ERC FUNDED PROJECTS

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

Comparative genomics revealed that ~5% of the human genome is conserved among mammals. This fraction is likely functional, and could harbor pathogenic mutations. We have shown (Nature 2002, Science 2003) that more than half of the constrained fraction of the genome consists of Conserved Non-Coding sequences (CNCs). Model organisms provided evidence for enhancer activity for a fraction of CNCs; in addition another fraction is part of large non-coding RNAs (lincRNA). However, the function of the majority of CNCs is unknown. Importantly, a few pathogenic mutations in CNCs have been associated with genetic disorders. We propose to i) perform functional analysis of CNCs, and ii) identify the spectrum of pathogenic CNC mutations in recognizable human phenotypes. The aims are: 1. Functional genomic connectivity of CNCs 1a. Use 4C in CNCs in various cell types and determine their physical genomic interactions. 1b. Perform targeted disruption of CNCs in cells and assess the functional outcomes. 2. Pathogenic variation of CNCs 2a. Assess the common variation in CNCs: i) common deletion/insertions in 350 samples by aCGH of all human CNCs; ii) common SNP/small indels using DNA selection and High Throughput Sequencing (HTS) of CNCs in 100 samples. 2b. Identify likely pathogenic mutations in developmental syndromes. Search for i) large deletions and duplications of CNCs using aCGH in 1500 samples with malformation syndromes, 1000 from spontaneous abortions, and 500 with X-linked mental retardation; and ii) point mutations in these samples by targeted HTS. The distinction between pathogenic and non-pathogenic variants is difficult, and we propose approaches to meet the challenge. 3. Genetic control (cis and trans eQTLs) of expression variation of CNC lincRNAs, using 200 samples.

2 353 920 €

Start date: 2010-07-01, End date: 2015-06-30

MicroRNAs (miRNAs) are a novel class of genes, accounting for >1% of genes in a typical animal genome. They constitute an important layer of gene regulation that affects diverse processes such as cell differentiation, apoptosis, and metabolism. Despite such critical roles, deciphering the mechanism of action of miRNAs has been difficult, leading to multiple, partially contradictory, models of miRNA activity. Moreover, adding an additional layer of complexity, it is now emerging that miRNA activity is regulated by various mechanisms that we are only beginning to identify. Our objective is to understand how miRNAs are regulated under physiological conditions, in the roundworm Caenorhabditis elegans. We will focus on pathways of miRNA turnover, an issue of fundamental importance that has received little attention because miRNAs are widely held to be highly stable molecules. However, miRNA over-accumulation causes aberrant development and disease, prompting us to test rigorously whether degradation can antagonize miRNA activity and either identify the machinery involved, or confirm the dominance of other regulatory modalities, whose components we will identify. C. elegans is the organism in which miRNAs and many components of the miRNA machinery were discovered. However, previous studies emphasized genetics and cell biology approaches, limiting the degree of mechanistic insight that could be obtained. In addition to exploiting the traditional strengths of C. elegans, we will therefore develop and apply biochemical and genomic techniques to obtain a comprehensive understanding of miRNA regulation, enabling us to demonstrate both molecular mechanisms and physiological relevance. Given the importance of miRNAs in development and disease, identifying the regulators of these tiny gene regulators will be both of scientific interest and biomedical relevance.

1 782 200 €

Start date: 2010-05-01, End date: 2015-04-30

Gene expression is one of the marks of cellular state and function. The relative abundance of transcripts defines and is a result of the differentiation status of a cell. Interrogation of gene expression levels and patterns in the human and other genomes can be informative about perturbations from the average pattern due to external stimuli or internal factors such as genetic variants. Gene expression profiles have been extensively used to assess developmental processes, pathways contributing to cell differentiation, and predicting the outcome of disease status. Understanding the effects of genetic variation in basic cellular processes such as gene expression is key to the dissection of the genetic contributions to whole organism phenotypes. We propose to interrogate the transcriptome of primary fibroblasts, primary T-cells and EBV-transformed B-cell (lymphoblastoid cell lines or LCLs) from umbilical cords of 200 individuals of European descent using next generation sequencing (mRNAseq). A subset will also be interrogated for transcriptionally engaged RNA polymerases (GROseq) and protein abundance. These data will be analyzed for the detection of eQTLs and other genetic effects associated with variation in alternative splicing and other properties of the transcripts and dissection of the genetic effects from primary transcription to protein and their tissue specific effects. These data will be integrated with genome-wide association studies and other efforts to dissect the genetic basis of complex traits and diseases in humans. In addition, we will develop bioinformatic models to understand the fine scale regulatory signals that are responsible for the regulatory patterns observed and how sequence variants have an effect on them.

1 500 000 €

Start date: 2011-05-01, End date: 2016-04-30

Elements operating in the context of a system generate results that are different from the simple addition of the results of each element. This notion is one of the basic tenants of systems science. In systems biology/medicine complex (disease) phenotypes arise from multiple interacting factors, specifically proteins. Yet, the biochemical and mechanistic base of complex phenotypes remain elusive. An array of powerful genomic technologies including GWAS, WGS, transcriptomics, epigenetic analyses and proteomics have identified numerous factors that contribute to complex phenotypes. It can be expected that over the next few years, genetic factors contributing to specific complex phenotypes will be comprehensively identified, while their interactions will remain elusive. The project “Proteomics 4D: The proteome in context “explores the concept, that complex phenotypes arise from the perturbation of modules of interacting proteins and that these modules integrate seemingly independent genomic variants into a single biochemical response. We will develop and apply a generic technology to directly measure the composition, topology and structure of wild type and genetically perturbed protein modules and relate structural changes to their functional output. This will be achieved by a the integration of quantitative proteomic and phosphoproteomic technologies determining molecular phenotypes, and hybrid structural methods consisting of chemical cross-linking and mass spectrometry, cryoEM and computational data integration to probe structural perturbations. The project will focus initially on the structural and functional effects of cancer associated mutations in protein kinase modules and then generalize to study perturbed modules in any tissue and disease state. The resources supporting this technology will be disseminated to catalyze a broad transformation of biology and molecular medicine towards the analysis of the proteome as a modular entity, the proteome in context.

2 208 150 €

Start date: 2015-09-01, End date: 2020-08-31

DNA and chromatin modifications are essential for proper control of gene expression during development. How these marks alter transcriptional programs and modulate binding patterns of sequence specific transcription factors (TF) remains poorly understood. This currently limits our interpretation of epigenomic maps towards their incorporation into predictive models of gene regulation. ReaDMe has the ambitious goal to systematically define the sensitivity of TFs to local levels of DNA methylation in vivo. We will use a combination of genomics, genome editing and proteomics tools to comprehensively identify transcriptional regulators that respond to DNA methylation. As a first approach, we will interrogate changes in the global TF binding landscape when DNA methylation is ablated from the genome. Using both embryonic stem cells and somatic cells, these experiments are aimed at identifying sites that are occupied by TFs in a DNA methylation dependent manner within different cellular context. Secondly, we will combine parallelized chromosomal insertions with targeted footprinting to determine the link between DNA sequence context, methylation density and TF binding. In a third approach we will define the global chromatin proteome as a function of DNA methylation. Through the use of a novel and orthogonal proteomics assay, we will characterize DNA methylation sensitive changes in the chromatin-bound proteome. Candidate factors predicted from all approaches will be validated and functionally characterized through direct genome-wide mapping as well as loss of function analysis. ERC funding would enable ReaDMe to develop an integrated setup to in vivo identify and characterize where DNA methylation influences the cis-regulatory landscape by modulating binding profiles of trans-acting factors. This goal represents a crucial step towards comprehensive understanding of the genomic readout of DNA methylation and its impact on gene regulation.

2 136 969 €

Start date: 2016-01-01, End date: 2020-12-31

RNA interference (RNAi) is a highly conserved, sequence-specific gene regulatory mechanism among eukaryotes. It is critical for a variety of important biological functions and is being pursued as a promising new tool for the treatment of a variety of human maladies. A surprising link between heterochromatin and the RNAi pathway was discovered a few years ago in fission yeast and plants, and similar mechanisms have more recently been described in various eukaryotes. However, to what extent the mechanisms we have been studying in yeast are conserved up to humans remains unknown. The goal of this proposal is to further our understanding of RNAi-mediated heterochromatin assembly by using fission yeast as a model organism, but also to investigate to role of RNAi in the nucleus of human cells. My proposal consists of three major aims. In aim 1 I propose to combine light and electron microscopy to address important and largely unanswered questions such as subcellular localization and temporal regulation of the RNAi pathway. Aim 2 builds on our recent discovery that RNAi factors physically associate with chromatin to control genome activity also outside constitutive heterochromatin. I am proposing experiments in fission yeast that aim at understanding the biological role of this new mode of genome regulation and its mechanistic dissection . However, we will also extend our analysis to human cells which will shed new light on the role of the RNAi pathway in the nucleus of higher eukaryotes. Finally, we are aiming at identifying the features a target locus in the S. pombe genome must have to become susceptible to RNAi-mediated silencing at the level of chromatin. Thus, the outcome of these experiments may substantially influence the developments of siRNA-based therapeutics.

1 599 992 €

Start date: 2012-01-01, End date: 2016-12-31