ColorEM & Nanotomy: Multimodal microscopy to identify molecules and structures in large-scale tissue EM maps

Session

Stream 3: Chemical Imaging of Biological Samples using Electron, Ion and X-ray Based Techniques

Authors

Ben Giepmans (1)

Affiliations

1. UMC Groningen

Keywords

Electron Microscopy, Correlated Microscopy, Elemental Dispersive X-ray analysis, biomedical, probes

Abstract text

Correlated microscopy allows biological processes and/or cellular building blocks to be identified and dynamically studied followed by analysis of the ultrastructural context with EM. Today, I will focus on (i)  probes, and (ii) additional modalities for identification of molecules (‘ColorEM’) in (iii) routinely acquired large-scale EM maps, which we name nanotomy [1]. 

 

Nanotomy is now a routine technique in our facility: scanning entire EM sections at high resolution, comparable to the slide scanners for histology. A bottleneck has been acquisition rate in our single-bundle EM. I will show the results of a new multi-bundle transmission EM that will scan 100* faster [2,3]. 

 

Identification of molecules or structures in these maps is further improved by genetically encoded modular proteins that fluoresce, can generate electron density and are targeted via a nanobody, allowing a single step affinity labeling in both living or fixed cells [4]. A benefit of the probes is the penetration to reach targets because being a single protein, these are much smaller than the standard multi-step IgG-mediated immunolabeling. 

 

ColorEM is an alternative identification method based on elemental analysis, which we now also routinely now add to the workflow to identify endogenous structures, paint structures or label molecules in 2D, while exploring its application in 3D [5,6]. All identification techniques above typically aid in identifying structures after a first identification in large-scale EM maps and therefore their broad implementation will be highly useful in EM labs and microscope facilities.

 

References

[1] www.nanotomy.org 

[2] Kruit P & Zuidema W. Microscopy & Microanalysis 2019:25:1034

[3] de Boer P & Giepmans BNG, Immun. Cell Biol. 2021; doi:10.1111/imcb.12450

[4] de Beer MA et al, Histochem Cell Biol. 2018;149:261

[5] Pirozzi NM et al. Histochem Cell Biol. 2018;150:509

[6] de Boer P/ Pirozzi NM et al. Nat Comm 2020: 11:2475