A New Method for Cryo-sectioning Cell Monolayers Using a Correlative Workflow

Cryo-electron microscopy (cryo-EM) techniques have made a huge advancement recently, providing close to atomic resolution of the structure of protein complexes. Interestingly, this imaging technique can be performed in cells, giving access to the molecular machines in their natural context, therefore bridging structural and cell biology. However, in situ structural electron microscopy faces one major challenge, which is the ability to focus on specific subcellular regions to capture the objects of interest. Correlative light and electron microscopy (CLEM) is one very efficient solution for this. Here we present a sample preparation technique that enables cryo-sections of vitrified cell monolayers in an orientation that places the cryo-section parallel to the fluorescence imaging plane. The main advantage of this approach is that it exploits the potentials of CLEM for cryo-EM investigation, for selecting specific cells of interest in a heterogeneous population, or for finding identified subcellular regions on sections.