Cryo-CLXEM introduces cryo-SXT to bridge the resolution gap in cryo-CLEM

Cryo-imaging in cellular biology provides the means to visualize the cellular interior at close-to-native conditions. A cornerstone in the field has been cryo-correlative light and electron microscopy (cryo-CLEM), with cryo-visible light fluorescent microscopy (cryo-VLFM) providing the specificity by tagging macromolecules or structures and cryo-electron tomography (cryo-ET) for the structural details at molecular level. The large resolution gap between these techniques, however, is limiting this correlative workflow as cryo-ET targets are often smaller than the resolution limit of cryo-VLFM. Here we introduce cryo-soft X-ray tomography (cryo-SXT) as an intermediate step that can compensate for the partial view caused by the lost cellular material due to FIB-milling and limited resolution of cryo-VLFM by providing invaluable cellular context information in 3D to the cryo-ET dataset within an integrated workflow. This work shows that X-ray and electron imaging are not mutually exclusive, creating opportunities for further correlative imaging strategies. An integrated cryo-imaging pipeline combining cryo-correlative light and electron tomography with cryo-soft X-ray tomography provides 3D cellular context information and improved cryolamellae targeting for in situ cellular studies.