• Published by: Denis CHRETIEN
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From molecules to cells

Cryo-electron microscopy of vitrified specimens has provided a great deal of new information concerning the structure and assembly mechanisms of microtubule assembled in vitro from purified components. Yet, our perception of microtubule structure in a cell environment remains limited, due to the constraints imposed by the classical methods of specimen preparation for electron microscopy (dehydration, resin embedding, "staining" with heavy metal salts, …). However, large progresses have been achieved in this field during the last years, and it is now possible to vitrify cells or tissues over a thickness of several tenth of micrometers, by combining a thermal choc with a large increase of the environmental pressure. Sections of the vitrified specimens are then performed using a diamond knife cooled to liquid nitrogen temperature, and are subsequently observed by cryo-electron microscopy. In combination with electron tomography, these new methods allow a faithful representation of the cell components in their native state, with a resolution on the order of the nanometer.

We apply these new methods to study supra-molecular assemblies such as the centrosome whose structure and biochemical composition remain poorly understood. This organelle is composed of two centrioles, each of them made of 9 microtubule triplets arranged according to a cylinder, and embedded in a "pericentriolar material" whose composition varies during the cell cycle. Cytoplasmic microtubules organize around a single centrosome in interphase. Just before cell division, the centrosome duplicates and organizes the mitotic bipolar spindle that triggers the segregation of chromosome during mitosis. Our aim is to obtain the structure in three dimensions of the centrosome at different stages of its duplication process, and to localize some proteins implicated in its biological activity.

Selected publications

  • Trehalose prevents aggregation of exosomes and cryodamage
    Bosch S., de Beaurepaire L., Allard M., Mosser M., Heichette C., Chrétien D., Jegou D., and J.-M. Bach Scientific Reports, 2016, 6:36162.
    Scientific Reports
    - SharedIt

  • Procentriole assembly revealed by cryo-electron tomography
    Guichard, P., Chrétien, D., Marco, S., and A.-M. Tassin
    The Embo Journal, 2010, 29:1565-72.
    Pubmed

  • Second harmonic microscopy of axonemes
    Odin, C., Heichette, C., Chrétien,D., and Y. Le Grand
    Optics Express, 2009, 17:9235–9240.
    Pubmed PDF (1.2 MB)