title: Visualization of cell microtubules in their native state.
abstract: BACKGROUND
  Over the past decades, cryo-electron microscopy of vitrified specimens has yielded a detailed understanding of the tubulin and microtubule structures of samples reassembled in vitro from purified components. However, our knowledge of microtubule structure in vivo remains limited by the chemical treatments commonly used to observe cellular architecture using electron microscopy.
  
  
  RESULTS
  We used cryo-electron microscopy and cryo-electron tomography of vitreous sections to investigate the ultrastructure of microtubules in their cellular context. Vitreous sections were obtained from organotypic slices of rat hippocampus and from Chinese-hamster ovary cells in culture. Microtubules revealed their protofilament ultrastructure, polarity and, in the most favourable cases, molecular details comparable with those visualized in three-dimensional reconstructions of microtubules reassembled in vitro from purified tubulin. The resolution of the tomograms was estimated to be approx. 4 nm, which enabled the detection of luminal particles of approx. 6 nm in diameter inside microtubules.
  
  
  CONCLUSIONS
  The present study provides a first step towards a description of microtubules, in addition to other macromolecular assemblies, in an unperturbed cellular context at the molecular level. As the resolution appears to be similar to that obtainable with plunge-frozen samples, it should allow for the in vivo identification of larger macromolecular assemblies in vitreous sections of whole cells and tissues.
authors.affiliation: Laboratory for Ultrastructural Analysis, Biophore, University of Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Cédric
authors.initials: C
authors.lastname: Bouchet-Marquis
authors.forename: Benoît
authors.initials: B
authors.lastname: Zuber
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Glynn
authors.forename: Mikhail
authors.initials: M
authors.lastname: Eltsov
authors.forename: Markus
authors.initials: M
authors.lastname: Grabenbauer
authors.forename: Kenneth N
authors.initials: KN
authors.lastname: Goldie
authors.forename: Daniel
authors.initials: D
authors.lastname: Thomas
authors.forename: Achilleas S
authors.initials: AS
authors.lastname: Frangakis
authors.forename: Jacques
authors.initials: J
authors.lastname: Dubochet
authors.forename: Denis
authors.initials: D
authors.lastname: Chrétien
mesh_terms: D000818:Animals; D016466:CHO Cells; D016764:Cell Polarity; D006224:Cricetinae; D003412:Cricetulus; D020285:Cryoelectron Microscopy; D006624:Hippocampus / Q000166:cytology / Q000648:ultrastructure; D008870:Microtubules / Q000648:ultrastructure*; D009474:Neurons / Q000166:cytology* / Q000648:ultrastructure*; D051381:Rats