ERC FUNDED PROJECTS

Each cell in our body has a specific biography that is defined by its pedigree relationship with other cells (lineage) and by its history of gene expression (trajectory). A fundamental question in cellular and developmental biology has been how the lineage and trajectory of a cell lead to its specification and differentiation. Remarkable progress in genome editing and single-cell sequencing has generated the opportunity to understand this process at global scales and single-cell resolution. We have recently developed methods to reconstruct the cellular ancestry and transcriptional trajectories of cells during embryogenesis. The resulting lineage and trajectory trees can be analyzed to gain comprehensive views of how cellular diversity arises and how differentiation leads to physiologically specialized cell types. To generate such global views of cellular development, we will: 1. Define the cellular diversity and gene expression trajectories during zebrafish embryogenesis and organogenesis. Trajectory trees will be generated from scRNA-seq data and analyzed to reconstruct the gene expression pathways underlying fate specification. 2. Reveal the relationships between lineage and transcriptional trajectories during fate specification. Lineage trees will be generated by marking cells via genome editing and combined with trajectory trees to reveal the cellular paths towards fate specification. 3. Discover the gene expression cascades that remodel cells into physiologically functional types. Cell biological modules will be identified by comparing gene enrichment in differentiation trajectories and reveal the specialized and shared mechanisms of differentiation. These studies will help provide the first comprehensive and global view of the trajectories and lineages underlying vertebrate development. Our focus is on the zebrafish model system, but the data and concepts developed in this project will be applicable to other developmental and cellular systems.

2 411 440 €

Start date: 2020-01-01, End date: 2024-12-31

Centrosome duplication entails the formation of a single procentriole next to each centriole once per cell cycle. The mechanisms governing procentriole formation are poorly understood and constitute a fundamental open question in cell biology. We will launch an innovative multidisciplinary research program to gain significant insight into these mechanisms using C. elegans and human cells. This research program is also expected to have a significant impact by contributing important novel assays to the field. Six specific aims will be pursued: 1) SAS-6 as a ZYG-1 substrate: mechanisms of procentriole formation in C. elegans. We will test in vivo the consequence of SAS-6 phosphorylation by ZYG-1. 2) Biochemical and structural analysis of SAS-6-containing macromolecular complexes (SAMACs). We will isolate and characterize SAMACs from C. elegans embryos and human cells, and analyze their structure using single-particle electron microscopy. 3) Novel cell-free assay for procentriole formation in human cells. We will develop such an assay and use it to test whether SAMACs can direct procentriole formation and whether candidate proteins are needed at centrioles or in the cytoplasm. 4) Mapping interactions between centriolar proteins in live human cells. We will use chemical methods developed by our collaborators to probe interactions between HsSAS-6 and centriolar proteins in a time- and space-resolved manner. 5) Functional genomic and chemical genetic screens in human cells. We will conduct high-throughput fluorescence-based screens in human cells to identify novel genes required for procentriole formation and small molecule inhibitors of this process. 6) Mechanisms underlying differential centriolar maintenance in the germline. In C. elegans, we will characterize how the sas-1 locus is required for centriole maintenance during spermatogenesis, as well as analyze centriole elimination during oogenesis and identify components needed for this process

2 004 155 €

Start date: 2009-04-01, End date: 2014-03-31

Deciphering and engineering the assembly of cellular organelles is a key pursuit in biology. The centriole is an evolutionarily conserved organelle well suited for this goal, and which is crucial for cell signaling, motility and division. The centriole exhibits a striking 9-fold radial symmetry of microtubules around a likewise symmetrical cartwheel containing stacked ring-bearing structures. Components essential for generating this remarkable architecture from alga to man have been identified. A next critical step is to engineer assays to probe the dynamics of centriole assembly with molecular precision to fully understand how these components together build a functional organelle. Our ambitious research proposal aims at taking groundbreaking steps in this direction through four specific aims: 1) Reconstituting cartwheel ring assembly dynamics. We will use high-speed AFM (HS-AFM) to dissect the biophysics of SAS-6 ring polymer dynamics at the root of cartwheel assembly. We will also use HS-AFM to analyze monobodies against SAS-6, as well as engineer surfaces and DNA origamis to further dissect ring assembly. 2) Deciphering ring stacking mechanisms. We will use cryo-ET to identify SAS-6 features that direct stacking of ring structures and set cartwheel height. Moreover, we will develop an HS-AFM stacking assay and a reconstituted stacking assay from human cells. 3) Understanding peripheral element contributions to centriole biogenesis. We will dissect the function of the peripheral centriole pinhead protein Cep135/Bld10p, as well as identify and likewise dissect peripheral A-C linker proteins. Furthermore, we will further engineer the HS-AFM assay to include such peripheral components. 4) Dissecting de novo centriole assembly mechanisms. We will dissect de novo centriole formation in human cells and water fern. We will also explore whether de novo formation involves a phase separation mechanism and repurpose the HS-AFM assay to probe de novo organelle biogenes

2 500 000 €

Start date: 2019-09-01, End date: 2024-08-31

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