ERC FUNDED PROJECTS

Humans diverged from our closest living relatives, chimpanzees and other great apes, 6-10 million years ago. Since this divergence, our ancestors acquired genetic changes that enhanced cognition, altered metabolism, and endowed our species with an adaptive capacity to colonize the entire planet and reshape the biosphere. Through genome comparisons between modern humans, Neandertals, chimpanzees and other apes we have identified genetic changes that likely contribute to innovations in human metabolic and cognitive physiology. However, it has been difficult to assess the functional effects of these genetic changes due to the lack of cell culture systems that recapitulate great ape organ complexity. Human and chimpanzee pluripotent stem cells (PSCs) can self-organize into three-dimensional (3D) tissues that recapitulate the morphology, function, and genetic programs controlling organ development. Our vision is to use organoids to study the changes that set modern humans apart from our closest evolutionary relatives as well as all other organisms on the planet. In ANTHROPOID we will generate a great ape developmental cell atlas using cortex, liver, and small intestine organoids. We will use single-cell transcriptomics and chromatin accessibility to identify cell type-specific features of transcriptome divergence at cellular resolution. We will dissect enhancer evolution using single-cell genomic screens and ancestralize human cells to resurrect pre-human cellular phenotypes. ANTHROPOID utilizes quantitative and state-of-the-art methods to explore exciting high-risk questions at multiple branches of the modern human lineage. This project is a ground breaking starting point to replay evolution and tackle the ancient question of what makes us uniquely human?

1 500 000 €

Start date: 2019-06-01, End date: 2024-05-31

In mammals, transcriptional control of many genes relies on cis-regulatory elements such as enhancers, which are often located tens to hundreds of kilobases away from their cognate promoters. Functional interactions between distal regulatory elements and target promoters require mutual physical proximity, which is linked to the three-dimensional structure of the chromatin fiber. Chromosome conformation capture studies revealed that chromosomes are partitioned into Topologically Associating Domains (TADs), sub-megabase domains of preferential physical interactions of the chromatin fiber. Genetic evidence showed that TAD boundaries restrict the genomic range of enhancer-promoter communication, and that interactions between regulatory sequences within TADs are further fine-tuned by smaller-scale structures. However, the mechanistic details of how physical interactions translate into transcriptional outputs are totally unknown. Here we propose to explore the biophysical mechanisms that link chromosome conformation and long-range transcriptional regulation using molecular biology, genetic engineering, single-cell experiments and physical modeling. We will measure chromosomal interactions in single cells and in time using a novel method that relies on an enzymatic process in vivo. Genetic engineering will be used to establish a cell system that allows quantitative measurement of how enhancer-promoter interactions relate to transcription at the population and single-cell levels, and to test the effects of perturbations without confounding effects. Finally, we will develop physical models of promoter operation in the presence of distal enhancers, which will be used to interpret the experimental data and formulate new testable predictions. With this integrated approach we aim at providing an entirely new layer of description of the general principles underlying transcriptional control, which could establish new paradigms for research in epigenetics and gene regulation.

1 500 000 €

Start date: 2018-01-01, End date: 2022-12-31

Bacterial biofilms are the primary cause of chronic infections and of resulting infection relapses. To be able to interfere with bacterial persistence it is vital to understand the molecular details of biofilm formation and to define how motile planktonic cells transit into surface-grown communities. The nucleotide second messenger cyclic di-guanosinemonophosphate (cdGMP) has emerged as a central regulatory factor governing bacterial surface adaptation and biofilm formation. Although cdGMP signaling may well represent the Achilles heel of bacterial communities, cdGMP networks in bacterial pathogens are exquisitely complex and an integrated cellular system to uncover the details of cdGMP dynamics is missing. To quantitatively describe cdGMP signaling we propose to exploit Caulobacter crescentus, an organism with a simple bimodal life-style that integrates the sessile-motile switch into its asymmetric division cycle. We aim to: 1) identify the role and regulation of all diguanylate cyclases and phosphodiesterases that contribute to the asymmetric cellular program with the goal to model the temporal and spatial distribution of cdGMP during development; 2) identify and characterize cdGMP effectors, their downstream targets and cellular pathways; 3) elucidate how cdGMP coordinates cell differentiation with cell growth and propagation; 4) unravel the role of cdGMP as an allosteric regulator in mechanosensation and in rapid adaptation of bacteria to growth on surfaces; 5) develop novel tools to quantitatively describe cdGMP network dynamics as the basis for mathematical modeling that provides the predictive power to experimentally test and refine important network parameters. We propose a multidisciplinary research program at the forefront of bacterial signal transduction that will provide the molecular and conceptual framework for a rapidly growing research field of second messenger signaling in pathogenic bacteria.

2 496 000 €

Start date: 2013-05-01, End date: 2018-04-30

"Throughout evolution both intestinal helminths and commensal bacteria have inhabited our intestines. This ""ménage à trois"" situation is likely to have exerted a strong selective pressure on the development of our metabolic and immune systems. Such pressures remain in developing countries, whilst the eradication of helminths in industrialized countries has shifted this evolutionary balance—possibly underlying the increased development of chronic inflammatory diseases. We hypothesize that helminth-bacterial interactions are a key determinant of healthy homeostasis. Preliminary findings from our laboratory indicate that helminth infection of mice alters the abundance and diversity of intestinal bacteria and impacts on the availability of immuno-modulatory metabolites; this altered environment correlates with a direct health advantage, protecting against inflammatory diseases such as asthma and rheumatoid arthritis. We intend to validate and extend these data in humans by performing bacterial phlyogenetic and metabolic analysis of stool samples collected from a large cohort of children living in a helminth endemic region of Ecuador. We further propose to test our hypothesis that helminth-bacterial interactions contribute to disease modulation using experimental models of infection and disease. We plan to develop and utilize mouse models to elucidate the mechanisms through which bacterial dysbiosis and helminth infection influence the development of chronic inflammatory diseases. These models will be utilized for germ-free and recolonization experiments, investigating the relative contribution of bacteria versus helminthes to host immunity, co-metabolism and disease modulation. Taking a trans-disciplinary approach, this research will break new ground in our understanding of the crosstalk and pressures between intestinal helminth infection and commensal bacterial communities, and the implications this has for human health."

1 480 612 €

Start date: 2013-04-01, End date: 2018-03-31

Viral infection or retrotransposon expansion in the genome often result in production of double-stranded RNA (dsRNA). dsRNA can be intercepted by RNase III Dicer acting in the RNA interference (RNAi) pathway, an ancient eukaryotic defense mechanism. Notably, endogenous mammalian RNAi appears dormant while its common and unique physiological roles remain poorly understood. A factor underlying mammalian RNAi dormancy is inefficient processing of dsRNA by the full-length Dicer. Yet, a simple truncation of Dicer leads to hyperactive RNAi, which is naturally present in mouse oocytes. The D-FENS project will use genetic animal models to define common, cell-specific and species-specific roles of mammalian RNAi. D-FENS has three complementary and synergizing objectives: (1) Explore consequences of hyperactive RNAi in vivo. A mouse expressing a truncated Dicer will reveal at the organismal level any negative effect of hyperactive RNAi, the relationship between RNAi and mammalian immune system, and potential of RNAi to suppress viral infections in mammals. (2) Define common and species-specific features of RNAi in the oocyte. Functional and bioinformatics analyses in mouse, bovine, and hamster oocytes will define rules and exceptions concerning endogenous RNAi roles, including RNAi contribution to maternal mRNA degradation and co-existence with the miRNA pathway. (3) Uncover relationship between RNAi and piRNA pathways in suppression of retrotransposons. We hypothesize that hyperactive RNAi in mouse oocytes functionally complements the piRNA pathway, a Dicer-independent pathway suppressing retrotransposons in the germline. Using genetic models, we will explore unique and redundant roles of both pathways in the germline. D-FENS will uncover physiological significance of the N-terminal part of Dicer, fundamentally improve understanding RNAi function in the germline, and provide a critical in vivo assessment of antiviral activity of RNAi with implications for human therapy.

1 950 000 €

Start date: 2015-07-01, End date: 2020-06-30

A major goal in plant biology is to understand how naturally occurring genetic variation leads to quantitative differences in economically important traits. Efforts to navigate the genotype-to-phenotype map are often focused on linear genetic interactions. As a result, crop breeding is mainly driven by loci with predictable additive effects. However, it has become clear that quantitative trait variation often results from perturbations of complex genetic networks. Thus, understanding epistasis, or interactions between genes, is key for our ability to predictably improve crops. To meet this challenge, this project will reveal and dissect epistatic interactions in gene regulatory networks that guide stem cell differentiation in the model crop tomato. In the first aim, I will utilize exhaustive allelic series for epistatic MADS-box genes that quantitatively regulate flower and fruit production as an experimental model system to study fundamental principles of epistasis that can be applied to other genetic networks. Genome-wide transcript profiling will be used to reveal molecular signatures of epistasis and potential targets for predictable crop improvement by advanced CRISPR/Cas9 gene editing technology. Further, my preliminary data suggests that epistasis is widespread and important across major productivity traits in tomato. Thus, in a second aim, I will access this untapped resource of cryptic genetic variation by sensitizing a tomato diversity panel for weak epistatic effects from unknown natural modifier loci of stem cell differentiation using trans-acting CRISPR/Cas9 editing cassettes. This screen represents a new approach to mutagenesis in plants with potential to reveal cryptic variation in other system. The outcomes of this project will advance our knowledge in a fundamental area of plant genome biology, help uncover and understand the functional architecture of epistasis, and have potential to bring significant improvements to agriculture.

1 499 903 €

Start date: 2019-08-01, End date: 2024-07-31

Epigenetic inheritance is the transmission of information, generally in the form of DNA methylation or post-translational modifications on histones that regulate the availability of underlying genetic information for transcription. RNA itself feeds back to contribute to histone modification. Sequence accessibility is both a matter of folding the chromatin fibre to alter access to recognition motifs, and the local concentration of factors needed for efficient transcriptional initiation, elongation, termination or mRNA stability. In heterochromatin we find a subset of regulatory factors in carefully balanced concentrations that are maintained in part by the segregation of active and inactive domains. Histone H3 K9 methylation is key to this compartmentation. C. elegans provides an ideal system in which to study chromatin-based gene repression. We have demonstrated that histone H3 K9 methylation is the essential signal for the sequestration of heterochromatin at the nuclear envelope in C. elegans. The recognition of H3K9me1/2/3 by an inner nuclear envelope-bound chromodomain protein, CEC-4, actively sequesters heterochromatin in embryos, and contributes redundantly in adult tissues. Epiherigans has the ambitious goal to determine definitively what targets H3K9 methylation, and identify its physiological roles. We will examine how this mark contributes to the epigenetic recognition of repeat vs non-repeat sequence, and mediates a stress-induced response to oxidative damage. We will examine the link between these and the spatial clustering of heterochromatic domains. Epiherigans will develop an integrated approach to identify in vivo the factors that distinguish repeats from non-repeats, self from non-self within genomes and will examine how H3K9me contributes to a persistent ROS or DNA damage stress response. It represents a crucial step towards understanding of how our genomes use heterochromatin to modulate, stabilize and transmit chromatin organization.

2 500 000 €

Start date: 2017-06-01, End date: 2022-05-31

The ubiquitous FIC domain catalyzes post-translational modifications (PTMs) of target proteins; i.e. adenylylation (=AMPylation) and, more rarely, uridylylation and phosphocholination. Fic proteins are thought to play critical roles in intrinsic signaling processes of prokaryotes and eukaryotes; however, a subset encoded by bacterial pathogens is translocated via dedicated secretion systems into the cytoplasm of mammalian host cells. Some of these host-targeted Fic proteins modify small GTPases leading to collapse of the actin cytoskeleton and other drastic cellular changes. Recently, we described a large set of functionally diverse homologues in pathogens of the genus Bartonella that are required for their “stealth attack” strategy and persistent course of infection [1, 2]. Our preliminary functional analysis of some of these host-targeted Fic proteins of Bartonella demonstrated adenylylation activity towards novel host targets (e.g. tubulin and vimentin). Moreover, in addition to the canonical adenylylation activity they may also display a competing kinase activity resulting from altered ATP binding to the FIC active site. Finally, we described a conserved mechanism of FIC active site auto- inhibition that is relieved by a single amino acid exchange [1], thus facilitating functional analysis of any Fic protein of interest. Despite this recent progress only a few Fic proteins have been functionally characterized to date; our understanding of the functional plasticity of the FIC domain in mediating diverse target PTMs and their specific roles in infection thus remains limited. In this project, we aim to study the vast repertoire of host-targeted Fic proteins of Bartonella to: 1) identify novel target proteins and types of PTMs; 2) study their physiological consequences and molecular mechanisms of action; and 3) analyze structure-function relationships critical for FIC-mediated PTMs and infer from these data determinants of target specificity, type of PTM and mode of regulation. At the forefront of infection biology research, this project is ground-breaking as (i) we will identify a plethora of novel host target PTMs that are critical for a “stealth attack” infection strategy and thus will open new avenues for investigating fundamental mechanisms of persistent infection; and (ii), we will unveil the molecular basis of the remarkable functional versatility of the structurally conserved FIC domain.

1 699 858 €

Start date: 2014-02-01, End date: 2019-01-31

T cells have a central role in most adaptive immune responses, including immunity to infection, cancer, and autoimmunity. Increasing evidence shows that even resting steady-state T cells form many different subsets with unique functions. Variable level of self-reactivity and previous antigenic exposure are most likely two major determinants of the T-cell diversity. However, the number, identity, and biological function of steady-state T-cell subsets are still very incompletely understood. Receptors to ligands from TNF and B7 families exhibit variable expression among T-cell subsets and are important regulators of T-cell fate decisions. We hypothesize that pathways triggered by these receptors substantially contribute to the functional diversity of T cells.The FunDiT project uses a set of novel tools to systematically identify steady-state CD8+ T cell subsets and characterize their biological roles. The project has three complementary objectives. (1) Identification of CD8+ T cell subsets. We will identify subsets based on single cell gene expression profiling. We will determine the role of self and foreign antigens in the formation of these subsets and match corresponding subsets between mice and humans. (2) Role of particular subsets in the immune response. We will compare antigenic responses of particular subsets using our novel model allowing inducible expression of a defined TCR. The activity of T-cell subsets in three disease models (infection, cancer, autoimmunity) will be characterized. (3) Characterization of key costimulatory/inhibitory pathways. We will use our novel mass spectrometry-based approach to identify receptors and signaling molecules involved in the signaling by ligands from TNF and B7 families in T cells. The results will provide understanding of the adaptive immunity in particular disease context and resolve long-standing questions concerning the roles of T-cell diversity in protective immunity and tolerance to healthy tissues and tumors.

1 725 000 €

Start date: 2019-01-01, End date: 2023-12-31