Project acronym BRAINCANNABINOIDS
Project Understanding the molecular blueprint and functional complexity of the endocannabinoid metabolome in the brain
Researcher (PI) István Katona
Host Institution (HI) INSTITUTE OF EXPERIMENTAL MEDICINE - HUNGARIAN ACADEMY OF SCIENCES
Call Details Starting Grant (StG), LS5, ERC-2009-StG
Summary We and others have recently delineated the molecular architecture of a new feedback pathway in brain synapses, which operates as a synaptic circuit breaker. This pathway is supposed to use a group of lipid messengers as retrograde synaptic signals, the so-called endocannabinoids. Although heterogeneous in their chemical structures, these molecules along with the psychoactive compound in cannabis are thought to target the same effector in the brain, the CB1 receptor. However, the molecular catalog of these bioactive lipids and their metabolic enzymes has been expanding rapidly by recent advances in lipidomics and proteomics raising the possibility that these lipids may also serve novel, yet unidentified physiological functions. Thus, the overall aim of our research program is to define the molecular and anatomical organization of these endocannabinoid-mediated pathways and to determine their functional significance. In the present proposal, we will focus on understanding how these novel pathways regulate synaptic and extrasynaptic signaling in hippocampal neurons. Using combination of lipidomic, genetic and high-resolution anatomical approaches, we will identify distinct chemical species of endocannabinoids and will show how their metabolic enzymes are segregated into different subcellular compartments in cell type- and synapse-specific manner. Subsequently, we will use genetically encoded gain-of-function, loss-of-function and reporter constructs in imaging experiments and electrophysiological recordings to gain insights into the diverse tasks that these new pathways serve in synaptic transmission and extrasynaptic signal processing. Our proposed experiments will reveal fundamental principles of intercellular and intracellular endocannabinoid signaling in the brain.
Summary
We and others have recently delineated the molecular architecture of a new feedback pathway in brain synapses, which operates as a synaptic circuit breaker. This pathway is supposed to use a group of lipid messengers as retrograde synaptic signals, the so-called endocannabinoids. Although heterogeneous in their chemical structures, these molecules along with the psychoactive compound in cannabis are thought to target the same effector in the brain, the CB1 receptor. However, the molecular catalog of these bioactive lipids and their metabolic enzymes has been expanding rapidly by recent advances in lipidomics and proteomics raising the possibility that these lipids may also serve novel, yet unidentified physiological functions. Thus, the overall aim of our research program is to define the molecular and anatomical organization of these endocannabinoid-mediated pathways and to determine their functional significance. In the present proposal, we will focus on understanding how these novel pathways regulate synaptic and extrasynaptic signaling in hippocampal neurons. Using combination of lipidomic, genetic and high-resolution anatomical approaches, we will identify distinct chemical species of endocannabinoids and will show how their metabolic enzymes are segregated into different subcellular compartments in cell type- and synapse-specific manner. Subsequently, we will use genetically encoded gain-of-function, loss-of-function and reporter constructs in imaging experiments and electrophysiological recordings to gain insights into the diverse tasks that these new pathways serve in synaptic transmission and extrasynaptic signal processing. Our proposed experiments will reveal fundamental principles of intercellular and intracellular endocannabinoid signaling in the brain.
Max ERC Funding
1 638 000 €
Duration
Start date: 2009-11-01, End date: 2014-10-31
Project acronym CholAminCo
Project Synergy and antagonism of cholinergic and dopaminergic systems in associative learning
Researcher (PI) Balazs Gyoergy HANGYA
Host Institution (HI) INSTITUTE OF EXPERIMENTAL MEDICINE - HUNGARIAN ACADEMY OF SCIENCES
Call Details Starting Grant (StG), LS5, ERC-2016-STG
Summary Neuromodulators such as acetylcholine and dopamine are able to rapidly reprogram neuronal information processing and dynamically change brain states. Degeneration or dysfunction of cholinergic and dopaminergic neurons can lead to neuropsychiatric conditions like schizophrenia and addiction or cognitive diseases such as Alzheimer’s. Neuromodulatory systems control overlapping cognitive processes and often have similar modes of action; therefore it is important to reveal cooperation and competition between different systems to understand their unique contributions to cognitive functions like learning, memory and attention. This is only possible by direct comparison, which necessitates monitoring multiple neuromodulatory systems under identical experimental conditions. Moreover, simultaneous recording of different neuromodulatory cell types goes beyond phenomenological description of similarities and differences by revealing the underlying correlation structure at the level of action potential timing. However, such data allowing direct comparison of neuromodulatory actions are still sparse. As a first step to bridge this gap, I propose to elucidate the unique versus complementary roles of two “classical” neuromodulatory systems, the cholinergic and dopaminergic projection system implicated in various cognitive functions including associative learning and plasticity. First, we will record optogenetically identified cholinergic and dopaminergic neurons simultaneously using chronic extracellular recording in mice undergoing classical and operant conditioning. Second, we will determine the postsynaptic impact of cholinergic and dopaminergic neurons by manipulating them both separately and simultaneously while recording consequential changes in cortical neuronal activity and learning behaviour. These experiments will reveal how major neuromodulatory systems interact to mediate similar or different aspects of the same cognitive functions.
Summary
Neuromodulators such as acetylcholine and dopamine are able to rapidly reprogram neuronal information processing and dynamically change brain states. Degeneration or dysfunction of cholinergic and dopaminergic neurons can lead to neuropsychiatric conditions like schizophrenia and addiction or cognitive diseases such as Alzheimer’s. Neuromodulatory systems control overlapping cognitive processes and often have similar modes of action; therefore it is important to reveal cooperation and competition between different systems to understand their unique contributions to cognitive functions like learning, memory and attention. This is only possible by direct comparison, which necessitates monitoring multiple neuromodulatory systems under identical experimental conditions. Moreover, simultaneous recording of different neuromodulatory cell types goes beyond phenomenological description of similarities and differences by revealing the underlying correlation structure at the level of action potential timing. However, such data allowing direct comparison of neuromodulatory actions are still sparse. As a first step to bridge this gap, I propose to elucidate the unique versus complementary roles of two “classical” neuromodulatory systems, the cholinergic and dopaminergic projection system implicated in various cognitive functions including associative learning and plasticity. First, we will record optogenetically identified cholinergic and dopaminergic neurons simultaneously using chronic extracellular recording in mice undergoing classical and operant conditioning. Second, we will determine the postsynaptic impact of cholinergic and dopaminergic neurons by manipulating them both separately and simultaneously while recording consequential changes in cortical neuronal activity and learning behaviour. These experiments will reveal how major neuromodulatory systems interact to mediate similar or different aspects of the same cognitive functions.
Max ERC Funding
1 499 463 €
Duration
Start date: 2017-05-01, End date: 2022-04-30
Project acronym DeCode
Project Dendrites and memory: role of dendritic spikes in information coding by hippocampal CA3 pyramidal neurons
Researcher (PI) Judit MAKARA
Host Institution (HI) INSTITUTE OF EXPERIMENTAL MEDICINE - HUNGARIAN ACADEMY OF SCIENCES
Call Details Consolidator Grant (CoG), LS5, ERC-2017-COG
Summary The hippocampus is essential for building episodic memories. Coding of locations, contexts or events in the hippocampus is based on the correlated activity of neuronal ensembles; however, the mechanisms promoting the recruitment of individual neurons into information-coding ensembles are poorly understood.
In particular, the recurrent synaptic network of pyramidal cells (PCs) in the hippocampal CA3 area, receiving external inputs from the entorhinal cortex and the dentate gyrus, is thought to be essential for associative memory. Current models of the associative functions of CA3 are mainly based on plasticity of these synaptic connections. Recent work by us and others however suggests that active, voltage-dependent properties of CA3PC dendrites may also promote ensemble functions. Dendritic voltage-dependent ion channels allow nonlinear amplification of spatiotemporally correlated synaptic inputs (such as those produced by ensemble activity) and can even generate local dendritic spikes, which may elicit specific action potential patterns and induce synaptic plasticity. Furthermore, dendritic processing may be modulated by activity-dependent regulation of dendritic ion channels. However, still little is known about the active properties of CA3PC dendrites and their functions during spatial coding or memory tasks.
The general aim of my research program is to understand the cellular mechanisms that underlie the formation of hippocampal memory-coding neuronal ensembles. Specifically, we will test the hypothesis that active input integration by dendrites of individual CA3PCs plays an important role in their recruitment into specific context-coding ensembles. By combining in vitro (patch-clamp electrophysiology and two-photon (2P) microscopy in slices) and in vivo (2P imaging and activity-dependent labelling in behaving rodents) approaches, we will provide an in-depth understanding of the dendritic components contributing to the generation of the CA3 ensemble code.
Summary
The hippocampus is essential for building episodic memories. Coding of locations, contexts or events in the hippocampus is based on the correlated activity of neuronal ensembles; however, the mechanisms promoting the recruitment of individual neurons into information-coding ensembles are poorly understood.
In particular, the recurrent synaptic network of pyramidal cells (PCs) in the hippocampal CA3 area, receiving external inputs from the entorhinal cortex and the dentate gyrus, is thought to be essential for associative memory. Current models of the associative functions of CA3 are mainly based on plasticity of these synaptic connections. Recent work by us and others however suggests that active, voltage-dependent properties of CA3PC dendrites may also promote ensemble functions. Dendritic voltage-dependent ion channels allow nonlinear amplification of spatiotemporally correlated synaptic inputs (such as those produced by ensemble activity) and can even generate local dendritic spikes, which may elicit specific action potential patterns and induce synaptic plasticity. Furthermore, dendritic processing may be modulated by activity-dependent regulation of dendritic ion channels. However, still little is known about the active properties of CA3PC dendrites and their functions during spatial coding or memory tasks.
The general aim of my research program is to understand the cellular mechanisms that underlie the formation of hippocampal memory-coding neuronal ensembles. Specifically, we will test the hypothesis that active input integration by dendrites of individual CA3PCs plays an important role in their recruitment into specific context-coding ensembles. By combining in vitro (patch-clamp electrophysiology and two-photon (2P) microscopy in slices) and in vivo (2P imaging and activity-dependent labelling in behaving rodents) approaches, we will provide an in-depth understanding of the dendritic components contributing to the generation of the CA3 ensemble code.
Max ERC Funding
1 990 314 €
Duration
Start date: 2018-06-01, End date: 2023-05-31
Project acronym FRONTHAL
Project Specificity of cortico-thalamic interactions and its role in frontal cortical functions
Researcher (PI) Laszlo ACSADY
Host Institution (HI) INSTITUTE OF EXPERIMENTAL MEDICINE - HUNGARIAN ACADEMY OF SCIENCES
Call Details Advanced Grant (AdG), LS5, ERC-2016-ADG
Summary Frontal cortical areas are responsible for a wide range of executive and cognitive functions. Frontal cortices communicate with the thalamus via bidirectional pathways and these connections are indispensable for frontal cortical operations. Still, we have very little information about the specificity of connections, synaptic interactions and plasticity between frontal cortex and thalamus and the roles of these interactions in frontal cortical functions.
In the present proposal, we will test the hypothesis that frontal cortical areas developed a highly specialized connectivity pattern with the thalamus. This supports unique interactions between the cortex and the thalamus according to the specific requirements of frontal cortical activity, including experience-dependent plastic changes.
The project will use cell type-specific viral tracing in mice and 3D electron microscopic reconstructions in mice and humans to identify circuit motifs that are evolutionarily conserved, yet, still specific to fronto-thalamic pathways. The physiological approach will employ in vivo optogenetics combined with intra-, juxta- and extracellular recordings. We will perform behavioral experiments by bidirectional modulation of well-defined elements in the network, in learning paradigms, which depend on the integrity of frontal cortex.
The project is the first systematic approach which aims to understand the nature of interaction between the frontal cortex and the thalamus. It will not only fill the tremendous gap in our knowledge regarding these pathways but will help us elucidate the functional organization of non-sensory thalamus in general.
Frontal cortices are involved in a wide range of major neurological disorders (e.g. Parkinson’s disease, epilepsy, schizophrenia, chronic pain) which affect executive functions and involve fronto-thalamic pathways. We believe that understanding fronto-thalamic interactions will lead to fundamentally novel insight into the nature of these diseases.
Summary
Frontal cortical areas are responsible for a wide range of executive and cognitive functions. Frontal cortices communicate with the thalamus via bidirectional pathways and these connections are indispensable for frontal cortical operations. Still, we have very little information about the specificity of connections, synaptic interactions and plasticity between frontal cortex and thalamus and the roles of these interactions in frontal cortical functions.
In the present proposal, we will test the hypothesis that frontal cortical areas developed a highly specialized connectivity pattern with the thalamus. This supports unique interactions between the cortex and the thalamus according to the specific requirements of frontal cortical activity, including experience-dependent plastic changes.
The project will use cell type-specific viral tracing in mice and 3D electron microscopic reconstructions in mice and humans to identify circuit motifs that are evolutionarily conserved, yet, still specific to fronto-thalamic pathways. The physiological approach will employ in vivo optogenetics combined with intra-, juxta- and extracellular recordings. We will perform behavioral experiments by bidirectional modulation of well-defined elements in the network, in learning paradigms, which depend on the integrity of frontal cortex.
The project is the first systematic approach which aims to understand the nature of interaction between the frontal cortex and the thalamus. It will not only fill the tremendous gap in our knowledge regarding these pathways but will help us elucidate the functional organization of non-sensory thalamus in general.
Frontal cortices are involved in a wide range of major neurological disorders (e.g. Parkinson’s disease, epilepsy, schizophrenia, chronic pain) which affect executive functions and involve fronto-thalamic pathways. We believe that understanding fronto-thalamic interactions will lead to fundamentally novel insight into the nature of these diseases.
Max ERC Funding
1 597 575 €
Duration
Start date: 2017-09-01, End date: 2022-08-31
Project acronym FunctionalProteomics
Project Proteomic fingerprinting of functionally characterized single synapses
Researcher (PI) Zoltan NUSSER
Host Institution (HI) INSTITUTE OF EXPERIMENTAL MEDICINE - HUNGARIAN ACADEMY OF SCIENCES
Call Details Advanced Grant (AdG), LS5, ERC-2017-ADG
Summary Our astonishing cognitive abilities are the consequence of complex connectivity within our neuronal networks and the large functional diversity of excitable nerve cells and their synapses. Investigations over the past half a century revealed dramatic diversity in shape, size and functional properties among synapses established by distinct cell types in different brain regions and demonstrated that the functional differences are partly due to different molecular mechanisms. However, synaptic diversity is also observed among synapses established by molecularly and morphologically uniform presynaptic cells on molecularly and morphologically uniform postsynaptic cells. Our hypothesis is that quantitative molecular differences underlie the functional diversity of such synapses. We will focus on hippocampal CA1 pyramidal cell (PC) to mGluR1α+ O-LM cell synapses, which show remarkable functional and molecular heterogeneity. In vitro multiple cell patch-clamp recordings followed by quantal analysis will be performed to quantify well-defined biophysical properties of these synapses. The molecular composition of the functionally characterized single synapses will be determined following the development of a novel postembedding immunolocalization method. Correlations between the molecular content and functional properties will be established and genetic up- and downregulation of individual synaptic proteins will be conducted to reveal causal relationships. Finally, correlations of the activity history and the functional properties of the synapses will be established by performing in vivo two-photon Ca2+ imaging in head-fixed behaving animals followed by in vitro functional characterization of their synapses. Our results will reveal quantitative molecular fingerprints of functional properties, allowing us to render dynamic behaviour to billions of synapses when the connectome of the hippocampal circuit is created using array tomography.
Summary
Our astonishing cognitive abilities are the consequence of complex connectivity within our neuronal networks and the large functional diversity of excitable nerve cells and their synapses. Investigations over the past half a century revealed dramatic diversity in shape, size and functional properties among synapses established by distinct cell types in different brain regions and demonstrated that the functional differences are partly due to different molecular mechanisms. However, synaptic diversity is also observed among synapses established by molecularly and morphologically uniform presynaptic cells on molecularly and morphologically uniform postsynaptic cells. Our hypothesis is that quantitative molecular differences underlie the functional diversity of such synapses. We will focus on hippocampal CA1 pyramidal cell (PC) to mGluR1α+ O-LM cell synapses, which show remarkable functional and molecular heterogeneity. In vitro multiple cell patch-clamp recordings followed by quantal analysis will be performed to quantify well-defined biophysical properties of these synapses. The molecular composition of the functionally characterized single synapses will be determined following the development of a novel postembedding immunolocalization method. Correlations between the molecular content and functional properties will be established and genetic up- and downregulation of individual synaptic proteins will be conducted to reveal causal relationships. Finally, correlations of the activity history and the functional properties of the synapses will be established by performing in vivo two-photon Ca2+ imaging in head-fixed behaving animals followed by in vitro functional characterization of their synapses. Our results will reveal quantitative molecular fingerprints of functional properties, allowing us to render dynamic behaviour to billions of synapses when the connectome of the hippocampal circuit is created using array tomography.
Max ERC Funding
2 498 750 €
Duration
Start date: 2018-10-01, End date: 2023-09-30
Project acronym INTERIMPACT
Project Impact of identified interneurons on cellular network mechanisms in the human and rodent neocortex
Researcher (PI) Gábor Tamás
Host Institution (HI) SZEGEDI TUDOMANYEGYETEM
Call Details Advanced Grant (AdG), LS5, ERC-2010-AdG_20100317
Summary This application addresses mechanisms linking the activity of single neurons with network events by defining the function of identified cell types in the cerebral cortex. The key hypotheses emerged from our experiments and propose that neurogliaform cells and axo-axonic cells achieve their function in the cortex through extreme forms of unspecificity and specificity, respectively. The project capitalizes on our discovery that neurogliaform cells reach GABAA and GABAB receptors on target cells through unitary volume transmission going beyond the classical theory which states that single cortical neurons act in or around synaptic junctions. We propose that the spatial unspecificity of neurotransmitter action leads to unprecedented functional capabilities for a single neuron simultaneously acting on neuronal, glial and vascular components of the surrounding area allowing neurogliaform cells to synchronize metabolic demand and supply in microcircuits. In contrast, axo-axonic cells represent extreme spatial specificity in the brain: terminals of axo-axonic cells exclusively target the axon initial segment of pyramidal neurons. Axo-axonic cells were considered as the most potent inhibitory neurons of the cortex. However, our experiments suggested that axo-axonic cells can be the most powerful excitatory neurons known to date by triggering complex network events. Our unprecedented recordings in the human cortex show that axo-axonic cells are crucial in activating functional assemblies which were implicated in higher order cognitive representations. We aim to define interactions between active cortical networks and axo-axonic cell triggered assemblies with an emphasis on mechanisms modulated by neurogliaform cells and commonly prescribed drugs.
Summary
This application addresses mechanisms linking the activity of single neurons with network events by defining the function of identified cell types in the cerebral cortex. The key hypotheses emerged from our experiments and propose that neurogliaform cells and axo-axonic cells achieve their function in the cortex through extreme forms of unspecificity and specificity, respectively. The project capitalizes on our discovery that neurogliaform cells reach GABAA and GABAB receptors on target cells through unitary volume transmission going beyond the classical theory which states that single cortical neurons act in or around synaptic junctions. We propose that the spatial unspecificity of neurotransmitter action leads to unprecedented functional capabilities for a single neuron simultaneously acting on neuronal, glial and vascular components of the surrounding area allowing neurogliaform cells to synchronize metabolic demand and supply in microcircuits. In contrast, axo-axonic cells represent extreme spatial specificity in the brain: terminals of axo-axonic cells exclusively target the axon initial segment of pyramidal neurons. Axo-axonic cells were considered as the most potent inhibitory neurons of the cortex. However, our experiments suggested that axo-axonic cells can be the most powerful excitatory neurons known to date by triggering complex network events. Our unprecedented recordings in the human cortex show that axo-axonic cells are crucial in activating functional assemblies which were implicated in higher order cognitive representations. We aim to define interactions between active cortical networks and axo-axonic cell triggered assemblies with an emphasis on mechanisms modulated by neurogliaform cells and commonly prescribed drugs.
Max ERC Funding
2 391 695 €
Duration
Start date: 2011-06-01, End date: 2017-05-31
Project acronym MicroCONtACT
Project Microglial control of neuronal activity in the healthy and the injured brain
Researcher (PI) Adam DENES
Host Institution (HI) INSTITUTE OF EXPERIMENTAL MEDICINE - HUNGARIAN ACADEMY OF SCIENCES
Call Details Consolidator Grant (CoG), LS5, ERC-2016-COG
Summary Microglia are the main immune cells of the brain, but their role in brain injury is highly controversial due to the difficulties in selectively manipulating and imaging microglial actions in real time. Specifically, it is unclear whether microglia control neuronal survival after injury via shaping the activity of complex neuronal networks in vivo. To this end, we have combined fast in vivo two-photon imaging of neuronal calcium responses with selective microglial manipulation for the first time. Our data suggest that microglia constantly monitor and control neuronal network activity and these actions are essential to limit excitotoxicity and neuronal death after acute brain injury. We also identify microglia as key regulators of spreading depolarization in vivo. However, the underlying mechanisms remained unexplored. Here, I propose that microglia control neuronal excitability and based on preliminary data I set out to investigate how this occurs. We will combine selective, CSF1R-mediated microglia depletion with advanced neurophysiological methods such as in vivo calcium imaging and intracranial EEG for the first time, to reveal how microglia shape activity of complex neuronal networks in the healthy and the injured brain. Then, we will study microglia-neuron interactions from the network level to nanoscale level using in vivo two-photon imaging and super-resolution microscopy. We will apply novel chemogenic and optogenetic approaches to manipulate microglia in real time, assess their role in neuronal activity changes and investigate the molecular mechanisms in vitro and in vivo. Our unpublished data also suggest that inflammation – a key contributor to brain diseases – could disrupt microglia-neuron signaling and we set out to investigate the underlying mechanisms. By using state-of the-art research tools that had not been applied previously in this context, our studies are likely to reveal novel pathophysiological mechanisms relevant for common brain diseases.
Summary
Microglia are the main immune cells of the brain, but their role in brain injury is highly controversial due to the difficulties in selectively manipulating and imaging microglial actions in real time. Specifically, it is unclear whether microglia control neuronal survival after injury via shaping the activity of complex neuronal networks in vivo. To this end, we have combined fast in vivo two-photon imaging of neuronal calcium responses with selective microglial manipulation for the first time. Our data suggest that microglia constantly monitor and control neuronal network activity and these actions are essential to limit excitotoxicity and neuronal death after acute brain injury. We also identify microglia as key regulators of spreading depolarization in vivo. However, the underlying mechanisms remained unexplored. Here, I propose that microglia control neuronal excitability and based on preliminary data I set out to investigate how this occurs. We will combine selective, CSF1R-mediated microglia depletion with advanced neurophysiological methods such as in vivo calcium imaging and intracranial EEG for the first time, to reveal how microglia shape activity of complex neuronal networks in the healthy and the injured brain. Then, we will study microglia-neuron interactions from the network level to nanoscale level using in vivo two-photon imaging and super-resolution microscopy. We will apply novel chemogenic and optogenetic approaches to manipulate microglia in real time, assess their role in neuronal activity changes and investigate the molecular mechanisms in vitro and in vivo. Our unpublished data also suggest that inflammation – a key contributor to brain diseases – could disrupt microglia-neuron signaling and we set out to investigate the underlying mechanisms. By using state-of the-art research tools that had not been applied previously in this context, our studies are likely to reveal novel pathophysiological mechanisms relevant for common brain diseases.
Max ERC Funding
2 000 000 €
Duration
Start date: 2017-04-01, End date: 2022-03-31
Project acronym MOLECMAP
Project Quantitative Molecular Map of the Neuronal Surface
Researcher (PI) Zoltan Jozsef Nusser
Host Institution (HI) INSTITUTE OF EXPERIMENTAL MEDICINE - HUNGARIAN ACADEMY OF SCIENCES
Call Details Advanced Grant (AdG), LS5, ERC-2011-ADG_20110310
Summary The most fundamental roles of nerve cells are the detection of chemical neurotransmitters to generate synaptic potentials; the summation of these potentials to create their output signals; and the consequent release of their own neurotransmitter molecules. All of these functions require the orchestrated work of hundreds of molecules targeted to specialized regions of the cells. In nerve cells, more than in any other cell type, a single molecule could fulfill very different functional roles depending on its subcellular location. For example, dendritic voltage-gated Ca2+ channels play a role in the integration and plasticity of synaptic inputs, whereas the same channels when concentrated in presynaptic active zones are essential for neurotransmitter release. Thus, the function of a protein in nerve cells cannot be understood from its expression or lack of it, but its precise subcellular location, density and molecular environment needs to be determined. The major aim of the present proposal is to create a quantitative molecular map of the surface of hippocampal pyramidal cells (PCs). We will start by examining voltage-gated ion channels due to their pivotal roles in input summation, output generation and neurotransmitter release. We will apply high resolution quantitative molecular neuroanatomical techniques to reveal their densities in 19 different axo-somato-dendritic plasma membrane compartments of CA1 PCs. Functional predictions will be generated using detailed, morphologically realistic multicompartmental PC models with experimentally determined ion channel distributions and densities. Such predictions will be tested by combining in vitro patch-clamp electrophysiology and imaging techniques with correlated light- and electron microscopy. Our results will provide the first quantitative molecular map of the neuronal surface and will reveal new mechanisms that increase the computational power and the functional diversity of nerve cells.
Summary
The most fundamental roles of nerve cells are the detection of chemical neurotransmitters to generate synaptic potentials; the summation of these potentials to create their output signals; and the consequent release of their own neurotransmitter molecules. All of these functions require the orchestrated work of hundreds of molecules targeted to specialized regions of the cells. In nerve cells, more than in any other cell type, a single molecule could fulfill very different functional roles depending on its subcellular location. For example, dendritic voltage-gated Ca2+ channels play a role in the integration and plasticity of synaptic inputs, whereas the same channels when concentrated in presynaptic active zones are essential for neurotransmitter release. Thus, the function of a protein in nerve cells cannot be understood from its expression or lack of it, but its precise subcellular location, density and molecular environment needs to be determined. The major aim of the present proposal is to create a quantitative molecular map of the surface of hippocampal pyramidal cells (PCs). We will start by examining voltage-gated ion channels due to their pivotal roles in input summation, output generation and neurotransmitter release. We will apply high resolution quantitative molecular neuroanatomical techniques to reveal their densities in 19 different axo-somato-dendritic plasma membrane compartments of CA1 PCs. Functional predictions will be generated using detailed, morphologically realistic multicompartmental PC models with experimentally determined ion channel distributions and densities. Such predictions will be tested by combining in vitro patch-clamp electrophysiology and imaging techniques with correlated light- and electron microscopy. Our results will provide the first quantitative molecular map of the neuronal surface and will reveal new mechanisms that increase the computational power and the functional diversity of nerve cells.
Max ERC Funding
2 494 446 €
Duration
Start date: 2012-02-01, End date: 2017-01-31
Project acronym nanoAXON
Project Nano-physiology of small glutamatergic axon terminals
Researcher (PI) Janos SZABADICS
Host Institution (HI) INSTITUTE OF EXPERIMENTAL MEDICINE - HUNGARIAN ACADEMY OF SCIENCES
Call Details Consolidator Grant (CoG), LS5, ERC-2017-COG
Summary We will reveal the neuronal mechanisms of fundamental hippocampal and axonal functions using direct patch clamp recordings from the small axon terminals of the major glutamatergic afferent and efferent pathways of the dentate gyrus region. Specifically, we will investigate the intrinsic axonal properties and unitary synaptic functions of the axons in the dentate gyrus that originate from the entorhinal cortex, the hilar mossy cells and the hypothalamic supramammillary nucleus. The fully controlled access to the activity of individual neuronal projections allows us to address the crucial questions how upstream regions of the dentate gyrus convey physiologically relevant spike activities and how these activities are translated to unitary synaptic responses in individual dentate gyrus neurons. The successful information transfers by these mechanisms ultimately generate specific dentate gyrus cell activity that contributes to hippocampal memory functions. Comprehensive mechanistic insights are essential to understand the impacts of the activity patterns associated with fundamental physiological functions and attainable with the necessary details only with direct recordings from individual axons. For example, these knowledge are necessary to understand how single cell activities in the entorhinal cortex (carrying primary spatial information) contribute to spatial representation in the dentate (i.e. place fields). Furthermore, because the size of these recorded axon terminals matches that of the majority of cortical synapses, our discoveries will demonstrate basic biophysical and neuronal principles of axonal signaling that are relevant for universal neuronal functions throughout the CNS. Thus, an exceptional repertoire of methods, including recording from anatomically identified individual small axon terminals, voltage- and calcium imaging and computational simulations, places us in an advantaged position for revealing unprecedented information about neuronal circuits.
Summary
We will reveal the neuronal mechanisms of fundamental hippocampal and axonal functions using direct patch clamp recordings from the small axon terminals of the major glutamatergic afferent and efferent pathways of the dentate gyrus region. Specifically, we will investigate the intrinsic axonal properties and unitary synaptic functions of the axons in the dentate gyrus that originate from the entorhinal cortex, the hilar mossy cells and the hypothalamic supramammillary nucleus. The fully controlled access to the activity of individual neuronal projections allows us to address the crucial questions how upstream regions of the dentate gyrus convey physiologically relevant spike activities and how these activities are translated to unitary synaptic responses in individual dentate gyrus neurons. The successful information transfers by these mechanisms ultimately generate specific dentate gyrus cell activity that contributes to hippocampal memory functions. Comprehensive mechanistic insights are essential to understand the impacts of the activity patterns associated with fundamental physiological functions and attainable with the necessary details only with direct recordings from individual axons. For example, these knowledge are necessary to understand how single cell activities in the entorhinal cortex (carrying primary spatial information) contribute to spatial representation in the dentate (i.e. place fields). Furthermore, because the size of these recorded axon terminals matches that of the majority of cortical synapses, our discoveries will demonstrate basic biophysical and neuronal principles of axonal signaling that are relevant for universal neuronal functions throughout the CNS. Thus, an exceptional repertoire of methods, including recording from anatomically identified individual small axon terminals, voltage- and calcium imaging and computational simulations, places us in an advantaged position for revealing unprecedented information about neuronal circuits.
Max ERC Funding
1 994 025 €
Duration
Start date: 2018-04-01, End date: 2023-03-31
Project acronym NETWORK EVOLUTION
Project Integrated evolutionary analyses of genetic and drug interaction networks in yeast
Researcher (PI) Csaba Pal
Host Institution (HI) SZEGEDI BIOLOGIAI KUTATOKOZPONT
Call Details Starting Grant (StG), LS5, ERC-2007-StG
Summary The ability of cellular systems to adapt to genetic and environmental perturbations is a fundamental but poorly understood process both at the molecular and evolutionary level. There are both physiological and evolutionary reasonings why mutations often have limited impact on cellular growth. First, perturbations that hit one target often have no effect on the overall performance of a complex system (such as metabolic networks), as perturbations can be adjusted by reorganizing fluxes in metabolic networks, or changing regulation and expression of genes. Second, due to the fast evolvability of microbes, the effect of a perturbation can readily be alleviated by the evolution of compensatory mutations at other sites of the network. Understanding the extent of intrinsic and evolved robustness in cellular systems demands integrated analyses that combine functional genomics and computational systems biology with microbial evolutionary experiments. In collaboration with several leading research teams in the field, we plan to investigate the following issues. First, we will ask how accurately genome-scale metabolic network models can predict the impact of genetic deletions and other non-heritable perturbations. Second, to understand how the impact of genetic and drug perturbations can be mitigated during evolution, we will pursue a large-scale lab evolutionary protocol, and compare the results with predictions of computational models. Our work may suggest avenues of research on the general rules of acquired drug resistance in microbes.
Summary
The ability of cellular systems to adapt to genetic and environmental perturbations is a fundamental but poorly understood process both at the molecular and evolutionary level. There are both physiological and evolutionary reasonings why mutations often have limited impact on cellular growth. First, perturbations that hit one target often have no effect on the overall performance of a complex system (such as metabolic networks), as perturbations can be adjusted by reorganizing fluxes in metabolic networks, or changing regulation and expression of genes. Second, due to the fast evolvability of microbes, the effect of a perturbation can readily be alleviated by the evolution of compensatory mutations at other sites of the network. Understanding the extent of intrinsic and evolved robustness in cellular systems demands integrated analyses that combine functional genomics and computational systems biology with microbial evolutionary experiments. In collaboration with several leading research teams in the field, we plan to investigate the following issues. First, we will ask how accurately genome-scale metabolic network models can predict the impact of genetic deletions and other non-heritable perturbations. Second, to understand how the impact of genetic and drug perturbations can be mitigated during evolution, we will pursue a large-scale lab evolutionary protocol, and compare the results with predictions of computational models. Our work may suggest avenues of research on the general rules of acquired drug resistance in microbes.
Max ERC Funding
1 280 000 €
Duration
Start date: 2008-07-01, End date: 2013-06-30
