Project: Research project

Project Details


Mature amphibian otolith hair cells display a variety of adaptation
kinetics which confer stimulus encoding and frequency selective
properties. Adapting hair cells do not retain information about sustained
hair bundle displacement, and thus are most sensitive to dynamic stimuli.
Adaptation is mediated by calcium and a cytoplasmic motor which releases
tension on the stereociliary tip-links, mechanically closing the
transduction channels. The most likely candidate for this cytoplasmic
motor is a myosin isoform. Thus, antisera against stereociliary myosin
and transduction channels can be used as markers of hair cell functional
maturity. Previous studies have also shown that hair cell regeneration
in amphibian otolith organs can occur in mitotically-blocked organotypic
cultures, and suggested that non-mitotic hair cell regeneration might be
accomplished by the phenotypic conversion of supporting cells into hair
cells. Alternatively, immature hair bundles might develop in damaged hair
cells undergoing repair, or post-mitotic progenitor cells undergoing
terminal differentiation.

We will use gentamicin sulfate to induce hair cell degeneration in
bullfrogs in vivo, and in organotypic cultures of bullfrog otolithic
organs. We will then use immunocytochemical, histochemical, and
ultrastructural techniques to study the subsequent labeling patterns in
regenerating hair bundles. The proposed experiments have been designed
to determine if in vitro labeling patterns for hair bundle regeneration
accurately reflect those in vivo. We will test the hypotheses that
immature hair bundles develop on either surviving. but damaged, hair
cells, and/or immature hair cells derived from either post-mitotic
progenitors or converting supporting cells in vivo and in mitotic and
mitotically-blocked organotypic cultures. We will also investigate the
temporal organization of soluble and filamentous actin in the early
stages of hair bundle repair in damaged hair cells and/or cuticular plate
and hair bundle development in post-mitotic progenitors and converting
supporting cells in mitotically-blocked cultures. This will reveal
labeling pafterns in damaged hair cells-undergoing repair, immature hair
cells derived from post-mitotic progenitors, and/or converting supporting
cells. We will also test the hypothesis that immature hair bundles
possess myosin and transduction channels, and if so, at what size of hair
bundle development they are expressed. The expression of myosin I- and
transduction channel proteins in a specific bundle size or larger will
allow these bundles to be selected and tested for hair cell function in
future electrophysiological studies. This work might suggest new
directions for rehabilitation of hair cell loss in hearing and vestibular
Effective start/end date1/1/9712/31/98


  • National Institute on Deafness and Other Communication Disorders
  • National Institute on Deafness and Other Communication Disorders


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