Tonofibril

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Tonofibrils are cytoplasmic protein structures in epithelial tissues that converge at desmosomes and hemidesmosomes. [1] They consist of bundles of keratin intermediate filaments (tonofilaments) in epithelial cells that are anchored to the cytoskeleton. [2] [3] They were discovered by Rudolf Heidenhain, and first described in detail by Louis-Antoine Ranvier in 1897. [4]

Contents

Composition

Tonofilaments are keratin intermediate filaments that make up tonofibrils in the epithelial tissue. They may also just be referred to as keratin intermediate filaments. [5] In epithelial cells, tonofilaments loop through desmosomes. Electron microscopy has advanced now to illustrate the tonofilaments more clearly. [1]

Transmission electron micrograph depicting tonofilaments, labeled tf, running longitudinally within the dorsal epidermal cells of the girdle of a chiton Chiton epidermis TEM.jpg
Transmission electron micrograph depicting tonofilaments, labeled tf, running longitudinally within the dorsal epidermal cells of the girdle of a chiton

The protein filaggrin is believed to be synthesized as a giant precursor protein, profilaggrin (>400 kDA in humans). When filaggrin binds to keratin intermediate filaments, the keratin aggregates into macrofibrils. [3]

References

  1. 1 2 "tonofibril" at Dorland's Medical Dictionary [ dead link ]
  2. ↑ "Keratinocytes". Kenhub. Retrieved 30 November 2025.
  3. 1 2 Sandilands, Aileen; Sutherland, Calum; Irvine, Alan D.; McLean, W. H. Irwin (2009-05-01). "Filaggrin in the frontline: role in skin barrier function and disease". J Cell Sci. 122 (9): 1285–1294. doi:10.1242/jcs.033969. ISSN   0021-9533. PMC   2721001 . PMID   19386895.
  4. ↑ Charles, Arwyn; Smiddy, F. G. (1957-09-01). "The Tonofibrils of the Human Epidermis1". Journal of Investigative Dermatology. 29 (5): 327–338. doi: 10.1038/jid.1957.108 . ISSN   0022-202X. PMID   13502588.
  5. ↑ Windoffer, R; Beil, M; Magin, TM; Leube, RE (5 September 2011). "Cytoskeleton in motion: the dynamics of keratin intermediate filaments in epithelia". The Journal of cell biology. 194 (5): 669–78. doi:10.1083/jcb.201008095. PMID   21893596.


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