Best Poster Awards – In Situ Structural Biology Workshop

The EMBO Workshop: In Situ Structural Biology: From Cryo-EM to Integrative Modelling was our final virtual conference of 2020, but there was no trace of Zoom fatigue amongst the 466 participants who joined us from 6 – 8 December!

80 international researchers presented their posters during the two posters sessions on the following topics:

  • Biophysical analysis in cells
  • COVID-19
  • Imaging across scales
  • Integrative modelling
  • Molecular sociology
  • Structural analysis in situ
  • Structural biology

Each of the participants had the chance to vote for their favourite poster, resulting in two posters winning the Best Poster Award kindly sponsored by EMBO Press.  Here are the winners:

New insights on the catalytic mechanism of arsenite oxidase

PHOTO: Filipa Engrola

Authors: Filipa Engrola, Márcia Correia, Teresa Santos-Silva, Maria Romao, (UCIBIO@FCT-NOVA, Portugal)

Arsenic (As) and antimony (Sb) are two metalloids that, due to anthropogenic and natural causes, pose an environmental  threat, considered as priority pollutants by the World Health Organisation and the United States Environmental Protection Agency. Although the safety guards recommend a maximum of 10 μg/L of As and Sb in drinking water, these values are exceeded in many regions worldwide, with no remediation approach that is simultaneously effective, clean and economically sustainable [1,2]. The ancient bioenergetic enzyme arsenite oxidase (Aio), from microorganisms Rhizobium sp. NT-26 (NT-26 Aio) and Alcaligenes faecalis (A.f. Aio), is currently being studied for its use as a biosensor and in bioremediation processes. Both Aio enzymes contain a large subunit (AioA) that harbours a molybdenum centre and a [3Fe-4S] cluster, and a small subunit (AioB) that possess a Rieske [2Fe-2S] cluster and have demonstrated to oxidise AsIII, as well as SbIII, into the easier to remove and less toxic forms of AsV and SbV, respectively [3,4]. Aiming to elucidate the catalysis mechanism of the enzymes, a combination of expression and purification of the proteins, crystallisation, structural analysis, enzyme kinetics and affinity tests were conducted. X-ray structures of the ligand-free form of the enzyme had been previously determined (PDB: 4AAY, 5NQD and 1G8K [3,5,6]). In our work, Aio crystals in complex with two different forms of the substrate analogue – Sb oxyanions, with a reaction kinetic 6500 times slower than AsIII [6] – diffracted up to ca 1.8 Å resolution. The structures show the reaction intermediates bound at the active site, with a μ-oxo bridge binding Sb to the Mo atom. Analysis of bond lengths and geometry of the ligands at the Mo active site allowed us to revisit the catalytic mechanism of As oxidation [7], contributing to the understanding and future biotechnological application of this family of enzymes in water treatment.

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Allosteric hotspot in the main protease of SARS-CoV-2

PHOTO: Léonie Ströhmich

Authors: Léonie Strömich, Sophia N Yaliraki, (Imperial College London, UK)

Since the beginning of 2020 we have seen the coronavirus SARS-CoV-2 causing a global pandemic with almost 34 million cases and over 1 million deaths worldwide [as of 01.10.2020] [1.] As a result, we have seen a surge in research efforts to develop effective treatments for the underlying disease, COVID-19. One approach is to target the main protease (Mpro) of SARS-CoV-2 as it is essential for virus replication in an early step of the viral life cycle [2.] Most efforts are centred on inhibiting the orthosteric binding site of the enzyme. However, considering allosteric sites on the protein allows for more selective drug design and widens the chemical search space. Here, we report an allosteric hotspot in the SARS-CoV-2 Mpro dimer by using novel atomistic graph theoretical methods: Markov transient analyses follow the propagation of a random walker on a graph and have been shown to successfully identify allosteric communication in catalytic proteins [3.] We further score the so identified allosteric hotspots against random sites in similar distances and thus identify a statistically significant putative allosteric site in the SARS-CoV-2 Mpro. We then simulate a binding event at this hotspot region using data from a recent XChem fragment screen by the Diamond Light Source [4.] which provides a starting point for rational drug design. This study uses highly efficient network theoretical models to shed light on allosteric communication and uncovers putative allosteric sites in the SARS-CoV-2 main protease. This provides a valuable contribution to the ongoing efforts to find a cure against COVID-19 by broadening the horizon for drug discovery efforts.

Image: Léonie Ströhmich

References:
[1.] Official World Health Organization COVID-19
dashboard: https://covid19.who.int (Accessed: 01.10.2020).
[2.] Hilgenfeld, R. (2014). FEBS Journal, 281(18), 4085-4096.
[3.] Amor, B., Yaliraki, S. N., Woscholski, R., & Barahona, M. (2014) Molecular BioSystems, 10(8), 2247-2258.
[4.] Douangamath, A., Fearon, D., Gehrtz, P., Krojer, T., Lukacik, P., Owen, C. D., … Walsh, M. A. (2020) Nature Communications, 11, 5047.

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Best Poster Awards – EMBO|EMBL Symposium: Organoids 2020

The recent virtual EMBO|EMBL Symposium on Organ Development and Disease in 3D Culture saw the highest number of registrations we have had since we launched the format. A total of 880 researchers from around the world got together online to discuss recent developments in the formation and maintenance of organoids and their use in disease studies and regenerative medicine.

Out of the 200 digital posters that were presented at the three poster sessions, four were distinguished with a poster prize by a committee appointed by the scientific organisers. Here are the winners:

Organoids model transcriptional hallmarks of oncogenic KRAS activation in lung epithelial progenitor cells

PHOTO: Antonella Dost

Authors: Aaron Moye (1), Antonella Dost (1), Marall Vedaie (2), Linh Tran (5), Eileen Fung (5), Dar Heinze (2), Carlos Villacorta-Martin (2), Jessie Huang (2), Ryan Hekman (2), Julian Kwan Kwan (2), Benjamin Blum (2), Sharon Louie (1), Sam Rowbotham (1), Julio Sainz de Aja (1), Mary Piper (4), Preetida Bhetariya (4), Roderick Bronson (3), Andrew Emili (2), Gustavo Mostoslavsky (2), Gregory Fishbein (5), William Wallace (5), Kostyantyn Krysan (5), Steven Dubinett (5), Jane Yanagawa (5), Darrell Kotton (2), Carla Kim (1)

Presenter: Antonella Dost (1)

Mutant KRAS is the most common oncogenic driver of epithelial cancers. Nevertheless, the molecular changes induced by KRAS activation in primary epithelial cells beyond activation of proliferation remain elusive. Here, we determined transcriptional changes at single-cell resolution after KRAS activation in distal lung epithelial cell populations. We developed a new in vitro organoid system to define the early oncogenic KRAS transcriptional program and model early-stage lung adenocarcinoma (LUAD) using primary murine lung cells. Alveolar epithelial progenitor (AT2) cells expressing oncogenic KRAS lost their mature identity and acquired a transcriptional program similar to lung development and progenitor cells. Similar changes were observed in an early-stage LUAD mouse model, in human induced pluripotent stem cell derived AT2 cells, and in stage I lung cancer patient samples, validating our organoid model. While these events have been observed in advanced lung cancers in mice and humans, we show that KRAS induced dedifferentiation occurs in early-stage lung cancer. This work provides a new organoid tool to rapidly recapitulate lung cancer progression in vitro and a window into the transcriptional changes that immediately follow oncogenic KRAS expression in epithelial cells, revealing candidate targets for early intervention of KRAS-driven lung cancer.

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(1) Boston Children’s Hospital, United States of America
(2) Boston University, United States of America
(3) Harvard Medical School, United States of America
(4) Harvard T. C. Chan School of Public Health, United States of America
(5) University of California Los Angeles, United States of America


Using human pluripotent stem cell-derived organoids to investigate regional-specific features of the small intestine

PHOTO: Guillermo Sanchez

Authors: J Guillermo Sanchez, Heather McCauley, Jacob Enriquez, James Wells, Cincinnati Children’s Hospital, United States of America

Presenter: J Guillermo Sanchez

The gastrointestinal tract is the largest endocrine organ in the body. Specialised nutrient sensing cells, called enteroendocrine cells, are embedded in the intestinal epithelium and secrete over 20 hormones that regulate processes such as satiety, gut motility and gastric emptying. Directed differentiation of human pluripotent stem cells into human intestinal organoids has been used to study and mimic intestinal development; however, most of these models generate intestinal tissue which resembles duodenum and proximal jejunum (Spence, et al 2011). The intestine displays distinct regional functions along the proximal-distal axis, with the ileum being important for unique enteroendocrine hormone secretion, bile acid resorption and interactions with the microbiome. It is known that major signaling pathways such as Wnt, FGF and BMP can affect the regional identity of the developing GI tract. Consistent with previous studies (Munera, Tsai) we found that manipulation of the exposure time of intestinal spheroids to these signaling pathways generated distal intestinal tissue by expression of epithelial markers, nutrient transporters, and hormone expression. These distally-patterned human intestinal organoids retain their regional identity after transplantation in vivo, and can be used to generate epithelial-only enteroid cultures. It remains unknown how diverse cellular types and functions are established along the proximal-distal axis of the small intestine. This model enables us to compare the early transcriptional changes involved in conferring regional-specific features, including enteroendocrine cell allocation, to the GI tract.

Poster currently not available


Recapitulating the somitogenesis in vitro to identify novel causative genes for congenital bone diseases

PHOTO: Marina Matsumiya

Authors: Marina Matsumiya (1), Mitsuhiro Matsuda (1), Nao Otomo (2), Yoshiro Yonezawa (2), Shiro Ikegawa (2), Miki Ebisuya (1)

Presenter: Marina Matsumiya

Somites are periodically formed though the segmentation of anterior parts of presomitic mesoderm (PSM) in embryos. This periodicity is controlled by the segmentation clock gene Hes7, which exhibits a wave-like oscillatory expression in the PSM. The periodical somite formation is a crucial event for body segment formation and abnormal somitogenesis leads to congenital bone diseases.

Spondylocostal dysostosis (SCD) is a bone malformation disease which is characterised by morphological abnormalities of vertebrae and ribs. Mutations in several somitogenesis-related genes, including HES7, are already known as the cause of SCD. As for 75% of SCD patients, however, the causative gene and at what stage of bone development the abnormality occurs are still unclear.

Thus, the aim of this study is to establish a method to recapitulate the somitogenesis in vitro and to identify novel a causative gene of SCD.

To recapitulate the somitogenesis in vitro, we previously reported a simple and efficient method to generate mouse embryonic stem (ES) cell-derived PSM-like tissues (Matsumiya et al., Development, 2018). In these tissues, Hes7 oscillation was synchronized among neighboring cells, the anterior-posterior axis was self-organised, and somite-like structures were observed. We are currently developing a similar method to recapitulate the human somitogenesis by using human induced pluripotent stem (iPS) cells instead mouse ES cells. Furthermore, by using human iPS cell lines that lack the candidate gene of SCD for the in vitro somitogenesis, we are trying to identify a novel causative gene of SCD.

Poster currently not available

(1) EMBL Barcelona, Spain
(2) RIKEN Center for Integrative Medical Sciences, Japan


Heme oxygenase 1 upregulation is induced by stress via alpha-synuclein aggregation in transgenic mice and in Parkinson’s disease derived brain organoids

PHOTO: Silke Frahm-Barske

Authors: Silke Frahm-Barske (2), Sebastian Diecke (2), Franz Theuring (1)

Presenter: Silke Frahm-Barske

Excessive accumulation of alpha-synuclein (a-syn) predisposes to the development of Parkinson’s disease (PD), a disorder characterised by neurodegeneration in the substantia nigra and concomitant motor impairments. It was previously shown that stress-induced release of glucocorticoids accelerates the progression of PD and that the glucocorticoid receptor (GR) is downregulated in several neurodegenerative as well as in stress-related diseases. The impact of altered a-syn protein levels on GR dysfunction and stress-related protein expression is largely unexplored, but may have severe implications for PD manifestation and disease progression. Therefore, we examined the effect of chronic stress in two models overexpressing human a-syn: a transgenic mouse model (h-a-synL62) and brain organoids derived from iPSCs of a PD patient. Wildtype mice that underwent daily restraint for 6 weeks presented typical chronic stress induced features, such as GR-deficiency and increased a-syn protein levels in prefrontal cortex and hippocampus. Importantly, these molecular alterations were reproduced in forebrain organoids generated from healthy donors after treatment with the synthetic glucocorticoid Dexamethasone for 2 weeks. In contrast, glucocorticoid exposure had no effect on GR expression and normalised the level of a-syn in h-a-synL62 mice and PD brain organoids. Accordingly, heme oxygenase 1 (HO-1), an antioxidant protein that can be induced by soluble oligomers and protofibrils and that triggers proteosomal degradation of a-syn, was upregulated. Together, our work provides a new link between a-syn overexpression, GR-deficiency and oxidative stress and their contribution to the development and progression of PD. Further, we established and validated a human 3D tissue culture model that can be used to study stress related diseases, offering replacement of research animals exposed to disturbing procedures.

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(1) Charité – University Medicine Berlin, Germany
(2) Max-Delbrück-Center, Germany


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Expanding the Druggable Proteome with Chemical Biology – Best Poster Awards

The 2020 conference season at the EMBL Advanced Training Centre kicked off with the EMBL Conference: Expanding the Druggable Proteome with Chemical Biology (5 – 7 February 2020). Meet the three poster prize winners from the conference – Patrick Zanon, Enric Ros and Rens de Vries.

Identification of novel antibiotic targets using covalent inhibitors and residue-specific proteomics

PHOTO: Patrick Zanon

Authors: Patrick Zanon (1), Stephan Hacker (1)

Bacterial resistance towards all marketed antibiotics poses an imminent threat to global health. In order to overcome this antibiotic crisis, drugs with novel mechanisms-of-action are desperately needed. Covalent inhibitors are especially promising in this regard as they are already prevalent as antibiotics (e.g. β-lactams and fosfomycin), allow targeting protein pockets that are hard to address with non-covalent interactions alone and hold the promise to overcome some mechanisms of resistance development.[1] Furthermore, covalent inhibitors are uniquely suited to identify new binding pockets on proteins using residue-specific proteomics and in this way to broaden the scope of targetable protein targets.
The vast majority of covalent inhibitors so far either hijack the enzymatic activity of the protein by modification of catalytic serines and tyrosines or address cysteines through their inherent outstanding nucleophilicity. Nevertheless, the number of potentially addressable proteins in the bacterial proteome is significantly limited by the requirement for these amino acids to be present in target proteins. By developing electrophilic groups that are selective for other amino acids (e.g. lysine), we strive to expand the number of exploitable interaction sites for covalent inhibitors in the bacterial proteome. Furthermore, to assess the reactivity and selectivity of covalent inhibitors and to streamline the discovery of novel antibiotic targets, we develop new methods for residue-specific activity-based protein profiling.[2,3] In this way, we are convinced, that we will be able to make important contributions to overcome the antibiotic crisis.

References:
[1] R. A. Bauer, Drug Discov. Today 2015, 20, 1061–1073.
[2] K. M. Backus et al., Nature 2016, 534, 570.
[3] P. R. A. Zanon, L. Lewald, S. M. Hacker Angew. Chem. Int. Ed., doi: 10.1002/anie.201912075.

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(1) Technical University of Munich, Germany


Incorporating 1,2,4,5-tetrazines into proteins: A method for targeted drug release

PHOTO: Enric Ros

Authors: Enric Ros (1), Antoni Riera (1), Lluís Ribas de Pouplana (1)

Bioorthogonal reactions, namely reactions that can take place under biocompatible conditions, are having a major impact in the development of new research tools and novel therapeutic strategies. In the latter case, the discovery of the reaction commonly referred to as “click-to-release” (CtR), which triggers the liberation of a given cargo (normally a drug or a fluorophore), has led to several applications in drug delivery. This reaction happens between a 1,2,4,5-Tetrazine (Tz) fragment and certain alkenes or alkynes and, in order to achieve drug delivery specifically at the site of action, one of the two reactant counterparts should be conjugated to a biomolecule acting as a carrier, ideally a protein.
We have synthetized the previously unreported 3-bromo-1,2,4,5-tetrazine and used its excellent reactivity to attain chemoselective protein labelling onto lysines. Due to the chemical features of the formed amino-Tz. The resulting labelled lysines can undergo fast CtR reactions with trans-cyclooctenes, thereby releasing a desired cargo under physiological conditions. To showcase the applicability of this approach, we have labelled the monoclonal antibody Trastuzumab (anti-Her2) and demonstrated the specific release of the cytotoxic drug doxorubicin upon reaction in a mammalian cell culture context, resulting in a decrease in cell viability.
Additionally, we have also used 3-bromo-1,2,4,5-tetrazine to synthetize an amino-Tz containing non-natural amino acid and used it to achieve protein labelling through its genetic incorporation by amber codon suppression in Escherichia coli. The resulting site-selectively labelled proteins can also trigger fast, high yielding CtR reactions.
To summarize, we have successfully applied a new compound, 3-bromo-1,2,4,5-tetrazine, as a reagent to achieve either chemoselective or site selective protein labelling. We have applied the bioconjugated proteins to demonstrate their potential use for targeted drug delivery in a relevant cellular model, opening new therapeutically useful methodologies.

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(1) IRB Barcelona, Spain


Modulation of nuclear receptors through ligand architecture

PHOTO: Rens de Vries

Authors: Rens de Vries (1), Femke Meijer (1), Luc Brunsveld (1)

Nuclear receptors (NRs) have been one of the primary drug targets over the last decades for their ability to regulate gene expression. The traditional approach of modulating NRs is to design small synthetic molecules that interact with the ligand-binding domain (LBD) of the NR. Ligands can thereby either enhance or inhibit gene transcription. Apart from the effects on transcription, recent research shows that minor changes in the ligand scaffold can have a significant impact on the behavior of the NR. In this research, we show how small-molecules can change both the dimerization behavior of NRs and the recruitment of allosteric modulators.
The Retinoic X Receptor α (RXRα) is known as a master regulator among NRs through its ability to heterodimerize with, and thereby modulate, other NRs. We show, using a novel NanoBIT complexation assay, that small directed changes in the RXR ligand scaffold can lead to selective formation of specific hetero- and homodimers. Using our structural data and focused compound library, a model was developed to help to understand this effect of the ligand. This information can serve as a blueprint to design small-molecules that selectively target specific NRs via RXR. This makes RXR as an exciting and versatile target for NR modulation, especially when classical modulation of the partner NR is not possible.
Recently, small-molecules have been found to bind to allosteric sites of NRs. Allosteric ligands are of interest since they do not compete with the endogenous ligand of the NR and often shown an increased selectivity towards their target. We show, using X-ray crystallography and biochemical assays, that there is communication between orthosteric and allosteric ligands in the RAR-related orphan receptor γ t (RORγt). We successfully solved eleven new ternary crystal structures of RORγt in the presence of both orthosteric and allosteric ligands. These structures mechanistically show how binding of the orthosteric ligand leads to positive cooperative binding of the allosteric ligand.

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(1) Eindhoven University of Technology, The Netherlands


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Best Poster Awards – Target Validation Using Genomics and Informatics

Meet Giovanni Spirito and Borja Gomez Ramos – the two poster prize winners at the recent EMBL – Wellcome Genome Campus Conference: Target Validation Using Genomics and Informatics (8 – 10 Dec 2019).

Identification and prioritization of candidate causal genomic variations from individuals affected by ASD

PHOTO: Giovanni Spirito

Authors: Giovanni Spirito (1), Diego Vozzi (2), Martina Servetti (3), Margherita Lerone (3), Maria Teresa Divizia (3), Giulia Rosti (3), Livia Pisciotta (4), Lino Nobili (4), Irene Serio (4), Stefano Gustincich (2), Remo Sanges (1)

Next generation sequencing (NGS) technologies enabled the extensive study of the genomics underlying human diseases. Namely whole exome sequencing (WES) represents a cost-efficient method which can lead to the detection of multiple classes of genomic variants and the discovery of novel disease-associated genes. One of the drawbacks of this approach however, is the large number of genomic variants detected in each analysis. Automated variant prioritization strategies are therefore required. This is particularly important in the case of complex disease such as ASD, whose genetic etiology is still poorly understood. To this aim we built a custom computational framework capable, from raw WES data, to automatically detect four classes of genomic variants (SNPs, indels, copy number variants and short tandem repeat variants) and prioritize them in regards to their relevance to a specific phenotype. We tested this framework on a selection of 29 trios including probands affected by severe and undiagnosed rare phenotypes and a small cohort of 10 trios all featuring healthy parents and one offspring affected by autism spectrum disorder (ASD). We were able to successfully detect rare and de novo high penetrance variants which have been validated and confirmed as causative among the undiagnosed probands. In the specific case of the ASD cohort we could highlight several genes which are not implicated in autism susceptibility, but nevertheless whose connections to genes relevant for ASD could suggest a possible involvement in the phenotype. Furthermore, our approach enabled us to detect several instances characterized by the presence of multiple candidate variants within genes belonging to the same canonical pathway in one proband. Our workflow allows to detect and prioritize multiple classes of genomic variants in order to both highlight rare high penetrance disease-causative mutation, and possibly reconstruct the genomics at the basis of complex ASD phenotypes.

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(1) SISSA, Italy, (2) IIT, Italy, (3) Gaslini Institute, Italy, (4) University of Genova, Italy


Omics data integration for the identification of cell-type-specific gene regulatory networks and regulatory variants in Parkinson’s disease

PHOTO: Borja Gomez Ramos

Authors: Borja Gomez Ramos (1,2), Jochen Ohnmacht (1,2), Nikola de Lange (2), Aurélien Ginolhac (1), Aleksandar Rakovic (5), Christine Klein (5), Roland Krause (2) , Marcel H. Schulz (6), Thomas Sauter (1), Rejko Krüger (2,3,4) and Lasse Sinkkonen (1)

Genome-Wide Association Studies (GWAS) have identified many variants associated with different diseases. However, it is still a challenge to make sense of this data as the majority of genetic variants are located in non-coding regions, complicating the understanding of their functionality. In the last few years, it has been found that non-coding genetic variants concentrate in regulatory regions in the genome, which are cell type and cell-stage specific. In this project, we seek to identify functional Parkinson’s disease GWAS non-coding genetic variants that could make carriers more prone to developing PD. To do so, we are using induced pluripotent stem cell (iPSC) technology to differentiate somatic cells into midbrain dopaminergic (mDA) neurons, astrocytes and microglia. Assessing their chromatin accessibility, active chromatin regions and transcriptome, we can identify crucial regulatory regions in the genome, key transcription factors and derive the gene regulatory networks for the three different cell types. Then, we will map the non-coding genetic variants to the different regulatory regions and predict their effect in silico for the subsequent validation in vitro. This innovative approach will also identify novel factors controlling cell fate and cell identity.

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(1) Life Sciences Research Unit, University of Luxembourg, Luxembourg, (2) Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, Luxembourg, (3) Centre Hospitalier de Luxembourg (CHL), Luxembourg, (4) Luxembourg Institute of Health (LIH), Luxembourg, (5) Institute of Neurogenetics, University of Lübeck, Germany, (6) Institute for Cardiovascular Regeneration, Uniklinikum and Goethe University Frankfurt, Germany


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Best Poster Awards – Metabolism Meets Epigenetics

In its first edition, the EMBO|EMBL Symposium: Metabolism Meets Epigenetics brought together 289 world-leading researchers who examined how metabolites and metabolic networks impact gene regulation, what their roles are in disease and how this opens novel therapeutic avenues.

In addition to the 21 invited speakers and 22 selected short talks, 142 posters were presented during the two poster sessions. Today we present three of the five award-winning posters decided by popular vote.

Citrate carrier links intermediate metabolism to histone acetylation upon ageing of mouse mesenchymal stem cells (MSCs)

PHOTO: Andromachi Pouikli

Authors: Andromachi Pouikli (1), Monika Maleszewska (2), Swati Parekh (1), Chrysa Nikopoulou (1), Maarouf Baghdadi (1), Linda Partridge (1), Peter Tessarz (1)

Chromatin and metabolism interact in a reciprocal manner; on one hand metabolism-related genes are subjected to epigenetic modifications, which regulate gene expression. On the other hand, intracellular metabolism provides metabolites which can serve as essential co-factors and substrates for chromatin-modifying enzymes, affecting their activity. Although, it is well established that the process of ageing is accompanied by changes in metabolism and by chromatin alterations, their interplay in this context remains still poorly understood. In this study we sought to determine how ageing impinges on the relationship between cellular metabolism and the epigenome, using mouse mesenchymal stem cells from the bone marrow (BM-MSCs). In brief, our data suggest that there is a strong and direct link between the metabolic and the epigenetic states of the cell, with ageing-driven changes in metabolism regulating gene transcription and BM-MSC’s stemness, via alterations of the chromatin structure. We conclude that physiological ageing elicits changes in metabolism, resulting in suppressed glycolysis and impaired lipid biogenesis. Moreover, we demonstrate that during ageing there are lower levels of histone acetylation, despite the higher acetyl-CoA levels. We provide a solid explanation for this apparent discrepancy, pointing to the impaired export of acetyl-CoA from mitochondria to the cytosol. Indeed, the protein levels of the citrate carrier Slc25a1 decrease dramatically upon ageing. Using inhibition and supplementation experiments we provide a causal relationship between Slc25a1 function and the levels of histone acetylation, which directly influence chromatin accessibility and plasticity. Collectively, our data establish a tight, age-dependent connection between metabolism, epigenome and stemness and identify citrate carrier as the responsible protein for the mitochondrial-nuclear communication.

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(1) Max Planck Institute for Biology of Ageing, Germany, (2) Personalis Inc, Germany


Epigenetics meets metabolism through histone acetyltransferase NAA40

PHOTO: Christina Demetriadou

Authors: Christina Demetriadou (1), Anastasia Raoukka (1), Agathi Elpidoforou  (1), Constantine Mylonas (2), Swati Parekh (2), Peter Tessarz (2), Antonis Kirmizis (1)

N-alpha-acetyltransferase 40 (NAA40) is distinct among other histone acetyltransferases (HATs) because it deposits an acetyl moiety on the alpha-amino group at the very N-terminal tip of histones H4 and H2A, instead on the lysine side chain. The biological function of this evolutionarily conserved enzyme remained unexplored for several decades because it was thought to mediate an inert modification. However, we previously showed that NAA40-mediated N-terminal acetylation of histone H4 (N-acH4) crosstalks with an adjacent arginine methylation mark to regulate yeast cellular aging in response to caloric restriction through transcriptional control of several metabolic genes. Therefore, we are currently interested in deciphering the function of human NAA40 in carcinogenesis. We recently showed that NAA40 is frequently upregulated in primary human colorectal cancer (CRC) samples. Remarkably, depletion of NAA40 and its accompanied reduction in N-acH4 blocked colon cancer cell proliferation and reduced cell survival in vitro and in xenograft models. We also found that loss of NAA40 expression or of its HAT activity markedly induce global histone methylation. Additionally, whole transcriptome analysis showed that NAA40 knockdown leads to upregulation of key enzymes involved in one-carbon metabolism. Intriguingly, silencing of methylenetetrahydrofolate reductase (MTHFR), which links the folate to methionine cycle, rescues the induction of global histone methylation and loss of cell viability triggered by NAA40 depletion. Hence, this recent work implies that NAA40 may transcriptionally regulate vital metabolic enzymes to control the flux of carbon units into the methionine cycle influencing S-adenosylmethionine (SAM) levels and triggering epigenome reprogramming of cancer cells. Overall, our findings thus far propose that NAA40 and its associated N-acH4 are crucial epigenetic modulators in tumourigenesis and implicate these factors in rewiring cancer cell metabolism.

Poster currently not available.

(1) University of Cyprus, Cyprus
(2) Max Planck Institute for Biology of Ageing, Germany


Role of MOF acetyl transferase in mitochondrial homeostasis

PHOTO: Sukanya Guhathakurta

Authors: Sukanya Guhathakurta (1), Christoph Martensson (2), Alexander Schendzielorz (3), Bettina Warsheid (3), Thomas Becker (2), Asifa Akhtar (1)

Mitochondria lies at the centre of cellular and organismal energy homeostasis, housing a large repertoire of enzymes that are required for the synergy of various metabolic pathways. Mitochondrial gene expression and protein acetylation are two important fundamental processes situated at the crossroad between mitochondrial function and metabolic status of a cell. Gene transcription in the mitochondria has been studied over several decades, but enzymatic acetylation of mitochondria proteins has stayed so far enigmatic. MOF acetyl transferase and its KANSL complex members dually localize to the nucleus and the mitochondria in mouse and human cells. The MOF-KANSL complex regulates metabolic gene transcription in the nucleus and expression of Electron Transport Chain (mtETC) components from the mtDNA, in a cell type dependent fashion. Regulation of nuclear gene transcription by MOF is well understood, however, its control of mitochondrial function remains elusive. Here, we report that loss of MOF leads to severe mitochondrial dysfunction in Mouse Embryonic Fibroblasts (MEFs), sprouting from a stalled oxidative phosphorylation. We address the mechanisms by which the enzyme maintains mitochondrial function in these cells by using a multi-omics approach. We discovered that the role of MOF-KANSL complex in the mitochondria of aerobically respiring cells could be decoupled from its regulation of steady state RNA levels, and could further be attributed to the acetylation of mitochondrial proteins. We characterize the role of acetylation on these proteins through generation of acetylated and non-acetylated mimics. Collectively our data, along with previously published works, suggests that MOF has emerged as a moderator to strike a harmony in the context of communication between the nucleus and the mitochondria. Recent progress on the project will be discussed.

(1) Max Planck Institute for Immunobiology and Epigenetics, Germany
(2) Institute of Biochemistry and Molecular Biology, Germany
(3) Institute for Biology II, Germany

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