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Funding
Funding
HFSP supports novel, innovative and interdisciplinary basic research focused on the complex mechanisms of living organisms. A clear emphasis is placed on novel collaborations that bring biologists together to focus on problems at the frontier of the life sciences.
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Awardees
Awardees
In this section you find information about the awardees in the HFSP scientific programs. This includes a searchable database of HFSP awardees, information on the HFSP Nakasone Award and other achievements by HFSP awardees.
- News & Impact
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Events
Events
HFSP promotes and participates in several events every year. We are committed to bringing together the scientific community and forging new opportunities to network and have scientific discussions that help to create bridges and partnerships for the future of frontier science.
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About
About
The Human Frontier Science Program is a program of funding for frontier research in the life sciences. It is implemented by the International Human Frontier Science Program Organization (HFSPO) with its office in Strasbourg. Here you can find all you need to know about the HFSPO.
Awardees
2024
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Long-Term Fellowships - LTF
Decoding mechano-epigenetic memories in tissue regeneration
HUSSIEN Amro (SUDAN)
Department of Cell and Tissue Dynamics - Max Planck Institute for molecular Biomedicine - Muenster - GERMANY
WICKSTRÖM Sara (Host supervisor)
Tissue regeneration is a life-essential process that requires efficient re-establishment of functional tissue architecture and its mechanical properties. However, as an evolutionary trade-off for terrestrial life, skin wounds in large mammals typically heal by fibrosis which can evolve into dysfunctional scars. Strategies to promote regenerative rather than maladaptive fibrotic healing have been limited, in part due to incomplete understanding of the fundamental mechanisms that derail adequate healing response. There is an emerging appreciation that tissue-resident cells accumulate “epigenetic memories” of past “stressful” experiences. Persistent scarring profoundly alters the mechanical cues of cellular niches, namely the stiffness and viscoelastic properties. While it is known that mechanical signals are critical for scarring behavior, the notion of epigenetic memories triggered by mechanical stress and impacting mechanochemical feedback loops in tissue regeneration has not been addressed? It remains unknown if mechanical memories can be bestowed in cells in vivo, what are the molecular mechanisms, and finally what are the pathophysiological consequences of such effects? Here, I will investigate how various skin stem cell populations respond to viscoelastic mechanical cues in scarring, and whether they have capacity to learn from past experiences by forming mechano-epigenetic memories to impact future healing outcomes. I will: - Map the mechano-epigenomic landscape in scarring using integrative atomic force microscopy and spatial ATAC-seq and CUT & Tag. - Elucidate how mechanical memories are induced and recalled in mouse models of skin scarring. - Dissect mechanistically how mechano-memory reshapes healing outcomes using in utero lentivirus overexpression of identified mechanical memory peaks. Central hypotheses: I hypothesize that: - Altered niche viscoelasticity in fibrotic scarring triggers epigenetic re-wiring of cells. - Skin cells in mechanically-stressed niches acquire “geographically” distributed mechanical memories, which can be decoupled from inflammatory memories. - Skin cells imprint acquired mechano-memory in their nuclear architecture and surrounding matrix. - Mechanical memory is sufficient to induce maladaptive scarring and to accentuate subsequent healing responses. Experimental systems: I will use an interdisciplinary approach combining in vivo mouse models, state-of-the-art hydrogel engineering and biophysical methods, with data-driven bulk and spatial epigenomics technologies. This perfectly combines my unique expertise in bioengineering and clinical medicine with the world leading expertise of the host lab in stem cell biology and mechanoregulation of chromatin architecture. Conclusions: This project will represent a breakthrough in understanding the molecular basis of mechano-epigenetic memories, and may open avenues for designing new strategies to erase maladaptive memories to drive scarless tissue regeneration.
2024
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Long-Term Fellowships - LTF
Elucidating the role of R-loops in hematopoiesis and bone marrow niche remodeling in aging
JAUREGUI-LOZANO Juan (COLOMBIA)
Structural and Computational Biology - European Molecular Biology Laboratory (EMBL-Heidelberg) - Heidelberg - GERMANY
ZAUGG Judith (Host supervisor)
Hematopoiesis is the process by which all cells in the blood are produced, and contributes to organismal health. During aging the hematopoietic system undergoes several changes, including a differentiation skew of the hematopoietic stem cells towards myeloid immune cells, that leads to a decrease in lymphoid immune cells. Accordingly, aging is a major risk factor for several blood malignancies. At the same time, the mesenchymal stroma cells (MSCs), crucial for supporting hematopoiesis, become skewed towards adipogenesis with age. However, the molecular mechanisms that contribute to this age-associated decline in the hematopoietic system remain understudied. R-loops, or DNA:RNA hybrids, are co-transcriptional molecules that when misprocessed lead to transcriptional dysregulation, DNA damage and genome instability. Due to these detrimental events, normal cells efficiently process and remove R-loops. A recent study by the applicant showed that aging neurons display defects in R-loop metabolism, which in turn has a detrimental effect in neuronal function, and concomitant changes to the transcriptional landscape. In addition, preliminary data from the host lab has identified key R-loop related enzymes downregulated upon ageing in bone-marrow derived mesenchymal stroma cells (MSCs). Altogether, these observations poise R-loops as a potential mechanism that contributes to the loss of hematopoiesis support during aging, and disease. In this basic research project, the applicant will connect for the first time R-loop metabolism and aging to changes in the hematopoietic stem cell niche. Our central hypothesis is that the age-associated changes of R-loop metabolism in the MSCs lead to transcriptional dysregulation of gene regulatory networks associated with differentiation potential, in turn remodeling the bone marrow niche. To test this hypothesis, we will determine the specific molecular pathways that are regulated by R-loops in MSCs, and to establish if modulation of R-loops can change the differentiation potential of MSCs, and remodel the bone marrow niche. We propose the following aims: 1. We will profile R-loops and R-loop binding proteins in MSCs from young and old mice and human samples. Data integration with RNA-seq will allow us to identify R-loop regulated genes and establish R-loop associated molecular pathways. 2. We will test how modulation of R-loop metabolism contributes to differentiation potential of MSCs using siRNA-mediated depletion of prioritized R-loop binding protein targets, followed by single cell (sc) RNA-seq and scATAC-seq of the bone marrow. For this, we will co-culture siRNA-loaded MSCs with hematopoietic stem/progenitor cells (HSPCs), followed by single cell multi-omic assays as a phenotypic readout of differentiation. From this project, we will elucidate how R-loops maintain MSCs homeostasis during aging, and how R-loop metabolism contributes to the bone marrow niche remodeling.
2024
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Cross Disciplinary Fellowships - CDF
Understanding far-from-equilibrium chemical kinetics inside biomolecular condensates
KANG Byunghwa (KOREA, REPUBLIC OF (SOUTH KOREA))
Institute for NanoBioTechnology - Johns Hopkins University JHURA - Baltimore - United States
SCHULMAN Rebecca (Host supervisor)
Subcellular compartments determine the fate of a living cell. Along with canonical lipid membrane-enclosed organelles, life extensively exploits condensed liquid-like structures that are formed by liquid-liquid phase separation to spatiotemporally regulate ubiquitous processes, such as the sequestration of specific species and the control of biochemical reaction rates. These membrane-free compartments, biomolecular condensates, also orchestrate far-from-equilibrium cellular behaviors, ranging from gene expression to signal transduction. However, despite the growing importance of biomolecular condensates in cellular biochemistry, it has remained elusive over the decades how these densely-packed spatial regions precisely control or up-regulate internal chemical kinetics. Previously, some artificial condensates have enhanced catalytic rates by localizing catalyst or reactant, but these are abiotic quasi-equilibrium phenomena that are inherently unattainable in living cells. Given that intracellular condensates are subject to various chemical processes, including transcription and translation, how can these processes, i.e., those are far-from-equilibrium, accelerate catalysis within biomolecular condensates? To understand membrane-less organelles, through the Human Frontier Science Program, we will focus on the following two aims: 1) design of natural-like biomolecular condensates subject to biologically-inherent far-from-equilibrium and 2) evaluation of catalytic kinetics in designed condensates. Our first goal is the design of nucleic acid-based condensate using DNAs as dual-functional materials that induce the phase separation and allow transcription when assembled with RNA polymerases. Our approach mimics intracellular transcription that occurs in condensates and drives far-from-equilibrium conditions. This can be strongly supported by the host laboratory led by Dr. Rebecca Schulman, who has developed many successful examples of spatiotemporally-regulated transcriptional networks. Next, we will aim to unravel catalytic kinetics inside biomolecular condensates. Inspired by natural transcription that is coupled to downstream catalytic reactions (post-transcriptional modifications and translation), we will investigate the effect of a transcriptional process on catalytic rates. Importantly, one hypothesis is that transcription of a trans-acting ribozyme and its substrate within the same condensate could accelerate catalysis beyond what equilibrium sequestration could. Additionally, we envision that catalytic rates are precisely regulated relying on transcription rates. Here, my Ph.D research skills in molecular probes to detect cellular targets and my expertise in aptamers and RNA biochemistry will be used. In conclusion, our approach to study chemical kinetics within biomolecular condensates will develop a new biological principle of how critical reactions could be regulated inside biomolecular condensates beyond what is currently known.
2024
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Grant Awardees - Program Grants
UV opsin as the sensor for magneto-sensation in animals
SCHAPIRO Igor (GERMANY)
- Technical University Dortmund (Technische Universität Dortmund) - Dortmund - GERMANY
MERLIN Christine (FRANCE)
- Texas A&M University - College Station - United States
KATO Hideaki (JAPAN)
- The University of Tokyo - Tokyo - JAPAN
KOSLOFF Mickey (ISRAEL)
- University of Haifa - Haifa - ISRAEL
The molecular mechanism of bio-magnetic sensing used for navigation by migrating animals is a major unsolved problem in contemporary science. We propose that opsin, the biological light-sensitive pigment, is the actual magneto-receptor. Opsins are transmembrane proteins arranged in membrane stacks within photoreceptor cells in the eye that transmit visual signals to the brain. Opsins covalently bind a retinal chromophore via a Schiff base bond, making these proteins light-sensitive. Our preliminary results from quantum chemical calculations suggest that certain opsins can populate triplet electronic states that are sensitive to a magnetic field. In this state, a quantum ”geometric phase” is accumulated upon a conformational change of the retinal relative to the magnetic field direction, yielding a true quantum biology effect. These specific opsins contain deprotonated retinal Schiff base as a chromophore, which absorbs light in the ultraviolet (UV) spectral range and are termed “UV-opsins” in this proposal. Such UV-opsins are found in insects and birds, and the architecture of photoreceptors in the retina orients them to the visual axis in a manner compatible with magneto-sensing. Specific in vivo support for the role of UV-opsins in the magnetic response of the migratory monarch butterfly came from the requirement of light in the UV range. Lastly, UV-opsin can transduce magneto-sensation to the brain directly via G protein/arrestin dependent visual signaling cascades.
We will test our hypothesis using a highly interdisciplinary approach that leverages genetic tools in the migratory monarch butterfly, a newly established model system for magneto-sensing, in synergy with quantum chemical simulations and 3D protein structure modeling, bioinformatics, cryo-electron microscopy, and behavioral neurogenetics. We will explore the role of opsins with a deprotonated retinal Schiff base chromophore in magnetic sensation, determine their structure and signaling activity upon magnetic induction, as well as validate their function in vivo by testing monarch mutants for loss of magnetic responses. This synergistic collaboration will elucidate a previously unexplored role for opsins in magneto-reception, one of the least understood senses in biology, and is likely to have broad implications for understanding magneto-reception across animals.
2024
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Grant Awardees - Program Grants
FUNCTIONAL ECOLOGY OF FLAGELLATES SHEDS NEW LIGHT ON EARLY EUKARYOTIC EVOLUTION.
KIORBOE Thomas (DENMARK)
- Technical University of Denmark - Kgs. Lyngby - DENMARK
SIMPSON Alastair (AUSTRALIA)
- Dalhousie University - Halifax - CANADA
WAN Kirsty (United Kingdom)
- University of Exeter - Exeter - United Kingdom
Phagotrophic flagellates are found in all the major branches of the Eukaryotic Tree of Life, and resolving their phylogenetic history is key to understanding early eukaryotic evolution and the origins of LECA – the Last Common Eukaryotic Ancestor. Phylogenies are traditionally inferred by molecular and morphological approaches, but both may be blurred by, respectively, horizontal gene transfer and the problem of distinguishing convergent vs homologous morphologies. Here we propose that functional ecology and biophysics provides a brand-new lens through which to explore phylogenies. Our aim is to study this in both ‘typical excavates’ flagellates, hypothesized to resemble LECA, as well as ‘excavate-like’ flagellates from other deep branches of the tree.
Morphological traits, if homologous, that are found in distant deep branches of the Tree are potential LECA traits. Evidence of similar morphologies with different functions may be a particularly strong argument for homologies that have underwent subsequent divergent evolutionary adaptations. Most ‘typical excavates’ are bacterivores and share morphological features: One of their two flagella beats in a ventral groove and is equipped with 1-3 vanes. This arrangement is thought to play a role in prey capture, but the details are unknown. ‘Excavate-like’ organisms have similar morphologies that may function in similar or different ways, but they are mainly eukaryovores.
We pose two hypotheses: H1: Typical excavate morphologies are homologous and play similar roles in prey acquisition; H2: Typical excavates and excavate-like flagellates have homologous morphologies but may have evolved different function in prey acquisition and propulsion. We will test this in selected typical excavates as well as excavate-like flagellates by (i) resolving cellular morphology using live imaging, and TEM and expansion microscopy of fixed specimens with a focus on cytoskeletal architecture to help distinguish convergent from homologous features; (ii) functional ecology using visualization and quantification of feeding flows, high-speed video-microscopy and micro-fluidics to quantify prey capture and motility, micro-holography to describe flagellar beat patterns, and fluid dynamic modelling to understand the underlying physical mechanisms; (iii) integrate the above insights with molecular phylogenetics to test H1,2.
2024
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Cross Disciplinary Fellowships - CDF
Teaching excitons how to walk: spatial reorganization in an artificial light-harvesting system
KITZMANN Winald (GERMANY)
Department of Chemistry - Massachusetts Institute of Technology - MIT - Cambridge - United States
SCHLAU-COHEN Gabriela (Host supervisor)
Background Photosynthetic organisms rely on light to synthesize important chemical feedstocks. On a molecular level, the flow of protons and electrons after absorption of a photon is controlled by sophisticated nano-machinery. Through this complex dance, biological systems power most life on Earth. Inspired by this remarkable achievement, researchers have been working to emulate this function through artificial model systems. Despite decades of effort, robust and efficient energy capture has not been achieved. Fundamentally, biological systems are non-equilibrium in nature. However, previous reports have been limited to static, equilibrium geometries, and so structural dynamics that are inherent to biological function have remained unexplored. Aims While there is vast knowledge on how nature uses light to fuel life, true understanding is proven by successful replication of the process. In the words of Richard Feynmann, "What I cannot create, I do not understand." This project aims to create synthetic nano-machinery with dynamic control over the excitons for energy capture and conversion. This platform will establish the limits of our current understanding and provide fundamental insight on the interplay of biological structure and dynamics. Central hypothesis I propose to construct a system at the molecular level with dynamic control over photonic energy. Specifically, I will program excitonic circuits made of dyes and charge-transporting moieties with tailored non-covalent interactions that introduce dynamic couplings. After initial conversion of photonic energy to an electron-hole pair, these transient bonds break, which pushes the system out of equilibrium. The resulting energy gradient triggers molecular reorganization and induces a spatial separation of charges, which can be harnessed to drive chemical transformations. Experimental system Precise control over the system’s geometry is necessary to exploit their full light-conversion potential. Synthetically, this can be achieved with a powerful biotechnological tool known as DNA origami. The efficiency of the system is determined by elementary steps such as energy transfer and charge separation. As these processes occur on ultrafast timescales, time-resolved optical spectroscopy with femtosecond resolution will be used to track the different species via their distinct absorption features. These in-depth spectroscopic studies will be used to fine-tune the molecular design of the artificial light-harvesting systems. Conclusion This project expands our understanding of photosynthesis by reverse-engineering its function in minimalistic excitonic circuits. The combination of atomically precise molecular design and state-of-the-art time-resolved spectroscopy allows identifying the key excitonic processes and optimizing them for maximum efficiency. Overall, this project will provide invaluable insight on one of the overarching questions in biology: how structure creates function.
2024
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Long-Term Fellowships - LTF
The role of simultaneous population dynamics in associative learning
KOL Adi (ISRAEL)
Neuroscience - Friedrich Miescher Institute (Friedrich Miescher Institute for Biomedical Research, FMI) - Basel - SWITZERLAND
LUETHI Andreas (Host supervisor)
Associative learning, of relations between stimuli and the outcome they predict, is a vital cognitive process in our daily functioning, as it allows us to acquire new information and to constantly adapt to changes in our surroundings. Although association learning was repeatedly shown to restructure the activity of numerous individual neurons across cortical and subcortical regions, it is still not clear how it is represented at the population level. Specifically, how learning-related activity patterns develop in single brain areas, how interregional interactions support it and how these widespread representations flexibly update as stimuli-outcome contingencies change. The primary goal for this proposal is to study the population dynamics underlying associative learning by combining behavior, population recordings and dynamical systems-based analytical framework. The prefrontal cortex (PFC) and the basolateral Amygdala (BLA) are two extensively interconnected learning hubs and thus offer an ideal anatomical infrastructure to investigate interregional communication effects on local learning-related activity patterns. I plan to harness the cortico-amygdala circuitry and use Neuropixel probes to concomitantly record population activity in PFC and BLA as mice perform appetitive associative reversal learning task where the cue-reward contingency is swiftly reversed after they have slowly learned the original contingency. This way, learning will be studied on multiple timescales, from a few minutes to whole days. Next, I will use population decoding to identify the neural correlates of the paradigm in PFC and BLA, examine the temporal interplay between them and investigate how information routing support population activity and consequently, shape learning. Lastly, I will examine the causality between interregional communication, local task-related representations and behavior by optogenetically manipulating the Amygdala-cortical projections. Here, I propose a novel hypothesis of mine, in which the formation of cue-outcome contingencies is paralleled with the development of distinct sequences of neurophysiological signatures both at the PFC and the BLA. These local signatures will co-evolve through inter-regional communication to mediate the selection and stability of stimuli-outcome contingencies with varying time constants that will determine individual learning rates. As the BLA is typically known to process salient information such as emotion, valence or motivation, I further suggest that it is the first to detect the positively valenced stimulus and then instruct the PFC to initiate learning via command signals routing from the BLA to the PFC. Such comprehensive mechanistic investigation of how PFC-BLA population dynamics underlies associative learning, on multiple timescales, can reveal general principles in how the brain utilizes interregional interactions to learn associations and, ultimately, shape behavior.
2024
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Grant Awardees - Program Grants
Mechanisms and evolutionary consequences of stress-induced mutagenesis
KUPIEC Martin (ISRAEL)
- Tel Aviv University - Tel Aviv - ISRAEL
TRAULSEN Arne (GERMANY)
- Max Planck Institute for Evolutionary Biology - Plön - GERMANY
Evolution is a two-step process: mutations arise among individuals in populations and those providing higher fitness are favored. It has become apparent that various stresses produce an increase in the level of mutagenesis. Such a phenomenon plays a pivotal role in the development of cancer, in the emergence of drug and antibiotic resistance, and in the emergence of new viral variants (e.g. COVID).
It is customary to think about fitness and evolutionary advantage at the level of individuals, but they only make sense on the level of a population. Here, we want to understand the control of variation at the population level. For example, are there inter-cellular signals that elicit variation in the population to help overcome stressful conditions? Can a population-level reaction to stress be evolutionarily advantageous, even when individual cells may be negatively affected?
This proposal is a collaboration between a molecular genetics lab (Kupiec) and a mathematical/computational lab (Traulsen). We will use the baker's yeast as a model, and carry out a combination of theoretical and experimental work aimed at answering very basic questions related to the induction of variation by stress. Yeast is a rapidly growing microorganism with great resources in genetics, biochemistry and molecular biology. Most importantly, it is easy to set up evolution experiments in the lab. We expect to obtain from these studies a better understanding of the evolutionary mechanisms that operate in times of stress, and their molecular details. Such an understanding is not only scientifically interesting: Medical problems such as bacterial infections and cancer can be understood in terms of evolution and antibiotic resistance and therapy failure in cancer is often based on the emergence of mutations. Our studies may present novel strategies to pre-empt such problems.
2024
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Long-Term Fellowships - LTF
Role of visual and emotion circuits in shaping neural spatial representations of aversive stimuli
LEPRINCE Erwan (FRANCE)
Department of Physiology, Development and Neuroscience - University of Cambridge - Cambridge - United Kingdom
BELTRAMO Riccardo (Host supervisor)
In order to survive, animals navigate the environment to find food, shelter and avoid predators. The development of internal spatial maps is believed to facilitate these tasks, with visual inputs providing critical information on the position and dynamics of external stimuli. These maps, found in the hippocampal and parahippocampal formations, are thought to help animals to define their position in the environment and locate their conspecifics. However, little is known about the neural networks that support spatial representations of explicitly dangerous and threatening visual stimuli, such as predators. This project aims at dissecting the circuits enabling the spatial representations of aversive visual stimuli and their association with emotional content, across the visual and spatial navigation systems. Two main systems process visual information: the "geniculate" and "collicular" pathways. The geniculate pathway transmits visual input to the primary visual cortex (V1), which extracts basic features from the visual scene. Intriguingly, clinically blind patients with complete V1 lesions are still able to navigate and react to threatening visual stimuli. This phenomenon, referred to as "blindsight", has been linked to the collicular pathway. The collicular system relays object motion information from the superior colliculus, an evolutionary ancient visual centre, to the postrhinal cortex (POR). POR is considered one of the main entry points of visual input to the hippocampus. In addition, POR is involved in contextual fear conditioning and is the only visual cortex reciprocally linked to the amygdala, a crucial structure for aversive information processing. For these reasons, we hypothesize that POR is critical to developing spatial representations of aversive stimuli by coupling object movement information, stimulus value, and animal self-position. By identifying salient and dangerous visual stimuli, POR would allow the animal to maintain an updated representation of the environment, and to adapt its behavior when changes occur. Through behavioral, electrophysiological, imaging and optogenetic approaches in freely-moving mice, I propose to: 1) record hippocampal and parahippocampal responses to moving visual stimuli, and optogenetically silence the geniculate and collicular pathways to determine their contributions to spatial representations of moving objects; 2) determine the influence of emotional content on the spatial representation of moving objects, by combining these stimuli with aversive ones; 3) disentangle the circuits involved, by focusing on amygdala/POR reciprocal connections. I will manipulate these projections to test their role in shaping the spatial representations of moving visual stimuli in fear learning paradigms. Overall, this project will provide crucial insight into how the visual and navigation systems process threatening stimuli, such as predators, to generate complex behaviors essential for survival.
2024
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Grant Awardees - Program Grants
Cognitive convergence: Vertebrate carnivore-like predatory planning behaviors in jumping spiders
LI Chen (United States)
- Johns Hopkins University JHURA - Baltimore - United States
LI Daiqin (New Zealand (Aotearoa))
- Hubei University - Wuhan - China, People's Republic of - Wuhan - CHINA
NELSON Ximena (New Zealand (Aotearoa))
- University of Canterbury - Christchurch - New Zealand (Aotearoa)
MACIVER Malcolm (CANADA)
- Northwestern University - Evanston Campus - Evanston - United States
Assessing options before taking action (planning) is cognitively demanding but helps enhance reward and reduce risk. Mammals and birds show evidence of planning, but members of the Portia genus of spider-eating jumping spiders (salticids) are the only terrestrial invertebrates that are thought to be capable of planning. Like a lion peeking over tall grass to stalk prey, Portia visually scans prey, assesses options, and takes long detours (~100 body lengths, ~1 hour) so as not to trigger escape or attack (its prey can kill Portia). Notably, Portia has 1 million times fewer brain neurons than us, but its visual acuity is only 6 times worse—better than cats—and much better than other invertebrates.
Recent modeling suggests that planning provides a selective benefit in visually-guided predator-prey interactions, but only for patchy (partially cluttered) terrain that enables visually hiding one’s approach. The predator benefits from planning because as the prey moves, the predator could become visible, and its selected trajectory must be aborted and a new route planned. Because Portia hunts other highly visual non-Portia salticids, our model indicates that Portia may need to plan for successful salticid hunts, by using partial clutter to hide its approach. If true, then the ability to plan may not require a large vertebrate brain, as traditionally thought; rather it emerges from the right combination of ecological features: patchy habitats with high visual acuity predators and prey. Further, how an animal with so few neurons is able to plan may, by necessity, be an entirely novel computational method far more efficient than that used by vertebrates.
To test this key idea, as well as to reveal the ranges of ecological parameters that potentially allow planning to emerge from such a small brain, we will perform the first systematic study of detouring behavior in Portia hunting other salticids, by integrating our expertise in field-based foraging behavior (DL) and lab-based planning and vision (XN) of Portia, complex terrain locomotion, sensing, and predator-prey interactions via creating new tools (CL), and modeling of planning (MM). Our work could advance understanding of crucial issues regarding what features of an animal’s sensory ecology and task demands select for planning ability, and whether there are deeply conserved, ancient features to planning.
2024
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Long-Term Fellowships - LTF
Chromatin rejuvenation and DNA damage responses during ageing of human chromosomes
LIAKOS Anastasios (GREECE)
Institute of Pathology - University Medical Center Göttingen - Göttingen - GERMANY
PAPANTONIS Argyris (Host supervisor)
Ageing represents an inevitable endpoint in metazoans and is characterized by multisystemic functional decline. This is often linked to the accumulation of DNA damage along chromosomes with time. Elevated reactive oxygen species (ROS) in particular, are produced as a byproduct of cellular metabolism and considered among the main drivers of the pathophysiology of ageing and age-related disorders. It would be expected that the process of ageing and the induction of genotoxic stress should impact all levels of gene regulation, however, little is known about the differential effects that distinct stimulants of DNA damage cause in the multiple levels of genome architecture and function. Thus, an in-depth elucidation of the oxidative damage-to-chromosome structure relationship at the molecular level is needed. A recent study led by the proposed host lab (Debes et al., Nature, 2023) demonstrated that ageing is characterized by abnormally high transcription elongation speeds in multiple cell types, tissues, and species, and that overexpression of histone proteins not only restores the kinetics of transcription to physiological levels, but also restricts the emergence of various ageing features in human cells. The inherent link between chromatin and 3D genome structure suggests that this histone-driven “rejuvenation” of ageing cells is bound to changes in the spatial architecture of chromosomes. Still, it remains unclear how these chromatin-based interventions can counter the ageing processes Putting these two together, I propose a study of the effects of chromatin rejuvenation on 3D chromosome architecture as well as on the genome’s ability to cope with oxidative damage. To this end, I will combine ultra-resolution 3D genomics with nascent epigenome mapping in aged (senescent) and “rejuvenated” primary human cells before and after inducing either chronic (low doses, prolonged treatment) or acute (high doses, one exposure) oxidative DNA damage. In a next step, these experiments can be complemented by in vivo dissection of rejuvenated mouse tissue at the single cell level. I expect these experiments to shed light on the molecular mechanisms and regulatory principles behind chromosomal stress responses during ageing. In conclusion, this research program will provide new insights into the crucial role of chromatin architecture during ageing, while deciphering differences in the ability of aged and rejuvenated cells to respond to oxidative stress induction. Thus, possible novel approaches for preventing and managing late-life disease by epigenome regulation might emerge.
2024
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Cross Disciplinary Fellowships - CDF
The bright side of life: fluorescence-detected ultrafast microspectroscopy
LUETTIG Julian (GERMANY)
Department of Physics - The Regents of the University of Michigan - Ann Arbor - United States
OGILVIE Jennifer (Host supervisor)
Photosynthesis provides almost all energy to life on earth. The complexity of nature is already revealed at the molecular level, where the photosynthetic protein scaffold controls the orientation, spacing and local environment between pigments, leading to delocalized excited states, i.e., excitons. The protein–pigment complexes form larger networks which act as an “energetic funnel” resulting in ultrafast exciton propagation to the reaction center where energy conversion occurs. Exciton dynamics have been studied in detail via pump–probe (PP) and two-dimensional (2D) spectroscopy. Most previous work has been performed on ensembles of isolated components, making it impossible to study the component interactions and heterogeneities. Examples for heterogeneity include structural variations, energetic disorder, and type of antenna complexes which all strongly influence the excitonic properties such as lifetime, transfer, and delocalization. We aim to develop methods to obtain a holistic picture of photosynthesis in space and time and to identify the influence of the local environment on each level of hierarchy – from organisms to single light-harvesting complexes. The outlined challenges require the combination of fluorescence-detected microscopy with femtosecond spectroscopy. Each of the isolated signals is sensitive to a specific excitonic property: the excitation spectrum is sensitive to the coupling, PP spectra characterize the lifetime, and 2D spectroscopy reveals energy transfer. Correlation of these properties results in a comprehensive picture of photosynthetic excitons. Our experimental approach leverages recent advances based on phase modulation with lock-in detection, allowing spatially-resolved 2D and PP from the same experimental setup, and employing phase-labeled photon counting detection to reach the single molecule limit. This unique combination of spectroscopic and imaging tools will allow us to investigate photosynthetic adaptation mechanisms of various systems both in vivo and in vitro. Previous experiments have shown that plants and bacteria grown under different light conditions change the relative composition and spatial distribution of antennas and reaction centers, incorporating modified pigments, and altering protein structures to tune electronic resonances and reroute energy transfer pathways. Our spectroscopic approaches will reveal alterations in the excitonic structure and energy transfer pathways due to adaptation. Next, we aim to proceed from averaged kinetics of an ensemble of complexes to measurements of distributions from individual complexes. This would enable the first single-molecule 2D experiment, revealing exciton dynamics in single light-harvesting complexes. The developed techniques would be widely applicable to other systems and spectral regions, providing powerful tools for studying biological samples with femtosecond and submicron resolution, such as melanin or the dynamics of proteins and nucleic acids.
2024
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Grant Awardees - Program Grants
Temporal structures in complex deep-sea versus surface marine life: from molecules to communities
TESSMAR-RAIBLE Kristin (GERMANY)
- University of Vienna (Universität Wien) - Vienna - AUSTRIA
MATABOS Marjolaine (FRANCE)
- French Research Institute for Exploitation of the Sea (Institut Français de Recherche pour l'Exploitation de la Mer, IFREMER) - Plouzané - FRANCE
OAKLEY Todd (United States)
- The Regents of the University of California, Santa Barbara - Santa Barbara - United States
PELEG Orit (ISRAEL)
- University of Colorado Boulder - Boulder - United States
While biological rhythms are crucial to life, the deep sea is often considered an acyclic exception. However, tidal inversions of local current flow cause extreme, but predictable changes in physico-chemical parameters at hydrothermal vents. Recent work indicates vent animals employ biological rhythms with a tide-matching period. How relevant are rhythms for life under these “alien” conditions and how do they work? We capitalize on our access to the Lucky Strike vent at -1700m with extensive scientific records, including 12 years of videos, and the key ecological engineer species Bathymodiolus azoricus, a vent mollusk. Specifically, we aim to understand the mathematical and molecular logic of deep-sea rhythms, the environmental stimuli that influence them, their ecological consequences, and evolutionary origins/adaptations from molecular level to organism and community scales. Tackling these aims is only possible by cross-disciplinary data, expertise, material exchanges:
An ecologist will provide expertise and access to deep-sea communities and environmental parameters, will perform experiments at deep sea vents to test predictions from models, including the influence of population size and environmental parameters (e.g. artificial illumination) on rhythmicity. A „wet-lab” cell- chronobiologist will probe molecular/cellular mechanisms of B. azoricus deep-sea rhythms on cell culture and organisms under constant and controlled-altered conditions (e.g. pressure, light/temp.). This includes possible sensory systems, tests for endogenous oscillator(s), changes in transcript and protein level/localization. An evolutionist with access to Modiolus, the closest shallow water relatives of Bathymodiolus, will compare putative rhythms (from molecules to populations) and responses to environmental signals between deep-sea and shallow water relatives to understand evolutionary changes. A biophysicist will use computer-vision for dataset analyses, develop models for rhythm emergence and stability, factoring in interactions among populations, environmental cues, and (possibly) correlated molecular changes. The model predictions will be experimentally tested by the team’s experimentalists. New data on ecological interactions, cues, sensors, and mechanisms will inform predictions on how temporally structured biological processes influence plasticity near the limits of life.
2024
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Cross Disciplinary Fellowships - CDF
Early Earth conditions as a selector for functional RNAs
MATREUX Thomas (GERMANY)
UMR CNRS-ESPCI Chemistry Biology and Innovation - The City of Paris Industrial Physics and Chemistry Higher Educational Institution (Ecole Supérieure de Physique et de Chimie Industrielles de la Ville de Paris, ESPCI) - PARIS - FRANCE
NGHE Philippe (Host supervisor)
Prebiotic scenarios rely on the emergence of sustained catalysis. One candidate molecule is RNA where various oligomerization mechanisms and numerous catalytic RNAs (ribozymes) have been discovered. However, a spontaneous transition in between seems improbable due to the scarcity of functional sequences among random strands. For instance, the medium-sized class I ligase is estimated to occur once in 1018 sequences. This leaves little opportunity for a ribozyme to appear by chance, lead to the formation of another ribozyme, and kick-start molecular evolution. The major transition thus begs for some form of external constraints that enrich functional sequences among the random ones. We suggest that geomaterial-RNA interactions could have acted as a filtering mechanism. Such interactions have been shown to catalyze RNA oligomerization, reduce RNA hydrolysis and select for longer oligomers. However, in the transition from random to functional RNAs, the geological context has so far been neglected. Since all catalytic RNAs and their substrates are partially folded, we expect their adsorption on geological surfaces to differ from that of unfolded or completely double-stranded sequences. My research plan consists of three parts: 1. Parsing of the folding space and proof of principle of the fold-dependent adsorption; 2. Inhibition and recovery of ribozyme activity within random pools; 3. Emergence and survival of reaction networks in random RNA pools. In part 1, I will design a repertoire of folds from statistics of known ribozymes and randomly picked motifs. I will quantify the fold-dependent adsorption on different surfaces (rocks, minerals and clays) and screen the effects of environmental conditions such as temperature, pH and salt during the adsorption and washing steps. Secondary structure predictions and thermodynamic adsorption models will serve to fit and predict adsorption of RNA folds. In part 2, I will study how binding of random oligomers to ribozymes leads to inhibition by probing the activity of various ribozymes within mixtures of increased randomness. The degree of enrichment of folded sequences required for function and the results from part 1 will enable me to establish how selective adsorption on geomaterials can restore activity. In part 3, I will explore conditions to sustain autocatalytic reaction networks in an open reactor that mimics connected rock cracks. Known reaction networks mixed with random pools will be submitted to rounds of adsorption on different minerals and washing. Using the findings of parts 1 and 2, I will determine the geological environments that enable the emergence of sustained autocatalysis despite inhibition and side-reactions caused by random RNAs. This project will provide a quantitative basis to assess the spontaneous emergence of function from random RNA pools and will identify the most plausible geological conditions for this crucial transition during the origin of life.
2024
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Long-Term Fellowships - LTF
Unraveling spatial landscape of Mycobacterium tuberculosis transcriptome & its role in TB pathology
MEHDIRATTA Kritee (INDIA)
Immunology and Infectious Diseases - President and Fellows of Harvard College, Harvard T. H. Chan School of Public Health - Boston - United States
RUBIN Eric (Host supervisor)
Despite the advent of BCG vaccination and antibiotics, the global burden of tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains high. Previously regarded as non-compartmentalised cellular system due to lack of well defined intracellular organelles, recent studies have shown Mycobacteria to possess defined cellular organisation with distinctive spatiotemporal localisation of proteins. In eukaryotes, it is well reported that targeting mRNA transcript to specific cellular locations is critical for spatial protein synthesis thereby highlighting RNA localisation as a driver of sub cellular organisation. Fascinatingly, only recently similar phenomenon of RNA localisation has been demonstrated in bacteria like E. coli. Bacterial mRNA can localise to nucleoid, cytoplasm, poles, and inner membrane. However, the underlying molecular mechanisms dictating their localisation is not completely understood. Interestingly, the transcriptome organisation of Mtb remains elusive so far. Moreover, the biological relevance of defined RNA localisation patterns in bacteria needs to be ascertained. Hypothesis- RNA localisation in eukaryotes is an important post transcriptional regulatory mechanism. However, the scope of RNA localisation in pathogens like Mtb remains unknown. The Mtb transcriptome might be spatiotemporally organised to maximise gene function and to provide fast and efficient regulation in response to changing host environmental stimuli. Aims- 1. Delineating spatiotemporal organisation of Mtb transcriptome under homeostasis & if there is reconfiguration in response to different physiological stresses. 2. Characterising molecular mechanisms driving Mtb RNA localisation & enabling tethering to specified location. 3. Investigating whether spatial information regulates transcriptional activity & if disruption of spatial organisation introduces vulnerabilities in Mtb growth and survival. To address these aims we will take advantage of methods recently developed in the Rubin lab to perform fluorescence in situ localisation (FISH) to localise transcripts in viable Mtb and to recreate pseudotemporal localisation in fixed bacteria. We will use cellular fractionation and RNA sequencing techniques to spatially map the complete Mtb transcriptome & immunoprecipitation studies to identify any interacting motor and cytoskeleton proteins. We will define sequence determinants that could direct transcripts to subcellular compartments and identify proteins that might play a role in localisation. Finally, will generate mutants that mislocalise RNAs and determine their physiological effects. Conclusion- RNA localisation adds a layer of complexity to prokaryotic cellular architecture. Understanding the physiological relevance of such dynamic spatial organisation of molecular components especially in clinically relevant pathogens like Mtb, might provide a new paradigm of gene regulation and function that can be therapeutically exploited in future.
2024
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Grant Awardees - Program Grants
Hormone-like Bacterial Signaling Molecules as Mediators of Gut-Brain Dialogues
XAVIER Karina (PORTUGAL)
- Fundação GIMM - Gulbenkian Institute for Molecular Medicine - Lisbon - PORTUGAL
MEIJLER Michael (ISRAEL)
- Ben-Gurion University of the Negev - Be'er-Sheva - ISRAEL
NEEDHAM Brittany (United States)
- Indiana University - Indianapolis - United States
Microbial symbionts inhabit all animals, with constant exchange of molecular cues between microbes and host. These communities of microbes, referred to as microbiota, influence many aspects of host physiology, including the brain and behavior. Specific signals and host receptors involved in these interactions remain largely unknown. To understand the permeating effects of interbacterial chemical crosstalk within the microbiota community, as well as signaling between the microbiota and the host, we will focus on the mammalian intestine, which houses a dense bacterial community and is ideal for elucidating these pathways. Recently, a novel family of bacterial signaling molecules, named pyrazinones, was found to regulate communication and virulence in bacterial intestinal pathogens. We predict that these pyrazinones are also produced by commensal members of a healthy gut microbiota. Intriguingly, bacterial pyrazinone receptors can sense human-derived neurotransmitters due to structural similarities between the compounds. This shared ligand profile between pyrazinones and host neurotransmitters, along with pyrazinone production by known (and potentially many unknown) microbes within the gut, offers a compelling new avenue of microbe-host connection. Pyrazinones are likely perceived by host neurotransmitter receptors, modulating the enteric, peripheral and/or central nervous systems. Thus, our proposal offers the transformative and unexplored notion that pyrazinones can serve as microbial-made neurotransmitters, impacting both animal behaviors and bacterial group behaviors. To test this, we will apply advance metabolomic methods to identify and characterize the pyrazinones produced by gut microbiota and synthesize novel chemical probes to identify host receptors and their spatial distribution in mice. We will genetically modify pyrazinone biosynthetic pathways in gut bacteria, allowing us to compare their effects in colonized mice. Once host receptors are characterized, we will use mutant mouse lines to confirm their involvement. Using these tools, we will study microbe-dependent neurological alterations and behavioral phenotypes to assess interplay with the nervous systems. Overall, we will determine how host monitoring of these microbial signals leads to altered host functions, establishing a new avenue of crosstalk between host and microbial symbionts.
2024
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Long-Term Fellowships - LTF
Reward-based learning of assemblies in olfaction
MIEHL Christoph (AUSTRIA)
Department of Neurobiology - The University of Chicago - Chicago - United States
DOIRON Brent (Host supervisor)
OSWALD Anne-Marie (Host supervisor)
It is widely accepted that groups of pyramidal neurons (PNs) that display synchronous activity and strong recurrent synaptic connectivity, often referred to as an ‘assembly’; represent a specific stimulus or concept, hence acting as a fundamental unit of memory storage. Understanding the mechanics of assembly formation is needed to link the biology of the nervous system to its function. In previous models, assemblies have formed from unsupervised learning of sensory stimuli via synaptic plasticity (see e.g. my PhD work). However, learning certainly depends on supervisory signals such as reward. While reward-based learning is widely used in machine learning applications like reinforcement learning, it is not clear how it is incorporated in biological circuits. In addition, unpublished data from the Oswald lab challenges the current working model of assembly learning: They present two odors to freely behaving mice, one rewarded and one unrewarded. Based on a combination of activity-dependent labeling, optogenetic stimulation, and in vitro (soon in vivo) recordings of neurons in the piriform cortex they find that, unintuitively, an assembly only forms for neurons selective to the rewarded odor. But how is reward-based learning implemented in a biological circuit? Published data from the Oswald lab suggests that activation of VIP inhibitory neurons (INs) can gate the synaptic plasticity essential for assembly formation (Canto-Bustos et al., 2022). Therefore, the following hypothesis of reward-based assembly learning emerges: Presenting an odor together with a reward activates VIP neurons, which gates synaptic plasticity among odor-specific PNs. Based on a close collaboration with the Oswald lab, my host supervisor’s experience in modeling circuits with multiple INs, and my prior knowledge in modeling plastic excitatory/inhibitory networks, I aim to uncover how reward-based learning is implemented in biologically plausible circuits. First, my aim is to build an experimentally constrained computational model of the piriform cortex circuitry, including PNs and the major INs (PV, SST, and VIP) with plastic synapses, to test the above-described hypothesis of reward-based assembly learning gated via VIP neurons. My second aim is to show that only rewarded odor-specific PNs form an assembly; here preliminary data suggests that SSTs play a pivot role. Third, I aim to extend the model to flexibly allow to encode multiple odor assemblies with overlapping chemical components in order to study how multiple components are combined to form a meaningful odor perception. My work will lead to a better understanding of 1) olfactory processing, 2) how cortical circuits are able to support reward-based learning paradigms, 3) be the biological basis of understanding more complex reward-based learning paradigms (e.g. reinforcement learning), and 4) my results will be generalizable to other brain regions involved with associative learning problems (such as hippocampus).
2024
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Long-Term Fellowships - LTF
Exploring the viral influence on the human gut microbiome
MILLMAN Adi (ISRAEL)
Department of Biology - Massachusetts Institute of Technology - MIT - Cambridge - United States
LAUB Michael (Host supervisor)
"Bacteriophages can either directly kill bacteria or integrate into bacterial genomes affecting their gene content. As a result, phages have a profound impact on their environments. This impact likely extends to bacterial communities within the human microbiome, and better understanding of phage-bacteria dynamics can shed light on the ecological and evolutionary forces shaping the microbiome. In this study I aim to elucidate how phages influence the bacterial composition of the gut by using a large longitudinal dataset of shotgun microbiome sequencing.
Studies show that phage ""kill-the-winner"" dynamics observed in the ocean do not apply in the gut microbiome. It is likely that phage-bacteria coexistence in the gut is achieved by the temperate phage lifestyle. To test that hypothesis, I plan to follow phage dynamics in the microbiome. By comparing the coverage of prophages to the coverage of the host genomes over time, I can estimate the amount of lytic replication in the microbiome. This ratio could also be indicative of the phage host range, as phages that outnumber the coverage on the host reference genome might be residing in multiple hosts. To test this, I plan to search for reads that represent new prophage-bacteria junctions.
Phages play a major role in horizontal gene transfer of the gut microbiome, equipping bacteria with various traits such as virulence, pathogenicity, antibiotic resistance, and antiphage resistance. To assess the contribution of phage transduction to bacterial adaptation in the gut, I plan to track the gene flow between phages and bacteria in patients and healthy individuals. Understanding what is the genetic cargo phages carry and transfer between genomes can shed light on the advantageous traits necessary to thrive in the gut. To measure the contribution of phage transduction to bacterial adaptation in the gut, I will monitor the rate of these events in the microbiome over a prolonged period of time.
To study whether bacteria have adapted to take advantage of phage transduction, I will analyze the gene content bacterial genomes encode in the vicinity of packaging (pac) sites that allow generalized transduction, and attachment (att) sites that allow specialized transduction. These genomic positions are likely enriched with genes contributing to bacterial fitness, as the genes in these positions have higher probability of being packaged and transduced by phages.
While most microbiome studies focus on the bacterial species composition in the gut, the prophages of these species are mostly overlooked. Analysis of prophage dynamics, their host range, and the cargo genes they carry can better illuminate the forces shaping the gut microbiome and expose the functions that help various bacterial species in the gut adapt to different conditions.".
2024
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Grant Awardees - Program Grants
From nano to organismal scale: structural regulation of regenerating jellyfish
SINIGAGLIA Chiara (ITALY)
- CNRS Languedoc-Roussillon - Montpellier - FRANCE
MODES Carl (United States)
- Max Planck Institute of Molecular Cell Biology and Genetics (Max-Planck-Institut für Molekulare Zellbiologie und Genetik) - Dresden - GERMANY
SHIMANOVICH Ulyana (ISRAEL)
- Weizmann Institute of Science - Rehovot - ISRAEL
Diverse species can recover lost body parts, but why not all injuries lead to regeneration, and how animals re-organise their bodies remain key open questions. Mechanical features, notably of the extracellular matrix (ECM), are known critical regulators of development - however they are only rarely considered by regeneration studies. New models are needed to understand how shapes re-emerge, able to address different cues across the molecular, cellular and organismal scales.
The small jellyfish Clytia hemisphaerica boasts excellent repair capacities: wounds heal within 12 hours, and organs regenerate in a week. Recovery is regulated by both transcriptional and mechanical cues, and the simple anatomy, wherein a thick ECM (mesoglea) is covered by contractile epithelia, offers an unexplored experimental paradigm. We propose a unified vision of regeneration, where mechano-chemical features of cells and tissues robustly modulate Clytia repair. Our central hypothesis is that processes related to organ regeneration in Clytia, including recruitment of progenitor cells, regulation of transcriptional responses and orchestration of cell differentiation, are linked to the mechanisms of tissue-matrix interaction, and to the mechanical and topological features of the injured tissues.
A purely in vivo investigation remains challenging, due to the complexity of living tissues and the ECM dynamics. Our solution is to combine in vivo manipulations with the power of analytical tools. We will thus be able to link the structural properties of the mesoglea (fibrillar network of structural and biologically active protein fibrils) with the forces generated within contractile epithelia (regenerative biology, in vivo – Sinigaglia). We will build topologically-informed mechanical models coupling the mesoglea network to the aligned patterns of actomyosin, enabling us to capture, in simple predictive rules, how different classes of injuries – to actomyosin pattern or mesogleal fidelity – affect regeneration (theoretical biophysics and computational biology, in silico – Modes). We will combine these manipulations with biomaterials engineering approaches to build synthetic analogues of self-repairing jellyfish-inspired biomaterial machinery (soft matter, biochemistry, in vitro – Shimanovich). Our regenerative platform, modular and cross-scale, will be adaptable to other contexts.
2024
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Long-Term Fellowships - LTF
Neural dynamics of social role-taking and role-reversal in the medial prefrontal cortex
MUGNAINI Matias (ARGENTINA)
Animal Physiology/ Systems Neurobiology and Neural Computation - Humboldt-Universität zu Berlin - Berlin - GERMANY
BRECHT Michael (Host supervisor)
Most current knowledge about the neural representations of social role-taking stems from the study of dominance-subordination hierarchies, mostly in the tube test (TT). This knowledge has only recently expanded to different social contexts with the rat-human version of hide-and-seek (HS). Unlike social status, social play tends to be pleasurable for all involved individuals and relies more on cooperative behaviors that allow animals to pretend to occupy roles that they usually do not. Despite these differences in the social context and in the freedom animals have to reverse roles, recent studies of the medial prefrontal cortex (mPFC) activity hint at the existence of a common neural code that pervades social roles in all contexts. Anecdotal evidence from these studies suggests that, although mPFC neurons encode specific behaviors in the TT and in HS, respectively, subsets of these neurons may underlie the abstract representation of social role itself. For example, in HS, where rats learn that the starting-box opening indicates them to be hiders (open) or seekers (closed), nearly 30% of mPFC neurons exhibit responses to the starting box closure during “seek” trials that are not explained by other variables, suggesting an influence on role definition. The current understanding of the high-level representation of social roles (i.e., independent of specific social contexts) is limited to a few results and has not been systematically addressed. The goal of this project is to study the neuronal representation of social roles across role-taking situations (i.e. playful or not) to disentangle the common neural code that may underlie them. The hypothesis is that abstract features associated with similar roles (i.e., dominance-seeking, subordinance-hiding) are redundantly encoded by mPFC neuronal subsets. Specifically, we aim to: 1) explore the high-dimensional neuronal space for common codes between tasks; 2) identify role-defining neurons to study their dynamics during task transitions and role-reversal; 3) use decoding tools to test the hypothesised code redundancies for similar roles; and 4) optogenetically manipulate role-taking by targeting mPFC neurons. To this end, Long-Evans rats will be chronically implanted with multiple-shank Neuropixels 2.0 or optic fibers in the Cingulate, Prelimbic and Infralimbic cortices, trained to play HS and tested in the TT to identify social ranks. Contrary to previous studies, this will allow the trial-by-trial simultaneous recording of hundreds of units across cortices and layers in the same animal and the comparison of activity across tasks and neural subpopulations. Unlike other role-plays (e.g., play fighting), HS does not involve direct aggression that could damage implants or produce confounding data related to effortful behaviors. Overall, this project will start to fill the gap in our knowledge of the neural underpinnings of social roles and the cortical dynamics by which they are adopted and reversed.