FL 32610, USA.
authors.forename: Felipe T
authors.initials: FT
authors.lastname: Salles
authors.affiliation: Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA; Present address: Laboratory of Molecular Genetics, Department of Otolaryngology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
authors.forename: M'hamed
authors.initials: M
authors.lastname: Grati
authors.affiliation: Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA; Present address: Section on Organelle Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Uri
authors.initials: U
authors.lastname: Manor
authors.affiliation: Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA. Electronic address: kacharb@nidcd.nih.gov.
authors.forename: Bechara
authors.initials: B
authors.lastname: Kachar
mesh_terms: D000818:Animals; D024043:Collagen Type II / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000378:metabolism / Q000648:ultrastructure; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D005613:Freeze Etching; D058851:GPI-Linked Proteins / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D015870:Gene Expression; D006168:Guinea Pigs; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D051379:Mice; D046529:Microscopy, Electron, Transmission; D009218:Myosins / Q000172:deficiency / Q000235:genetics; D009925:Organ of Corti / Q000378:metabolism* / Q000648:ultrastructure; D011485:Protein Binding; D051381:Rats; D013680:Tectorial Membrane / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D024043:Collagen Type II; D016326:Extracellular Matrix Proteins; D058851:GPI-Linked Proteins; D008565:Membrane Proteins; C114013:Myo15 protein, mouse; C105350:Tecta protein, mouse; C512625:beta-tectorin, mouse; D009218:Myosins
keywords: Electron microscopy; Extracellular matrix; Immunogold-labeling; Tectorial membrane; Tectorins