Electron Tomography of Cryo-Fixed and Resin-Embedded Samples

Room-temperature electron tomography of sections prepared from high-pressure frozen, freeze-substituted and resin-embedded cells is a powerful method to study intracellular architecture. The accessibility and versatility of this approach permit addressing many ultrastructural questions in cell and tissue biology. Such questions span different scales, from the localisation and organisation of protein assemblies to intricate cell remodeling processes during development. The robustness and high throughput of room-temperature electron tomography of resin samples facilitate identification and characterization of rare or transient cellular events as well as compilation of large datasets for quantitative analysis. Resistance to radiation damage enables dual-axis and montage tomography acquisitions for more isotropic resolution and for imaging large fields of view, respectively, thereby providing a wider context with equal detail. Electron tomography can also be performed on serial sections which allows entire cells or tissue volumes to be reconstructed at high resolution. Further, high precision correlative microscopy workflows can be implemented, permitting to combine information on molecular composition with ultrastructural detail. Here, we discuss the potential and limitations of electron tomography of cryo-fixed, resin-embedded cells, as well as its complementarity with electron cryo-tomography.