Stereocilia bundle stiffness and mechano-electrical transduction in the auditory hair cells

Researchers in the Laboratory of Molecular Genetics at the NIDCD/NIH developed a mouse model of nonsyndromic deafness DFNB79 (TD-AG5). These mice have deletion of Tprn, a gene encoding taperin that is localized at the base of mechanosensory stereocilia of the inner ear hair cells. Based on this localization and sequence similarity to other actin-binding proteins, it was proposed that taperin may be involved in the formation and/or maintenance of the actin core at the base of stereocilia. Thus, a taperin deficiency may alter mechanical properties of the hair cell stereocilia bundles and/or mechano-electrical transduction in the hair cells of homozygous TD-AG5 mice. The first goal of this contract is to compare the mechanical stiffness of hair cell bundles in homozygous, heterozygous, and wild type TD-AG5 littermates. Due to subject-to-subject variability, each experimental group requires 6-10 organ of Corti explants. To separate the effects of taperin deficiency from the changes of hair bundle stiffness normally occurring during postnatal development, the experiments need to be performed at least at two different ages. The second goal of this contract is to determine whether homozygous TD-AG5 mice possess normal mechano-electrical transduction. Similar to our previous experience with Triobp mutant mice, another actin-binding protein at the base of stereocilia, we may not observe significant changes in mechano-transduction in TD-AG5 mice. However, it must still be confirmed experimentally, because taperin may be involved in anchoring acting filaments at the base of stereocilia, which may interfere with trafficking of important components of the transduction machinery to the stereocilia tips. Both raw and analyzed data will be provided upon completion of this contract. All experimental procedures of this contract have been approved by the University of Kentucky Animal Care and Use Committee (protocol #00903M2005, latest approval on 04/09/2014).