The Jackson Laboratory

Overview

The overall goals of our research program are to identify molecules and pathways that are important in the development and physiology of the ear. We study mouse mutations that disrupt these processes and develop these mutations as 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.

Scientific report

Genetic studies of hearing impairment in mice

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 18,000 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 website 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 (Willott et al., 2003) and with Dr. David Bergstrom, The Jackson Laboratory, and Dr. Sherri Jones, East Carolina University, to assess vestibular function in mice (Jones et al., 2004, 2005, 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 that exhibit progressive hearing loss as models (Noben-Trauth and Johnson, 2009). We previously showed that a locus (ahl) on Chromosome 10 (Keithley et al., 2004) 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 splice site variant of the cadherin 23 gene (Cdh23^G753A) (Noben-Trauth et al., 2003).

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 (Zheng et al., 2008), and a locus on distal Chromosome 11 (ahl8) that contributes to hearing loss in DBA/2J mice (Johnson et al., 2008). 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

Mouse deafness mutations provide valuable models of human hearing disorders and entry points into molecular pathways important to the hearing process. 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. We have a total of more than 50 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 and below describe five such genes and their corresponding mutant phenotypes that we have recently characterized.

Tmhs: We discovered that a mutation in a previously uncharacterized gene was responsible for the deafness and circling phenotype of a new mouse mutation we called hurry-scurry (hscy). We named the gene "tetraspan membrane protein of hair cell stereocilia" (Tmhs) because of its predicted protein structure and inner ear localization (Longo-Guess et al., 2005). Subsequently, mutations in the human TMHS gene were shown to be responsible for DFNB67, an autosomal recessive nonsyndromic deafness locus. We then genetically engineered a mouse with a targeted null allele and lacZ reporter gene that demonstrated high expression in the cochlear and vestibular hair cells of the inner ear, from E15.5 to P15, a duration that supports the involvement of Tmhs in stereocilia development (Longo-Guess et al. 2007b).

Clic5: We showed that the spontaneous jitterbug (jbg) mutation, which causes deafness and vestibular dysfunction when homozygous, is a mutation of the chloride intracellular channel 5 gene, Clic5 (Gagnon et al., 2006). CLIC5 immunofluorescence was detected in stereocilia of both cochlear and vestibular hair cells and in microvilli on the apical surface of Kolliker's organ during inner ear development, consistent with the known association of this protein with actin-based cytoskeletal structures of other polarized epithelial cells. Further supporting these results, mass spectrometry analysis identified high levels of CLIC5 in hair cell bundles isolated from the chicken utricle.

Ush1c: We mapped two new recessive mutations causing circling behavior and deafness to the same region on Chromosome 7 and showed they are allelic by complementation analysis. One was named "deaf circler" (allele symbol dfcr) and the other "deaf circler 2 Jackson" (allele symbol dfcr-2J). Both were shown to be mutations of the Ush1c gene (Johnson et al. 2003) and provided the first mouse models for human Usher syndrome type IC and for the nonsyndromic deafness disorder DFNB18. The qualitatively different mutations provided a means to evaluate the functional domains of the USH1C protein.

Otof: We demonstrated that the ENU-induced deaf5jcs mutation, imported from John Schimenti (Cornell U., NY), is a missense mutation of the otoferlin (Otof) gene and assessed the auditory and vestibular function of Otof^Deaf5jcs mutant mice by ABR and VsEP electrophysiological analyses . Otoferlin is essential for vesicle exocytosis at the inner hair cell synapse. Otof^Deaf5jcs mutant mice are deaf but exhibit normal outer hair cell function and normal vestibular behavior. The mice provide a new model for the human nonsyndromic deafness disorder DFNB9, which is caused by mutations of the orthologous human OTOF gene.

Duox2: We showed that a spontaneous mouse mutation causing congenital hypothyroidism with associated dwarfism and profound hearing impairment is a missense mutation (named thyroid dyshormonogenesis, thyd) in the dual oxidase 2 (Duox2) gene (Johnson et al., 2007). DUOX2 is an NADPH oxidase that generates hydrogen peroxide in thyroid follicular cells, which is used by thyroid peroxidase for the oxidation of iodide and the production of thyroid hormone. This mutant provides the first mouse model for DUOX2-related hypothyroidism.

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 Atp2b2^dfw, Tub^tub, and Eya1^bor. More recently, we published a paper on Cdh23^ahl modification of the Gpr98^frings mutation (Johnson et al., 2005), another paper on strain background effects on hearing in Jackson circler (jc) mutant mice (Calderon et al., 2006), and a review paper describing these and other hearing modifiers (Johnson et al., 2006). We have several other projects in progress to identify and evaluate new genetic modifiers and gene interactions involved in hearing. We mapped a hearing modifier of the dwarf (dw) mutation of the Pou1f1 gene (Karolyi et al., 2007) 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 (Keithley et al., 2005). We now are investigating a possible interaction between Sod1 deficiency and the ahl allele of Cdh23. In collaboration with Q.Y. Zheng (Case Western University) and X.Z. Liu (University of Miami), we recently published a paper describing a genetic interaction between mutations of the cadherin genes Cdh23 and Pcdh15 that causes a progressive hearing loss in digenic heterozygous mice and in human patients with compound mutations.

Lab staff

Principal Investigator: Kenneth R. Johnson, Ph.D.
Research Assistant III: Leona H. Gagnon, B.A., Chantal Longo-Guess, B.S.
Research Assistant I: Sandra Gray, Kelly L. Kane, B.S.

Publication listings

Noben-Trauth K, Johnson KR. 2009. Inheritance patterns of progressive hearing loss in laboratory strains of mice. Brain Res 1277: 42-51

Johnson KR, Longo-Guess C, Gagnon LH, Yu H, Zheng QY. 2008. A locus on distal Chromosome 11 (ahl8) and its interaction with Cdh23^ahl underlie the early onset, age-related hearing loss of DBA/2J mice. Genomics 92:219-225.

Zheng QY, Ding DL, Yu H, Salvi RJ, Johnson KR. 2008. A locus on distal Chromosome 10 (ahl4) affecting age-related hearing loss in A/J mice. Neurobiol Aging [Epub ahead of print]

Longo-Guess CM, Gagnon LH, Bergstrom DE, Johnson KR. 2007a. A missense mutation in the conserved C2B domain of otoferlin causes deafness in a new mouse model of DFNB9. Hear Res 234: 21-28.

Longo-Guess CM, Gagnon LH, Fritzsch B, Johnson KR. 2007b. Targeted knockout and lacZ reporter expression of the mouse Tmhs deafness gene and characterization of the hscy-2J mutation. Mamm Genome 18: 646-656.

Karolyi IJ, Dootz GA, Halsey K, Probst FJ, Johnson KR, Parlow AF, Dolan DF, Camper SA. 2007. Dietary thyroid hormone replacement ameliorates hearing deficits in hypothyroid mice. Mamm Genome 18: 596-608

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 the mouse dual oxidase 2 gene, Duox2. Mol Endocrinol 21: 1593-1602.

Gagnon LH, Longo-Guess CM, Berryman M, Shin JB, Saylor KW, Yu H, Gillespie PG, Johnson KR. 2006. The chloride intracellular channel protein CLIC5 is expressed at high levels in hair cell stereocilia and is essential for normal inner ear function. J Neurosci 26:10188-10198.

Calderon A, Derr A, Stagner BB, Johnson KR, Martin G, Noben-Trauth K. 2006. Cochlear developmental defect and background-dependent hearing thresholds in the Jackson circler (jc) mutant mouse. Hear Res 221: 44-58.

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.

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-Ghodsian 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 USA. 102: 7894-7899.

Johnson KR, Zheng QY, Weston MD, Ptacek LJ, Noben-Trauth K. 2005. The Mass1^frings mutation underlies early-onset hearing impairment in BUB/BnJ mice, a model for the auditory pathology of Usher Syndrome IIC. Genomics 85:
582-590.

Zheng QY, Yan D, Ouyang XM, Li F, Du LL, Yu H, Johnson KR, Liu XZ. 2005. Digenic inheritance of deafness caused by mutations in the genes encoding cadherin 23 and protocadherin 15 in mice and humans. Hum Mol Genet 14: 103-111.

Jones SM, Erway LC, Johnson KR, Yu H, Jones TA. 2004. Gravity receptor function in mice with graded otoconial deficiencies. Hear 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.

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.

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.

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