Hair cell function – it's all a matter of organization

Abstract

The mechanosensory cells that detect sound – the outer and inner hair cells – are located in the organ of Corti of the cochlea. Fig. 1a shows the apical surface of these cells, viewed with a scanning electron microscope. This image shows that the sensory hair cells are precisely arranged into three rows of outer hair cells (ohc) and one row of inner hair cells (ihc), and that each hair cell projects many ‘hair’-like structures, called stereocilia. These structures are themselves organized into rows of different lengths to produce a ‘staircase’-like pattern (Fig. 1c). Extracellular filaments (tip links) form between stereocilia in adjacent rows, so that when the bundle is deflected in response to sound, the tip links are stretched, and this leads to the opening of ion channels, and depolarization of the cell 1. Exactly how the hair cell organizes and maintains its cytoskeleton in this highly specialized form is poorly understood. However, it is an important question to investigate, as mutations in genes involved in this process have been shown to underlie some forms of deafness in humans 2.