Project acronym AAA
Project Adaptive Actin Architectures
Researcher (PI) Laurent Blanchoin
Host Institution (HI) CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS
Call Details Advanced Grant (AdG), LS3, ERC-2016-ADG
Summary Although we have extensive knowledge of many important processes in cell biology, including information on many of the molecules involved and the physical interactions among them, we still do not understand most of the dynamical features that are the essence of living systems. This is particularly true for the actin cytoskeleton, a major component of the internal architecture of eukaryotic cells. In living cells, actin networks constantly assemble and disassemble filaments while maintaining an apparent stable structure, suggesting a perfect balance between the two processes. Such behaviors are called “dynamic steady states”. They confer upon actin networks a high degree of plasticity allowing them to adapt in response to external changes and enable cells to adjust to their environments. Despite their fundamental importance in the regulation of cell physiology, the basic mechanisms that control the coordinated dynamics of co-existing actin networks are poorly understood. In the AAA project, first, we will characterize the parameters that allow the coupling among co-existing actin networks at steady state. In vitro reconstituted systems will be used to control the actin nucleation patterns, the closed volume of the reaction chamber and the physical interaction of the networks. We hope to unravel the mechanism allowing the global coherence of a dynamic actin cytoskeleton. Second, we will use our unique capacity to perform dynamic micropatterning, to add or remove actin nucleation sites in real time, in order to investigate the ability of dynamic networks to adapt to changes and the role of coupled network dynamics in this emergent property. In this part, in vitro experiments will be complemented by the analysis of actin network remodeling in living cells. In the end, our project will provide a comprehensive understanding of how the adaptive response of the cytoskeleton derives from the complex interplay between its biochemical, structural and mechanical properties.
Summary
Although we have extensive knowledge of many important processes in cell biology, including information on many of the molecules involved and the physical interactions among them, we still do not understand most of the dynamical features that are the essence of living systems. This is particularly true for the actin cytoskeleton, a major component of the internal architecture of eukaryotic cells. In living cells, actin networks constantly assemble and disassemble filaments while maintaining an apparent stable structure, suggesting a perfect balance between the two processes. Such behaviors are called “dynamic steady states”. They confer upon actin networks a high degree of plasticity allowing them to adapt in response to external changes and enable cells to adjust to their environments. Despite their fundamental importance in the regulation of cell physiology, the basic mechanisms that control the coordinated dynamics of co-existing actin networks are poorly understood. In the AAA project, first, we will characterize the parameters that allow the coupling among co-existing actin networks at steady state. In vitro reconstituted systems will be used to control the actin nucleation patterns, the closed volume of the reaction chamber and the physical interaction of the networks. We hope to unravel the mechanism allowing the global coherence of a dynamic actin cytoskeleton. Second, we will use our unique capacity to perform dynamic micropatterning, to add or remove actin nucleation sites in real time, in order to investigate the ability of dynamic networks to adapt to changes and the role of coupled network dynamics in this emergent property. In this part, in vitro experiments will be complemented by the analysis of actin network remodeling in living cells. In the end, our project will provide a comprehensive understanding of how the adaptive response of the cytoskeleton derives from the complex interplay between its biochemical, structural and mechanical properties.
Max ERC Funding
2 349 898 €
Duration
Start date: 2017-09-01, End date: 2022-08-31
Project acronym C18Signaling
Project Regulation of Cellular Growth and Metabolism by C18:0
Researcher (PI) Aurelio TELEMAN
Host Institution (HI) DEUTSCHES KREBSFORSCHUNGSZENTRUM HEIDELBERG
Call Details Consolidator Grant (CoG), LS3, ERC-2016-COG
Summary My lab studies how cells regulate their growth and metabolism during normal development and in disease. Recent work in my lab, published last year in Nature, identified the metabolite stearic acid (C18:0) as a novel regulator of mitochondrial function. We showed that dietary C18:0 acts via a novel signaling route whereby it covalently modifies the cell-surface Transferrin Receptor (TfR1) to regulate mitochondrial morphology. We found that modification of TfR1 by C18:0 ('stearoylation') is analogous to protein palmitoylation by C16:0 - it is a covalent thio-ester link and requires a transferase enzyme. This work made two conceptual contributions. 1) It uncovered a novel signaling route regulating mitochondrial function. 2) Relevant to this grant application, we found by mass spectrometry multiple other proteins that are stearoylated in mammalian cells. This thereby opens a new avenue of research, suggesting that C18:0 signals via several target proteins to regulate cellular growth and metabolism. I propose here to study this C18:0 signaling.
To study C18:0 signaling we will exploit tools recently developed in my lab to 1) identify as complete a set as possible of proteins that are stearoylated in human and Drosophila cells, thereby characterizing the cellular 'stearylome', 2) study how stearoylation affects the molecular function of these target proteins, and thereby cellular growth and metabolism, and 3) study how stearoylation is added, and possibly removed, from target proteins.
This work will change the way we view C18:0 from simply being a metabolite to being an important dietary signaling molecule that links nutritional uptake to cellular physiology. Via unknown mechanisms, dietary C18:0 is clinically known to have special properties for cardiovascular risk. Hence this proposal, discovering how C18:0 signals to regulate cells, will have implications for both normal development and for disease.
Summary
My lab studies how cells regulate their growth and metabolism during normal development and in disease. Recent work in my lab, published last year in Nature, identified the metabolite stearic acid (C18:0) as a novel regulator of mitochondrial function. We showed that dietary C18:0 acts via a novel signaling route whereby it covalently modifies the cell-surface Transferrin Receptor (TfR1) to regulate mitochondrial morphology. We found that modification of TfR1 by C18:0 ('stearoylation') is analogous to protein palmitoylation by C16:0 - it is a covalent thio-ester link and requires a transferase enzyme. This work made two conceptual contributions. 1) It uncovered a novel signaling route regulating mitochondrial function. 2) Relevant to this grant application, we found by mass spectrometry multiple other proteins that are stearoylated in mammalian cells. This thereby opens a new avenue of research, suggesting that C18:0 signals via several target proteins to regulate cellular growth and metabolism. I propose here to study this C18:0 signaling.
To study C18:0 signaling we will exploit tools recently developed in my lab to 1) identify as complete a set as possible of proteins that are stearoylated in human and Drosophila cells, thereby characterizing the cellular 'stearylome', 2) study how stearoylation affects the molecular function of these target proteins, and thereby cellular growth and metabolism, and 3) study how stearoylation is added, and possibly removed, from target proteins.
This work will change the way we view C18:0 from simply being a metabolite to being an important dietary signaling molecule that links nutritional uptake to cellular physiology. Via unknown mechanisms, dietary C18:0 is clinically known to have special properties for cardiovascular risk. Hence this proposal, discovering how C18:0 signals to regulate cells, will have implications for both normal development and for disease.
Max ERC Funding
2 000 000 €
Duration
Start date: 2017-03-01, End date: 2022-02-28
Project acronym CancerFluxome
Project Cancer Cellular Metabolism across Space and Time
Researcher (PI) Tomer Shlomi
Host Institution (HI) TECHNION - ISRAEL INSTITUTE OF TECHNOLOGY
Call Details Starting Grant (StG), LS2, ERC-2016-STG
Summary The metabolism of cancer cells is altered to meet cellular requirements for growth, providing novel means to selectively target tumorigenesis. While extensively studied, our current view of cancer cellular metabolism is fundamentally limited by lack of information on variability in metabolic activity between distinct subcellular compartments and cells.
We propose to develop a spatio-temporal fluxomics approach for quantifying metabolic fluxes in the cytoplasm vs. mitochondria as well as their cell-cycle dynamics, combining mass-spectrometry based isotope tracing with cell synchronization, rapid cellular fractionation, and computational metabolic network modelling.
Spatio-temporal fluxomics will be used to revisit and challenge our current understanding of central metabolism and its induced adaptation to oncogenic events – an important endeavour considering that mitochondrial bioenergetics and biosynthesis are required for tumorigenesis and accumulating evidences for metabolic alterations throughout the cell-cycle.
Our preliminary results show intriguing oscillations between oxidative and reductive TCA cycle flux throughout the cell-cycle. We will explore the extent to which cells adapt their metabolism to fulfil the changing energetic and anabolic demands throughout the cell-cycle, how metabolic oscillations are regulated, and their benefit to cells in terms of thermodynamic efficiency. Spatial flux analysis will be instrumental for investigating glutaminolysis - a ‘hallmark’ metabolic adaptation in cancer involving shuttling of metabolic intermediates and cofactors between mitochondria and cytoplasm.
On a clinical front, our spatio-temporal fluxomics analysis will enable to disentangle oncogene-induced flux alterations, having an important tumorigenic role, from artefacts originating from population averaging. A comprehensive view of how cells adapt their metabolism due to oncogenic mutations will reveal novel targets for anti-cancer drugs.
Summary
The metabolism of cancer cells is altered to meet cellular requirements for growth, providing novel means to selectively target tumorigenesis. While extensively studied, our current view of cancer cellular metabolism is fundamentally limited by lack of information on variability in metabolic activity between distinct subcellular compartments and cells.
We propose to develop a spatio-temporal fluxomics approach for quantifying metabolic fluxes in the cytoplasm vs. mitochondria as well as their cell-cycle dynamics, combining mass-spectrometry based isotope tracing with cell synchronization, rapid cellular fractionation, and computational metabolic network modelling.
Spatio-temporal fluxomics will be used to revisit and challenge our current understanding of central metabolism and its induced adaptation to oncogenic events – an important endeavour considering that mitochondrial bioenergetics and biosynthesis are required for tumorigenesis and accumulating evidences for metabolic alterations throughout the cell-cycle.
Our preliminary results show intriguing oscillations between oxidative and reductive TCA cycle flux throughout the cell-cycle. We will explore the extent to which cells adapt their metabolism to fulfil the changing energetic and anabolic demands throughout the cell-cycle, how metabolic oscillations are regulated, and their benefit to cells in terms of thermodynamic efficiency. Spatial flux analysis will be instrumental for investigating glutaminolysis - a ‘hallmark’ metabolic adaptation in cancer involving shuttling of metabolic intermediates and cofactors between mitochondria and cytoplasm.
On a clinical front, our spatio-temporal fluxomics analysis will enable to disentangle oncogene-induced flux alterations, having an important tumorigenic role, from artefacts originating from population averaging. A comprehensive view of how cells adapt their metabolism due to oncogenic mutations will reveal novel targets for anti-cancer drugs.
Max ERC Funding
1 481 250 €
Duration
Start date: 2017-02-01, End date: 2022-01-31
Project acronym CHROMONUMBER
Project Chromosome number variations in vivo: probing mechanisms of genesis and elimination
Researcher (PI) Renata BASTO
Host Institution (HI) INSTITUT CURIE
Call Details Consolidator Grant (CoG), LS3, ERC-2016-COG
Summary How variations in whole chromosome number impact organism homeostasis remains an open question. Variations to the normal euploid genome content are frequently found in healthy animals and are thought to contribute with phenotypic variability in adverse situations. Yet they are also at the basis of several human diseases, including neuro-developmental disorders and cancer. Our preliminary data shows that physiological aneuploidy can be identified in certain cells during development. Moreover, we have observed that when induced through mutations, non-euploid cells are effectively eliminated from the cycling population. A quantitative view of the frequency of non-euploid karyotypes and the mechanisms underlying their genesis is lacking in the literature. Further, the tissue specific responses at play to eliminate non-euploid cells, when induced through mutations are not understood. The objectives of this proposal are to quantitatively assess the occurrence of physiological chromosome number variations gaining insight into mechanisms involved in generating it. Additionally, we will identify the tissue-specific pathways involved in maintaining organism homeostasis through the elimination of non-euploid cells. We will use a novel genetic approach to monitor individual chromosome loss at the level of the entire organism, combine it with quantitative methods and state-of-the art-microscopy, and focus on two model organisms - Drosophila and mouse - during development and adulthood. We predict that the findings resulting from this proposal will significantly impact the fields of cell, developmental and animal physiology, generating novel concepts that will bridge the existing gaps in the field, and expand our understanding of the links between karyotype variations, animal development and disease establishment.
Summary
How variations in whole chromosome number impact organism homeostasis remains an open question. Variations to the normal euploid genome content are frequently found in healthy animals and are thought to contribute with phenotypic variability in adverse situations. Yet they are also at the basis of several human diseases, including neuro-developmental disorders and cancer. Our preliminary data shows that physiological aneuploidy can be identified in certain cells during development. Moreover, we have observed that when induced through mutations, non-euploid cells are effectively eliminated from the cycling population. A quantitative view of the frequency of non-euploid karyotypes and the mechanisms underlying their genesis is lacking in the literature. Further, the tissue specific responses at play to eliminate non-euploid cells, when induced through mutations are not understood. The objectives of this proposal are to quantitatively assess the occurrence of physiological chromosome number variations gaining insight into mechanisms involved in generating it. Additionally, we will identify the tissue-specific pathways involved in maintaining organism homeostasis through the elimination of non-euploid cells. We will use a novel genetic approach to monitor individual chromosome loss at the level of the entire organism, combine it with quantitative methods and state-of-the art-microscopy, and focus on two model organisms - Drosophila and mouse - during development and adulthood. We predict that the findings resulting from this proposal will significantly impact the fields of cell, developmental and animal physiology, generating novel concepts that will bridge the existing gaps in the field, and expand our understanding of the links between karyotype variations, animal development and disease establishment.
Max ERC Funding
2 000 000 €
Duration
Start date: 2017-07-01, End date: 2022-06-30
Project acronym cis-CONTROL
Project Decoding and controlling cell-state switching: A bottom-up approach based on enhancer logic
Researcher (PI) Stein Luc AERTS
Host Institution (HI) VIB
Call Details Consolidator Grant (CoG), LS2, ERC-2016-COG
Summary Cell-state switching in cancer allows cells to transition from a proliferative to an invasive and drug-resistant phenotype. This plasticity plays an important role in cancer progression and tumour heterogeneity. We have made a striking observation that cancer cells of different origin can switch to a common survival state. During this epigenomic reprogramming, cancer cells re-activate genomic enhancers from specific regulatory programs, such as wound repair and epithelial-to-mesenchymal transition.
The goal of my project is to decipher the enhancer logic underlying this canalization effect towards a common survival state. We will then employ this new understanding of enhancer logic to engineer synthetic enhancers that are able to monitor and manipulate cell-state switching in real time. Furthermore, we will use enhancer models to identify cis-regulatory mutations that have an impact on cell-state switching and drug resistance. Such applications are currently hampered because there is a significant gap in our understanding of how enhancers work.
To tackle this problem we will use a combination of in vivo massively parallel enhancer-reporter assays, single-cell genomics on microfluidic devices, computational modelling, and synthetic enhancer design. Using these approaches we will pursue the following aims: (1) to identify functional enhancers regulating cell-state switching by performing in vivo genetic screens in mice; (2) to elucidate the dynamic trajectories whereby cells of different cancer types switch to a common survival cell-state, at single-cell resolution; (3) to create synthetic enhancer circuits that specifically kill cancer cells undergoing cell-state switching.
Our findings will have an impact on genome research, characterizing how cellular decision making is implemented by the cis-regulatory code; and on cancer research, employing enhancer logic in the context of cancer therapy.
Summary
Cell-state switching in cancer allows cells to transition from a proliferative to an invasive and drug-resistant phenotype. This plasticity plays an important role in cancer progression and tumour heterogeneity. We have made a striking observation that cancer cells of different origin can switch to a common survival state. During this epigenomic reprogramming, cancer cells re-activate genomic enhancers from specific regulatory programs, such as wound repair and epithelial-to-mesenchymal transition.
The goal of my project is to decipher the enhancer logic underlying this canalization effect towards a common survival state. We will then employ this new understanding of enhancer logic to engineer synthetic enhancers that are able to monitor and manipulate cell-state switching in real time. Furthermore, we will use enhancer models to identify cis-regulatory mutations that have an impact on cell-state switching and drug resistance. Such applications are currently hampered because there is a significant gap in our understanding of how enhancers work.
To tackle this problem we will use a combination of in vivo massively parallel enhancer-reporter assays, single-cell genomics on microfluidic devices, computational modelling, and synthetic enhancer design. Using these approaches we will pursue the following aims: (1) to identify functional enhancers regulating cell-state switching by performing in vivo genetic screens in mice; (2) to elucidate the dynamic trajectories whereby cells of different cancer types switch to a common survival cell-state, at single-cell resolution; (3) to create synthetic enhancer circuits that specifically kill cancer cells undergoing cell-state switching.
Our findings will have an impact on genome research, characterizing how cellular decision making is implemented by the cis-regulatory code; and on cancer research, employing enhancer logic in the context of cancer therapy.
Max ERC Funding
1 999 660 €
Duration
Start date: 2017-06-01, End date: 2022-05-31
Project acronym ComplexAssembly
Project The birth of protein complexes
Researcher (PI) Martin BECK
Host Institution (HI) EUROPEAN MOLECULAR BIOLOGY LABORATORY
Call Details Consolidator Grant (CoG), LS2, ERC-2016-COG
Summary Protein complexes are central to many cellular functions but our knowledge of how cells assemble protein complexes remains very sparse. Biophysical and structural data of assembly intermediates are extremely rare. Particularly in higher eukaryotes, it has become clear that complex assembly by random collision of subunits cannot cope with the spatial and temporal complexity of the intricate architecture of many cellular machines. Here I propose to combine systems biology approaches with in situ structural biology methods to visualize protein complex assembly. I want to investigate experimentally in which order the interfaces of protein complexes are formed and to which extent structures of assembly intermediates resemble those observed in fully assembled complexes. I want develop methods to systematically screen for additional factors involved in assembly pathways. I furthermore want to test the hypothesis that mechanisms must exist in eukaryotes that coordinate local mRNA translation with the ordered formation of protein complex interfaces. I believe that in order to understand assembly pathways, these processes, that so far are often studied autonomously, need to be considered jointly and in a protein complex centric manner. The research proposed here will bridge across these different scientific disciplines. In the long term, a better mechanistic understanding of protein complex assembly and the structural characterization of critical intermediates will be of high relevance for scenarios under which a cell’s protein quality control system has to cope with stress, such as aging and neurodegenerative diseases. It might also facilitate the more efficient industrial production of therapeutically relevant proteins.
Summary
Protein complexes are central to many cellular functions but our knowledge of how cells assemble protein complexes remains very sparse. Biophysical and structural data of assembly intermediates are extremely rare. Particularly in higher eukaryotes, it has become clear that complex assembly by random collision of subunits cannot cope with the spatial and temporal complexity of the intricate architecture of many cellular machines. Here I propose to combine systems biology approaches with in situ structural biology methods to visualize protein complex assembly. I want to investigate experimentally in which order the interfaces of protein complexes are formed and to which extent structures of assembly intermediates resemble those observed in fully assembled complexes. I want develop methods to systematically screen for additional factors involved in assembly pathways. I furthermore want to test the hypothesis that mechanisms must exist in eukaryotes that coordinate local mRNA translation with the ordered formation of protein complex interfaces. I believe that in order to understand assembly pathways, these processes, that so far are often studied autonomously, need to be considered jointly and in a protein complex centric manner. The research proposed here will bridge across these different scientific disciplines. In the long term, a better mechanistic understanding of protein complex assembly and the structural characterization of critical intermediates will be of high relevance for scenarios under which a cell’s protein quality control system has to cope with stress, such as aging and neurodegenerative diseases. It might also facilitate the more efficient industrial production of therapeutically relevant proteins.
Max ERC Funding
1 957 717 €
Duration
Start date: 2018-02-01, End date: 2023-01-31
Project acronym CrackEpitranscriptom
Project Cracking the epitranscriptome
Researcher (PI) Schraga SCHWARTZ
Host Institution (HI) WEIZMANN INSTITUTE OF SCIENCE
Call Details Starting Grant (StG), LS2, ERC-2016-STG
Summary Over 100 types of distinct modifications are catalyzed on RNA molecules post-transcriptionally. In an analogous manner to well-studied chemical modifications on proteins or DNA, modifications on RNA - and particularly on mRNA - harbor the exciting potential of regulating the complex and interlinked life cycle of these molecules. The most abundant modification in mammalian and yeast mRNA is N6-methyladenosine (m6A). We have pioneered approaches for mapping m6A in a transcriptome wide manner, and we and others have identified factors involved in encoding and decoding m6A. While experimental disruption of these factors is associated with severe phenotypes, the role of m6A remains enigmatic. No single methylated site has been shown to causally underlie any physiological or molecular function. This proposal aims to establish a framework for systematically deciphering the molecular function of a modification and its underlying mechanisms and to uncover the physiological role of the modification in regulation of a cellular response. We will apply this framework to m6A in the context of meiosis in budding yeast, as m6A dynamically accumulates on meiotic mRNAs and as the methyltransferase catalyzing m6A is essential for meiosis. We will (1) aim to elucidate the physiological targets of methylation governing entry into meiosis (2) seek to elucidate the function of m6A at the molecular level, and understand its impact on the various steps of the mRNA life cycle, (3) seek to understand the mechanisms underlying its effects. These aims will provide a comprehensive framework for understanding how the epitranscriptome, an emerging post-transcriptional layer of regulation, fine-tunes gene regulation and impacts cellular decision making in a dynamic response, and will set the stage towards dissecting the roles of m6A and of an expanding set of mRNA modifications in more complex and disease related systems.
Summary
Over 100 types of distinct modifications are catalyzed on RNA molecules post-transcriptionally. In an analogous manner to well-studied chemical modifications on proteins or DNA, modifications on RNA - and particularly on mRNA - harbor the exciting potential of regulating the complex and interlinked life cycle of these molecules. The most abundant modification in mammalian and yeast mRNA is N6-methyladenosine (m6A). We have pioneered approaches for mapping m6A in a transcriptome wide manner, and we and others have identified factors involved in encoding and decoding m6A. While experimental disruption of these factors is associated with severe phenotypes, the role of m6A remains enigmatic. No single methylated site has been shown to causally underlie any physiological or molecular function. This proposal aims to establish a framework for systematically deciphering the molecular function of a modification and its underlying mechanisms and to uncover the physiological role of the modification in regulation of a cellular response. We will apply this framework to m6A in the context of meiosis in budding yeast, as m6A dynamically accumulates on meiotic mRNAs and as the methyltransferase catalyzing m6A is essential for meiosis. We will (1) aim to elucidate the physiological targets of methylation governing entry into meiosis (2) seek to elucidate the function of m6A at the molecular level, and understand its impact on the various steps of the mRNA life cycle, (3) seek to understand the mechanisms underlying its effects. These aims will provide a comprehensive framework for understanding how the epitranscriptome, an emerging post-transcriptional layer of regulation, fine-tunes gene regulation and impacts cellular decision making in a dynamic response, and will set the stage towards dissecting the roles of m6A and of an expanding set of mRNA modifications in more complex and disease related systems.
Max ERC Funding
1 402 666 €
Duration
Start date: 2016-11-01, End date: 2021-10-31
Project acronym CYCLODE
Project Cyclical and Linear Timing Modes in Development
Researcher (PI) Helge GROSSHANS
Host Institution (HI) FRIEDRICH MIESCHER INSTITUTE FOR BIOMEDICAL RESEARCH FONDATION
Call Details Advanced Grant (AdG), LS3, ERC-2016-ADG
Summary Organismal development requires proper timing of events such as cell fate choices, but the mechanisms that control temporal patterning remain poorly understood. In particular, we know little of the cyclical timers, or ‘clocks’, that control recurring events such as vertebrate segmentation or nematode molting. Furthermore, it is unknown how cyclical timers are coordinated with the global, or linear, timing of development, e.g. to ensure an appropriate number of cyclical repeats. We propose to elucidate the components, wiring, and properties of a prototypic developmental clock by studying developmental timing in the roundworm C. elegans. We build on our recent discovery that nearly 20% of the worm’s transcriptome oscillates during larval development – an apparent manifestation of a clock that times the various recurring events that encompass each larval stage. Our aims are i) to identify components of this clock using genetic screens, ii) to gain insight into the system’s architecture and properties by employing specific perturbations such as food deprivation, and iii) to understand the coupling of this cyclic clock to the linear heterochronic timer through genetic manipulations. To achieve our ambitious goals, we will develop tools for mRNA sequencing of individual worms and for their developmental tracking and microchamber-based imaging. These important advances will increase temporal resolution, enhance signal-to-noise ratio, and achieve live tracking of oscillations in vivo. Our combination of genetic, genomic, imaging, and computational approaches will provide a detailed understanding of this clock, and biological timing mechanisms in general. As heterochronic genes and rhythmic gene expression are also important for controlling stem cell fates, we foresee that the results gained will additionally reveal regulatory mechanisms of stem cells, thus advancing our fundamental understanding of animal development and future applications in regenerative medicine.
Summary
Organismal development requires proper timing of events such as cell fate choices, but the mechanisms that control temporal patterning remain poorly understood. In particular, we know little of the cyclical timers, or ‘clocks’, that control recurring events such as vertebrate segmentation or nematode molting. Furthermore, it is unknown how cyclical timers are coordinated with the global, or linear, timing of development, e.g. to ensure an appropriate number of cyclical repeats. We propose to elucidate the components, wiring, and properties of a prototypic developmental clock by studying developmental timing in the roundworm C. elegans. We build on our recent discovery that nearly 20% of the worm’s transcriptome oscillates during larval development – an apparent manifestation of a clock that times the various recurring events that encompass each larval stage. Our aims are i) to identify components of this clock using genetic screens, ii) to gain insight into the system’s architecture and properties by employing specific perturbations such as food deprivation, and iii) to understand the coupling of this cyclic clock to the linear heterochronic timer through genetic manipulations. To achieve our ambitious goals, we will develop tools for mRNA sequencing of individual worms and for their developmental tracking and microchamber-based imaging. These important advances will increase temporal resolution, enhance signal-to-noise ratio, and achieve live tracking of oscillations in vivo. Our combination of genetic, genomic, imaging, and computational approaches will provide a detailed understanding of this clock, and biological timing mechanisms in general. As heterochronic genes and rhythmic gene expression are also important for controlling stem cell fates, we foresee that the results gained will additionally reveal regulatory mechanisms of stem cells, thus advancing our fundamental understanding of animal development and future applications in regenerative medicine.
Max ERC Funding
2 358 625 €
Duration
Start date: 2017-10-01, End date: 2022-09-30
Project acronym DissectPcG
Project Dissecting the Function of Multiple Polycomb Group Complexes in Establishing Transcriptional Identity
Researcher (PI) Diego PASINI
Host Institution (HI) UNIVERSITA DEGLI STUDI DI MILANO
Call Details Consolidator Grant (CoG), LS3, ERC-2016-COG
Summary The activities of the Polycomb group (PcG) of repressive chromatin modifiers are required to maintain correct transcriptional identity during development and differentiation. These activities are altered in a variety of tumours by gain- or loss-of-function mutations, whose mechanistic aspects still remain unclear.
PcGs can be classified in two major repressive complexes (PRC1 and PRC2) with common pathways but distinct biochemical activities. PRC1 catalyses histone H2A ubiquitination of lysine 119, and PRC2 tri-methylation of histone H3 lysine 27. However, PRC1 has a more heterogeneous composition than PRC2, with six mutually exclusive PCGF subunits (PCGF1–6) essential for assembling distinct PRC1 complexes that differ in subunit composition but share the same catalytic core.
While up to six different PRC1 forms can co-exist in a given cell, the molecular mechanisms regulating their activities and their relative contributions to general PRC1 function in any tissue/cell type remain largely unknown. In line with this biochemical heterogeneity, PRC1 retains broader biological functions than PRC2. Critically, however, no molecular analysis has yet been published that dissects the contribution of each PRC1 complex in regulating transcriptional identity.
We will take advantage of newly developed reagents and unpublished genetic models to target each of the six Pcgf genes in either embryonic stem cells or mouse adult tissues. This will systematically dissect the contributions of the different PRC1 complexes to chromatin profiles, gene expression programs, and cellular phenotypes during stem cell self-renewal, differentiation and adult tissue homeostasis. Overall, this will elucidate some of the fundamental mechanisms underlying the establishment and maintenance of cellular identity and will allow us to further determine the molecular links between PcG deregulation and cancer development in a tissue- and/or cell type–specific manner.
Summary
The activities of the Polycomb group (PcG) of repressive chromatin modifiers are required to maintain correct transcriptional identity during development and differentiation. These activities are altered in a variety of tumours by gain- or loss-of-function mutations, whose mechanistic aspects still remain unclear.
PcGs can be classified in two major repressive complexes (PRC1 and PRC2) with common pathways but distinct biochemical activities. PRC1 catalyses histone H2A ubiquitination of lysine 119, and PRC2 tri-methylation of histone H3 lysine 27. However, PRC1 has a more heterogeneous composition than PRC2, with six mutually exclusive PCGF subunits (PCGF1–6) essential for assembling distinct PRC1 complexes that differ in subunit composition but share the same catalytic core.
While up to six different PRC1 forms can co-exist in a given cell, the molecular mechanisms regulating their activities and their relative contributions to general PRC1 function in any tissue/cell type remain largely unknown. In line with this biochemical heterogeneity, PRC1 retains broader biological functions than PRC2. Critically, however, no molecular analysis has yet been published that dissects the contribution of each PRC1 complex in regulating transcriptional identity.
We will take advantage of newly developed reagents and unpublished genetic models to target each of the six Pcgf genes in either embryonic stem cells or mouse adult tissues. This will systematically dissect the contributions of the different PRC1 complexes to chromatin profiles, gene expression programs, and cellular phenotypes during stem cell self-renewal, differentiation and adult tissue homeostasis. Overall, this will elucidate some of the fundamental mechanisms underlying the establishment and maintenance of cellular identity and will allow us to further determine the molecular links between PcG deregulation and cancer development in a tissue- and/or cell type–specific manner.
Max ERC Funding
2 000 000 €
Duration
Start date: 2017-11-01, End date: 2022-10-31
Project acronym Epiherigans
Project Writing, reading and managing stress with H3K9me
Researcher (PI) Susan GASSER
Host Institution (HI) FRIEDRICH MIESCHER INSTITUTE FOR BIOMEDICAL RESEARCH FONDATION
Call Details Advanced Grant (AdG), LS2, ERC-2016-ADG
Summary Epigenetic inheritance is the transmission of information, generally in the form of DNA methylation or post-translational modifications on histones that regulate the availability of underlying genetic information for transcription. RNA itself feeds back to contribute to histone modification. Sequence accessibility is both a matter of folding the chromatin fibre to alter access to recognition motifs, and the local concentration of factors needed for efficient transcriptional initiation, elongation, termination or mRNA stability. In heterochromatin we find a subset of regulatory factors in carefully balanced concentrations that are maintained in part by the segregation of active and inactive domains. Histone H3 K9 methylation is key to this compartmentation.
C. elegans provides an ideal system in which to study chromatin-based gene repression. We have demonstrated that histone H3 K9 methylation is the essential signal for the sequestration of heterochromatin at the nuclear envelope in C. elegans. The recognition of H3K9me1/2/3 by an inner nuclear envelope-bound chromodomain protein, CEC-4, actively sequesters heterochromatin in embryos, and contributes redundantly in adult tissues.
Epiherigans has the ambitious goal to determine definitively what targets H3K9 methylation, and identify its physiological roles. We will examine how this mark contributes to the epigenetic recognition of repeat vs non-repeat sequence, and mediates a stress-induced response to oxidative damage. We will examine the link between these and the spatial clustering of heterochromatic domains. Epiherigans will develop an integrated approach to identify in vivo the factors that distinguish repeats from non-repeats, self from non-self within genomes and will examine how H3K9me contributes to a persistent ROS or DNA damage stress response. It represents a crucial step towards understanding of how our genomes use heterochromatin to modulate, stabilize and transmit chromatin organization.
Summary
Epigenetic inheritance is the transmission of information, generally in the form of DNA methylation or post-translational modifications on histones that regulate the availability of underlying genetic information for transcription. RNA itself feeds back to contribute to histone modification. Sequence accessibility is both a matter of folding the chromatin fibre to alter access to recognition motifs, and the local concentration of factors needed for efficient transcriptional initiation, elongation, termination or mRNA stability. In heterochromatin we find a subset of regulatory factors in carefully balanced concentrations that are maintained in part by the segregation of active and inactive domains. Histone H3 K9 methylation is key to this compartmentation.
C. elegans provides an ideal system in which to study chromatin-based gene repression. We have demonstrated that histone H3 K9 methylation is the essential signal for the sequestration of heterochromatin at the nuclear envelope in C. elegans. The recognition of H3K9me1/2/3 by an inner nuclear envelope-bound chromodomain protein, CEC-4, actively sequesters heterochromatin in embryos, and contributes redundantly in adult tissues.
Epiherigans has the ambitious goal to determine definitively what targets H3K9 methylation, and identify its physiological roles. We will examine how this mark contributes to the epigenetic recognition of repeat vs non-repeat sequence, and mediates a stress-induced response to oxidative damage. We will examine the link between these and the spatial clustering of heterochromatic domains. Epiherigans will develop an integrated approach to identify in vivo the factors that distinguish repeats from non-repeats, self from non-self within genomes and will examine how H3K9me contributes to a persistent ROS or DNA damage stress response. It represents a crucial step towards understanding of how our genomes use heterochromatin to modulate, stabilize and transmit chromatin organization.
Max ERC Funding
2 500 000 €
Duration
Start date: 2017-06-01, End date: 2022-05-31
