ERC FUNDED PROJECTS

Diabetes has become one of the most widespread metabolic disorders with epidemic dimensions affecting almost 6% of the world’s population. Despite modern treatments, the life expectancy of patients with Type 1 diabetes remains reduced as compared to healthy subjects. There is therefore a need for alternative therapies. Towards this aim, using the mouse, we recently demonstrated that the in vivo forced expression of a single factor in pancreatic alpha-cells is sufficient to induce a continuous regeneration of alpha-cells and their subsequent conversion into beta-like cells, such converted cells being capable of reversing the consequences of chemically-induced diabetes in vivo (Collombat et al. Cell, 2009). The PI and his team therefore propose to further decipher the mechanisms involved in this alpha-cell-mediated beta-cell regeneration process and determine whether this approach may be applied to adult animals and whether it would efficiently reverse Type 1 diabetes. Furthermore, a major effort will be made to verify whether our findings could be translated to human. Specifically, we will use a tri-partite approach to address the following issues: (1) Can the in vivo alpha-cell-mediated beta-cell regeneration be induced in adults mice? What would be the genetic determinants involved? (2) Can alpha-cell-mediated beta-cell regeneration reverse diabetes in the NOD Type 1 diabetes mouse model? (3) Can adult human alpha-cells be converted into beta-like cells? Together, these ambitious objectives will most certainly allow us to gain new insight into the mechanisms defining the identity and the reprogramming capabilities of mouse and human endocrine cells and may thereby open new avenues for the treatment of diabetes. Similarly, the determination of the molecular triggers implicated in the beta-cell regeneration observed in our diabetic mice may lead to exciting new findings, including the identification of “drugable” targets of importance for human diabetic patients.

1 500 000 €

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

Cardiovascular disease keeps the top spot in mortality statistics in Europe with 2 million deaths annually and although prevention and therapy have continuously been improved, the prevalence of heart failure continues to rise. While contractile (systolic) dysfunction is readily accessible to pharmacological treatment, there is a lack of therapeutic options for reduced ventricular filling (diastolic dysfunction). The diastolic properties of the heart are largely determined by the giant sarcomeric protein titin, which is alternatively spliced to adjust the elastic properties of the cardiomyocyte. We have recently identified a titin splice factor that plays a parallel role in cardiac disease and postnatal development. It targets a subset of genes that concertedly affect biomechanics, electrical activity, and signal transduction and suggests alternative splicing as a novel therapeutic target in heart disease. Here we will build on the titin splice factor to identify regulatory principles and cofactors that adjust cardiac isoform expression. In a complementary approach we will investigate titin mRNA binding proteins to provide a comprehensive analysis of factors governing titin’s differential splicing in cardiac development, health, and disease. Based on its distinctive role in ventricular filling we will evaluate titin splicing as a therapeutic target in diastolic heart failure and use a titin based reporter assay to identify small molecules to interfere with titin isoform expression. Finally, we will evaluate the effects of altered alternative splicing on diastolic dysfunction in vivo utilizing the splice deficient mutant and our available animal models for diastolic dysfunction. The overall scientific goal of the proposed work is to investigate the regulation of cardiac alternative splicing in development and disease and to evaluate if splice directed therapy can be used to improve diastolic function and specifically the elastic properties of the heart.

1 499 191 €

Start date: 2012-01-01, End date: 2017-06-30

The regulation of ion concentrations in the cytoplasm and in the lumen of intracellular vesicles provides suitable environments for biochemical reactions, gradients for signal transduction, and generates osmotic gradients for the regulation of the volume of cells and intracellular organelles. Changes in the ion homeostasis and volume of cells and organelles may in turn influence processes like cell division and migration or the budding of vesicles from cellular membranes. Volume changes of cells, and possibly also of intracellular organelles, in turn regulate ion transport across their membranes. Whereas several swelling-activated plasma membrane ion transporters and channels are known, the molecular identity of a key player, the swelling-activated anion channel VRAC, and its impact on cellular functions remain elusive. Only sketchy information is available on ion homeostasis and volume regulation of intracellular organelles like endosomes and lysosomes, in spite of their importance for several diseases. We propose to perform a genome-wide RNAi screen to finally identify the long-sought swelling-activated Cl- channel VRAC at the molecular level. This screen will also identify genes involved in the regulation of VRAC. The network involved in cell volume regulation will be investigated at the structural, biochemical and cellular level as well as with genetically modified mice. In parallel we will examine the ion homeostasis of endosomes and lysosomes. Until recently only the regulation of luminal H+ and Ca++ concentration was studied, but our recent work demonstrated a crucial role of luminal Cl- and hinted at an important role of cations. A combination of proteomics, siRNA screens, candidate approaches, and mouse models will be used to elucidate the ion homeostasis of endosomes/lysosomes and the impact on organellar function and associated pathologies. We expect that our work will break new ground in ion transport physiology, pathology, and cell biology.

2 499 600 €

Start date: 2012-04-01, End date: 2017-03-31

"DNA methylation patterns are frequently perturbed in human diseases such as imprinting disorders and cancer. In cancer increased aberrant DNA methylation is believed to work as a silencing mechanism for tumor suppressor genes such as INK4A, RB1 and MLH1. The high frequency of abnormal DNA methylation found in cancer might be due to the inactivation of a proofreading and/or fidelity system regulating the correct patterns of DNA methylation. Currently we have very limited knowledge about such mechanisms. In this research proposal, we will focus on elucidating the biological function of a novel protein family, which catalyzes the conversion of 5-methyl-cytosine (5-mC) to 5-hydroxymethyl cytosine (5-hmC). By catalyzing this reaction the TET proteins most likely work as DNA demethylases, and they might therefore have a role in regulating DNA methylation fidelity. Interestingly, accumulated data has in the last 2 years shown that TET2 is one of the most frequently mutated genes in various hematological cancers. We propose to investigate the molecular mechanisms by which TET2 regulates normal hematopoiesis, how its inactivation leads to hematopoietic malignancies and how the protein contributes to the regulation of DNA methylation patterns and transcription. Furthermore, we propose several experimental approaches for identifying proteins required for the recruitment of TET proteins to target genes and to analyze their role in the regulation of DNA methylation patterns and in cancer. Finally, we will investigate the potential functional role of 5-hmC and explore the potential mechanisms by which this modification could be erased. We expect to provide new insights into the biology of DNA methylation, hydroxymethylation and contribute to unravel the roles of TET proteins in normal physiology and cancer."

2 298 000 €

Start date: 2012-07-01, End date: 2017-06-30