Modeling the Complex Geometry of Organelle Membranes Inside Cells with Cryo-Electron Tomography

Cryo-electron tomography (cryo-ET) enables reconstructions of 3-dimensional views of the membranes, filaments, and macromolecular complexes in a cell with subnanometer resolution, and the advent of cryo-focused ion beam milling has enabled imaging in sections of cells that would otherwise be too thick for electron transmission. We present a semi-automated workflow to segment membranes and reconstruct their underlying surface geometry in cryo-ET. This workflow allows the straightforward reconstruction of even very complex and high curvature membranes, such as the endoplasmic reticulum and the mitochondrial inner membrane cristae, with high fidelity.