ERC FUNDED PROJECTS

Familial forms of neurodegenerative diseases are caused by mutations in a single gene. It is unknown whether distinct mutations in the same gene or in functionally related genes cause disease through similar or disparate mechanisms. Furthermore, the precise molecular mechanisms underlying virtually all neurodegenerative disorders are poorly understood, and effective treatments are typically lacking. This is also the case for Charcot-Marie-Tooth (CMT) peripheral neuropathy caused by mutations in five distinct tRNA synthetase (aaRS) genes. We previously generated Drosophila CMT-aaRS models and used a novel method for cell-type-specific labeling of newly synthesized proteins in vivo to show that impaired protein translation may represent a common pathogenic mechanism. In this proposal, I aim to determine whether translation is also inhibited in CMT-aaRS mouse models, and whether all mutations cause disease through gain-of-toxic-function, or alternatively, whether some mutations act through a dominant-negative mechanism. In addition, I will evaluate whether all CMT-aaRS mutant proteins inhibit translation, and I will test the hypothesis, raised by our unpublished preliminary data shown here, that a defect in the transfer of the (aminoacylated) tRNA from the mutant synthetase to elongation factor eEF1A is the molecular mechanism underlying CMT-aaRS. Finally, I will validate the identified molecular mechanism in CMT-aaRS mouse models, as the most disease-relevant mammalian model. I expect to elucidate whether all CMT-aaRS mutations cause disease through a common molecular mechanism that involves inhibition of translation. This is of key importance from a therapeutic perspective, as a common pathogenic mechanism allows for a unified therapeutic approach. Furthermore, this proposal has the potential to unravel the detailed molecular mechanism underlying CMT-aaRS, what would constitute a breakthrough and a requirement for rational drug design for this incurable disease.

2 000 000 €

Start date: 2018-06-01, End date: 2023-05-31

The basal ganglia consist of a set of neuroanatomical structures that participate in the representation and execution of action sequences. Dopamine neurotransmission in the striatum, the main input nucleus of the basal ganglia, is a fundamental mechanism involved in learning and regulation of such actions. The striatum has multiple functional units, where the limbic striatum is thought to mediate motivational aspects of actions (e.g., goal-directedness) and the sensorimotor striatum their automation (e.g., habit formation). A long-standing question in the field is how limbic and sensorimotor domains communicate with each other, and specifically if they do so during the automation of action sequences. It has been suggested that such coordination is implemented by reciprocal loop connections between striatal projection neurons and the dopaminergic midbrain. Although very influential in theory the effectiveness of this limbic-sensorimotor “bridging” principle has yet to be verified. I hypothesize that during the automation of behaviour regional dopamine signalling is governed by a striatal hierarchy and that dysregulation of this coordination leads to compulsive execution of automatic actions characteristic of several psychiatric disorders. To test this hypothesis, we will conduct electrochemical measurements with real-time resolution simultaneously in limbic and sensorimotor striatum to assess the regional coordination of dopamine release in behaving animals. We developed novel chronically implantable electrodes to enable monitoring of dopamine dynamics throughout the development of habitual behaviour and its compulsive execution in transgenic rats - a species suitable for our complex behavioural assays. Novel rabies virus-mediated gene delivery for in vivo optogenetics in these rats will give us the unique opportunity to test whether specific loop pathways govern striatal dopamine transmission and are causally involved in habit formation and compulsive behaviour.

1 500 000 €

Start date: 2015-05-01, End date: 2020-04-30

The regulated secretion of chemical signals in the brain occurs principally from two organelles, synaptic vesicles and dense core vesicles (DCVs). Synaptic vesicle secretion accounts for the well characterized local, fast signalling in synapses. DCVs contain a diverse collection of cargo, including many neuropeptides that trigger a multitude of modulatory effects with quite robust impact, for instance on memory, mood, pain, appetite or social behavior. Disregulation of neuropeptide secretion is firmly associated with many diseases such as cognitive and mood disorders, obesity and diabetes. In addition, many other signals depend on DCVs, for instance trophic factors and proteolytic enzymes, but also signals that typically do not diffuse like guidance cues and pre-assembled active zones. Hence, it is beyond doubt that DCV signalling is a central factor in brain communication. However, many fundamental questions remain open on DCV trafficking and secretion. Therefore, the aim of this proposal is to characterize the molecular principles that account for DCV delivery at release sites and their secretion. I will address 4 fundamental questions: What are the molecular factors that drive DCV fusion in mammalian CNS neurons? How does Ca2+ trigger DCV fusion? What are the requirements of DCV release sites and where do they occur? Can DCV fusion be targeted to synthetic release sites in vivo? I will exploit >30 mutant mouse lines and new cell biological and photonic approaches that allow for the first time a quantitative assessment of DCV-trafficking and fusion of many cargo types, in living neurons with a single vesicle resolution. Preliminary data suggest that DCV secretion is quite different from synaptic vesicle and chromaffin granule secretion. Together, these studies will produce the first systematic evaluation of the molecular identity of the core machinery that drives DCV fusion in neurons, the Ca2+-affinity of DCV fusion and the characteristics of DCV release sites.

2 439 315 €

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

A major challenge in neuroscience is to understand how information is stored and coded within single nerve cells (neurons) and across neuron populations in the brain. Nerve cell fibres (axons) are thought to provide the wiring to connect neurons and conduct the electrical nerve impulse (action potential; AP). Recent discoveries, however, show that the initial part of axons actively participates in modulating APs and providing a means to enhance the computational repertoire of neurons in the central nervous system. To decrease the temporal delay in information transmission over long distances most axons are myelinated. Here, we will test the hypothesis that the degree of myelination of single axons directly and indirectly influences the mechanisms of AP generation and neural coding. We will use a novel approach of patch-clamp recording combined with immunohistochemical and ultrastructural identification to develop a detailed model of single myelinated neocortical axons. We also will investigate the neuron-glia interactions responsible for the myelination process and measure whether their development follows an activity-dependent process. Finally, we will elucidate the physiological and molecular similarities and discrepancies between myelinated and experimentally demyelinated single neocortical axons. These studies will provide a novel methodological framework to study central nervous system axons and yield basic insights into myelin physiology and pathophysiology.

1 994 640 €

Start date: 2011-04-01, End date: 2016-03-31