Structural Support of Hair Cell Transduction : Freeze-fracture-etching of the Sensory Epithelia of the Inner Ear
✍ Scribed by Andrew Forge
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 2007
- Weight
- 241 KB
- Volume
- 9
- Category
- Article
- ISSN
- 1439-4243
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✦ Synopsis
Freeze-fracture-etching of the Sensory Epithelia of the Inner Ear
Transduction of sound is dependent upon the organisation of the cytoskeletal structures that form and support the stereociliary bundle of cochlear hair cells. Freeze-fracture followed by deep etching reveals the organisation of the hair cell cytoskeleton and indicates how mechanical support for stereocilia is provided. This can offer explanations of why mutations in certain genes that are widely expressed in the body have effects only upon the functioning of auditory hair cells to cause non-syndromic deafness. on a platform, the "cuticular plate" in the apical cytoplasm of the hair cell (fig. 1b). The cuticular plate, which appears relatively unstructured in thin sections (fig. 1b), is composed of actin with a variety of actin-interacting proteins [3]. More recently, analysis of the mutations in a number of different genes that cause hereditary deafness has identified several other cytoskeletal proteins that are essential to the formation and maintenance of the transduction apparatus [4]. Identifying how these proteins are organised and interact structurally is crucial to understanding how hair cells work and how they go wrong.
Freeze-fracture and Deep-etching Procedures
Deep-etching of tissue following freezefracture provides a means to visualise the internal structures of cells at high resolution. Freeze-fracture alone exposes membrane leaflets in face view and thus the membrane-faces of the cell and of organelles; cytoplasmic structures are not usually revealed because they do not deflect the fracture plane to impart topographic contrast. Sublimation of ice from the fractured surface ("etching") exposes structure otherwise obscured. To enable etching, non-volatile cryoprotective agents such as glycerol must be avoided during