Hair cells use an adaptation mechanism to ensure that their transduction channels operate at their point of optimal sensitivity. Determination of the molecular identity of proteins responsible for adaptation is important for several reasons: First, such identification should assist us in attempts to discover other members of the transduction apparatus. Second, because hair cells are such a scarce source of material to study, identification of the responsible gene will permit us to express its protein in abundance for biochemical and biophysical studies. Finally, should human deafnesses derive from mutated genes encoding the adaptation motor or associated proteins, future gene-replacement therapies employing a functional gene could conceivably correct such deficits. The best candidate for the hair cell's adaptation motor is myosin IB, an unconventional myosin isozyme that is found at stereociliary tips. Because hair cells are so scarce and because hair-bundle displacements directly open transduction channels, proof that myosin IB is the adaptation motor using biochemical methods is extremely difficult, if not impossible, to obtain. To test whether myosin IB is indeed the adaptation motor, we will instead eliminate its gene from the mouse's genome, and study the consequences on auditory and vestibular function that ensue. Because a complete knockout of myosin IB's gene may have broad effects that may confound our ability to assess its specific role in adaptation, we will also express in transgenic mice mutant myosin genes that should have predictable effects on adaptation. This proposal draws on the strengths of three laboratories: the Mercer laboratory, with extensive experience in mouse genetics and molecular cloning, and the Gillespie and Corey laboratories, with strengths in biochemical analysis and physiological assessment of adaptation in both amphibian and mammalian hair cells. The experiments proposed here will directly test whether myosin IB is indeed the hair cell's adaptation motor.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC003279-02
Application #
2856626
Study Section
Hearing Research Study Section (HAR)
Project Start
1998-01-01
Project End
2000-12-31
Budget Start
1999-01-01
Budget End
1999-12-31
Support Year
2
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Mc Laughlin Research Institute
Department
Type
DUNS #
City
Great Falls
State
MT
Country
United States
Zip Code
59405
Karcher, Ryan L; Provance, D William; Gillespie, Peter G et al. (2007) Chemical-genetic inhibition of sensitized mutant unconventional myosins. Methods Mol Biol 392:231-40
Senften, Mathias; Schwander, Martin; Kazmierczak, Piotr et al. (2006) Physical and functional interaction between protocadherin 15 and myosin VIIa in mechanosensory hair cells. J Neurosci 26:2060-71
LeMasurier, Meredith; Gillespie, Peter G (2005) Hair-cell mechanotransduction and cochlear amplification. Neuron 48:403-15
Stauffer, Eric A; Scarborough, John D; Hirono, Moritoshi et al. (2005) Fast adaptation in vestibular hair cells requires myosin-1c activity. Neuron 47:541-53
Gillespie, Peter G; Dumont, Rachel A; Kachar, Bechara (2005) Have we found the tip link, transduction channel, and gating spring of the hair cell? Curr Opin Neurobiol 15:389-96
Provance Jr, D William; Gourley, Christopher R; Silan, Colleen M et al. (2004) Chemical-genetic inhibition of a sensitized mutant myosin Vb demonstrates a role in peripheral-pericentriolar membrane traffic. Proc Natl Acad Sci U S A 101:1868-73
Gillespie, Peter G (2004) Myosin I and adaptation of mechanical transduction by the inner ear. Philos Trans R Soc Lond B Biol Sci 359:1945-51
Colclasure, J Chris; Holt, Jeffrey R (2003) Transduction and adaptation in sensory hair cells of the mammalian vestibular system. Gravit Space Biol Bull 16:61-70
Strassmaier, Meredith; Gillespie, Peter G (2002) The hair cell's transduction channel. Curr Opin Neurobiol 12:380-6
Dumont, Rachel A; Zhao, Yi-Dong; Holt, Jeffrey R et al. (2002) Myosin-I isozymes in neonatal rodent auditory and vestibular epithelia. J Assoc Res Otolaryngol 3:375-89

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