Overview
The overall goal of our research program is to develop mouse models of human deafness disorders and age-related hearing loss. We have established a screening program to identify inbred and mutant mice with hearing impairment, which we assess by auditory brainstem response (ABR) analysis. In collaboration with colleagues we identified the first known gene in the mouse to cause age-related hearing loss (AHL), the most common type of human hearing impairment. We have mapped gene loci that contribute to AHL and are now refining their map positions as well as testing candidate genes that may underlie these effects. Our research team is also investigating new mouse mutations that cause hearing impairment. By identifying the genes underlying these mutations and studying their functions, we hope to gain a better understanding of the molecular mechanisms involved in the auditory process. The mutant mice also provide valuable models for studying human non-syndromic deafness disorders and human syndromes with associated deafness.
Research details
Genetic studies of hearing impairment in mice
The overall goal of our research program is to develop mouse models of human deafness disorders and age-related hearing loss. We have established a screening program to identify inbred and mutant mice with hearing impairment, which we assess by auditory brainstem response (ABR) analysis. Since 1996, we have screened more than 17,500 mice from The Jackson Laboratory's large collection of inbred and mutant strains. Information from this screening project is accessible on the Hereditary Hearing Impairment in Mice website. This web site also presents updated, comprehensive information on genes and mutations responsible for mouse and human hearing disorders. Once hearing impaired mice are identified, we examine their inner ears for pathological abnormalities and undertake a genetic analysis to map, identify, and characterize the responsible genes.
In addition to the research described in this report, we have ongoing collaborations with Dr. James Willott, University of South Florida, to study central auditory processing, and with Dr. David Bergstrom, The Jackson Laboratory, and Dr. Sherri Jones, East Carolina University, to assess vestibular function in mice (Jones et al., 2006).
Age-related hearing loss in mice
Age-related hearing loss (AHL), or presbycusis, is the most common type of human hearing impairment, affecting about half the population by age 80. Little is known about the genetic causes of human presbycusis because of confounding factors such as noise trauma, disease, or ototoxic drugs. Our approach for investigating the genetic basis of human presbycusis is to use inbred mouse strains as models. We previously showed that a locus (ahl) on Chromosome 10 is a major contributor to AHL in several inbred mouse strains and, in collaboration with Dr. Konrad Noben-Trauth (NIDCD), showed that ahl is a variant of the cadherin 23 gene (Cdh23G753A). This same variant can act as a hearing modifier for other mutations (Johnson et al., 2006).
We have mapped additional AHL loci by analyses of linkage crosses and recombinant inbred strains. We mapped a locus on Chromosome 5 (ahl2) that contributes to hearing loss in NOD/LtJ mice, a locus on distal Chromosome 10 (ahl4) that contributes to hearing loss in A/J mice, and a locus on distal Chromosome 11 (ahl8) that contributes to hearing loss in DBA/2J mice. We are now refining these map positions, producing congenic strains to isolate the effects of the individual AHL loci, and testing candidate genes that may underlie these effects.
Mouse mutations causing hearing impairment
We assess hearing in all abnormal mice that are chosen from the Laboratory's Deviant Search program (see Genetic Resources report in this volume), from mutagenesis programs, or from our own research colonies. If the deviant mice have an inherited hearing impairment, genetic crosses are set up to map the mutation. During the past year, we selected 19 new deviants with hearing or vestibular defects (circling and head tossing); 5 were discarded because they were not heritable or could not be recovered, and 14 are still being studied. We have a total of more than 60 hearing-related mutations with research still in progress.
We use the positional cloning-candidate gene approach to identify the genes underlying new mutations that cause hearing impairment. This past year, we identified and characterized new mutations in three previously identified deafness genes: Ush1gjs-2J, Kcnq1vtg-4J, and Myo6sv-2J (described on the Mouse Mutant Resource webpage). We also identified a deafness-causing mutation in a gene not previously associated with hearing. We showed that the spontaneous jitterbug (jbg) mutation, which causes deafness and vestibular dysfunction when homozygous, is a 97-base pair intragenic deletion of the chloride intracellular channel 5 gene, Clic5 (Gagnon et al., 2006). The mutation causes skipping of exon 5, creating a translational frameshift and premature stop codon. Histological analysis of jbg mutant inner ears revealed dysmorphic stereocilia and progressive hair cell degeneration. Using an antibody provided by our collaborator Mark Berryman, Ohio University, we detected specific CLIC5 immunofluorescence in stereocilia of both cochlear and vestibular hair cells and in microvilli on the apical surface of Kolliker's organ during development, consistent with the known association of this protein with actin-based cytoskeletal structures of other polarized epithelial cells. Our collaborator Peter Gillespie, Oregon Hearing Research Center, showed by mass spectrometry that CLIC5 is expressed at high levels in hair bundles isolated from the chicken utricle, in an approximate 1:1 molar ratio with radixin. These results suggest that CLIC5 associates with radixin at the basal region of the hair bundle and may help form or stabilize connections between the plasma membrane and the filamentous actin core.
Hearing modifiers and gene interactions
Mouse mutations often show variable phenotypes on different strain backgrounds. We and others have identified genetic modifiers of hearing in mice with mutations in several different deafness-related genes, including Atp2b2dfw, Gpr98frings, Tubtub, and Eya1bor. This year we published a review paper on these and other hearing modifiers (Johnson et al., 2006) and a paper on strain background effects on hearing in Jackson circler (jc) mutant mice (Calderon et al., 2006). We have several other projects in progress to identify and evaluate new genetic modifiers and gene interactions involved in hearing. We have mapped a hearing modifier of the dwarf (dw) mutation of the Pou1f1 gene and are evaluating an interesting candidate gene that may modify hearing loss associated with thyroid hormone deficiency. Antioxidant enzymes such as Cu/Zn superoxide dismutase (SOD1) protect cells from toxic, reactive oxygen species and may be involved in age-related degeneration. We previously reported that the absence of SOD1 in Sod1 knockout mice results in hearing loss at an earlier age than in wildtype mice. We are now investigating a possible interaction between Sod1 deficiency and the ahl allele of Cdh23.
Lab staff
Principal Investigator: Kenneth R. Johnson, Ph.D.
Research Assisant III: Patricia Ward-Bailey, M.S.
Research Assistant II: Leona H. Gagnon, B.A., Chantal Longo-Guess, B.S., Louise Dionne
Research Assistant I: Sandra Gray, Kelly L. Kane, B.S.
Biomedical Technologist III: Belinda S. Harris, B.S.
Visiting Investigators: James F. Willott, Ph.D., University of South Florida, Sherri M. Jones, Ph.D., East Carolina University
Publication listings
Donahue LR, Chang B, Subburaman M, Miyakoshi N, Wergedal JE, Baylink DJ, Hawes NL, Rosen CJ, Ward-Bailey P, Zheng QY, Bronson RT, Johnson KR, Davisson MT. 2003. A missense mutation in the mouse Col2al gene causes spondyloepiphyseal dysplasia, hearing loss, and retinoschisis. J Bone Miner Res 18(9):1612-1621.
Johnson KR, Gagnon LH, Webb LS, Peters LL, Hawes NL, Chang B, Zheng QY. 2003. Mouse models of USH1C and DFNB18: Phenotypic and molecular analyses of two new spontaneous mutations of the Ush1c gene. Hum Mol Genet 12:3075-3086.
Johnson KR, Lane PW, Cook SA, Harris BS, Ward-Bailey PF, Bronson RT, Lyons BL, Shultz LD, Davisson MT. 2003. Curly bare (cub), a new mouse mutation on Chr11 causing skin and hair abnormalities, and a modifer gene (mcub) on Chr 5. Genomics 81(1):6-14.
Noben-Trauth K, Zheng QY, Johnson KR. 2003. Association of cadherin-23 with polygenic inheritance and genetic modification of sensorineural hearing loss. Nat Genet 35:21-23.
Willott JF, Tanner L, O’Steen J, Johnson KR, Bogue MA, and Gagnon L. 2003. Acoustic startle and prepulse inhibition in forty inbred strains of mice. Behav Neurosci 117:728-737.
Zheng QY, Johnson KR. 2003. Genetic mouse models for otitis media. Journal of Xi'an Jiaotong University (Medical Sciences) 24(6):521-526.
Jones SM, Erway LC, Johnson KR, Yu H, Jones TA. 2004. Gravity receptor function in mice with graded otoconial deficiencies. Hearing Res 191:34-40.
Keithley EM, Canto C, Zheng QY, Fischel-Ghodsian N, Johnson KR. 2004. Age-related hearing loss and the ahl locus in mice. Hear Res 188:21-28.
Lorenz-Depiereux B, Guido VE, Johnson KR, Zheng QY, Gagnon LH, Bauschatz JD, Davisson MT, Washburn LL, Donahue LR, Strom TM, Eicher EM. 2004. New intragenic deletions in the Phex gene clarify XLH-related abnormalities in mice. Mamm Genome 15:151-161.
Zheng QY, Harris BS, Yu H, Letts VA, Ward-Bailey P, Bronson RT, Davisson MT, Johnson KR. 2004. Fine mapping of a deafness mutation hml on Mouse Chromosome 10. Academic Journal of Xi'an Jiaotong University 25(2):105-109.
Johnson KR, Zheng QY, Weston MD, Ptacek LJ, Noben-Trauth K. 2005. The Mass1frings mutation underlies early onset hearing impairment in BUB/BnJ mice, a model for the auditory pathology of Usher syndrome IIC. Genomics 85(5):582-590.
Jones SM, Johnson KR, Yu H, Erway LC, Alagramam KN, Pollak N, Jones TA. 2005. A quantitative survey of gravity receptor function in mutant mouse strains. J Assoc Res Otolaryngol 6:297-310.
Keithley EM, Canto C, Zheng QY, Wang X, Fischel-Ghodsia N, Johnson KR. 2005. Cu/Zn superoxide dismutase and age-related hearing loss. Hear Res 209: 76-85.
Longo-Guess CM, Gagnon LH, Cook SA, Wu J, Zheng QY, Johnson KR. 2005. A missense mutation in the previously undescribed gene Tmhs underlies deafness in hurry-scurry hscy mice. Proc Natl Acad Sci U S A 102(22):7894-7899.
Zheng QY, Yan D, Ouyang XM, Du LL, Yu H, Chang B, Johnson KR, Liu XZ. 2005. Digenic inheritance of deafness caused by mutations in genes encoding cadherin 23 and protocadherin 15 in mice and humans. Hum Mol Genet 14(1):103-111.
Alagraman KN, Brown SDM, Davis RR, Johnson KR, Zheng QY, Zuo J. 2006. Special issue: mouse models for hearing research. Brain Res 1091:1-2.
Gagnon LH, Longo-Guess CM, Berryman M, Shin J-B, Saylor KW, Yu H, Gillespie PG, Johnson KR. 2006. The chloride intracelluar channel protein CLIC5 is expressed at high levels in hair cell stereocilia and is essential for normal inner ear function. J Neurosci 26(40):10188-10198.
Johnson KR, Zheng QY, Noben-Trauth K. 2006. Strain background effects and genetic modifiers of hearing in mice. Brain Res 1091:79-88.
Jones SM, Jones TA, Johnson KR, Yu H, Erway LC, Zheng QY. 2006. A comparison of vestibular and auditory phenotypes in inbred mouse strains. Brain Res 1091:40-46.
Johnson KR, Marden CC, Ward-Bailey P, Gagnon LH, Bronson RT, Donahue LR. 2007. Congenital hypothyroidism, dwarfism, and hearing impairment caused by a missense mutation in mouse dual oxidase 2 gene, Duox2. Mol Endocrinol 21(7):1593-1602.
Karolyi IJ, Dootz GA, Halsey K, Beyer L, Probst FJ, Johnson KR, Parlow AF, Raphael Y, Dolan DF, Camper SA. 2007. Dietary thyroid hormone replacement ameliorates hearing deficits in hypothyroid mice. Mamm Genome 18:596-608.
Longo-Guess C, Gagnon LH, Bergstrom DE, Johnson KR. 2007. A missense mutation in the conserved C2B domain of otoferlin causes deafness in a new mouse model of DFNB9. Hear Res 234:21-28.
