ERC FUNDED PROJECTS

Despite the discovery of amyloidosis more than a century ago, the molecular and cellular mechanisms of these devastating human disorders remain obscure. In addition to their involvement in disease, amyloid fibrils perform physiological functions, whilst others have potentials as biomaterials. To realise their use in nanotechnology and to enable the development of amyloid therapies, there is an urgent need to understand the molecular pathways of amyloid assembly and to determine how amyloid fibrils interact with cells and cellular components. The challenges lie in the transient nature and low population of aggregating species and the panoply of amyloid fibril structures. This molecular complexity renders identification of the culprits of amyloid disease impossible to achieve using traditional methods. Here I propose a series of exciting experiments that aim to cast new light on the molecular and cellular mechanisms of amyloidosis by exploiting approaches capable of imaging individual protein molecules or single protein fibrils in vitro and in living cells. The proposal builds on new data from our laboratory that have shown that amyloid fibrils (disease-associated, functional and created from de novo designed sequences) kill cells by a mechanism that depends on fibril length and on cellular uptake. Specifically, I will (i) use single molecule fluorescence and non-covalent mass spectrometry and to determine why short fibril samples disrupt biological membranes more than their longer counterparts and electron tomography to determine, for the first time, the structural properties of cytotoxic fibril ends; (ii) develop single molecule force spectroscopy to probe the interactions between amyloid precursors, fibrils and cellular membranes; and (iii) develop cell biological assays to discover the biological mechanism(s) of amyloid-induced cell death and high resolution imaging and electron tomography to visualise amyloid fibrils in the act of killing living cells.

2 498 465 €

Start date: 2013-05-01, End date: 2019-04-30

ATM is the protein kinase that is mutated in the hereditary autosomal recessive disease ataxia telangiectasia (A-T). A-T patients display immune deficiencies, cancer predisposition and radiosensitivity. The molecular role of ATM is to respond to DNA damage by phosphorylating its substrates, thereby promoting repair of damage or arresting the cell cycle. Following the induction of double-strand breaks (DSBs), the NBS1 protein is required for activation of ATM. But ATM can also be activated in the absence of DNA damage. Treatment of cultured cells with hypotonic stress leads to the activation of ATM, presumably due to changes in chromatin structure. We have recently described a second ATM cofactor, ATMIN (ATM INteractor). ATMIN is dispensable for DSBs-induced ATM signalling, but ATM activation following hypotonic stress is mediated by ATMIN. While the biological role of ATM activation by DSBs and NBS1 is well established, the significance, if any, of ATM activation by ATMIN and changes in chromatin was up to now completely enigmatic. ATM is required for class switch recombination (CSR) and the suppression of translocations in B cells. In order to determine whether ATMIN is required for any of the physiological functions of ATM, we generated a conditional knock-out mouse model for ATMIN. ATM signaling was dramatically reduced following osmotic stress in ATMIN-mutant B cells. ATMIN deficiency led to impaired CSR, and consequently ATMIN-mutant mice developed B cell lymphomas. Thus ablation of ATMIN resulted in a severe defect in ATM function. Our data strongly argue for the existence of a second NBS1-independent mode of ATM activation that is physiologically relevant. While a large amount of scientific effort has gone into characterising ATM signaling triggered by DSBs, essentially nothing is known about NBS1-independent ATM signaling. The experiments outlined in this proposal have the aim to identify and understand the molecular pathway of ATMIN-dependent ATM signaling.

1 499 881 €

Start date: 2012-02-01, End date: 2018-01-31

A PubMed search for ‘epigenetic’ identifies nearly 35,000 entries, yet the molecular mechanisms by which chromatin modification and gene expression patterns are actually inherited during chromosome replication — mechanisms which lie at the heart of epigenetic inheritance of gene expression — are still largely uncharacterised. Understanding these mechanisms would be greatly aided if we could reconstitute the replication of chromosomes with purified proteins. The past few years have seen great progress in understanding eukaryotic DNA replication through the use of cell-free replication systems and reconstitution of individual steps in replication with purified proteins and naked DNA. We will use these in vitro replication systems together with both established and novel chromatin assembly systems to understand: a) how chromatin influences replication origin choice and timing, b) how nucleosomes on parental chromosomes are disrupted during replication and are distributed to daughter chromatids, and c) how chromatin states and gene expression patterns are re-established after passage of the replication fork. We will begin with simple, defined templates to learn basic principles, and we will use this knowledge to reconstitute genome-wide replication patterns. The experimental plan will exploit our well-characterised yeast systems, and where feasible explore these questions with human proteins. Our work will help explain how epigenetic inheritance works at a molecular level, and will complement work in vivo by many others. It will also underpin our long-term research goals aimed at making functional chromosomes from purified, defined components to understand how DNA replication interacts with gene expression, DNA repair and chromosome segregation.

1 983 019 €

Start date: 2015-11-01, End date: 2020-10-31

The unexpected connection between the primary cilium and cell-to-cell signalling is one of the most exciting discoveries in cell and developmental biology in the last decade. In particular, the Hedgehog (Hh) pathway relies on the primary cilium to fulfil its fundamental functions in orchestrating vertebrate development. This microtubule-based antenna, up to 5 µm long, protrudes from the plasma membrane of almost every human cell and is the essential compartment for the entire Hh signalling cascade. All its molecular components, from the most upstream transmembrane Hh receptor down to the ultimate transcription factors, are dynamically localised and enriched in the primary cilium. The aim of this proposal, which combines structural biology and live cell imaging, is to understand the function and signalling consequences of the multivalent interactions between Hh signal transducer proteins as well as their spatial and temporal regulation in the primary cilium. The key questions my laboratory will address are: What are the rules for assembly of Hh signal transduction complexes? How dynamic are these complexes in size and organisation? How are these processes linked to the transport and accumulation in the primary cilium? I will combine state-of-the art structural biology techniques (with an emphasis on X-ray crystallography) to study the molecular architecture of binary and higher-order Hh signal transduction complexes and live cell fluorescence microscopy (for protein localisation and direct protein interactions). These two approaches will allow me to identify and define specific protein-protein interfaces at the atomic level and test their functional consequences in the cell in real time. My goal is to consolidate a world-class morphogen signal transduction laboratory, deciphering fundamental biological insights. Importantly, my results and reagents can potentially feed into the development of novel anti-cancer therapeutics and reagents promoting stem cell therapy.

1 727 456 €

Start date: 2015-08-01, End date: 2020-07-31