Correlative Microscopy for Cell Biology

Correlative microscopy for cell biology

Correlative light and electron microscopy (CLEM) has a broad range of applications in the life sciences. However, CLEM is particularly useful when objects of interests are sparsely distributed across the sample. The labelling power of the optical microscope combined with the high-resolution structural information provided by the electron microscope provides the ideal means to identify the complex processes occuring in a cell or tissue. It is thus an important technique for cell biology. For instance, when looking for transfected cells, fluorescence can be used to locate the cells that are transfected and the electron microscope serves to provide information about the structural details.

Imaging thin sections

Using CLEM to study thin sections allows one to use fluorescent markers for pinpointing certain regions of interest, locating rare events, screening large areas and identifying subcellular structures on a molecular basis. By using a multicolor labelling one can have the enormous toolbox of fluorescent markers available in nanometer resolution electron images.

Overlay of fluorescence and electron microscopy

Figure 1: Localization of the lipid diacylglycerol within cellular membranes of HeLa cell expressing GFP-C1. 

Overlay of fluorescence and electron microscopy

Figure 2: Hela Kyoto cells stably expressing GalNAC-T2-GFP and Histone 2B-mcherry. The cells were grown on carbon coated sapphire disks and high pressure frozen. The cells were then freeze substituted with 0.1% UA in glass distilled acetone in Lowicryl HM20.

Overlay of fluorescence and electron microscopy

Figure 3: Human umbilical vein endothelial cells (HUVEC) contain rod-like storage granules called Wiebel-Palade boddies which store Von Willebrand factor (VWF) These organelles play an important role in blood coagulation. Actin (Phalloidin Alexa 488) and VWF (Alexa 568).

Imaging cultured cells

CLEM is also the perfect method to accurately inspect the morphology and surface topology of cultured cells. With integrated CLEM one has the unique opportunity to simultaneously image fluorescent markers together with all the different types of contrast available for SEM. This provides a fast and straightforward method to study the cell morphology in correlation with specific proteins of interest.

Growing cells on a substrate is routine work in cell biology, and with just some small alterations in sample preparation one can take advantage of the high resolution of electron microscopy.

Other CLEM applications