title: TRPML3 mutations cause impaired mechano-electrical transduction and depolarization by an inward-rectifier cation current in auditory hair cells of varitint-waddler mice.
abstract: TRPML3 (mucolipin-3) belongs to one of the transient-receptor-potential (TRP) ion channel families. Mutations in the Trpml3 gene cause disorganization of the stereociliary hair bundle, structural aberrations in outer and inner hair cells and stria vascularis defects, leading to deafness in the varitint-waddler (Va) mouse. Here we refined the stereociliary localization of TRPML3 and investigated cochlear hair cell function in varitint-waddler (Va(J)) mice carrying the TRPML3<I362T/A419P> mutations. Using a TRPML3-specific antibody we detected a approximately 68 kDa protein with near-equal expression levels in cochlea and vestibule of wild-type and Va(J) mutants. At postnatal days 3 and 5, we observed abundant localization of TRPML3 at the base of stereocilia near the position of the ankle links. This stereociliary localization domain was absent in Va(J) heterozygotes and homozygotes. Electrophysiological recordings revealed reduced mechano-electrical transducer currents in hair cells from Va(J)/+ and Va(J)/Va(J) mice. Furthermore, FM1-43 uptake and [(3)H]gentamicin accumulation were decreased in hair cells in cultured organs of Corti from Va(J)/+ and Va(J)/Va(J) mice. We propose that TRPML3 plays a critical role at the ankle-link region during hair-bundle growth and that an adverse effect of mutant TRPML3 on bundle development and mechano-electrical transduction is the main cause of hearing loss in Va(J)/+ mutant mice. Outer hair cells of Va(J)/Va(J) mice additionally had depolarized resting potentials due to an inwardly rectifying leak conductance formed by the mutant channels, leading over time to hair-cell degeneration and contributing to their deafness. Our findings argue against TRPML3 being a component of the hair-cell transducer channel.
authors.affiliation: School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK.
authors.forename: Alexander F J
authors.initials: AF
authors.lastname: van Aken
authors.forename: Margaret
authors.initials: M
authors.lastname: Atiba-Davies
authors.forename: Walter
authors.initials: W
authors.lastname: Marcotti
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Goodyear
authors.forename: Jane E
authors.initials: JE
authors.lastname: Bryant
authors.forename: Guy P
authors.initials: GP
authors.lastname: Richardson
authors.forename: Konrad
authors.initials: K
authors.lastname: Noben-Trauth
authors.forename: Corné J
authors.initials: CJ
authors.lastname: Kros
mesh_terms: D000818:Animals; D001483:Base Sequence; D003051:Cochlea / Q000503:physiopathology; D017931:DNA Primers / Q000235:genetics; D003638:Deafness / Q000235:genetics / Q000503:physiopathology; D004594:Electrophysiology; D006198:Hair Cells, Auditory / Q000502:physiology*; D006579:Heterozygote; D006720:Homozygote; D040542:Mechanotransduction, Cellular / Q000235:genetics / Q000502:physiology; D051379:Mice; D020297:Mice, Congenic; D008809:Mice, Inbred C3H; D008817:Mice, Mutant Strains; D009154:Mutation; D050053:TRPM Cation Channels / Q000235:genetics* / Q000502:physiology*; D046509:Tissue Culture Techniques
chemical_list: D017931:DNA Primers; D050053:TRPM Cation Channels
references.citation: Proc Natl Acad Sci U S A. 1995 Oct 24;92(22):10297-301
references.pmid: 7479771
references.citation: Neuron. 1995 Dec;15(6):1311-21
references.pmid: 8845155
references.citation: Biophys J. 1997 Apr;72(4):1622-32
references.pmid: 9083666
references.citation: Proc Biol Sci. 1997 Apr 22;264(1381):611-21
references.pmid: 9149428
references.citation: J Physiol. 1997 May 15;501 ( Pt 1):111-24
references.pmid: 9174998
references.citation: Hear Res. 1998 Sep;123(1-2):125-36
references.pmid: 9745961
references.citation: Audiol Neurootol. 2005 Jan-Feb;10(1):22-34
references.pmid: 15486441
references.citation: J Comp Neurol. 2005 Apr 25;485(1):75-85
references.pmid: 15776440
references.citation: J Physiol. 1999 Nov 1;520 Pt 3:653-60
references.pmid: 10545133
references.citation: EMBO J. 2000 Nov 15;19(22):6020-9
references.pmid: 11080149
references.citation: J Neurosci. 2001 Sep 15;21(18):7013-25
references.pmid: 11549711
references.citation: Proc Natl Acad Sci U S A. 2002 Nov 12;99(23):14994-9
references.pmid: 12403827
references.citation: J Assoc Res Otolaryngol. 2003 Mar;4(1):83-90
references.pmid: 12209292
references.citation: J Neurosci. 2003 May 15;23(10):4054-65
references.pmid: 12764092
references.citation: Nature. 2003 Dec 4;426(6966):517-24
references.pmid: 14654832
references.citation: Proc Natl Acad Sci U S A. 2004 Feb 24;101(8):2601-6
references.pmid: 14983055
references.citation: FEBS Lett. 2004 Jun 4;567(2-3):219-24
references.pmid: 15178326
references.citation: Hear Res. 1986;22:279-93
references.pmid: 3525484
references.citation: Hear Res. 1987 Nov;31(1):9-24
references.pmid: 3429352
references.citation: Proc Natl Acad Sci U S A. 1989 Apr;86(8):2918-22
references.pmid: 2468161
references.citation: J Physiol. 1989 Dec;419:405-34
references.pmid: 2621635
references.citation: Proc Biol Sci. 1992 Aug 22;249(1325):185-93
references.pmid: 1280836
references.citation: Genomics. 2005 May;85(5):582-90
references.pmid: 15820310
references.citation: J Physiol. 2005 Sep 1;567(Pt 2):505-21
references.pmid: 15994187
references.citation: Cell Calcium. 2005 Sep-Oct;38(3-4):233-52
references.pmid: 16098585
references.citation: Pflugers Arch. 2005 Oct;451(1):277-85
references.pmid: 15971078
references.citation: Hum Mol Genet. 2005 Dec 15;14(24):3921-32
references.pmid: 16301217
references.citation: J Membr Biol. 2006 Feb-Mar;209(2-3):71-88
references.pmid: 16773495
references.citation: J Neurosci. 2006 Jun 14;26(24):6543-53
references.pmid: 16775142
references.citation: J Biol Chem. 2006 Jun 23;281(25):17517-27
references.pmid: 16606612
references.citation: EMBO Rep. 2006 Sep;7(9):880-5
references.pmid: 16953201
references.citation: J Physiol. 2006 Oct 1;576(Pt 1):23-8
references.pmid: 16901942
references.citation: J Neurosci. 2006 Oct 25;26(43):10992-1000
references.pmid: 17065441
references.citation: J Neurosci. 2007 Jun 13;27(24):6478-88
references.pmid: 17567809
references.citation: Biochim Biophys Acta. 2007 Aug;1772(8):1022-7
references.pmid: 17300924
references.citation: Biochim Biophys Acta. 2007 Aug;1772(8):1028-31
references.pmid: 17329082
references.citation: Proc Natl Acad Sci U S A. 2007 Nov 13;104(46):18321-6
references.pmid: 17989217
references.citation: J Biol Chem. 2007 Dec 14;282(50):36138-42
references.pmid: 17962195
references.citation: Proc Natl Acad Sci U S A. 2007 Dec 4;104(49):19583-8
references.pmid: 18048323
references.citation: J Neurosci. 2007 Dec 12;27(50):13890-902
references.pmid: 18077701
references.citation: Proc Natl Acad Sci U S A. 2008 Jan 8;105(1):353-8
references.pmid: 18162548
references.citation: EMBO J. 2008 Apr 23;27(8):1197-205
references.pmid: 18369318