Project acronym 3DCellPhase-
Project In situ Structural Analysis of Molecular Crowding and Phase Separation
Researcher (PI) Julia MAHAMID
Host Institution (HI) EUROPEAN MOLECULAR BIOLOGY LABORATORY
Call Details Starting Grant (StG), LS1, ERC-2017-STG
Summary This proposal brings together two fields in biology, namely the emerging field of phase-separated assemblies in cell biology and state-of-the-art cellular cryo-electron tomography, to advance our understanding on a fundamental, yet illusive, question: the molecular organization of the cytoplasm.
Eukaryotes organize their biochemical reactions into functionally distinct compartments. Intriguingly, many, if not most, cellular compartments are not membrane enclosed. Rather, they assemble dynamically by phase separation, typically triggered upon a specific event. Despite significant progress on reconstituting such liquid-like assemblies in vitro, we lack information as to whether these compartments in vivo are indeed amorphous liquids, or whether they exhibit structural features such as gels or fibers. My recent work on sample preparation of cells for cryo-electron tomography, including cryo-focused ion beam thinning, guided by 3D correlative fluorescence microscopy, shows that we can now prepare site-specific ‘electron-transparent windows’ in suitable eukaryotic systems, which allow direct examination of structural features of cellular compartments in their cellular context. Here, we will use these techniques to elucidate the structural principles and cytoplasmic environment driving the dynamic assembly of two phase-separated compartments: Stress granules, which are RNA bodies that form rapidly in the cytoplasm upon cellular stress, and centrosomes, which are sites of microtubule nucleation. We will combine these studies with a quantitative description of the crowded nature of cytoplasm and of its local variations, to provide a direct readout of the impact of excluded volume on molecular assembly in living cells. Taken together, these studies will provide fundamental insights into the structural basis by which cells form biochemical compartments.
Summary
This proposal brings together two fields in biology, namely the emerging field of phase-separated assemblies in cell biology and state-of-the-art cellular cryo-electron tomography, to advance our understanding on a fundamental, yet illusive, question: the molecular organization of the cytoplasm.
Eukaryotes organize their biochemical reactions into functionally distinct compartments. Intriguingly, many, if not most, cellular compartments are not membrane enclosed. Rather, they assemble dynamically by phase separation, typically triggered upon a specific event. Despite significant progress on reconstituting such liquid-like assemblies in vitro, we lack information as to whether these compartments in vivo are indeed amorphous liquids, or whether they exhibit structural features such as gels or fibers. My recent work on sample preparation of cells for cryo-electron tomography, including cryo-focused ion beam thinning, guided by 3D correlative fluorescence microscopy, shows that we can now prepare site-specific ‘electron-transparent windows’ in suitable eukaryotic systems, which allow direct examination of structural features of cellular compartments in their cellular context. Here, we will use these techniques to elucidate the structural principles and cytoplasmic environment driving the dynamic assembly of two phase-separated compartments: Stress granules, which are RNA bodies that form rapidly in the cytoplasm upon cellular stress, and centrosomes, which are sites of microtubule nucleation. We will combine these studies with a quantitative description of the crowded nature of cytoplasm and of its local variations, to provide a direct readout of the impact of excluded volume on molecular assembly in living cells. Taken together, these studies will provide fundamental insights into the structural basis by which cells form biochemical compartments.
Max ERC Funding
1 228 125 €
Duration
Start date: 2018-02-01, End date: 2023-01-31
Project acronym Acclimatize
Project Hypothalamic mechanisms of thermal homeostasis and adaptation
Researcher (PI) Jan SIEMENS
Host Institution (HI) UNIVERSITATSKLINIKUM HEIDELBERG
Call Details Consolidator Grant (CoG), LS5, ERC-2017-COG
Summary Mammalian organisms possess the remarkable ability to maintain internal body temperature (Tcore) within a narrow range close to 37°C despite wide environmental temperature variations. The brain’s neural “thermostat” is made up by central circuits in the hypothalamic preoptic area (POA), which orchestrate peripheral thermoregulatory responses to maintain Tcore. Thermogenesis requires metabolic fuel, suggesting intricate connections between the thermoregulatory centre and hypothalamic circuits controlling energy balance. How the POA detects and integrates temperature and metabolic information to achieve thermal balance is largely unknown. A major question is whether this circuitry could be harnessed therapeutically to treat obesity.
We have recently identified the first known molecular temperature sensor in thermoregulatory neurons of the POA, transient receptor potential melastatin 2 (TRPM2), a thermo-sensitive ion channel. I aim to use TRPM2 as a molecular marker to gain access to and probe the function of thermoregulatory neurons in vivo. I propose a multidisciplinary approach, combining local, in vivo POA temperature stimulation with optogenetic circuit-mapping to uncover the molecular and cellular logic of the hypothalamic thermoregulatory centre and to assess its medical potential to counteract metabolic syndrome.
Acclimation is a beneficial adaptive process that fortifies thermal responses upon environmental temperature challenges. Thermoregulatory neuron plasticity is thought to mediate acclimation. Conversely, maladaptive thermoregulatory changes affect obesity. The cell-type-specific neuronal plasticity mechanisms underlying these changes within the POA, however, are unknown.
Using ex-vivo slice electrophysiology and in vivo imaging, I propose to characterize acclimation- and obesity-induced plasticity of thermoregulatory neurons. Ultimately, I aim to manipulate thermoregulatory neuron plasticity to test its potential counter-balancing effect on obesity.
Summary
Mammalian organisms possess the remarkable ability to maintain internal body temperature (Tcore) within a narrow range close to 37°C despite wide environmental temperature variations. The brain’s neural “thermostat” is made up by central circuits in the hypothalamic preoptic area (POA), which orchestrate peripheral thermoregulatory responses to maintain Tcore. Thermogenesis requires metabolic fuel, suggesting intricate connections between the thermoregulatory centre and hypothalamic circuits controlling energy balance. How the POA detects and integrates temperature and metabolic information to achieve thermal balance is largely unknown. A major question is whether this circuitry could be harnessed therapeutically to treat obesity.
We have recently identified the first known molecular temperature sensor in thermoregulatory neurons of the POA, transient receptor potential melastatin 2 (TRPM2), a thermo-sensitive ion channel. I aim to use TRPM2 as a molecular marker to gain access to and probe the function of thermoregulatory neurons in vivo. I propose a multidisciplinary approach, combining local, in vivo POA temperature stimulation with optogenetic circuit-mapping to uncover the molecular and cellular logic of the hypothalamic thermoregulatory centre and to assess its medical potential to counteract metabolic syndrome.
Acclimation is a beneficial adaptive process that fortifies thermal responses upon environmental temperature challenges. Thermoregulatory neuron plasticity is thought to mediate acclimation. Conversely, maladaptive thermoregulatory changes affect obesity. The cell-type-specific neuronal plasticity mechanisms underlying these changes within the POA, however, are unknown.
Using ex-vivo slice electrophysiology and in vivo imaging, I propose to characterize acclimation- and obesity-induced plasticity of thermoregulatory neurons. Ultimately, I aim to manipulate thermoregulatory neuron plasticity to test its potential counter-balancing effect on obesity.
Max ERC Funding
1 902 500 €
Duration
Start date: 2018-09-01, End date: 2023-08-31
Project acronym ACoolTouch
Project Neural mechanisms of multisensory perceptual binding
Researcher (PI) James Francis Alexander Poulet
Host Institution (HI) MAX DELBRUECK CENTRUM FUER MOLEKULARE MEDIZIN IN DER HELMHOLTZ-GEMEINSCHAFT (MDC)
Call Details Consolidator Grant (CoG), LS5, ERC-2015-CoG
Summary Sensory perception involves the discrimination and binding of multiple modalities of sensory input. This is especially evident in the somatosensory system where different modalities of sensory input, including thermal and mechanosensory, are combined to generate a unified percept. The neural mechanisms of multisensory binding are unknown, in part because sensory perception is typically studied within a single modality in a single brain region. I propose a multi-level approach to investigate thermo-tactile processing in the mouse forepaw system from the primary sensory afferent neurons to thalamo-cortical circuits and behaviour.
The mouse forepaw system is the ideal system to investigate multisensory binding as the sensory afferent neurons are well investigated, cell type-specific lines are available, in vivo optogenetic manipulation is possible both in sensory afferent neurons and central circuits and we have developed high-resolution somatosensory perception behaviours. We have previously shown that mouse primary somatosensory forepaw cortical neurons respond to both tactile and thermal stimuli and are required for non-noxious cooling perception. With multimodal neurons how, then, is it possible to both discriminate and bind thermal and tactile stimuli?
I propose 3 objectives to address this question. We will first, perform functional mapping of the thermal and tactile pathways to cortex; second, investigate the neural mechanisms of thermo-tactile discrimination in behaving mice; and third, compare neural processing during two thermo-tactile binding tasks, the first using passively applied stimuli, and the second, active manipulation of thermal objects.
At each stage we will perform cell type-specific neural recordings and causal optogenetic manipulations in awake and behaving mice. Our multi-level approach will provide a comprehensive investigation into how the brain performs multisensory perceptual binding: a fundamental yet unsolved problem in neuroscience.
Summary
Sensory perception involves the discrimination and binding of multiple modalities of sensory input. This is especially evident in the somatosensory system where different modalities of sensory input, including thermal and mechanosensory, are combined to generate a unified percept. The neural mechanisms of multisensory binding are unknown, in part because sensory perception is typically studied within a single modality in a single brain region. I propose a multi-level approach to investigate thermo-tactile processing in the mouse forepaw system from the primary sensory afferent neurons to thalamo-cortical circuits and behaviour.
The mouse forepaw system is the ideal system to investigate multisensory binding as the sensory afferent neurons are well investigated, cell type-specific lines are available, in vivo optogenetic manipulation is possible both in sensory afferent neurons and central circuits and we have developed high-resolution somatosensory perception behaviours. We have previously shown that mouse primary somatosensory forepaw cortical neurons respond to both tactile and thermal stimuli and are required for non-noxious cooling perception. With multimodal neurons how, then, is it possible to both discriminate and bind thermal and tactile stimuli?
I propose 3 objectives to address this question. We will first, perform functional mapping of the thermal and tactile pathways to cortex; second, investigate the neural mechanisms of thermo-tactile discrimination in behaving mice; and third, compare neural processing during two thermo-tactile binding tasks, the first using passively applied stimuli, and the second, active manipulation of thermal objects.
At each stage we will perform cell type-specific neural recordings and causal optogenetic manipulations in awake and behaving mice. Our multi-level approach will provide a comprehensive investigation into how the brain performs multisensory perceptual binding: a fundamental yet unsolved problem in neuroscience.
Max ERC Funding
1 999 877 €
Duration
Start date: 2016-09-01, End date: 2021-08-31
Project acronym ActiveCortex
Project Active dendrites and cortical associations
Researcher (PI) Matthew Larkum
Host Institution (HI) HUMBOLDT-UNIVERSITAET ZU BERLIN
Call Details Advanced Grant (AdG), LS5, ERC-2014-ADG
Summary Converging studies from psychophysics in humans to single-cell recordings in monkeys and rodents indicate that most important cognitive processes depend on both feed-forward and feedback information interacting in the brain. Intriguingly, feedback to early cortical processing stages appears to play a causal role in these processes. Despite the central nature of this fact to understanding brain cognition, there is still no mechanistic explanation as to how this information could be so pivotal and what events take place that might be decisive. In this research program, we will test the hypothesis that the extraordinary performance of the cortex derives from an associative mechanism built into the basic neuronal unit: the pyramidal cell. The hypothesis is based on two important facts: (1) feedback information is conveyed predominantly to layer 1 and (2) the apical tuft dendrites that are the major recipient of this feedback information are highly electrogenic.
The research program is divided in to several workpackages to systematically investigate the hypothesis at every level. As a whole, we will investigate the causal link between intrinsic cellular activity and behaviour. To do this we will use eletrophysiological and optical techniques to record and influence cell the intrinsic properties of cells (in particular dendritic activity) in vivo and in vitro in rodents. In vivo experiments will have a specific focus on context driven behaviour and in vitro experiments on the impact of long-range (feedback-carrying) fibers on cell activity. The study will also focus on synaptic plasticity at the interface of feedback information and dendritic electrogenesis, namely synapses on to the tuft dendrite of pyramidal neurons. The proposed program will not only address a long-standing and important hypothesis but also provide a transformational contribution towards understanding the operation of the cerebral cortex.
Summary
Converging studies from psychophysics in humans to single-cell recordings in monkeys and rodents indicate that most important cognitive processes depend on both feed-forward and feedback information interacting in the brain. Intriguingly, feedback to early cortical processing stages appears to play a causal role in these processes. Despite the central nature of this fact to understanding brain cognition, there is still no mechanistic explanation as to how this information could be so pivotal and what events take place that might be decisive. In this research program, we will test the hypothesis that the extraordinary performance of the cortex derives from an associative mechanism built into the basic neuronal unit: the pyramidal cell. The hypothesis is based on two important facts: (1) feedback information is conveyed predominantly to layer 1 and (2) the apical tuft dendrites that are the major recipient of this feedback information are highly electrogenic.
The research program is divided in to several workpackages to systematically investigate the hypothesis at every level. As a whole, we will investigate the causal link between intrinsic cellular activity and behaviour. To do this we will use eletrophysiological and optical techniques to record and influence cell the intrinsic properties of cells (in particular dendritic activity) in vivo and in vitro in rodents. In vivo experiments will have a specific focus on context driven behaviour and in vitro experiments on the impact of long-range (feedback-carrying) fibers on cell activity. The study will also focus on synaptic plasticity at the interface of feedback information and dendritic electrogenesis, namely synapses on to the tuft dendrite of pyramidal neurons. The proposed program will not only address a long-standing and important hypothesis but also provide a transformational contribution towards understanding the operation of the cerebral cortex.
Max ERC Funding
2 386 304 €
Duration
Start date: 2016-01-01, End date: 2020-12-31
Project acronym AMYLOID
Project Identification and modulation of pathogenic Amyloid beta-peptide species
Researcher (PI) Christian Haass
Host Institution (HI) LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN
Call Details Advanced Grant (AdG), LS5, ERC-2012-ADG_20120314
Summary The frequency of Alzheimer's disease (AD) will dramatically increase in the ageing western society during the next decades. Currently, about 18 million people suffer worldwide from AD. Since no cure is available, this devastating disorder represents one of the most challenging socio-economical problems of our future. As onset and progression of AD is triggered by the amyloid cascade, I will put particular attention on amyloid ß-peptide (Aß). The reason for this approach is, that even though 20 years ago the Aß generating processing pathway was identified (Haass et al., Nature 1992a & b), the identity of the Aß species, which initiate the deadly cascade is still unknown. I will first tackle this challenge by investigating if a novel and so far completely overlooked proteolytic processing pathway is involved in the generation of Aß species capable to initiate spreading of pathology and neurotoxicity. I will then search for modulating proteins, which could affect generation of pathological Aß species. This includes a genome-wide screen for modifiers of gamma-secretase, one of the proteases involved in Aß generation as well as a targeted search for RNA binding proteins capable to posttranscriptionally regulate beta- and alpha-secretase. In a disease-crossing approach, RNA binding proteins, which were recently found not only to be deposited in Frontotemporal Lobar Degeneration and Amyotrophic Lateral Sclerosis but also in many AD cases, will be investigated for their potential to modulate Aß aggregation and AD pathology. Modifiers and novel antibodies specifically recognizing neurotoxic Aß assemblies will be validated for their potential not only to prevent amyloid plaque formation, but also spreading of pathology as well as neurotoxicity. In vivo validations include studies in innovative zebrafish models, which allow life imaging of neuronal cell death, as well as the establishment of microPET amyloid imaging for longitudinal studies in individual animals.
Summary
The frequency of Alzheimer's disease (AD) will dramatically increase in the ageing western society during the next decades. Currently, about 18 million people suffer worldwide from AD. Since no cure is available, this devastating disorder represents one of the most challenging socio-economical problems of our future. As onset and progression of AD is triggered by the amyloid cascade, I will put particular attention on amyloid ß-peptide (Aß). The reason for this approach is, that even though 20 years ago the Aß generating processing pathway was identified (Haass et al., Nature 1992a & b), the identity of the Aß species, which initiate the deadly cascade is still unknown. I will first tackle this challenge by investigating if a novel and so far completely overlooked proteolytic processing pathway is involved in the generation of Aß species capable to initiate spreading of pathology and neurotoxicity. I will then search for modulating proteins, which could affect generation of pathological Aß species. This includes a genome-wide screen for modifiers of gamma-secretase, one of the proteases involved in Aß generation as well as a targeted search for RNA binding proteins capable to posttranscriptionally regulate beta- and alpha-secretase. In a disease-crossing approach, RNA binding proteins, which were recently found not only to be deposited in Frontotemporal Lobar Degeneration and Amyotrophic Lateral Sclerosis but also in many AD cases, will be investigated for their potential to modulate Aß aggregation and AD pathology. Modifiers and novel antibodies specifically recognizing neurotoxic Aß assemblies will be validated for their potential not only to prevent amyloid plaque formation, but also spreading of pathology as well as neurotoxicity. In vivo validations include studies in innovative zebrafish models, which allow life imaging of neuronal cell death, as well as the establishment of microPET amyloid imaging for longitudinal studies in individual animals.
Max ERC Funding
2 497 020 €
Duration
Start date: 2013-03-01, End date: 2018-02-28
Project acronym ARCID
Project The Role of Arl Proteins in Retinal and other Ciliary Diseases
Researcher (PI) Alfred Wittinghofer
Host Institution (HI) MAX-PLANCK-GESELLSCHAFT ZUR FORDERUNG DER WISSENSCHAFTEN EV
Call Details Advanced Grant (AdG), LS1, ERC-2010-AdG_20100317
Summary Arl (Arf-like) proteins, GTP-binding proteins of the Ras superfamily, are molecular switches that cycle between a GDP-bound inactive and GTP-bound active state. There are 16 members of the Arl subfamily in the human genome whose basic mechanistic function is unknown. The interactome of Arl2/3 includes proteins involved in retinopathies and other ciliary diseases such as Leber¿s Congenital Amaurosis (LCA) and kidney diseases such as nephronophthisis. Arl6 has been found mutated in Bardet Biedl Syndrome, another pleiotropic ciliary disease. In the proposed interdisciplinary project I want to explore the function of the protein network of Arl2/3 and Arl6 by a combination of biochemical, biophysical and structural methods and use the knowledge obtained to probe their function in live cells. As with other subfamily proteins of the Ras superfamily which have been found to mediate similar biological functions I want to derive a basic understanding of the function of Arl proteins and how it relates to the development and function of the ciliary organelle and how they contribute to ciliary diseases. The molecules in the focus of the project are: the GTP-binding proteins Arl2, 3, 6; RP2, an Arl3GAP mutated in Retinitis pigmentosa; Regulators of Arl2 and 3; PDE¿ and HRG4, effectors of Arl2/3, which bind lipidated proteins; RPGR, mutated in Retinitis pigmentosa, an interactor of PDE¿; RPGRIP and RPGRIPL, interactors of RPGR mutated in LCA and other ciliopathies; Nephrocystin, mutated in nephronophthisis, an interactor of RPGRIP and Arl6, mutated in Bardet Biedl Syndrome, and the BBS complex. The working hypothesis is that Arl protein network(s) mediate ciliary transport processes and that the GTP switch cycle of Arl proteins is an important element of regulation of these processes.
Summary
Arl (Arf-like) proteins, GTP-binding proteins of the Ras superfamily, are molecular switches that cycle between a GDP-bound inactive and GTP-bound active state. There are 16 members of the Arl subfamily in the human genome whose basic mechanistic function is unknown. The interactome of Arl2/3 includes proteins involved in retinopathies and other ciliary diseases such as Leber¿s Congenital Amaurosis (LCA) and kidney diseases such as nephronophthisis. Arl6 has been found mutated in Bardet Biedl Syndrome, another pleiotropic ciliary disease. In the proposed interdisciplinary project I want to explore the function of the protein network of Arl2/3 and Arl6 by a combination of biochemical, biophysical and structural methods and use the knowledge obtained to probe their function in live cells. As with other subfamily proteins of the Ras superfamily which have been found to mediate similar biological functions I want to derive a basic understanding of the function of Arl proteins and how it relates to the development and function of the ciliary organelle and how they contribute to ciliary diseases. The molecules in the focus of the project are: the GTP-binding proteins Arl2, 3, 6; RP2, an Arl3GAP mutated in Retinitis pigmentosa; Regulators of Arl2 and 3; PDE¿ and HRG4, effectors of Arl2/3, which bind lipidated proteins; RPGR, mutated in Retinitis pigmentosa, an interactor of PDE¿; RPGRIP and RPGRIPL, interactors of RPGR mutated in LCA and other ciliopathies; Nephrocystin, mutated in nephronophthisis, an interactor of RPGRIP and Arl6, mutated in Bardet Biedl Syndrome, and the BBS complex. The working hypothesis is that Arl protein network(s) mediate ciliary transport processes and that the GTP switch cycle of Arl proteins is an important element of regulation of these processes.
Max ERC Funding
2 434 400 €
Duration
Start date: 2011-04-01, End date: 2016-03-31
Project acronym assemblyNMR
Project 3D structures of bacterial supramolecular assemblies by solid-state NMR
Researcher (PI) Adam Lange
Host Institution (HI) FORSCHUNGSVERBUND BERLIN EV
Call Details Starting Grant (StG), LS1, ERC-2013-StG
Summary Supramolecular assemblies – formed by the self-assembly of hundreds of protein subunits – are part of bacterial nanomachines involved in key cellular processes. Important examples in pathogenic bacteria are pili and type 3 secretion systems (T3SS) that mediate adhesion to host cells and injection of virulence proteins. Structure determination at atomic resolution of such assemblies by standard techniques such as X-ray crystallography or solution NMR is severely limited: Intact T3SSs or pili cannot be crystallized and are also inherently insoluble. Cryo-electron microscopy techniques have recently made it possible to obtain low- and medium-resolution models, but atomic details have not been accessible at the resolution obtained in these studies, leading sometimes to inaccurate models.
I propose to use solid-state NMR (ssNMR) to fill this knowledge-gap. I could recently show that ssNMR on in vitro preparations of Salmonella T3SS needles constitutes a powerful approach to study the structure of this virulence factor. Our integrated approach also included results from electron microscopy and modeling as well as in vivo assays (Loquet et al., Nature 2012). This is the foundation of this application. I propose to extend ssNMR methodology to tackle the structures of even larger or more complex homo-oligomeric assemblies with up to 200 residues per monomeric subunit. We will apply such techniques to address the currently unknown 3D structures of type I pili and cytoskeletal bactofilin filaments. Furthermore, I want to develop strategies to directly study assemblies in a native-like setting. As a first application, I will study the 3D structure of T3SS needles when they are complemented with intact T3SSs purified from Salmonella or Shigella. The ultimate goal of this proposal is to establish ssNMR as a generally applicable method that allows solving the currently unknown structures of bacterial supramolecular assemblies at atomic resolution.
Summary
Supramolecular assemblies – formed by the self-assembly of hundreds of protein subunits – are part of bacterial nanomachines involved in key cellular processes. Important examples in pathogenic bacteria are pili and type 3 secretion systems (T3SS) that mediate adhesion to host cells and injection of virulence proteins. Structure determination at atomic resolution of such assemblies by standard techniques such as X-ray crystallography or solution NMR is severely limited: Intact T3SSs or pili cannot be crystallized and are also inherently insoluble. Cryo-electron microscopy techniques have recently made it possible to obtain low- and medium-resolution models, but atomic details have not been accessible at the resolution obtained in these studies, leading sometimes to inaccurate models.
I propose to use solid-state NMR (ssNMR) to fill this knowledge-gap. I could recently show that ssNMR on in vitro preparations of Salmonella T3SS needles constitutes a powerful approach to study the structure of this virulence factor. Our integrated approach also included results from electron microscopy and modeling as well as in vivo assays (Loquet et al., Nature 2012). This is the foundation of this application. I propose to extend ssNMR methodology to tackle the structures of even larger or more complex homo-oligomeric assemblies with up to 200 residues per monomeric subunit. We will apply such techniques to address the currently unknown 3D structures of type I pili and cytoskeletal bactofilin filaments. Furthermore, I want to develop strategies to directly study assemblies in a native-like setting. As a first application, I will study the 3D structure of T3SS needles when they are complemented with intact T3SSs purified from Salmonella or Shigella. The ultimate goal of this proposal is to establish ssNMR as a generally applicable method that allows solving the currently unknown structures of bacterial supramolecular assemblies at atomic resolution.
Max ERC Funding
1 456 000 €
Duration
Start date: 2014-05-01, End date: 2019-04-30
Project acronym AstroNeuroCrosstalk
Project Astrocyte-Neuronal Crosstalk in Obesity and Diabetes
Researcher (PI) Cristina GARCÍA CÁCERES
Host Institution (HI) HELMHOLTZ ZENTRUM MUENCHEN DEUTSCHES FORSCHUNGSZENTRUM FUER GESUNDHEIT UND UMWELT GMBH
Call Details Starting Grant (StG), LS5, ERC-2017-STG
Summary Despite considerable efforts aimed at prevention and treatment, the prevalence of obesity and type 2 diabetes has increased at an alarming rate worldwide over recent decades. Given the urgent need to develop safe and efficient anti-obesity drugs, the scientific community has to intensify efforts to better understand the mechanisms involved in the pathogenesis of obesity. Based on human genome-wide association studies and targeted mouse mutagenesis models, it has recently emerged that the brain controls most aspects of systemic metabolism and that obesity may be a brain disease. I have recently shown that like neurons, astrocytes also respond to circulating nutrients, and they cooperate with neurons to efficiently regulate energy metabolism. So far, the study of brain circuits controlling energy balance has focused on neurons, ignoring the presence and role of astrocytes. Importantly, our studies were the first to describe that exposure to a high-fat, highsugar (HFHS) diet triggers hypothalamic astrogliosis prior to significant body weight gain, indicating a potentially important role in promoting obesity. Overall, my recent findings suggest a novel model in which astrocytes are actively involved in the central nervous system (CNS) control of metabolism, likely including active crosstalk between astrocytes and neurons. To test this hypothetical model, I propose to develop a functional understanding of astroglia-neuronal communication in the CNS control of metabolism focusing on: 1) dissecting the ability of astrocytes to release gliotransmitters to neurons, 2) assessing how astrocytes respond to neuronal activity, and 3) determining if HFHS-induced astrogliosis interrupts this crosstalk and contributes to the development of obesity and type 2 diabetes. These studies aim to uncover the molecular underpinnings of astrocyte-neuron inputs regulating metabolism in health and disease so as to
inspire and enable novel therapeutic strategies to fight diabetes and obesity.
Summary
Despite considerable efforts aimed at prevention and treatment, the prevalence of obesity and type 2 diabetes has increased at an alarming rate worldwide over recent decades. Given the urgent need to develop safe and efficient anti-obesity drugs, the scientific community has to intensify efforts to better understand the mechanisms involved in the pathogenesis of obesity. Based on human genome-wide association studies and targeted mouse mutagenesis models, it has recently emerged that the brain controls most aspects of systemic metabolism and that obesity may be a brain disease. I have recently shown that like neurons, astrocytes also respond to circulating nutrients, and they cooperate with neurons to efficiently regulate energy metabolism. So far, the study of brain circuits controlling energy balance has focused on neurons, ignoring the presence and role of astrocytes. Importantly, our studies were the first to describe that exposure to a high-fat, highsugar (HFHS) diet triggers hypothalamic astrogliosis prior to significant body weight gain, indicating a potentially important role in promoting obesity. Overall, my recent findings suggest a novel model in which astrocytes are actively involved in the central nervous system (CNS) control of metabolism, likely including active crosstalk between astrocytes and neurons. To test this hypothetical model, I propose to develop a functional understanding of astroglia-neuronal communication in the CNS control of metabolism focusing on: 1) dissecting the ability of astrocytes to release gliotransmitters to neurons, 2) assessing how astrocytes respond to neuronal activity, and 3) determining if HFHS-induced astrogliosis interrupts this crosstalk and contributes to the development of obesity and type 2 diabetes. These studies aim to uncover the molecular underpinnings of astrocyte-neuron inputs regulating metabolism in health and disease so as to
inspire and enable novel therapeutic strategies to fight diabetes and obesity.
Max ERC Funding
1 499 938 €
Duration
Start date: 2018-01-01, End date: 2022-12-31
Project acronym ATMMACHINE
Project Structural mechanism of recognition, signaling and resection of DNA double-strand breaks
Researcher (PI) Karl-Peter Hopfner
Host Institution (HI) LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN
Call Details Advanced Grant (AdG), LS1, ERC-2012-ADG_20120314
Summary DNA double-strand breaks are perhaps the most harmful DNA damages and result in carcinogenic chromosome aberrations. Cells protect their genome by activating a complex signaling and repair network, collectively denoted DNA damage response (DDR). A key initial step of the DDR is the activation of the 360 kDa checkpoint kinase ATM (ataxia telangiectasia mutated) by the multifunctional DSB repair factor Mre11-Rad50-Nbs1 (MRN). MRN senses and tethers DSBs, processes DSBs for further resection, and recruits and activates ATM to trigger the DDR. A mechanistic basis for the activities of the core DDR sensor MRN has not been established, despite intense research over the past decade. Our recent breakthroughs on structures of core Mre11-Rad50 and Mre11-Nbs1 complexes enable us now address three central questions to finally clarify the mechanism of MRN in the DDR:
- How does MRN interact with DNA or DNA ends in an ATP dependent manner?
- How do MRN and associated factors such as CtIP process blocked DNA ends?
- How do MRN and DNA activate ATM?
We will employ an innovative structural biology hybrid methods approach by combining X-ray crystallography, electron microscopy and small angle scattering with crosslink mass spectrometry and combine the structure-oriented techniques with validating in vitro and in vivo functional studies. The anticipated outcome will clarify the structural mechanism of one of the most important but enigmatic molecular machineries in maintaining genome stability and also help understand the molecular defects associated with several prominent cancer predisposition and neurodegenerative disorders.
Summary
DNA double-strand breaks are perhaps the most harmful DNA damages and result in carcinogenic chromosome aberrations. Cells protect their genome by activating a complex signaling and repair network, collectively denoted DNA damage response (DDR). A key initial step of the DDR is the activation of the 360 kDa checkpoint kinase ATM (ataxia telangiectasia mutated) by the multifunctional DSB repair factor Mre11-Rad50-Nbs1 (MRN). MRN senses and tethers DSBs, processes DSBs for further resection, and recruits and activates ATM to trigger the DDR. A mechanistic basis for the activities of the core DDR sensor MRN has not been established, despite intense research over the past decade. Our recent breakthroughs on structures of core Mre11-Rad50 and Mre11-Nbs1 complexes enable us now address three central questions to finally clarify the mechanism of MRN in the DDR:
- How does MRN interact with DNA or DNA ends in an ATP dependent manner?
- How do MRN and associated factors such as CtIP process blocked DNA ends?
- How do MRN and DNA activate ATM?
We will employ an innovative structural biology hybrid methods approach by combining X-ray crystallography, electron microscopy and small angle scattering with crosslink mass spectrometry and combine the structure-oriented techniques with validating in vitro and in vivo functional studies. The anticipated outcome will clarify the structural mechanism of one of the most important but enigmatic molecular machineries in maintaining genome stability and also help understand the molecular defects associated with several prominent cancer predisposition and neurodegenerative disorders.
Max ERC Funding
2 498 019 €
Duration
Start date: 2013-05-01, End date: 2018-04-30
Project acronym AttentionCircuits
Project Modulation of neocortical microcircuits for attention
Researcher (PI) Johannes Jakob Letzkus
Host Institution (HI) MAX-PLANCK-GESELLSCHAFT ZUR FORDERUNG DER WISSENSCHAFTEN EV
Call Details Starting Grant (StG), LS5, ERC-2013-StG
Summary At every moment in time, the brain receives a vast amount of sensory information about the environment. This makes attention, the process by which we select currently relevant stimuli for processing and ignore irrelevant input, a fundamentally important brain function. Studies in primates have yielded a detailed description of how attention to a stimulus modifies the responses of neuronal ensembles in visual cortex, but how this modulation is produced mechanistically in the circuit is not well understood. Neuronal circuits comprise a large variety of neuron types, and to gain mechanistic insights, and to treat specific diseases of the nervous system, it is crucial to characterize the contribution of different identified cell types to information processing. Inhibition supplied by a small yet highly diverse set of interneurons controls all aspects of cortical function, and the central hypothesis of this proposal is that differential modulation of genetically-defined interneuron types is a key mechanism of attention in visual cortex. To identify the interneuron types underlying attentional modulation and to investigate how this, in turn, affects computations in the circuit we will use an innovative multidisciplinary approach combining genetic targeting in mice with cutting-edge in vivo 2-photon microscopy-based recordings and selective optogenetic manipulation of activity. Importantly, a key set of experiments will test whether the observed neuronal mechanisms are causally involved in attention at the level of behavior, the ultimate readout of the computations we are interested in. The expected results will provide a detailed, mechanistic dissection of the neuronal basis of attention. Beyond attention, selection of different functional states of the same hard-wired circuit by modulatory input is a fundamental, but poorly understood, phenomenon in the brain, and we predict that our insights will elucidate similar mechanisms in other brain areas and functional contexts.
Summary
At every moment in time, the brain receives a vast amount of sensory information about the environment. This makes attention, the process by which we select currently relevant stimuli for processing and ignore irrelevant input, a fundamentally important brain function. Studies in primates have yielded a detailed description of how attention to a stimulus modifies the responses of neuronal ensembles in visual cortex, but how this modulation is produced mechanistically in the circuit is not well understood. Neuronal circuits comprise a large variety of neuron types, and to gain mechanistic insights, and to treat specific diseases of the nervous system, it is crucial to characterize the contribution of different identified cell types to information processing. Inhibition supplied by a small yet highly diverse set of interneurons controls all aspects of cortical function, and the central hypothesis of this proposal is that differential modulation of genetically-defined interneuron types is a key mechanism of attention in visual cortex. To identify the interneuron types underlying attentional modulation and to investigate how this, in turn, affects computations in the circuit we will use an innovative multidisciplinary approach combining genetic targeting in mice with cutting-edge in vivo 2-photon microscopy-based recordings and selective optogenetic manipulation of activity. Importantly, a key set of experiments will test whether the observed neuronal mechanisms are causally involved in attention at the level of behavior, the ultimate readout of the computations we are interested in. The expected results will provide a detailed, mechanistic dissection of the neuronal basis of attention. Beyond attention, selection of different functional states of the same hard-wired circuit by modulatory input is a fundamental, but poorly understood, phenomenon in the brain, and we predict that our insights will elucidate similar mechanisms in other brain areas and functional contexts.
Max ERC Funding
1 466 505 €
Duration
Start date: 2014-02-01, End date: 2019-01-31
