Submitted by Livia Harriman on Tue, 12/04/2022 - 12:11
Most ultrastructural herpesvirus research is done using transmission electron microscopy—however, research led by Kamal Nahas and collaborators from Stephen Graham's Laboratory and Colin Crump's Laboratory has demonstrated that an emerging imaging technique, known as cryo-soft-X-ray tomography, could also be used and has a few advantages over other imaging methods.
One is that the samples are prepared by cryopreservation, which protects their ultrastructure in a near-native state, whereas transmission electron microscopy typically involves artefact-inducing chemical fixation and treatment.
This means that the emerging technique can be used to more reliably study cellular architecture and virus assembly. Electron microscopy requires contrast-enhancing stains and the sample needs to be sectioned into thin slices before staining.
Cryo-soft-X-ray tomography doesn’t require any staining on the other hand because carbon-rich features in the cell (e.g. membranes and capsids) naturally absorb the X rays. As a result, the entire depth of the sample can be imaged without the need for any sectioning.
The ability to image the entire depth of the cell allowed the researchers to capture a greater number of rare or short-lived events, such as the transient migration of virus particles across the nuclear envelope.
The researchers were able to use this technique to document various stages of virus assembly and plan to study individual stages in greater detail moving forward. The researchers also studied how different organelles change morphology and distribution during infection and found striking changes in mitochondria, vesicles, and lipid droplets.
They followed up on these findings with confocal microscopy and super-resolution structured illumination microscopy and found that the Golgi complex became fragmented and dispersed with infection and that the microtubule network, which is intimately linked with all of the studied organelles, broke down during infection.
These findings suggest large-scale changes occur in the cell during infection and could signify an antiviral response by the cell or a virus-induced modification of cellular organelles.
Future work could elucidate the mechanisms underpinning these events and whether they’re driven by host or viral factors.
This research is a collaboration between Kamal Nahas, Atomic Virology, Beamline B24 and the Colin Crump Lab.
The preprint for this research: Contour, semi-automated segmentation and quantitation tool for cryo-soft-X-ray tomography is available here: https://www.biorxiv.org/content/10.1101/2021.10.11.463900v2
Check out Kamal's tweetorial for this work>>
Kamal Nahas
Kamal Nahas is a PhD student joint between the Department of Pathology (co-supervised by Colin Crump and Stephen Graham) and the Diamond Light Source (co-supervised by Maria Harkiolaki).
Keep up with Kamal and his research on Twitter @KLNahas