ERC FUNDED PROJECTS

Ciliopathies are pleiotropic diseases with a wide spectrum of human phenotypes. These include cyst formation in the liver and pancreas, respiratory disorders and a predisposition to diabetes and cancer. The pleiotropic nature of these disorders may reflect the many roles cilia play in physiology and signalling, highlighting the clinical importance of understanding their function in organ development and homeostasis. Despite the biological importance of cilia and decades of research, many aspects of cilia assembly and disassembly remain elusive. The earliest steps of cilia assembly involve conversion of the centrosome into a basal body, which anchors the cilia to the plasma membrane. Odf2 is one of the only proteins known to be important for this process, thus Ofd2 mutant cells lack cilia. During cell cycle re-entry primary cilia disassemble, the basal body dislodges from the plasma membrane and duplicates to serve as the mitotic centrosome. We recently identified Pitchfork, which functions in basal body-to-centrosome conversion and regulates embryonic patterning. The overall aim of this proposal is to better understand the cellular and bio-molecular mechanisms underlying ciliary disease. We will conditionally delete Odf2 and Pitchfork during embryogenesis and organogenesis. This will reveal the different requirements for the process of cilia assembly and disassembly in embryonic development, organ formation and homeostasis. The phenotypes will be analyzed at all levels of complexity. Subcellular imaging and identification of protein interaction partners will uncover the molecular basis of cilia assembly and disassembly. In summary, this project will decipher mechanisms underlying a wide spectrum of human ciliary disease and will open new avenues of clinical research.

1 449 640 €

Start date: 2010-02-01, End date: 2015-01-31

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

In this proposal, we study collective signaling oscillations during embryonic patterning. Signaling oscillations during vertebrate embryo segmentation are governed by a molecular oscillatory machinery referred to as segmentation clock (Palmeirim et al., 1997). The segmentation clock is linked to periodic activity of the Notch, Wnt and Fgf pathway in presomitic mesoderm (PSM) cells (period~2 hours in mouse embryos). Importantly, PSM cells display complex, collective synchronization and, as a result, wave-like activity patterns (phase waves) sweep periodically along the embryonic axis. We have previously shown that phase waves are an emergent and collective phenomenon in PSM cells (Tsiairis and Aulehla, 2016). Conceptually, this proposal builds on our previous discovery that the relative timing between Wnt/Notch oscillations is critical for proper mesoderm patterning (Sonnen et al., 2018). What are the principles underlying the emergence of collective synchronization and how do PSM cells decode relative timing of signalling oscillations? As outlined in this proposal, we are now in a unique position to address these fundamental questions in novel ways. Importantly, we have established an entrainment strategy that enables, for the first time, precise experimental control of oscillation dynamics (Sonnen et al., 2018). Our strategy is to further expand the entrainment approach, including the future use of optogenetics, and also combine it with our expertise in quantitative, multi-scale analysis of signalling dynamics and functional, genetic perturbations. A central aim of this ERC proposal is to build on discoveries made in versatile in vitro assays that we developed and to address their significance in vivo. To this end, we propose a novel line of research using the medaka fish model. We will entrain and challenge collective synchronization in vivo to address how signalling oscillations are integrated with growth dynamics to yield robust embryonic patterning.

2 153 310 €

Start date: 2020-09-01, End date: 2025-08-31

Animals display a tremendous diversity of patterns ‒from the colourful designs that adorn their body to repeated segmented appendages. Natural patterns result from the formation of discrete domains within developing tissues through the integration of positional cues by cells that consequently adopt specific fates and produce spatial heterogeneity. How can such developmental processes underlie the apparent complexity and diversity of natural patterns? We propose to address this long-standing question with an innovative experimental design: we will make use of natural variation as a powerful tool to facilitate the identification of patterning molecules and morphogenetic events. We will study colour pattern, a crucial adaptive trait that varies extensively in nature, from large colour domains to periodic designs. In amniotes, colour pattern is formed by spatial differences in the distribution of pigment cells and integumentary appendages. While the pigmentation system has been well characterized, the mechanisms governing the formation of compartments in the skin of wild animals have remained unclear, largely because laboratory models do not display ecologically-relevant colour patterns. We will use a combination of forward genetics, developmental biology, modelling, and imaging to study natural variation in the large colour domains of Estrildid finches and the periodic stripes of Galliform birds. For both phenotypes, we will characterize the organization of the embryonic skin and the mode of patterning (i.e., instructional patterning via external cues vs locally-occurring self-organization) underlying their formation, and identify the molecular factors and developmental processes contributing to their variation. Results from these studies will elucidate the biochemical events and tissue rearrangements orchestrating colour patterning in development and shed light on how these processes shape natural variation in this trait‒ and more generally, in natural patterns.

1 483 144 €

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