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2013 -
Grant Awardees - Early Career

Assessing the function of neocortical Layer 1 with genetically-encoded indicators of synaptic activity

PETREANU Leopoldo (ARGENTINA)

Champalimaud Neuroscience Programme - Champalimaud Foundation - Lisboa - PORTUGAL

TIAN Lin (USA)

Dept. of Biochemistry and Molecular Medicine/ Tian Lab - Universiy of California, Davis/School of Medicine - Davis - USA

Given its anatomical organization, it is clear that Layer (L)1 of the neocortex plays a key role in cortical function. L1 is composed almost exclusively of afferent axons originating from distal brain areas and the dendrites of their postsynaptic targets. Thus, L1 acts as an integration hub of distant and local activity. Despite the vast amount of neocortical recordings amassed over the past decades, L1 remains largely uncharacterized. Existing methods are unable to record afferent activity from the acellular L1 neuropil. Genetically encoded calcium indicators (GECIs) allow recording activity from presynaptic structures of defined neuronal populations. However, current sensors diffuse poorly to distant synapses or photobleach significantly when imaged in small compartments, reducing the signal-to-noise ratio. Here, we propose to develop novel specialized sensors for studying the connections linking distant brain regions, such as L1 afferents. First, we will develop genetic strategies for the efficient targeting of GECIs to presynaptic compartments while preserving their sensitivity and photostability during synaptic optical recordings. Second, we will develop methods to optically record activity from synapses with known connectivity. Combining the expertise of each team we will rapidly test these novel sensors in vivo and ex vivo in axons representing the three main classes of L1 inputs. The sensitivity of the different sensors is going to be measured by imaging L1 axonal boutons in acute brain slices. The performance of the synaptic sensors in vivo is going to be characterized by imaging L1 axonal boutons in awake behaving mice. By applying these novel sensors we will describe the basic functional organization of L1. We will characterize afferent activity from cholinergic and thalamic projections to L1 in behaving animals with synaptic resolution. In addition we are going to determine whether functionally diverse cortico-cortical signals intermingled in L1 target different pyramidal neurons. Our project will shed light on the functional organization of L1. Importantly, the tools to be generated will have wide applications in neuroscience by allowing recordings from afferents of any length scale and relating their function with connectivity.

2013 -
Long-Term Fellowships - LTF

Discovery of key genetic alterations of stem-like circulating tumor cells in human cancer patients

ACETO Nicola (ITALY)

Department of Medicine - Harvard Medical School - Boston - USA

HABER Daniel (Host supervisor)

Metastasis is the major cause of cancer-related death. This process is realized by circulating tumor cells (CTCs) that shed from the primary tumor site and colonize distant organs. Despite the enormous clinical implications, little is known about the key genetic events that allow only certain CTCs to successfully initiate a metastatic lesion. In fact, the number of CTCs largely exceeds the number of clonal metastatic lesions in patients, suggesting a cellular hierarchy within CTCs and indicating that majority of CTCs is likely to die in the bloodstream, with only a minor CTC fraction being effectively stem-like metastatic precursors. We aim to characterize the genetic alterations accumulated by single CTCs to gain insights into CTCs heterogeneity and to ultimately identify metastasis-relevant genes in human pancreatic cancer patients. To this end, we will use a newly developed device for the isolation of CTCs from blood samples of cancer patients combined with single-cell next generation sequencing. First, we will sequence multiple single human CTCs and single cells from matched primary tumors to retrieve the mutation profile of each gene and the frequency of each mutation in CTCs and corresponding primary tumors. Second, we will use sphere-formation assay to screen all the candidate mutations which were enriched or unique in CTCs. Third, focusing on the strongest hits, we will assess whether doxycycline-inducible expression and/or knockdown of a candidate mutated gene affects CTCs number and metastasis in xenografts. Our studies will ultimately lead to the discovery of metastasis-relevant genes altered predominantly in stem-like CTCs.

2013 -
Long-Term Fellowships - LTF

Role of inhibition in experience-dependent structural synaptic plasticity

ADLER Avital (ISRAEL)

Department of Physiology and Neuroscience - New York University School of Medicine - New York - USA

GAN Wenbiao (Host supervisor)

Morphological synaptic changes, specifically those of dendritic spine remodeling, have been directly linked with functional aspects of learning and memory by rewiring and/or controlling the level of connectivity within the neural network. Following learning, the degree of dendritic spine remodeling correlates with behavioral performance, and is therefore suggested to represent a structural correlate of learning and memory. One factor which controls the regulation of spine and synapse turnover appears to be the excitation/inhibition balance of cortical networks. Furthermore, imbalance of excitation/inhibition is associated with cognitive disorders such as autism and schizophrenia. However, it remains unclear how exactly modulation of the excitatory/inhibitory balance can promote or reduce cortical plasticity. I therefore intend to examine how manipulating the activity of inhibitory interneurons will affect the learning and/or performance of a cognitive task, how it will affect the experience-dependent structural and functional connectivity within the network. To this end I will use newly developed genetic and optogenetic tools to activate or deactivate a specific sub group of cortical inhibitory interneurons during different stages of learning and performance. I will then examine the animals' behavior, the spine turnover (using two photon microscopy) and the neuronal connectivity (using electrophysiology) across the different perturbations. I hope these studies will shed light on the causal relationship between cortical structure and function to learning and memory processes.

2013 -
Grant Awardees - Program

Cell fate decision by integration of information from multiple plant hormones

AERTS Stein (BELGIUM)

Center for Brain & Disease Research - VIB-KU Leuven - Leuven - BELGIUM

SMOLKE Christina D. (USA)

Dept. of Bioengineering - Stanford University - Stanford - USA

VERNOUX Teva (FRANCE)

Dép. de Reproduction et Developpement des Plantes - Ecole Normale Supérieure - Lyon - FRANCE

We propose to elucidate the basis for positional information by hormones during plant morphogenesis. While it is known that cell fate decisions require simultaneous input from multiple hormones, to-date a precise understanding of how these signals are coordinated and act together to drive morphogenesis does not exist. Our limited mechanistic understanding is largely due to the difficulty to quantify the distribution of these small molecules in space and time. To explore this fundamental question, we will exploit recent advances in synthetic biology to engineer an RNA-based biosensor platform applicable to a broad range of small molecules and in particular to hormones. Using live-imaging technologies, we will use the sensors to obtain quantitative dynamic 3D maps of hormone distributions and relate these maps to the spatio-temporal distribution of cell identities, both during normal morphogenesis and upon perturbations of hormone levels. This analysis will be done on the shoot apical meristem, one of the best-characterized developmental systems in higher plants. In this context, mathematical approaches will be essential to analyze and establish a predictive model for how multiple hormones influence cell fate in a spatio-temporal manner.

2013 -
Grant Awardees - Program

Visual control of flight modes and transitions in birds

ALTSHULER Douglas (USA)

Dept. of Zoology - University of British Columbia - Vancouver - CANADA

LENTINK David (NETHERLANDS)

Dept. of Mechanical Engineering - Stanford University - Stanford - USA

SRINIVASAN Mandyam V. (AUSTRALIA)

Queensland Brain Institute - University of Queensland - Brisbane - AUSTRALIA

A bird that flies rapidly through dense foliage to land on a branch– as birds often do – engages in a veritable three-dimensional slalom, in which it has to continually dodge branches and leaves, and plan a collision-free path to the goal in real time. Here we aim to study how birds control the speed of their cruising flight, fly safely through narrow gaps, decelerate to a smooth landing, and how they transition seamlessly through these different flight modes. Research with insects indicates that there are neural programs for controlling specific features of flight, such as regulation of velocity and altitude, measuring distance flown, and homing. However, we do not know how these programs are organized to generate the complex flight trajectories that we observe in nature. There is an analogous deficit in our understanding of flight mechanics because most studies concern single modes of flight, such as take-off, cruising, hovering, or turning. We know little about how animals make transitions between flight modes. Our research will address these fundamental gaps in our understanding of animal flight by studying visual control of flight and wing kinematics in three bird species: two parrots, which are specialized for cruising flight (Budgerigars: Srinivasan; Lovebirds: Lentink) and a hummingbird, specialized for hovering flight (Altshuler). We focus on birds because they are visually agile, and can be trained to perform complex behaviors. The project will begin by characterizing the visual control of key flight modes: take-off, cruise, obstacle avoidance, and landing. We will then study transitions between these modes. The most effective way to study how vision is used to control flight involves the use of virtual reality environments. We will develop tools for instantaneously tracking the position and orientation of a bird’s head, and also tracking its wing position although not in real time. The head tracker will be combined with a video presentation system to create an arena in which what the bird sees can be manipulated relative to how it flies. The results from these experiments will have implications for the design of bio-inspired aircraft and of bird-friendly man-made structures, such as wind farms.

2013 -
Long-Term Fellowships - LTF

A novel C. elegans based approach to decipher the alternative lengthening of telomeres

ARNOULT Nausica (FRANCE)

Molecular and Cell Biology Laboratory - The Salk Institute for Biological Studies - La Jolla - USA

KARLSEDER Jan (Host supervisor)

The ends of linear chromosomes are protected from degradation and fusions by specialized structures called telomeres, which are composed of repetitive DNA bound by specialized proteins. In the absence of a maintenance mechanism, telomeres shorten during each cell division, due to the inability of conventional DNA polymerases to fully replicate the DNA end. This process limits the replicative capacity of somatic cells and therefore controls the aging process: once telomeres are too short, they loose their protective properties and cells stop dividing or simply die. To circumvent telomere shortening-associated aging and senescence and to gain immortality, cancer cells must maintain their telomeres. Most cancers do so by activating telomerase, but approximately 10% use the alternative ALT pathway. However, in response to telomerase inhibition, cells react with ALT activation, stressing the need to understand the ALT mechanism for cancer therapy. ALT mechanisms rely on recombination between telomeres, giving rise to features, such as heterogeneous telomere length, presence of extra-chromosomal telomeric DNA and telomeric sister chromatid exchange events are likely the cause and/or consequence of de-regulated telomere recombination. However, what allows such recombination events and the pathways leading to them is not currently understood. The Karlseder lab has recently engineered a worm strain that exclusively relies on ALT for telomere maintenance. Here, I propose to use this unique and powerful model to understand how ALT is activated and the molecular mechanism underlying telomere elongation by ALT in nematodes and mammals.

2013 -
Long-Term Fellowships - LTF

Mechanism of double-strand break repair via end-joining in Caulobacter crescentus

BADRINARAYANAN Anjana (INDIA)

Department of Biology - Massachusetts Institute of Technology - Cambridge - USA

LAUB Michael T. (Host supervisor)

Maintenance of life requires the preservation of genome integrity. DNA damage is a threat to genome stability and unrepaired damage such as double-strand breaks (DSB) can lead to loss of genetic information, cell death or cancer. Hence cells in all three domains of life have highly conserved mechanisms to repair DSBs. While repair via homologous recombination is most faithful, cells with only a single copy of their chromosome must employ alternative end-joining pathways, which can result in loss of genetic information or mutations. Little is understood about the molecular mechanism of action or regulation of end-joining (particularly in bacteria). This study proposes to establish Caulobacter crescentus as a model system to study DSB repair. While little is known about this process in C. crescentus, my preliminary experiments indicate that an end-joining pathway is active in this bacterium. The project aims to understand the mechanism of end-joining, and to find and characterize the proteins required for DSB repair via this pathway. I will utilize genetic tools developed in the host laboratory such as high-throughput mutagenesis screens and Chromosome-Conformation-Capture, along with traditional genetic read-outs to understand the mechanisms of DSB break repair in C. crescentus and its effects on chromosome function. Studies in this tractable system could provide insight into DSB repair in other pathogenic bacteria as well as humans.

2013 -
Grant Awardees - Program

An innovative, interdisciplinary model system for studying the developmental origins of sleep and brain rhythms

BALABAN Evan (USA)

Psychology Department & Behavioral Neurosciences Program - Stewart Biological Sciences Building - Montreal - CANADA

DI PASCOLI Stefano (ITALY)

Dept. of Information Engineering - University of Pisa - Pisa - ITALY

RATTENBORG Niels (USA)

Laboratory of Sleep and Flight in Birds - Max Planck Institute for Ornithology - Seewiesen - GERMANY

VAQUERO Juan José (SPAIN)

Depart. de Bioingeniería e Ingeniería Aeroespacial - Universidad Carlos III de Madrid - Leganes - SPAIN

This project combines our collective expertise in developmental biology, neuroscience, engineering, sleep biology and in-vivo molecular imaging to create an innovative chick embryo model for advancing scientific understanding of the developmental origins of sleep, waking and brain rhythms in higher vertebrate animals. Using a novel extension of embryo microsurgical techniques, an accessible port to the embryo head through the eggshell and respiratory membranes will be made at 1/10 of embryonic development (day 2 of a 21-day incubation period), and microscopic devices engineered to measure and wirelessly report brain temperature will be surgically implanted in the brain ventricles of individual embryos, to learn when rhythmic changes in brain temperature first emerge. Eggs are then sealed until 16 days of incubation, when the embryo head will be accessed, and skull electrodes implanted. The electrodes are connected to a miniature electroencephalography (EEG) system specifically engineered for continuous wireless recording from the eggs. Individual eggs will also be attached to a device for recording embryo heartbeat and behavior from vibrations on the eggshell. During continuous EEG and behavioral recording, eggs will have periodic PET/CT images taken of their brains to relate EEG patterns to brain metabolic activity patterns using a novel dynamic imaging procedure with sub-millimeter spatial resolution and a temporal resolution of between 30 seconds and 5 minutes (CT images will be used to developmentally stage individual embryos). This information will allow us to identify characteristics reliably associated with different embryo brain states. This “phenotyping” procedure permits embryo brains to be collected when they either have been in a particular brain state for a certain period of time, or at the transition between brain states, greatly facilitating the histological and molecular characterization of the role of changes in immediate-early gene expression and neurotransmitter system function that previous work has implicated in the control of adult sleep states and brain state changes, and permitting manipulative experiments. This system will significantly accelerate the identification of the neural systems organizing the initial emergence of these important systems brain functions, and of the mechanisms through which they operate.

2013 -
Grant Awardees - Early Career

Foot in motion: materials, mechanics and control

BANDI Mahesh (INDIA)

Collective Interactions Unit - Okinawa Institute of Science and Technology Graduate University - Onna - JAPAN

MANDRE Shreyas (INDIA)

School of Engineering - Brown University - Providence - USA

VENKADESAN Madhusudhan (INDIA)

Department of Mechanical Engineering and Materials Science - Yale University - New Haven - USA

The exquisitely complex mechanism of the human feet encompasses over a quarter of the body’s bones. How and why did the foot structure evolve to this current form? How do the demands of walking and running stably with low energy consumption affect foot evolution? The arched human foot reduces energy consumption by storing and releasing elastic energy like a bow and string. But does the foot’s elasticity also aid in maintaining stability of gait on uneven terrains? We have assembled an international team of researchers spanning the fields of physics, mathematics, and biomechanics to address how the foot has evolved and how it is controlled to balance the needs for stability and energy consumption during locomotion.
A soft foot smoothes out the ground’s uneven features, which may help stabilize running on realistic, uneven terrains. We expect that the neural system actively controls the softness of the foot by modulating the geometry of its arched form. We verify this hypothesis using a combination of measurements on human subjects running on uneven terrains and mathematical analysis of the foot’s elasticity. Our experiments will measure the spatial distribution of 3D forces under the foot using a newly developed high resolution photoelastic technique. These simultaneous and detailed physiological and mechanical measurements give us the ability to detect subtle changes in the mechanics of the foot, thus enabling the development of an anatomically faithful, mathematically rigorous model of foot function. These models then help us glean invariant principles of foot function used to mathematically design feet that optimally balance stability and energy consumption based on the terrain unevenness. We use these theories to also augment physical replicas of ancestral foot skeletons with muscle-like springs and motors in order to assess their functional capabilities against human performance. We hope, this comparative analysis will explain the time course of foot evolution, from the advent of regular walking 3.6 million years ago, to regular endurance running and emergence of a human-like form 1.5 million years ago. Our results also have implications to the design of prosthetic and robotic feet that could help in striking the right balance between energy storage and stability on real world uneven terrains.

2013 -

Exploring DNA-origami as pathway-specific immune adjuvants

BASTINGS Maartje (NETHERLANDS)

Dana Farber Cancer Institute - Harvard University - Boston - USA

SHIH William (Host supervisor)

The main goal of this proposal is to develop DNA-origami nanoparticles as immune adjuvants, modulating shape and site-specific modification with various ligands and chemical functionalities that can elicit potent and specific immune responses from targeted subsets of dendritic cells (DCs). Towards the development of vaccines with enhanced potency and specificity of DC activation, we propose to study how nanoscale shape and site-specific ligand functionalization of DNA-origami virus-like nanoparticles impact the magnitude and specificity of DC activation. By systematic screening of immune-pathway activation of DNA-origamis combined with antigens and danger-signals, our adjuvants will provide valuable insights into the complex mechanisms of our immune system.

2013 -
Long-Term Fellowships - LTF

Fluorescent sensors for monitoring the activity of DNA repair enzymes

BEHARRY Andrew (CANADA)

Department of Chemistry - Stanford University - Stanford - USA

KOOL Eric (Host supervisor)

Monitoring enzymatic DNA repair activity is important for cancer prognosis and treatment. Activity levels can be used to predict a patient’s response to a given drug and assess any resistance that is acquired during therapy. In addition, new DNA repair enzymes as potential drug targets may be discovered by correlating their activity levels within various cancer types. Current methods to measure DNA repair activity however are slow, laborious and often indirect in reporting repair activity. These tedious approaches prevent clinical researchers in measuring activity despite their high relevance to cancer. In this proposal, I discuss the design, synthesis and characterization of fluorescent chemosensors that will allow for a fast and simple assay for DNA repair activity. These sensors are built as small DNA oligomers containing a fluorescent nucleobase and the damaged base of interest, which itself will act as a quencher. Enzymatic repair of the damaged base will then lead to an increase in fluorescent signal, thereby providing a direct read-out of activity. The fluorescent probes will allow for in vitro and in vivo detection of the clinically important O6-methylguanine-DNA-methyltransferase (repair of guanine) and the newly studied ABH3 enzyme (repair of adenine). These probes will be valuable to clinicians who are evaluating the association of these enzymes to cancer therapy and medicinal chemists who are in search for new drug targets.

2013 -
Career Development Awards

Function and evolution of post-translational regulatory networks

BELTRAO Pedro (PORTUGAL)

European Bioinformatics Institute - EMBL - Hinxton - UK

Cells have evolved intricate systems to sense changes in internal and external conditions. These cues are relayed from sensors to actuators usually through post-translational modifications (PTMs) of proteins that allow cells to control cellular activities and generate an appropriate response. However, little is known about how these PTM regulatory networks change during evolution. In the past, comparative genomics has been crucial to study genome evolution and to identify functional DNA elements. In analogy to these studies, this project aims to advance our knowledge of cell signalling and evolution by performing a cross-species study of PTM regulation. Recent improvements in mass-spectrometry (MS) are unveiling a complex world of post-translational regulation with thousands of PTMs now routinely identified per study. PTMs have been shown to diverge quickly during evolution and it is not clear to what extent these changes have functional consequences. This rapid divergence underscores the importance of cross-species studies and urges the need to develop models of functionally relevant PTM regulatory networks. With this in mind, the main goals of this proposal are to: 1) experimentally determine PTMs for different species and predict the enzymes and binding domains that regulate them; 2) and develop and validate computational methods to predict the mechanistic functional role of PTMs. This work we will ultimately allow for a better understanding of how species adapt their regulatory networks during evolution and how genetic variability can generate diversity of PTM interactions that result in novel cell signaling responses.

2013 -
Long-Term Fellowships - LTF

Mechanisms of diabetes remission following gastric bypass surgery

BEN-ZVI Danny (ISRAEL)

Stem Cell and Regenerative Biology Department - Harvard University - Cambridge - USA

MELTON Douglas A. (Host supervisor)
RAMANATHAN Sharad (Host supervisor)

Diabetes is a growing public health concern, with over 300 million type II diabetic patients worldwide. In the last decade, it has been shown that gastric bypass surgery leads to lasting diabetes remission in obese patients. Surprisingly, blood glucose level is normalized in a matter of days, before any significant weight loss. This clinical observation suggests that there are yet unknown mechanisms of diabetes remission evoked by the surgical procedure. Uncovering those mechanisms holds promise to identify new and less invasive treatments to diabetes, and gain new understanding on basic metabolic processes that come into play after this anatomical reconfiguration.
I will use a gastric bypass model in a diet induced obesity diabetic mice to comprehensively characterize of the dynamics of the metabolic shift following surgery. This will be carried by analyzing transcriptomics and histology data of the intestine, liver and pancreas, and metabolomics data of the portal vein connecting these tissues. As controls I will use sham operated obese and weight matched mice as well as healthy lean mice. The data will integrated to generate a wholistic view of metabolism, identify metabolic and signaling pathways key to diabetes remission and define the new metabolic state of the animal after surgery. In particular, I will study the changes in the endocrine of pancreas after surgery as a model for recovery from diabetes. Finally, I will use the gastric bypass model to study intestinal adaptation. This will be done by comparing gene expression and histology of the different intestinal limbs and using the intestinal crypt culture system.

2013 -
Long-Term Fellowships - LTF

How cell-to-cell variability in membrane tension impacts on caveolae-mediated mechanotransduction

BERCHTOLD Doris (GERMANY)

Institute of Molecular Life Sciences - University of Zurich - Zurich - SWITZERLAND

PELKMANS Lucas (Host supervisor)

Caveolae are cup-shaped plasma membrane invaginations and play a crucial role in mechanotransduction. Upon membrane stretch, caveolar integrity is lost and clustered lipids and proteins are released. Redistribution of the major caveolar component is implicated in the activation of multiple kinases, but the mechanism remains unclear. It is not known how caveolar disassembly is regulated and what determines the intensity and type of the stress response. Recent high-content imaging screens revealed that monoclonal cells display cell-to-cell variability in biochemical activities and cellular processes depending on their population context. I hypothesize that membrane tension and caveolae formation are heterogeneous in a cell population, and that mechanical stress results in different biochemical responses, undetectable by population-averaged studies. Thus, I will image caveolae formation and disassembly in large populations of cells and use computational image analysis to cluster individual cells into subpopulations with similar social context. I will monitor the stretch-mediated activation of diverse kinases with high spatiotemporal resolution at single cell level in a population context, and correlate their activation profiles with caveolar disassembly. Identified patterns might reveal novel regulatory networks of caveolar mechanotransduction, as well as mechanisms by which individual cells adapt caveolar integrity and dynamics to their social context. Together, this study will provide important insights into the underlying mechanisms of how cells adapt to membrane stress, and will advance our perception of the fundamental concept of population-determined heterogeneity.

2013 -
Grant Awardees - Program

Taking snapshots of photosynthetic water oxidation: simultaneous X-ray spectroscopy and crystallography

BERGMANN Uwe (USA)

Linac Coherent Light Source - SLAC National Accelerator Laboratory - Menlo Park - USA

WERNET Philippe (GERMANY)

Helmholtz-Zentrum Berlin - Institute for Methods and Instrumentation for Synchrotron Radiation Research - Berlin - GERMANY

YANO Junko (JAPAN)

LINAC Coherent Light Source, - SLAC National Accelerator Laboratory - Menlo Park - USA

ZOUNI Athina (GERMANY)

Institut für Biologie - Humboldt-Universität - Berlin - GERMANY

Oxygen, that supports all aerobic life, is abundant in the atmosphere because of its constant regeneration by photosynthetic water oxidation by green plants, algae, and cyanobacteria. This reaction is catalyzed by a Mn4CaO5 cluster associated with photosystem II (PSII), a multi-subunit membrane protein complex. Given the role of PSII in maintaining life in the biosphere and the future vision of a renewable energy economy, understanding the mechanism of the photosynthetic water oxidation is considered to be one of science’s grand challenges. Although the structure of PSII and the chemistry at the catalytic site have been studied intensively, an understanding of the atomic-scale chemistry from light absorption to water-oxidation requires a new approach beyond the conventional steady state X-ray crystallography and X-ray spectroscopy at cryogenic temperatures. Following the dynamic changes in the geometric and electronic structure of the Mn4CaO5 cluster and PSII at ambient conditions, while overcoming the severe X-ray damage to the redox active catalytic center, is key for deriving the reaction mechanism. The intense and ultra-short femtosecond (fs) X-ray pulses of the LCLS (Linac Coherent Light Source) X-ray free electron laser provide an opportunity to overcome the current limitations of room temperature data collection for biological samples at regular X-ray sources. The fs X-ray pulses make it possible to acquire the signal before the sample is destroyed, which realizes the light-induced snap-shot study proposed here. The objective of this proposal is to study the protein structure and dynamics of PSII, as well as the chemical structure and dynamics of the Mn4CaO5 cluster (charge, spin, and covalency) during the light-driven process of PSII to elucidate the mechanism by which water is oxidized to dioxygen. We will design and apply a full suite of time-resolved X-ray diffraction and X-ray absorption/emission spectroscopy methods to follow the reaction at room temperature, that will provide an unprecedented combination of correlated data between the protein, the co-factors, and the Mn4CaO5 cluster, all of which are necessary for a complete understanding of photosynthetic water oxidation.

2013 -
Grant Awardees - Program

Artificial synthesis of the bacterial flagellar motor with DNA nanostructures

BERRY Richard (UK)

Dept. of Physics - University of Oxford - Oxford - UK

LEE Lawrence (AUSTRALIA)

Dept. of Single Molecule Science - UNSW Medicine Centre - Randwick - AUSTRALIA

NAMBA Keiichi (JAPAN)

Graduate School of Frontier Biosciences - Osaka University - Suita - JAPAN

TURBERFIELD Andrew (UK)

Dept. of Physics - University of Oxford - Oxford - UK

This project aims to artificially assemble a functional ‘switch complex’ of the bacterial flagellar motor (BFM) using DNA self-assembly to build a structural scaffold. The switch complex is a ~4 mega Dalton protein superstructure that converts a flux of ions across a membrane into mechanical rotation at speeds of up to 1700 Hz and consists of a reverse gear that switches rotation direction in a handful of milliseconds, making the BFM the most sophisticated nanoscale rotary motor known.
Building biology on a molecular scale is a fundamentally new approach to the Biological Sciences, which adopts a ‘top-down’ approach where the subcomponents are teased out of complete systems rather than pieced together from the bottom up. This suits the study of biological systems, which conveniently self assemble in vivo, but also limits our ability to manipulate systems to understand them. The BFM is one such example which can only be assembled and functionally characterised in vivo. As a result, elucidating a molecular picture of its structure and function is extremely difficult or impossible, and proposed molecular models remain controversial and not conclusively tested. However, the BFM may also present an important opportunity to study biology from the bottom-up. It is one of the best-characterised large protein complexes and decades of study have given us a blue print outlining the requirements for building the switch complex, which include a circular nanoscale structural scaffold. Recent advances in DNA self-assembly make it possible to build such a scaffold, allowing the programmed construction of nanoscale 3D objects at near-atomic precision.
We will design and build DNA nanostructures as structural scaffolds to artificially assemble the BFM switch complex ex vivo. By controlling and manipulating the assembly process, we will exploit remarkable new opportunities to address long-standing questions about the BFM and large, dynamic protein complexes in general, including the elucidation of a complete atomic-scale picture of this ~4 mega Dalton protein superstructure.

2013 -
Long-Term Fellowships - LTF

Role of receptor-membrane interactions in the regulation of EGFR activation

BHATTACHARYYA Moitrayee (INDIA)

Molecular Cell Biology - University of California, Berkeley - Berkeley - USA

KURIYAN John (Host supervisor)

The epidermal growth factor receptor (EGFR), a prime target for cancer drugs, plays a key role in intercellular signal transduction. Activation of EGFR is modulated by several layers of regulation that is built into its structural components, a breakdown of which has been implicated in many cancers. It is therefore important to uncover the detailed molecular mechanism that regulates EGFR activity. Although the significance of the EGFR-plasma membrane interactions is realized, the molecular details of such interactions are poorly understood. The proposed project aims at gaining insights into receptor-membrane interactions and the effect of perturbation of such interactions on the activation of EGFR.
I will examine the effect of specific charge interactions, between the receptor and the plasma membrane, on the activation of EGFR. Quantitative response of EGFR to charge reversal mutations, leading to a breakdown of EGFR-membrane interactions, will be assayed in the cell based context. This will enable identification of a set of mutations that would lift the inhibitory interactions with the membrane and stimulate the full length receptor in the absence of ligand. Additionally, I will investigate the influence of membrane localization on the activity of EGFR. The other question aims to test the hypothesis that membrane attachment of the amphipathic helix in the juxtamembrane segments leads to EGFR autoinhibition. I will adopt experimental (single-cell microscopy assays) and theoretical (molecular dynamics simulations) approaches to address these questions.

2013 -

Statistical mechanics of self-assembly

BITBOL Anne-Florence (FRANCE)

Lewis-Sigler Institute for Integrative Genomics - Princeton University - Princeton - USA

WINGREEN Ned S. (Host supervisor)
BIALEK William S. (Host supervisor)

This project aims to elucidate the principles of self-assembly of multiprotein complexes through statistical mechanics. Key questions are how self-assembly is constrained and how it can be optimized. Specifically, I aim to understand the observed necessity for "excess" numbers of copies of multiprotein complex constituents, and to examine the importance of cooperativity and nucleation barriers in self-assembly. I will initially focus on chemoreceptor arrays and flagellar motors in bacteria, two tractable and well-studied multiprotein complexes. My study will benefit from the long-term collaboration of Prof. Ned Wingreen at my host institution with the experimental group of Prof. Victor Sourjik at Heidelberg on chemotaxis. First, I plan to develop a coarse-grained model for extended multiprotein complexes, where self-assembly corresponds to a phase separation between a rich phase (e.g., rich in chemoreceptors) and a poor phase. I will study how the presence of a large variety and a large quantity of bystander proteins affects the efficiency and extent of phase separation. Second, I plan to investigate in more microscopic detail the interactions involved in self-assembly. Both direct protein-protein interactions and membrane-mediated interactions will be considered, with emphasis on their anisotropy, which yields specific assembly shapes. In particular, I will investigate the existence of an optimal strength of specific interactions, and I will study under what conditions a nucleation barrier exists, whether it is necessary for robust self-assembly, and how it constrains the range of possible self-assembled structures.

2013 -
Grant Awardees - Program

The birth and death of the chloroplast

BOCK Ralph (GERMANY)

Dept. III - Max Planck Institute of Molecular Plant Physiology - Potsdam-Golm - GERMANY

REICH Ziv (ISRAEL)

Dept. of Biological Chemistry - Weizmann Institute of Science - Rehovot - ISRAEL

Photosynthesis is essential for all life on Earth and has enormous environmental and agricultural impacts. The most advanced photosynthetic machinery is that of higher-plant chloroplasts, where it is hosted by one of the most complex membranous systems found in cells. Notably, this massive and elaborate system forms essentially from scratch, commencing with undifferentiated plastids that contain no or very little photosynthetic proteins or internal membranes. Equally remarkable, upon aging of leaves, seasonal changes, or the plant’s transition to the reproductive phase, this system, along with other components of the chloroplast, breaks down and is recycled in a highly regulated process reminiscent of programmed cell death. In addition to being of fundamental scientific interest, these processes bear an immediate agricultural relevance as they have a direct impact on biomass production, plant longevity, flowering, fruiting and seed production. Despite their importance, the processes underlying the biogenesis and breakdown of the photosynthetic machinery in higher-plant chloroplasts are largely elusive. This is because their study necessitates an integrative approach that combines structural and biophysical studies with high-throughput transcriptomic, proteomic and metabolomic analyses, all of which must be performed along the entire developmental pathway of the plastids, from incipient chloroplast differentiation to senescence. Here we propose to undertake such an interdisciplinary approach to comprehensively characterize the buildup and disintegration of the photosynthetic machinery in the chloroplasts of dicots – the largest group of flowering plants, which includes many agriculturally important plant species as well as most trees. These studies, along with subsequent systems analysis and reverse genetic approaches, are expected to significantly advance our knowledge of the elementary processes that underlie differentiation and senescence of higher-plant chloroplasts and, in this way, the construction and dismantling of the most efficient energy conversion device that exists in nature. In addition, they will aid future in silico modeling approaches, as well as efforts to improve photosynthesis by breeding or genetic engineering.

2013 -
Grant Awardees - Program

Revealing the fundamental limits of cell growth

BOLLENBACH Tobias (GERMANY)

Institute for Genetics - University of Cologne - Cologne - GERMANY

EHRENBERG Måns (SWEDEN)

Dept. of Cell and Molecular Biology - Uppsala University - Uppsala - SWEDEN

PAULSSON Johan (SWEDEN)

Dept. of Systems Biology, HMS - Harvard University - Boston - USA

TOPRAK Erdal (TURKEY)

Green Center for Systems Biology - UT Southwestern Medical Center - Dallas - USA

This project takes a multidisciplinary quantitative approach to investigate the consequences of maximal growth rates. It draws on a range of cutting-edge approaches, from in vitro biochemistry to evolution and high-throughput characterization. It will also be guided by mathematics at every step. In addition to the insights into cell physiology, we expect to set a new world record in rapid growth of biomass.