This is a collaborative international project with the laboratory of Anthony Holtmaat (University of Geneva, Switzerland), funded by the Weave cross-European initiative. The project is at the interface of the expertise of the De Wit lab (molecular mechanisms of synaptic connectivity) and of the Holtmaat lab (synaptic integration of sensory input and context in cortical circuits). The project will unravel molecular mechanisms of synaptic specificity in cortical and thalamocortical circuits. Our recent work has shown that higher-order thalamocortical inputs and cortical inputs to pyramidal neurons in the somatosensory cortex display striking differences in their synaptic properties, even when intermingled on the same cortical dendrite. This project will explore the molecular mechanisms that mediate this specificity and test how these regulate structure and function of higher-order thalamocortical inputs in cortical circuits. The applicant will use a broad array of technologies including super-resolution imaging, CRISPR/Cas9 gene editing, viral vectors, conditional knockout mice, optogenetics, and in vivo imaging. The successful candidate will be based in Leuven, Belgium. The two labs will interact regularly via zoom and in-person meetings, and there will be several visits to the Holtmaat lab to transfer skills and exchange results during this project.

This is a collaborative international project with the laboratory of Anthony Holtmaat (University of Geneva, Switzerland), funded by the Weave cross-European initiative. The project is at the interface of the expertise of the De Wit lab (molecular mechanisms of synaptic connectivity) and of the Holtmaat lab (synaptic integration of sensory input and context in cortical circuits). The project will unravel molecular mechanisms of synaptic specificity in cortical and thalamocortical circuits. Our recent work has shown that higher-order thalamocortical inputs and cortical inputs to pyramidal neurons in the somatosensory cortex display striking differences in their synaptic properties, even when intermingled on the same cortical dendrite. This project will explore the molecular mechanisms that mediate this specificity and test how these regulate structure and function of higher-order thalamocortical inputs in cortical circuits. The applicant will use a broad array of technologies including super-resolution imaging, CRISPR/Cas9 gene editing, viral vectors, conditional knockout mice, optogenetics, and in vivo imaging.

Humans and other animals evolved in habitats fraught with a range of environmental challenges to their bodies and brains. Accordingly, cells and organ systems possess adaptive stress-responsive signaling pathways that enable them to not only withstand environmental challenges, but also to prepare for future challenges and function more efficiently. These phylogenetically conserved processes are the foundation of the hormesis principle in which repeated exposures to low to moderate amounts of an environmental challenge improve cellular and organismal fitness. Here I describe cellular and molecular mechanisms by which cells in the brain and body respond to intermittent fasting and exercise in ways that enhance performance and counteract aging and disease processes. Switching back and forth between adaptive stress response (during fasting and exercise) and growth and plasticity (eating, resting, sleeping) modes enhances the performance and resilience of various organ systems. While pharmacological interventions that engage a particular hormetic mechanism are being developed, it seems unlikely that any will prove superior to fasting and exercise.

The transit of food through the gastrointestinal tract is critical for nutrient absorption and survival, and the gastrointestinal tract has the ability to initiate motility reflexes triggered by luminal distention. This complex function depends on the crosstalk between extrinsic and intrinsic neuronal innervation within the intestine, as well as local specialized enteroendocrine cells. However, the molecular mechanisms and the subset of sensory neurons underlying the initiation and regulation of intestinal motility remain largely unknown. Here, we show that humans lacking PIEZO2 exhibit impaired bowel sensation and motility. Piezo2 in mouse dorsal root but not nodose ganglia is required to sense gut content, and this activity slows down food transit rates in the stomach, small intestine, and colon. Indeed, Piezo2 is directly required to detect colon distension in vivo. Our study unveils the mechanosensory mechanisms that regulate the transit of luminal contents throughout the gut, which is a critical process to ensure proper digestion, nutrient absorption, and waste removal. These findings set the foundation of future work to identify the highly regulated interactions between sensory neurons, enteric neurons and non- neuronal cells that control gastrointestinal motility.

MicroRNAs are small noncoding RNAs that provide a critical layer of gene expression control. Individual microRNAs variably exert effects across networks of genes via sequence-specific binding to mRNAs, fine-tuning protein levels. This helps coordinate the timing and specification of cell fate transitions during brain development and maintains neural circuit function and plasticity by activity-dependent (re)shaping of synapses and the levels of neurotransmitter components. MicroRNA levels have been found to be altered in tissue from the epileptogenic zone resected from adults with drug-resistant focal epilepsy and this has driven efforts to explore their therapeutic potential, in particular using antisense oligonucleotide (ASOs) inhibitors termed antimirs. Here, we review the molecular mechanisms by which microRNAs control brain excitability and the latest progress towards a microRNA-based treatment for temporal lobe epilepsy. We also look at whether microRNA-based approaches could be used to treat genetic epilepsies, correcting individual genes or dysregulated pathways. Finally, we look at how cells have evolved to maximise the efficiency of the microRNA system via RNA editing, where single base changes is capable of altering the repertoire of genes under the control of a single microRNA. The findings improve our understanding of the molecular landscape of the epileptic brain and may lead to new therapies.

The overall aim of my research is to understand how the organisation of the synapse, with particular reference to the postsynaptic proteome (PSP) of excitatory synapses in the brain, informs the fundamental mechanisms of learning, memory and behaviour and how these mechanisms go awry in neurological dysfunction. The PSP indeed bears a remarkable burden of disease, with components being disrupted in disorders (synaptopathies) including schizophrenia, depression, autism and intellectual disability. Our work has been fundamental in revealing and then characterising the unprecedented complexity (>1000 highly conserved proteins) of the PSP in terms of the subsynaptic architecture of postsynaptic proteins such as PSD95 and how these proteins assemble into complexes and supercomplexes in different neurons and regions of the brain. Characterising the PSPs in multiple species, including human and mouse, has revealed differences in key sets of functionally important proteins, correlates with brain imaging and connectome data, and a differential distribution of disease-relevant proteins and pathways. Such studies have also provided important insight into synapse evolution, establishing that vertebrate behavioural complexity is a product of the evolutionary expansion in synapse proteomes that occurred ~500 million years ago. My lab has identified many mutations causing cognitive impairments in mice before they were found to cause human disorders. Our proteomic studies revealed that >130 brain diseases are caused by mutations affecting postsynaptic proteins. We uncovered mechanisms that explain the polygenic basis and age of onset of schizophrenia, with postsynaptic proteins, including PSD95 supercomplexes, carrying much of the polygenic burden. We discovered the “Genetic Lifespan Calendar”, a genomic programme controlling when genes are regulated. We showed that this could explain how schizophrenia susceptibility genes are timed to exert their effects in young adults. The Genes to Cognition programme is the largest genetic study so far undertaken into the synaptic molecular mechanisms underlying behaviour and physiology. We made important conceptual advances that inform how the repertoire of both innate and learned behaviours is built from unique combinations of postsynaptic proteins that either amplify or attenuate the behavioural response. This constitutes a key advance in understanding how the brain decodes information inherent in patterns of nerve impulses, and provides insight into why the PSP has evolved to be so complex, and consequently why the phenotypes of synaptopathies are so diverse. Our most recent work has opened a new phase, and scale, in understanding synapses with the first synaptome maps of the brain. We have developed next-generation methods (SYNMAP) that enable single-synapse resolution molecular mapping across the whole mouse brain and extensive regions of the human brain, revealing the molecular and morphological features of a billion synapses. This has already uncovered unprecedented spatiotemporal synapse diversity organised into an architecture that correlates with the structural and functional connectomes, and shown how mutations that cause cognitive disorders reorganise these synaptome maps; for example, by detecting vulnerable synapse subtypes and synapse loss in Alzheimer’s disease. This innovative synaptome mapping technology has huge potential to help characterise how the brain changes during normal development, including in specific cell types, and with degeneration, facilitating novel pathways to diagnosis and therapy.

Lifestyle factors such as sleep, diet, stress, and exercise, profoundly influence cardiovascular health. Seeking to understand how lifestyle affects our biology is important for at least two reasons. First, it can expose a particular lifestyle’s biological impact, which can be leveraged for adopting specific public health policies. Second, such work may identify crucial molecular mechanisms central to how the body adapts to our environments. These insights can then be used to improve our lives. In this talk, I will focus on recent work in the lab exploring how lifestyle factors influence cardiovascular health. I will show how combining tools of neuroscience, hematology, immunology, and vascular biology helps us better understand how the brain shapes leukocytes in response to environmental perturbations. By “connecting the dots” from the brain to the vessel wall, we can begin to elucidate how lifestyle can both maintain and perturb salutogenesis.

Experience-dependent transcription is a key molecular mechanisms for regulating the development and plasticity of synapses and neural circuits and is thought to underlie cognitive functions such as perception, learning and memory. After two years of COVID-pandemic, the goal of this online conference is to allow investigators in the field to reconnect and to discuss their recent scientific findings.

Adult hippocampal neurogenesis is implicated in memory formation and mood regulation. The Thuret lab investigates environmental and molecular mechanisms controlling the production of these adult-born neurons and how they impact mental health. We study neurogenesis in healthy ageing as well as in the context of diseases such as Alzheimer’s and depression. By approaching neurogenesis in health and disease, the strategy is two folds: (i) Validating the neurogenic process as a target for prevention and pharmacological interventions. (ii) Developing neurogenesis as a biomarker of disease prediction and progression. In this talk, I will focus on presenting some recent human studies demonstrating how hippocampal neural stem cells fate can be used as biomarkers of cognitive aging and dementia.

Puberty is a brain-driven phenomenon, which is under the control of sophisticated regulatory networks that integrate a large number of endogenous and environmental signals, including metabolic and nutritional cues. Puberty onset is tightly bound to the state of body energy reserves, and deregulation of energy/metabolic homeostasis is often associated with alterations in the timing of puberty. However, despite recent progress in the field, our knowledge of the specific molecular mechanisms and pathways whereby our brain decode metabolic information to modulate puberty onset remains fragmentary and incomplete. Compelling evidence, gathered over the last fifteen years, supports an essential role of hypothalamic neurons producing kisspeptins, encoded by Kiss1, in the neuroendocrine control of puberty. Kiss1 neurons are major components of the hypothalamic GnRH pulse generator, whose full activation is mandatory pubertal onset. Kiss1 neurons seemingly participate in transmitting the regulatory actions of metabolic cues on pubertal maturation. However, the modulatory influence of metabolic signals (e.g., leptin) on Kiss1 neurons might be predominantly indirect and likely involves also the interaction with other transmitters and neuronal populations. In my presentation, I will review herein recent work of our group, using preclinical models, addressing the molecular mechanisms whereby Kiss1 neurons are modulated by metabolic signals, and thereby contribute to the nutritional control of puberty. In this context, the putative roles of the energy/metabolic sensors, AMP-activated protein kinase (AMPK) and SIRT1, in the metabolic control of Kiss1 neurons and puberty will be discussed. In addition, I will summarize recent findings from our team pointing out a role of central de novo ceramide signaling in mediating the impact of obesity of (earlier) puberty onset, via non-canonical, kisspeptin-related pathways. These findings are posed of translational interest, as perturbations of these molecular pathways could contribute to the alterations of pubertal timing linked to conditions of metabolic stress in humans, ranging from malnutrition to obesity, and might become druggable targets for better management of pubertal disorders.

Lifelong devotion to headache research has led to many discoveries. First a series of studies of brain blood flow during attacks of migraine. The results showed changes compatible with cortical spreading depression in migraine without aura effectively negating the then prevailing vasospastic/ischemic theory. In migraine without aura no changes in brain blood flow. This difference was crucial for the separation of migraine with aura and migraine without aura in the first and subsequent editions of the international headache classification headed by me. Then a human migraine provocation model that has elucidated the molecular mechanisms of migraine. Successively we showed in series of papers the importance of nitric oxide, histamine, CGRP, PACAP and prostanoids. Therapeutic effectiveness of antagonizing these provokers by tonabersat, L-NMMA, CGRP receptor antagonists and monoclonal antibodies and of NSAIDs. Present and future attempts to put all these signaling mechanisms into a framework but it is not easy

Animals constantly modify their behavior through experience. Flexible behavior is key to our ability to adapt to the ever-changing environment. My laboratory is interested in studying the activity of neuronal ensembles in behaving animals, and how it changes with learning. We have recently set up a paradigm where mice learn to associate sensory information (two different odors) to motor outputs (lick vs no-lick) under head-fixation. We combined this with two-photon calcium imaging, which can monitor the activity of a microcircuit of many tens of neurons simultaneously from a small area of the brain. Imaging the motor cortex during the learning of this task revealed neurons with diverse task-related response types. Intriguingly, different response types were spatially intermingled; even immediately adjacent neurons often had very different response types. As the mouse learned the task under the microscope, the activity coupling of neurons with similar response types specifically increased, even though they are intermingled with neurons with dissimilar response types. This suggests that intermingled subnetworks of functionally-related neurons form in a learning-related way, an observation that became possible with our cutting-edge technique combining imaging and behavior. We are working to extend this study. How plastic are neuronal microcircuits during other forms of learning? How plastic are they in other parts of the brain? What are the cellular and molecular mechanisms of the microcircuit plasticity? Are the observed activity and plasticity required for learning? How does the activity of identified individual neurons change over days to weeks? We are asking these questions, combining a variety of techniques including in vivo two-photon imaging, optogenetics, electrophysiology, genetics and behavior.

The nervous system and the immune system share the common ability to exert gatekeeper roles at the interfaces between internal and external environment. Although interaction between these two evolutionarily highly conserved systems is long recognized, the pathophysiological mechanisms regulating their reciprocal crosstalk in cardiovascular diseases became object of investigation only more recently. In the last years, our group elucidated how the autonomic nervous system controls the splenic immunity recruited by hypertensive challenges. In my talk, I will focus on the molecular mechanisms that regulate the neuro-immune crosstalk in hypertension. I will elaborate on the mechanistic insights into this brain-spleen axis led us uncover a new molecular pathway mediating the neuroimmune interaction established by noradrenergic-mediated release in the spleen of placental growth factor (PlGF), an angiogenic growth factor potentially targetable with pharmacological approaches.

Broadly, the Mauro Costa-Mattioli laboratory (The MCM Lab) encompasses two complementary lines of research. The first one, more traditional but very important, aims at unraveling the molecular mechanisms underlying memory formation (e.g., using state-of-the-art molecular and cell-specific genetic approaches). Learning and memory disorders can strike the brain during development (e.g., Autism Spectrum Disorders and Down Syndrome), as well as during adulthood (e.g., Alzheimer’s disease). We are interested in understanding the specific circuits and molecular pathways that are primarily targeted in these disorders and how they can be restored. To tackle these questions, we use a multidisciplinary, convergent and cross-species approach that combines mouse and fly genetics, molecular biology, electrophysiology, stem cell biology, optogenetics and behavioral techniques. The second line of research, more recent and relatively unexplored, is focused on understanding how gut microbes control CNS driven-behavior and brain function. Our recent discoveries, that microbes in the gut could modulate brain function and behavior in a very powerful way, have added a whole new dimension to the classic view of how complex behaviors are controlled. The unexpected findings have opened new avenues of study for us and are currently driving my lab to answer a host of new and very interesting questions: - What are the gut microbes (and metabolites) that regulate CNS-driven behaviors? Would it be possible to develop an unbiased screening method to identify specific microbes that regulate different behaviors? - If this is the case, can we identify how members of the gut microbiome (and their metabolites) mechanistically influence brain function? - What is the communication channel between the gut microbiota and the brain? Do different gut microbes use different ways to interact with the brain? - Could disruption of the gut microbial ecology cause neurodevelopmental dysfunction? If so, what is the impact of disruption in young and adult animals? - More importantly, could specific restoration of selected bacterial strains (new generation probiotics) represent a novel therapeutic approach for the targeted treatment of neurodevelopmental disorders? - Finally, can we develop microbiota-directed therapeutic foods to repair brain dysfunction in a variety of neurological disorders?

The synapse is the core component of the nervous system and synapse formation is the critical step in the assembly of neuronal circuits. The assembly and maturation of synapses requires the contribution of secreted and membrane-associated proteins, with neuronal activity playing crucial roles in regulating synaptic strength, neuronal membrane properties, and neural circuit refinement. The molecular mechanisms of synapse assembly and refinement have been so far largely examined on a gene-by-gene basis and with a perspective fully centered on neuronal cells. However, in the last years, the involvement of non-neuronal cells has emerged. Among these, microglia, the resident immune cells of the central nervous system, have been shown to play a key role in synapse formation and elimination. Contacts of microglia with dendrites in the somatosensory cortex were found to induce filopodia and dendritic spines via Ca2+ and actin-dependent processes, while microglia-derived BDNF was shown to promote learning-dependent synapse formation. Microglia is also recognized to have a central role in the widespread elimination (or pruning) of exuberant synaptic connections during development. Clarifying the processes by which microglia control synapse homeostasis is essential to advance our current understanding of brain functions. Clear answers to these questions will have important implications for our understanding of brain diseases, as the fact that many psychiatric and neurological disorders are synaptopathies (i.e. diseases of the synapse) is now widely recognized. In the last years, my group has identified TREM2, an innate immune receptor with phagocytic and antiinflammatory properties expressed in brain exclusively by microglia, as essential for microglia-mediated synaptic refinement during the early stages of brain development. The talk will describe the role of TREM2 in synapse elimination and introduce the molecular actors involved. I will also describe additional pathways by which the immune system may affect the formation and homeostasis of synaptic contacts.

The establishment of synaptic connections is essential for normal brain function, yet the molecular mechanisms responsible for the precise connectivity of specific neural circuits remain largely unknown. Previous work has shown that the assembly of cortical circuits requires specific functions of molecular signalling complexes at different classes of synapses. In this talk, I will describe the molecular logic through which specific pyramidal cell-interneuron circuits are established in the cerebral cortex of the mouse, and how alterations in some of these connectivity motifs might be liked to disease.

The Aging Brain Initiative is an ambitious interdisciplinary effort by MIT focusing on understanding neurodegeneration and efforts to find hallmarks of aging, both in health and disease. The Initiative is broad, made up of scientists in several areas, including systems neuroscience, cell biology, engineering and computational biology, with core investigators from the Departments of Biology, Brain & Cognitive Sciences, Biological Engineering, and Computer Science & Artificial Intelligence Labs. "The theme of this symposium is Cellular & Molecular Mechanisms of Neurodegeneration.

Diets rich in sugar, salt, and fat alter taste perception and food intake, leading to obesity and metabolic disorders, but the molecular mechanisms through which this occurs are unknown. Here we show that in response to a high sugar diet, the epigenetic regulator Polycomb Repressive Complex 2.1 (PRC2.1) persistently reprograms the sensory neurons of D. melanogaster flies to reduce sweet sensation and promote obesity. In animals fed high sugar, the binding of PRC2.1 to the chromatin of the sweet gustatory neurons is redistributed to repress a developmental transcriptional network that modulates the responsiveness of these cells to sweet stimuli, reducing sweet sensation. Importantly, half of these transcriptional changes persist despite returning the animals to a control diet, causing a permanent decrease in sweet taste. Our results uncover a new epigenetic mechanism that, in response to the dietary environment, regulates neural plasticity and feeding behavior to promote obesity.

Our research team runs several related projects studying the cellular and molecular mechanisms involved in the development of axonal connections in the brain. In particular, our aim is to uncover the principles underlying thalamocortical axonal wiring, maintenance and ultimately the rewiring of connections, through an integrated and innovative experimental programme. The development of the thalamocortical wiring requires a precise topographical sorting of its connections. Each thalamic nucleus receives specific sensory information from the environment and projects topographically to its corresponding cortical. A second level of organization is achieved within each area, where thalamocortical connections display an intra-areal topographical organization, allowing the generation of accurate spatial representations within each cortical area. Therefore, the level of organization and specificity of the thalamocortical projections is much more complex than other projection systems in the CNS. The central hypothesis of our laboratory is that thalamocortical input influences and maintains the functional architecture of the sensory cortices. We also believe that rewiring and plasticity events can be triggered by activity-dependent mechanisms in the thalamus. Three major questions are been focused in the laboratory: i) the role of spontaneous patterns of activity in thalamocortical wiring and cortical development, ii) the role of the thalamus and its connectivity in the neuroplastic cortical changes following sensory deprivation, and iii) reprogramming thalamic cells for sensory circuit restoration. Within these projects we are using several experimental programmes, these include: optical imaging, manipulation of gene expression in vivo, cell and molecular biology, biochemistry, cell culture, sensory deprivation paradigms and electrophysiology. The results derived from our investigations will contribute to our understating of how reprogramming of cortical wiring takes place following brain damage and how cortical structure is maintained.

The concerted production of the correct number and diversity of neurons and glia by neural stem cells is essential for intricate neural circuit assembly. In the developing cerebral cortex, radial glia progenitors (RGPs) are responsible for producing all neocortical neurons and certain glia lineages. We recently performed a clonal analysis by exploiting the genetic MADM (Mosaic Analysis with Double Markers) technology and discovered a high degree of non-stochasticity and thus deterministic mode of RGP behaviour. However, the cellular and molecular mechanisms controlling RGP lineage progression remain unknown. To this end we use quantitative MADM-based genetic paradigms at single cell resolution to define the cell-autonomous functions of signaling pathways controlling cortical neuron/glia genesis and postnatal stem cell behaviour in health and disease. Here I will outline our current understanding of the mechanistic framework instructing neural stem cell lineage progression and discuss new data about the role of genomic imprinting – an epigenetic phenomenon - in cortical development.