ERC FUNDED PROJECTS

The molecular mechanisms that mediate cell competition, cell fitness and cell selection is gaining interest. With innovative approaches, molecules and ground-breaking hypothesis, this field of research can help understand several biological processes such as development, cancer and tissue degeneration. The project has 3 clear and ambitious objectives: 1. We propose to identify all the key genes mediating cell competition and their molecular mechanisms. In order to reach this objective we will use data from two whole genome screens in Drosophila where we have identified 7 key genes. By the end of this CoG grant, we should have no big gaps in our knowledge of how slow dividing cells are recognised and eliminated in Drosophila. 2. In addition, we will explore how general the cell competition pathways are and how they can impact biomedical research, with a focus in cancer and tissue degeneration. The interest in cancer is based on experiments in Drosophila and mice where we and others have found that an active process of cell selection determines tumour growth. Preliminary results suggest that the pathways identified do not only play important roles in the elimination of slow dividing cells, but also during cancer initiation and progression. 3. We will further explore the role of cell competition in neuronal selection, specially during neurodegeneration, development of the retina and adult brain regeneration in Drosophila. This proposal is of an interdisciplinary nature because it takes a basic cellular mechanism (the genetic pathways that select cells within tissues) and crosses boundaries between different fields of research: development, cancer, regeneration and tissue degeneration. In this ERC CoG proposal, we are committed to continue our efforts from basic science to biomedical approaches. The phenomena of cell competition and its participating genes have the potential to discover novel biomarkers and therapeutic strategies against cancer and tissue degeneration.

1 968 062 €

Start date: 2014-06-01, End date: 2019-05-31

Centrioles are essential for the formation of several microtubule organizing structures including cilia, flagella and centrosomes. These structures are involved in a variety of functions, from cell motility to division. Centrosome defects are seen in many cancers, while abnormalities in cilia and flagella can lead to a variety of human diseases, such as polycystic kidney disease. The molecular mechanisms regulating centriole biogenesis have only recently started to be unravelled, opening new ways to answer a wide range of questions that have fascinated biologists for more than a century. In this grant we are asking two fundamental questions that are central to human disease: how is centriole structure and number established and regulated in the eukaryotic cell? To address these questions we propose to identify new molecular players, and to test the role of these and known players in the context of specific mechanistic hypothesis, using in vitro and in vivo models. We propose to develop novel assays for centriole structure and regulation in order to address mechanistic problems not accessible with today s assays. In our search for novel components we will use a multidisciplinary approach combining bioinformatics with high throughput screening. The use of in vitro systems will permit the quantitative dissection of molecular mechanisms, while the study of those mechanisms in Drosophila will allow us to understand them at the whole organism level. Furthermore, this analysis, together with studies in human tissue culture cells, will allow us to understand the consequences of misregulation of these fundamental centriole properties for human disease, such as ciliopathies and cancer. My group is already collaborating with medical doctors in the study of centriole aberrations in human disease (cancer and ciliopathies), which will be invaluable to bringing the results of this study to the translational level.

1 500 000 €

Start date: 2011-01-01, End date: 2016-12-31

During the human lifetime 10000 trillion cell divisions take place to ensure tissue homeostasis and several vital functions in the organism. Mitosis is the process that ensures that dividing cells preserve the chromosome number of their progenitors, while deviation from this, a condition known as aneuploidy, represents the most common feature in human cancers. Here we will test two original concepts with strong implications for chromosome segregation fidelity. The first concept is based on the “tubulin code” hypothesis, which predicts that molecular motors “read” tubulin post-translational modifications on spindle microtubules. Our proof-of-concept experiments demonstrate that tubulin detyrosination works as a navigation system that guides chromosomes towards the cell equator. Thus, in addition to regulating the motors required for chromosome motion, the cell might regulate the tracks in which they move on. We will combine proteomic, super-resolution and live-cell microscopy, with in vitro reconstitutions, to perform a comprehensive survey of the tubulin code and the respective implications for motors involved in chromosome motion, mitotic spindle assembly and correction of kinetochore-microtubule attachments. The second concept is centered on the recently uncovered chromosome separation checkpoint mediated by a midzone-associated Aurora B gradient, which delays nuclear envelope reformation in response to incompletely separated chromosomes. We aim to identify Aurora B targets involved in the spatiotemporal regulation of the anaphase-telophase transition. We will establish powerful live-cell microscopy assays and a novel mammalian model system to dissect how this checkpoint allows the detection and correction of lagging/long chromosomes and DNA bridges that would otherwise contribute to genomic instability. Overall, this work will establish a paradigm shift in our understanding of how spatial information is conveyed to faithfully segregate chromosomes during mitosis.

2 323 468 €

Start date: 2016-07-01, End date: 2021-06-30

Epigenetic mechanisms heritably maintain gene expression states and chromosome organization across cell division. These include chromatin-based factors that are propagated independent of local DNA sequence elements, and are critical for normal development and prevent reprogramming, e.g. during induction of pluripotency. We focus on the role of nucleosomes, the histone-DNA complexes that make up chromatin. While prominently implicated in epigenetic memory, how histones and their local modifications can actually be inherited is largely unknown. We take aim at three fundamental aspects that we argue are central to this problem: stability of the epigenetic mark, self-templated duplication, and cell cycle coupling. We developed a unique pulse-labeling strategy to determine whether silent and active chromatin can be inherited and how this relates to transcription, both in cancer cells and in vitro differentiating stem cells. By coupling this strategy to an imaging-based RNAi screen we aim to identify components controlling nucleosome assembly and heritability. We achieve this by focusing on the human centromere, the chromosome locus essential for chromosome segregation which serves as an ideal model for epigenetic memory. This locus is specified by nucleosomes carrying the histone H3 variant, CENP-A that we have previously shown to be highly stable in cycling cells and to be replicated in a strict cell cycle coupled manner. We build on our previous successes to uncover the molecular mechanism and cellular consequences of the coupling between CENP-A propagation and the cell cycle which we postulate, ensures proper centromere size and mitotic fidelity. Furthermore, by genome engineering we developed a strategy to delete an endogenous centromere to determine how centromeres can form de novo and how CENP-A chromatin, once formed, can template its own duplication. With this multi-facetted approach we aim to uncover general mechanistic principles of chromatin-based memory.

1 621 400 €

Start date: 2014-06-01, End date: 2019-05-31