Generating meaningful images – a report from Seeing is Believing 2019

By event reporters Liz Haynes @actin_crazy and Stephan Daetwyler @Daetwyler_St

Seeing is Believing event reporters Liz Haynes & Stephan Daetwyler, PHOTO: Liz Haynes/Stephan Daetwyler

The field of biology owes some of its most compelling discoveries to careful visual observation. From Van Leeuwenhoek’s use of new microscopes to describe microscopic “animalcules” in the late 1600s, to Ramon y Cajal’s pioneering 19th century work illustrating beautiful and complex neuronal architecture. Images inspire us, help us generate new hypotheses, and shed light into the tiny worlds yet unexplored. Indeed, these observations uniquely help us understand the structures and dynamics of life, something that would not be achievable with approaches like biochemistry alone.

The images are only as valuable as the amount of information that we can deduce from it.

Generating meaningful images, however, is not an easy task. There have always been limits to what we can observe, due to the properties of the sample or the techniques that we can apply to it. These are the boundaries that microscopists seek to push. A successful imaging experiment requires an amenable sample, a contrast agent to reveal the structures of interest, and a microscope that is capable of capturing an image at a relevant scale. Moreover, the images are only as valuable as the amount of information that we can deduce from it. Therefore, image storage, accessibility and analysis are crucial. Each one of these steps offers opportunities for optimisation and new technologies.

Co-organiser Jan Ellenberg opens the Seeing is Believing symposium, PHOTO: Liz Haynes & Stephan Daetwyler

The EMBO | EMBL Symposium “Seeing is Believing: Imaging the Molecular Processes of Life” (9-12 October 2019) presented us with exciting new developments in all of these fields, coupled with a drive to make new progress available as quickly as possible to the community through preprints, open-source initiatives, and resource sharing.

Advances in sample preparation

At the heart of every imaging approach is the sample. Even the best microscope is ineffective with dim or improperly prepared samples. At Seeing is Believing, we saw an emphasis on using expansion of samples to help overcome the resolution limits of microscopy and solve some traditionally difficult problems. In particular, we were impressed with expansion-based approaches to study centriole structure (Paul Guichard, Ultrastructural Expansion Microscopy) and resolve microtubules tightly packed within axons (Lukas C. Kapitein). By far, the biggest emphasis in sample improvement was on the development of new fluorescent probes and biosensors. Kai Johnsson presented design strategies for the improvement of live cell dyes, and introduced new MaP dyes that are SNAP and HALO compatible, and importantly require no wash to clear unbound probe. Periklis Pantazis presented a mechanosensor based on the Piezo1 stretch activated ion channel, allowing users to visualise mechanical stress within a live cell. Atsushi Miyawaki wowed the audience by meeting the challenge to “be better than a firefly” with a new variant of luciferase named AkaBLI, which his lab generated through targeted evolution. This improved luciferase allowed them to visualise neuronal activity within freely behaving mice and marmosets.

Advances in microscopy

New imaging methods on show at Seeing is Believing, PHOTO: EMBL Events

The features of our microscopes directly determine which questions we can address. Seeing is Believing highlighted exciting new development in building cutting-edge microscopy tools. Reto Fiolka presented a novel single-objective light-sheet microscope enabling imaging of live cells in microfluidics devices or 3D environments with 200 nm lateral resolution. Kevin Dean complemented novel light-sheet development by presenting an axially swept light-sheet microscope ideally suited for all clearing techniques that provides an unprecedented field of view enabling whole tissue imaging with sub-micron resolution. With her imaging approach, Alexandra Pacureanu surprised the audience with how X-ray holographic nano-tomography is capable of resolving the fine, dense and complex neuronal circuitry in large tissues or even organism providing a new route to understand how the nervous system processes information.

Nobel Prize winner Stefan Hell spoke on how to attain 1 nm resolution with super-resolution microscopy, PHOTO: Liz Haynes & Stephan Daetwyler

Further impressive advances were presented in fast volumetric imaging (Lars Hufnagel, light field imaging) and high-resolution imaging, e.g. MINFLUX by Stefan Hell, correlative EM imaging by Harald Hess and Lucy Collinson, GI-SIM/LLS-SIM by Dong Li, and 3D-STED deep in a tissue by Joerg Bewersdorf.

Advances in data analysis

All acquired data is meaningless if we cannot extract information from it. At Seeing is Believing, it became obvious how artificial neuronal networks have become important for image analysis. Applications range from segmentation to denoising an image (BGnet, W.E. Moerner and Noise2Void, A. Krull/Florian Jug). Particularly, the convolutional network architecture U-Net has become an important tool. To provide a user-friendly environment to apply those state-of-the art image analysis tools, Anna Kreshuk presented the iLastik platform as an easy to use tool. A new fundamental approach to handle, visualise and process the large amount of data coming from the microscopes was presented by Ivo Sbalzarini. Instead of using pixels to save an image, adaptive particles approximate the image content. Furthermore, Gaudenz Danuser gave a thought-provoking talk on how current perturbation-based approaches in cell biology can mislead us in our analysis. Danuser emphasised that the observed phenotype from a perturbation of a system (e.g. loss of a protein’s function) is not equal to the real function of the gene. For example, cutting a wire from the battery to the electronic board of radio would lead to the “phenotype” loss of sound. However, the function of the wire was simply to provide power to the radio, not to produce sound! As a better perturbation-free alternative, Danuser introduced a concept used in econometrics known as Granger causality.

Advances in biology

All of these new developments culminated in impressive new insights into biological processes. There were many talks on mitochondria and endoplasmic reticulum dynamics revealed by novel live-cell super-resolution techniques. Suliana Manley gave one of the most intriguing of those talks, on modes of asymmetric and symmetric mitochondrial division.

Co-organiser Jennifer Lippincott-Schwartz presents how RNA moves around the cell and is translated at different locations, PHOTO: Liz Haynes & Stephan Daetwyler

Jennifer Lippincott-Schwartz also gave a stunning presentation on how RNA granules can hitch a ride through an ANXA-11 mediated connection to lysosomes, and how ALS associated mutations in ANXA-11 break this connection. Furthermore, an intriguing new mRNA reading frame sensor (Moon and Sun tags) was presented by Sanne Boersma of the Tanenbaum lab to understand stochasticity of mRNA translation.

To conclude, the field of microscopy has grown so much that some may feel we have solved all the theoretical problems, and only engineering challenges are left – hardware improvements, new materials, new engineering solutions. At the closing dinner of the conference, however, Atsushi Miyawaki from RIKEN beautifully summarised how he felt about the future of microscopy, and of Seeing is Believing. Standing in the banquet hall of the Heidelberg Castle, he told us that castles in Japan remain unfinished. This state of incompletion is not due to any fault of the architects, but a feature of beauty, as it was believed that things that were incomplete had room to grow, and that growth is valuable. No matter how high our achievements are in the field of microscopy and image analysis, there will always be unforeseen avenues of growth. Attending Seeing is Believing has hopefully prepared us to follow those avenues, and to share what we find so we may all grow together.

For a more comprehensive summary of all talks presented at Seeing is Believing, and to get links to preprints, publications, and resources, visit our blog at https://seeingbelievingweb.wordpress.com/

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Best Poster Awards – The Non-Coding Genome

Taking place for the third time,  the EMBO|EMBL Symposium: The Non-Coding Genome (16 – 19 October 2019) brought together 305 RNA experts to discuss the roles of non-coding RNAs in both prokaryotes and eukaryotes, gene regulation and function. 

A total of 189 posters were presented, from which two were singled out as the winners by popular vote.

Characterization of the genomic and splicing features of long non-coding RNAs using bioinformatics approaches

Monah Abou Alezz is a Ph.D student in genetics, molecular and cellular biology at the University of Pavia, Italy. PHOTO: Monah Abou Alezz

Authors: Monah Abou Alezz, Ludovica Celli, Giulia Belotti, Silvia Bione, Institute of Molecular Genetics L. L Cavalli-Sforza – National Research Council, Italy

Recent developments in deep sequencing approaches have simulated the continuous discovery of a significantly large number of novel long non-coding RNA (lncRNA) genes loci in the genomes. Long non-coding RNAs are recognized as a new class of regulatory molecules despite very little is known about their functions in the cellular processes. Due to their overall low expression level and tissue-specificity, the identification and annotation of lncRNA genes still remains challenging. The characterization of lncRNAs’ features is crucial to understand and get functional insights on their mechanisms of action. We exploited recent annotations by the GENCODE compendium to characterize the genomic and splicing features of long non-coding genes, in comparison to protein-coding ones, in the human and mouse genome by using bioinformatics approaches. Our analysis highlighted differences between the two classes of genes in terms of gene architecture regarding exons and introns length, GC-content, and the combinatorial patterns of chromatin marks and states. Moreover, significant differences in the splice sites usage were observed between long non-coding and protein-coding genes. While the frequency of non-canonical GC-AG splice junctions represents about 0.8% of total splice sites in protein-coding genes, we identified a remarkable enrichment of the GC-AG splice sites in long non-coding genes, both in human (3.0%) and mouse (1.9%). In addition, we identified peculiar characteristics of the GC-AG introns in terms of donor and acceptor splice sites strength, poly-pyrimidine tract, intron length, and a positional bias of GC-AG junctions being enriched in the first intron. Genes containing at least one GC-AG intron were found conserved in many species across large evolutionary distances, more prone to alternative splicing and a functional analysis pointed toward their enrichment in specific biological processes such as
DNA repair.

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MirGeneDB 2.0: The metazoan microRNA complement

Bastian Fromm is a Senior Researcher at Science for Life Laboratory, Stockholm University, Sweden. PHOTO: Bastian Fromm

Authors: Bastian Fromm (1), Diana Domanska (2), Eirik Hoye (3), Vladimir Ovchinnikov (4), Wenjing Kang (5), Ernesto Aparicio-Puerta (6), Morten Johansen (7), Kjersti Flatmark (3), Anthony Mathelier (8), Hovig
Eivind (3), Michael Hackenberg (6), Marc Friedländer (5), Kevin Peterson (9)

Non-coding RNAs (ncRNA) have gained substantial attention due to their roles in human disorders and animal development. microRNAs (miRNAs) are unique within this class as they are the only ncRNAs with individual gene sequences conserved across the animal kingdom. Bona fide miRNAs can be clearly distinguished from the myriad small RNAs generated in cells by a set of unique criteria. Unfortunately, recognition and utilization of these clear and mechanistically well understood features is not a  common practice. We addressed this by extensively expanding our curated miRNA gene database MirGeneDB to 45 organisms that represent the breadth of Metazoa. By consistently annotating and naming more than 11,000 miRNA genes in these organisms, we show that previous miRNA annotations contained not only many false positives, but surprisingly many false negatives as well. Indeed, curated miRNA complements of closely related organisms are very similar and can be used to reconstruct evolution of miRNA genes, families and biogenesis across more than 1 billion years of evolution. MirGeneDB represents a robust platform for providing deeper and more significant insights into the biology of miRNAs, possible sources of mis-regulation, and evolutionary mechanisms. MirGeneDB is publicly and freely available under http://mirgenedb.org/.

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Fromm, B. et al. MirGeneDB 2.0: the metazoan microRNA complement. Nucleic Acids Research, gkz885, (2019), https://doi.org/10.1093/nar/gkz885

(1) Science for Life Laboratory, Sweden
(2) Department of Informatics, University of Oslo, Oslo, Norway
(3) Department of Tumor Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
(4) School of Life Sciences, Faculty of Health and Life Sciences, University of Nottingham, United Kingdom
(5) Stockholm University, SciLifeLab, Sweden
(6) Department of Genetics, Faculty of Sciences, University of Granada, Granada, Spain
(7) Institute for Medical Informatics, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
(8) Centre for Molecular Medicine Norway (NCMM), Nordic EMBL Partnership, University of Oslo, Oslo, Norway
(9) Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, United States of America


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Best Poster Awards – Seeing is Believing

For the 5th time, the EMBL Advanced Training Centre played host to 466 researchers and imaging specialists at the EMBO|EMBL Symposium: Seeing is Believing – Imaging the Molecular Processes of Life (9 – 12 October 2019), where cutting-edge applications illustrated how imaging can answer biological questions and capture the dynamics of life. 

Out of the 248 posters presented, 2 stood out from the rest and were awarded a poster prize based on popular vote. Here we present the abstracts and posters of the winners.

CalQTrace: Simultaneous Calculation and Quantification of 100,000 immune activation Traces at single-cell resolution using CNN

Liliana Barbieri is a doctoral student at the Biomedical Imaging Doctoral Training Centre, University of Oxford, UK. PHOTO: Liliana Barbieri

Authors: Liliana Barbieri (1), Kseniya Korobchevskaya (2), Azeem Ahmad (3), Huw Colin-York (1), Aurelien Barbotin (4), Glykeria Karanika (1), Loic Peters (5), Isabela Pedroza-Pacheco (4), Angela Lee (1), Lena Cords (1), Anish Priyadarshi (3), Dominic Waithe (6), Jana Kohler (6), Christoffer Lagerholm (6), Balpreet Singh Ahluwalia (3), Marco Fritzsche (2)

Quantification of immune cell activation is essential to the understanding of their effector function. Tracing activation signatures like cellular calcium release and the expression of surface markers in response to activation signals allows the classification of the course of immune cell activation from early triggering events to late differentiation. However, robust quantitative platforms for such measurements represent a major challenge, restricting the analysis to small single-cell population or more recently to cell ensembles with high-dimensional parameter analysis tools. Here, we introduce a combination of a convolutional neural network-based CalQTrace (Calculation and Quantification of Trace) software, together with a Graphical User Interface, and an optical high-throughput light-sheet platform, allowing the simultaneous fully automated quantitation of immune cell activation traces of >100,000 live immune cells. CalQTrace enables user-independent statistically robust classification and quantification of multiple fluorescent activation markers including calcium, CD25+/- expression, and cell viability tracking single cells in space and time within a 5 mm x 5 mm large-field-of-view, opening-up unprecedented insights into physiological activation tracing in living immune cells.

(1) MRC Human Immunology Unit, University of Oxford, United Kingdom
(2) Kennedy Institute for Rheumatology, University of Oxford, United Kingdom
(3) The Arctic University of Norway, Norway
(4) University of Oxford, United Kingdom
(5) University College London, United Kingdom
(6) Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom

Poster currently not available


Bleaching-insensitive STED microscopy with exchangeable fluorescent probes

Mike Heilemann is a Principal Investigator at Johann Wolfgang Goethe-University, Frankfurt, Germany. PHOTO: Mike Heilemann

Authors: Christoph Spahn (1), Florian Hurter (1), Mathilda Glaesmann (1), Jonathan Grimm (2), Luke Lavis (2), Hans-Dieter Barth (1), Marko Lampe (3), Mike Heilemann (1)

Photobleaching affects image quality and resolution in fluorescence microscopy, and thus limits the extractable information. This is in particular relevant for super-resolution microscopy where typically high laser intensities are used. In order to minimize photobleaching, we repurposed the use of exchangeable fluorescent probes, as used in single-molecule localisation microscopy methods such as Point Accumulation for Imaging in Nanoscale Tomography (PAINT) [1], for STED microscopy. We demonstrate pseudo-permanent labeling of target structures and constant exchange of photobleached fluorophores. This concept allows for whole-cell, 3D, multi-color and live-cell STED microscopy [2]. Using transiently binding hydrophobic dyes and fluorophore-labeled major minor groove binders [3, 4], we visualised the nanostructure of chromatin, cell membranes and organelles in bacterial and mammalian cells in 3D. To expand the range of targets, we employed oligonucleotide-labeled antibodies that transiently bind fluorophore-labeled oligonucleotides, as used in single-molecule super-resolution imaging with DNA-PAINT [5], and demonstrate multi-color STED imaging.

References:
[1] Sharanov and Hochstrasser, PNAS 103 (50), 18911-18916 (2006)
[2] Spahn et al., Nano Letters 19 (1), 500-505 (2019)
[3] Lukinavičius et al., Nature Communications 6, 8497 (2015)
[4] Spahn et al., Scientific Reports 8, 14768 (2018)
[5] Schnitzbauer et al., Nature Protocols 12(6), 1198-1228 (2017)

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(1) Johann Wolfgang Goethe-University Frankfurt, Germany
(2) HHMI – Janelia Research Campus, United States of America
(3) EMBL Heidelberg, Germany


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