Figure 1: On section CLEM: the signal from fluorescent proteins is used to target the EM analysis to specific subcellular timepoints during the endocytic process (adapted from Avinoam, et al. 2015).

Figure 1: On section CLEM: the signal from fluorescent proteins is used to target the EM analysis to specific subcellular timepoints during the endocytic process (adapted from Avinoam, et al. 2015).

live-cell CLEM

Figure 2: Live-cell correlative light and FIB-SEM captures specific stages of anaphase in dividing HeLa cells, revealing the formation of new nuclear envelope and the integration of nuclear pores. Adapted with permission from Otsuka et al. 2018

Equipment available

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The facility provides advanced expertise in electron microscopy, from sample preparation to image analysis, for a wide variety of biological samples

The EMCF activities cover a large spectrum of EM techniques with a major focus on sample preparation, immuno-localisation of proteins, ultrastructural analysis in 2D and 3D, correlative light and electron microscopy and data processing. Staff in the facility can help you to define optimal experimental conditions for your project – we have experience spanning virtually the full spectrum of biological specimens, with high-level resources for both research and training.

Major projects and accomplishments

Advanced equipment: Besides the EM imaging, we offer access to a high-pressure freezing machine. These instruments are routinely used to vitrify biological samples. Specimens can then be dehydrated, stabilised and embedded in resins in specific freeze-substitution units. Strong expertise has been developed for yeast cells, adherent cultured cells, Drosophila embryos, nematodes, zebrafish embryos, and mouse tissues. A microwave-assisted sample processor, used for chemical fixation, dehydration and embedding, greatly reduces time spent preparing the samples (from days to hours). For Tomography,  two transmission electron microscopes (a FEI TECNAI F30 300kV  and a 200kV JEOL JEM 2100Plus) are available. EMCF services include access to EMBL IT's central storage and compute facilities for 3D reconstruction and cellular modelling.

The Electron microscopist ‘savoir faire’: We are deeply involved in method development and training. A recent example in correlative light and electron microscopy (CLEM) is the implementation of a technique developed by the Briggs and Kaksonen groups, which tracks the signal of fluorescent proteins in resin sections with high precision.

We have just published a detailed step-by-step video tutorial on this method in EMBL's e-learning channel.

The future in perspective: Since 2014, the facility has started to provide services in automated serial imaging in scanning electron microscopy (ASI-SEM), such as focused ion beam SEM (FIB-SEM). This technique complements our portfolio of 3D imaging applications (serial section, electron tomography) by providing new opportunities for understanding the cellular fine architecture of multi-cellular specimens. The facility is also offering support for the recently developed cryo-CLEM techniques (see Schorb and Briggs 2014, 2016), which will nicely bridge structural and cell biology.

Recent achievements

Postmitotic nuclear pore assembly proceeds by radial dilation of small membrane openings.
Otsuka S, Steyer AM, Schorb M, Hériché JK, Hossain MJ, Sethi S, Kueblbeck M, Schwab Y, Beck M, Ellenberg J.
Nat Struct Mol Biol. 2018 Jan;25(1):21-28. doi: 10.1038/s41594-017-0001-9. | Abstract

Pre-assembled Nuclear Pores Insert into the Nuclear Envelope during Early Development.
Hampoelz B, Mackmull MT, Machado P, Ronchi P, Bui KH, Schieber N, Santarella-Mellwig R, Necakov A, Andrés-Pons A, Philippe JM, Lecuit T, Schwab Y, Beck M.
Cell 2016, 166(3):664-78. doi: 10.1016/j.cell.2016.06.015 | Abstract

ESCRT-III drives the final stages of CUPS maturation for unconventional protein secretion.
Curwin AJ, Brouwers N, Alonso Y Adell M, Teis D, Turacchio G, Parashuraman S, Ronchi P, Malhotra V.
Elife 2016, 5. pii: e16299. doi: 10.7554/eLife.16299 | Abstract

ENDOCYTOSIS. Endocytic sites mature by continuous bending and remodeling of the clathrin coat.
Avinoam O, Schorb M, Beese CJ, Briggs JA, Kaksonen M.
Science 2015, 348(6241):1369-1372. doi: 10.1126/science.aaa9555 | Abstract

Endocytic membrane turnover at the leading edge is driven by a transient interaction between Cdc42 and GRAF1.
Francis MK, Holst MR, Vidal-Quadras M, Henriksson S, Santarella-Mellwig R, Sandblad L, Lundmark R.
J Cell Sci 2015, 128:4183-4195. doi: 10.1242/jcs.174417 | Abstract

An arp2/3 nucleated f-actin shell fragments nuclear membranes at nuclear envelope breakdown in starfish oocytes.
Mori M, Somogyi K, Kondo H, Monnier N, Falk HJ, Machado P, Bathe M, Nédélec F, Lénárt P.
Curr. Biol. 2014, 24(12):1421-1428. doi: 10.1016/j.cub.2014.05.019 | Abstract

Quality control of inner nuclear membrane proteins by the Asi complex.
Foresti O, Rodriguez-Vaello V, Funaya C, Carvalho P.
Science. 2014, 346(6210):751-5. doi: 10.1126/science.1255638. Epub 2014 Sep 18. Abstract

Correlated fluorescence and 3D electron microscopy with high sensitivity and spatial precision.
Kukulski W, Schorb M, Welsch S, Picco A, Kaksonen M & Briggs JA.
J Cell Biol. 2011 Jan 10, 192(1):111-9. doi: 10.1083/jcb.201009037. Epub 2011 Jan 3. Abstract

Services provided

Single-particle and tomography cryo-EM for structural biology projects is offered through the cryo-EM service platform.

Techniques