Auditory mechanotransduction in the absence of functional myosin-XVa

J Physiol. 2006 Nov 1;576(Pt 3):801-8. doi: 10.1113/jphysiol.2006.118547. Epub 2006 Sep 14.

Abstract

In hair cells of all vertebrates, a mechanosensory bundle is formed by stereocilia with precisely graded heights. Unconventional myosin-XVa is critical for formation of this bundle because it transports whirlin and perhaps other molecular components responsible for programmed elongation of stereocilia to the stereocilia tips. A tip of a stereocilium is the site of stereocilia growth and one of the proposed sites of mechano-electrical transduction. In adult shaker 2 mice, a mutation that disables the motor function of myosin-XVa results in profound deafness and abnormally short stereocilia that lack stereocilia links, an indispensable component of mechanotransduction machinery. Therefore, it was assumed that myosin-XVa is required for proper formation of the mechanotransduction apparatus. Here we show that in young postnatal shaker 2 mice, abnormally short stereocilia bundles of auditory hair cells have numerous stereocilia links and 'wild type' mechano-electrical transduction. We compared the mechanotransduction current in auditory hair cells of young normal-hearing littermates, myosin-XVa-deficient shaker 2 mice, and whirler mice that have similarly short stereocilia but intact myosin-XVa at the stereocilia tips. This comparison revealed that the absence of functional myosin-XVa does not disrupt adaptation of the mechanotransduction current during sustained bundle deflection. Thus, the hair cell mechanotransduction complex forms and functions independently from myosin-XVa-based hair bundle morphogenesis.

Publication types

  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cilia / physiology
  • Deafness / etiology
  • Deafness / genetics
  • Deafness / physiopathology
  • Evoked Potentials, Auditory, Brain Stem / genetics
  • Evoked Potentials, Auditory, Brain Stem / physiology*
  • Hair Cells, Auditory, Outer / cytology
  • Hair Cells, Auditory, Outer / pathology
  • Hair Cells, Auditory, Outer / physiology
  • Mechanotransduction, Cellular / genetics
  • Mechanotransduction, Cellular / physiology*
  • Mice
  • Mutation / genetics*
  • Myosins / genetics*
  • Myosins / physiology*
  • Organ of Corti / cytology
  • Organ of Corti / pathology
  • Organ of Corti / physiology
  • Patch-Clamp Techniques

Substances

  • Myo15 protein, mouse
  • Myosins