ERC FUNDED PROJECTS

Cells sense, affect and respond to their environment through the fundamental function of adhesion. Several types of adhesion sites, which are mediated via dynamically maintained multi-protein structures, anchor extracellular-matrix proteins to the cytoskeleton. Despite considerable efforts, the long-standing questions of how adhesion sites are formed, structured and regulated remain unanswered. In this research plan we will investigate desmosomes and adherens junctions by cryo-electron tomography of cells and tissue. The principal objectives are: (a) to visualize the molecular architecture and reveal the structural differences of the adhesion sites under various conditions and influences, i.e. mutations, wounds, etc. (b) to reveal their molecular association to the cytoskeleton (intermediate and actin filaments respectively), and to chart the network of interactions underlying cellular adhesion, and (c) to develop novel pattern recognition and classification techniques in order to structurally characterize the adhesion sites in toto by cryo-electron tomography of vitreous sections. We will use pattern recognition techniques and locally averaged cryo-electron sub-tomograms to quantify the macromolecular complexes in terms of stoichiometry and protein interactions in situ at high resolution (~3 nm). In particular, we aim to reveal how a pool of constituent proteins is organized in the two adhesion sites. Significant amounts of information coming from immunogold electron microscopy, fragments from X-ray structures, force measurements with atomic force microscopy, and structural bioinformatics will be integrated into our cryo-electron tomograms. This research will pioneer structural comparisons of protein networks at nanometer resolution in situ and in toto. The experimental and theoretical methods that will be developed would be indispensable for studying any spatially constrained protein network whose state depends on local properties.

1 724 400 €

Start date: 2010-01-01, End date: 2015-12-31

The goal of this research proposal is to unravel the molecular and cell biological basis underlying the expansion of the human cerebral cortex. Specifically, we wish to identify the genes responsible for the increase in the generation of cortical neurons from neural stem and progenitor cells that occurs during primate evolution. We will take two complementary approaches. One is to characterize the differences between mouse and human cerebral cortex with regard to the molecular and cell biological features of neural stem and progenitor cells, their mode of division, and the generation of neurons from these cells. Among the observed differences, human-specific features of cortical progenitor cells will then be identified by comparison with various non-human primates. The resulting candidate genes will be expressed in mouse embryonic cortical progenitors by in utero electroporation and tested for their ability to reconstitute human-like cortical progenitors in vivo. The second approach is based on a novel technology that allows us to introduce the total pool of mRNAs expressed in human cortical progenitors into mouse cortical progenitors in organotypic slice culture. This technology will be used to functionally screen for human genes able to generate human-like cortical progenitors in the mouse embryonic cortex. Human genes validated by these two approaches will then be used to generate acute transgenic mouse embryos and transgenic mouse lines that show a gyrencephalic, primate-like cerebral cortex. This research proposal will provide fundamental insight into the process of human cortical expansion, which provides the cellular basis of higher brain function, and establish an essential basis for future progenitor cell-based therapies for the diseased human brain.

2 496 000 €

Start date: 2010-10-01, End date: 2016-09-30

In eukaryotic cells the DNA is packaged into nucleosomes and higher order structures which lead to a condensation and protection of the DNA. During important cellular processes such as transcription or replication access to the DNA has to be granted. This is facilitated by ATP dependent nucleosome remodelling. The mechanistic details how the involved remodelling complexes succeed in providing access to the nucleosomal DNA are currently in spite of large experimental efforts not well understood. The aim of the proposal is to unravel the molecular mechanism of nucleosome remodelling using single-molecule fluorescence resonance energy transfer (FRET). By putting labels on the nucleosomal DNA, the histones or the remodellers we will - step by step - determine the conformational changes that occur during remodelling and use this information to build a mechanistic model. We will also use the controlled assembly of 30 nm fibers from purified components in order to determine how remodelling occurs in this structurally restricted environment. The large size of the chromatin fibers will dictate that in addition to FRET measurements, which will again be used to investigate local motion, super-resolution microscopy need to be employed to obtain information about long-distance movements. To this end we will use stochastic optical reconstruction microscopy (STORM), which allows for accuracy below 10 nm, thus ideally complementing the FRET approach. In summary our experiments will lead us to a mechanistic understanding of ATP dependent nucleosome remodelling, both on mono-nucleosomes as well as in higher order structures. This knowledge will in return stimulate new initiatives aimed at understanding the nature and regulation of chromatin dynamics in vivo.

1 395 381 €

Start date: 2009-11-01, End date: 2014-10-31

This proposal describes experiments aimed at defining the multiple roles of vesicular glutamate transporters (VGLUTs) in central synapses. Classically, VGLUTs transport glutamate from the cytoplasm into synaptic vesicles. Deletion of these genes disrupts synaptic glutamate release and their expression suffices to determine neurons as glutamatergic. We recently discovered that VGLUTs control additional key parameters such as quantal size and vesicular release probability, suggesting that they are fundamental regulators of synaptic strength and synaptic plasticity. To study these novel functions, we will first address whether the number of VGLUTs per vesicle (VGLUT content) can affect the amount of stored glutamate and in addition, the probability of vesicle release. We will subsequently explore the underlying mechanisms. Second, we will test the hypothesis that different VGLUT paralogs contribute to functional differences in discrete synapse populations, as implied by our preliminary data and the distribution pattern of the two main paralogs VGLUT1 and VGLUT2 in the brain. Subsequently, we will perform structure function studies on VGLUTs in native synapses to identify the underlying molecular interactions. Finally, the little understood VGLUT3 paralog is expressed mainly in subclasses of cholinergic, dopaminergic and GABAergic neurons, but no evidence exists that demonstrates VGLUT3 s role in glutamate release. We will address whether VGLUT3 is used to co-release glutamate with other neurotransmitters, and will test whether presence of glutamate in synaptic vesicles interferes with the storage or release of other neurotransmitters. Our studies will yield important insights into how these transporters operate, and how modulation of VGLUTs affects synaptic encoding and brain function. Because of observed profound regulation of VGLUTs in schizophrenia, depression and Parkinsons disease, these findings will also contribute to diagnosis and treatment of mental illness.

2 413 200 €

Start date: 2010-04-01, End date: 2015-03-31