Project acronym DCRIDDLE
Project A novel physiological role for IRE1 and RIDD..., maintaining the balance between tolerance and immunity?
Researcher (PI) Sophie Janssens
Host Institution (HI) VIB VZW
Call Details Consolidator Grant (CoG), LS3, ERC-2018-COG
Summary Dendritic cells (DCs) play a crucial role as gatekeepers of the immune system, coordinating the balance between protective immunity and tolerance to self antigens. What determines the switch between immunogenic versus tolerogenic antigen presentation remains one of the most puzzling questions in immunology. My team recently discovered an unanticipated link between a conserved stress response in the endoplasmic reticulum (ER) and tolerogenic DC maturation, thereby setting the stage for new insights in this fundamental branch in immunology.
Specifically, we found that one of the branches of the unfolded protein response (UPR), the IRE1/XBP1 signaling axis, is constitutively active in murine dendritic cells (cDC1s), without any signs of an overt UPR gene signature. Based on preliminary data we hypothesize that IRE1 is activated by apoptotic cell uptake, orchestrating a metabolic response from the ER to ensure tolerogenic antigen presentation. This entirely novel physiological function for IRE1 entails a paradigm shift in the UPR field, as it reveals that IRE1’s functions might stretch far from its well-established function induced by chronic ER stress. The aim of my research program is to establish whether IRE1 in DCs is the hitherto illusive switch between tolerogenic and immunogenic maturation. To this end, we will dissect its function in vivo both in steady-state conditions and in conditions of danger (viral infection models). In line with our data, IRE1 has recently been identified as a candidate gene for autoimmune disease based on Genome Wide Association Studies (GWAS). Therefore, I envisage that my research program will not only have a large impact on the field of DC biology and apoptotic cell clearance, but will also yield new insights in diseases like autoimmunity, graft versus host disease or tumor immunology, all associated with disturbed balances between tolerogenic and immunogenic responses.
Summary
Dendritic cells (DCs) play a crucial role as gatekeepers of the immune system, coordinating the balance between protective immunity and tolerance to self antigens. What determines the switch between immunogenic versus tolerogenic antigen presentation remains one of the most puzzling questions in immunology. My team recently discovered an unanticipated link between a conserved stress response in the endoplasmic reticulum (ER) and tolerogenic DC maturation, thereby setting the stage for new insights in this fundamental branch in immunology.
Specifically, we found that one of the branches of the unfolded protein response (UPR), the IRE1/XBP1 signaling axis, is constitutively active in murine dendritic cells (cDC1s), without any signs of an overt UPR gene signature. Based on preliminary data we hypothesize that IRE1 is activated by apoptotic cell uptake, orchestrating a metabolic response from the ER to ensure tolerogenic antigen presentation. This entirely novel physiological function for IRE1 entails a paradigm shift in the UPR field, as it reveals that IRE1’s functions might stretch far from its well-established function induced by chronic ER stress. The aim of my research program is to establish whether IRE1 in DCs is the hitherto illusive switch between tolerogenic and immunogenic maturation. To this end, we will dissect its function in vivo both in steady-state conditions and in conditions of danger (viral infection models). In line with our data, IRE1 has recently been identified as a candidate gene for autoimmune disease based on Genome Wide Association Studies (GWAS). Therefore, I envisage that my research program will not only have a large impact on the field of DC biology and apoptotic cell clearance, but will also yield new insights in diseases like autoimmunity, graft versus host disease or tumor immunology, all associated with disturbed balances between tolerogenic and immunogenic responses.
Max ERC Funding
1 999 196 €
Duration
Start date: 2019-02-01, End date: 2024-01-31
Project acronym DIVISIONPLANESWITCH
Project Control mechanisms that pattern microtubules for switching cell division planes during plant morphogenesis
Researcher (PI) Pankaj Bacharam Dhonukshe
Host Institution (HI) VIB VZW
Call Details Starting Grant (StG), LS3, ERC-2012-StG_20111109
Summary Oriented cell divisions dictate morphogenesis by shaping tissues and organs of multicellular organisms. Oriented cell divisions have profound influence in plants because their cell positions are locked by shared cell walls. A relay of cell divisions involving precise division plane switches determines embryonic body plan, organ layout and organ architecture in plants. Cell division planes in plants are specified by reorganization of premitotic cortical microtubule array and how this occurs is a long-standing key question.
My recent results establish, for the first time in plants, an in vivo inducible and traceable, precise 90º cell division plane switch system. With this system I identified a pathway that proceeds from transcriptional activation through a signaling module all the way to the activation of microtubule regulators that orchestrate switches in premitotic microtubule organization and cell division planes. My findings provide a first paradigm in plants of how genetic circuitry patterns cell division planes via feeding onto cellular machinery and pave the way for unraveling mechanistic control of cell division plane switch.
By establishing a precise cell division plane switch system I am in a unique position to answer:
1. What transcriptional program and molecular players control premitotic microtubule reorganization?
2. Which mechanisms switch premitotic microtubule array?
3. What influence do identified players and mechanisms have on different types of oriented cell divisions in plants?
For this I propose a systematic research plan combining (i) forward genetics and expression profile screens for identifying a suite of microtubule regulators, (ii) state-of-the-art microscopy and modeling approaches for uncovering mechanisms of their actions and (iii) their tissue-specific manipulations to modify plant form.
By unraveling players and mechanisms this proposal shall resolve regulation of oriented cell divisions and expand plant engineering toolbox.
Summary
Oriented cell divisions dictate morphogenesis by shaping tissues and organs of multicellular organisms. Oriented cell divisions have profound influence in plants because their cell positions are locked by shared cell walls. A relay of cell divisions involving precise division plane switches determines embryonic body plan, organ layout and organ architecture in plants. Cell division planes in plants are specified by reorganization of premitotic cortical microtubule array and how this occurs is a long-standing key question.
My recent results establish, for the first time in plants, an in vivo inducible and traceable, precise 90º cell division plane switch system. With this system I identified a pathway that proceeds from transcriptional activation through a signaling module all the way to the activation of microtubule regulators that orchestrate switches in premitotic microtubule organization and cell division planes. My findings provide a first paradigm in plants of how genetic circuitry patterns cell division planes via feeding onto cellular machinery and pave the way for unraveling mechanistic control of cell division plane switch.
By establishing a precise cell division plane switch system I am in a unique position to answer:
1. What transcriptional program and molecular players control premitotic microtubule reorganization?
2. Which mechanisms switch premitotic microtubule array?
3. What influence do identified players and mechanisms have on different types of oriented cell divisions in plants?
For this I propose a systematic research plan combining (i) forward genetics and expression profile screens for identifying a suite of microtubule regulators, (ii) state-of-the-art microscopy and modeling approaches for uncovering mechanisms of their actions and (iii) their tissue-specific manipulations to modify plant form.
By unraveling players and mechanisms this proposal shall resolve regulation of oriented cell divisions and expand plant engineering toolbox.
Max ERC Funding
1 500 000 €
Duration
Start date: 2013-01-01, End date: 2017-12-31
Project acronym EXECUT.ER
Project Dissecting the molecular mechanisms that execute developmental programmed cell death in plants
Researcher (PI) Moritz NOWACK
Host Institution (HI) VIB VZW
Call Details Consolidator Grant (CoG), LS3, ERC-2019-COG
Summary Programmed Cell Death (PCD) is fundamental to the development and health of multicellular organisms. However, our knowledge on developmentally controlled PCD in plants remains fragmentary, despite its undoubted significance for plant growth and reproduction.
My team has established the Arabidopsis root cap as a novel model system for developmental PCD in plants. This model has enabled us to identify a gene regulatory network controlling the preparation of PCD. However, the molecular processes that terminate the vital functions of a plant cell during the final steps of PCD execution remain unknown.
Exploiting the accessibility of the root cap for live-cell analysis of PCD execution, we obtained preliminary data revealing an unexpected succession of distinct membrane permeabilization events in which the endoplasmic reticulum breaks up before the central vacuole. I hypothesize that this sequential de-compartmentalization is the mechanism underlying the irreversible and orderly execution of PCD.
Recent advances in several key technologies provide unprecedented opportunities to test this hypothesis and make a quantum leap in our understanding of the mechanisms carrying out PCD execution.
I will employ correlative super-resolution light and electron microscopy to analyse PCD execution in unparalleled spatial and temporal resolution. RNA sequencing of single cells at the onset of PCD execution will provide information on the genes that are required for this rapid process. Advanced proteomics techniques will provide a direct route to identify proteins acting on membrane permeabilization during PCD execution. Lastly, multiplex and tissue-specific mutagenesis via innovative CRISPR screens will enable me to overcome genetic redundancy and lethality in the PCD context.
The detailed understanding of plant PCD execution generated by this research program will shed light on a fundamental principle of plant development and open new avenues for crop improvement and protection.
Summary
Programmed Cell Death (PCD) is fundamental to the development and health of multicellular organisms. However, our knowledge on developmentally controlled PCD in plants remains fragmentary, despite its undoubted significance for plant growth and reproduction.
My team has established the Arabidopsis root cap as a novel model system for developmental PCD in plants. This model has enabled us to identify a gene regulatory network controlling the preparation of PCD. However, the molecular processes that terminate the vital functions of a plant cell during the final steps of PCD execution remain unknown.
Exploiting the accessibility of the root cap for live-cell analysis of PCD execution, we obtained preliminary data revealing an unexpected succession of distinct membrane permeabilization events in which the endoplasmic reticulum breaks up before the central vacuole. I hypothesize that this sequential de-compartmentalization is the mechanism underlying the irreversible and orderly execution of PCD.
Recent advances in several key technologies provide unprecedented opportunities to test this hypothesis and make a quantum leap in our understanding of the mechanisms carrying out PCD execution.
I will employ correlative super-resolution light and electron microscopy to analyse PCD execution in unparalleled spatial and temporal resolution. RNA sequencing of single cells at the onset of PCD execution will provide information on the genes that are required for this rapid process. Advanced proteomics techniques will provide a direct route to identify proteins acting on membrane permeabilization during PCD execution. Lastly, multiplex and tissue-specific mutagenesis via innovative CRISPR screens will enable me to overcome genetic redundancy and lethality in the PCD context.
The detailed understanding of plant PCD execution generated by this research program will shed light on a fundamental principle of plant development and open new avenues for crop improvement and protection.
Max ERC Funding
1 999 963 €
Duration
Start date: 2020-06-01, End date: 2025-05-31
Project acronym EXPAND
Project Defining the cellular dynamics leading to tissue expansion
Researcher (PI) Cedric Blanpain
Host Institution (HI) UNIVERSITE LIBRE DE BRUXELLES
Call Details Consolidator Grant (CoG), LS3, ERC-2013-CoG
Summary Stem cells (SCs) ensure the development of the different tissues during morphogenesis, their physiological turnover during adult life and tissue repair after injuries. .
Our lab has recently developed new methods to study by lineage tracing the cellular hierarchy that sustains homeostasis and repair of the epidermis and to identify distinct populations of SCs and progenitors ensuring mammary gland and prostate postnatal development.
While quantitative clonal analysis combined with mathematical modeling has been used recently to decipher the cellular basis of tissue homeostasis, such experimental approaches have never been used so far in mammals to investigate the cellular hierarchy acting during tissue expansion such as postnatal development and tissue repair.
In this project, we will use a multi-disciplinary approach combining mouse genetic lineage tracing and clonal analysis, mathematical modeling, proliferation kinetics, transcriptional profiling, and functional experiments to investigate the cellular and molecular mechanisms regulating tissue expansion during epithelial development and tissue repair and how the fate of these cells is controlled during this process.
1. We will define the clonal and proliferation dynamics of tissue expansion in the epidermis, the mammary gland and the prostate during postnatal growth and adult tissue regeneration.
2. We will define the clonal and proliferation dynamics of tissue expansion in the adult epidermis following wounding and mechanical force mediated tissue expansion.
3. We will define the mechanisms that regulate the switch from multipotent to unipotent cell fate during development of glandular epithelia.
Defining the cellular and molecular mechanisms underlying tissue growth and expansion during development and how these mechanisms differ from tissue regeneration in adult may have important implications for understanding the causes of certain developmental defects and for regenerative medicine.
Summary
Stem cells (SCs) ensure the development of the different tissues during morphogenesis, their physiological turnover during adult life and tissue repair after injuries. .
Our lab has recently developed new methods to study by lineage tracing the cellular hierarchy that sustains homeostasis and repair of the epidermis and to identify distinct populations of SCs and progenitors ensuring mammary gland and prostate postnatal development.
While quantitative clonal analysis combined with mathematical modeling has been used recently to decipher the cellular basis of tissue homeostasis, such experimental approaches have never been used so far in mammals to investigate the cellular hierarchy acting during tissue expansion such as postnatal development and tissue repair.
In this project, we will use a multi-disciplinary approach combining mouse genetic lineage tracing and clonal analysis, mathematical modeling, proliferation kinetics, transcriptional profiling, and functional experiments to investigate the cellular and molecular mechanisms regulating tissue expansion during epithelial development and tissue repair and how the fate of these cells is controlled during this process.
1. We will define the clonal and proliferation dynamics of tissue expansion in the epidermis, the mammary gland and the prostate during postnatal growth and adult tissue regeneration.
2. We will define the clonal and proliferation dynamics of tissue expansion in the adult epidermis following wounding and mechanical force mediated tissue expansion.
3. We will define the mechanisms that regulate the switch from multipotent to unipotent cell fate during development of glandular epithelia.
Defining the cellular and molecular mechanisms underlying tissue growth and expansion during development and how these mechanisms differ from tissue regeneration in adult may have important implications for understanding the causes of certain developmental defects and for regenerative medicine.
Max ERC Funding
2 400 000 €
Duration
Start date: 2014-06-01, End date: 2019-05-31
Project acronym PREDATOR
Project Revealing the cell biology of a predatory bacterium in space and time
Researcher (PI) Géraldine LALOUX
Host Institution (HI) UNIVERSITE CATHOLIQUE DE LOUVAIN
Call Details Starting Grant (StG), LS3, ERC-2018-STG
Summary The model predatory bacterium Bdellovibrio bacteriovorus feeds upon other Gram-negative bacteria, including pathogenic strains. Upon entry inside the periplasmic space of the prey envelope, B. bacteriovorus initiates an exquisite developmental program in which it digests the host resources while ensuring the osmotic stability of its niche. In the periplasm, the predator cell grows as a polyploid filament, before releasing a variable, odd or even number of daughter cells upon a non-binary division event. The progeny is then liberated to hunt for new prey. B. bacteriovorus is now attracting a revived attention as several in vivo models of infection established its promising “living antibiotic” potential. Despite this remarkable lifestyle, the fields of bacterial cell biology and antibiotics research still lack a comprehensive understanding of how this micro-predator thrives inside the envelope of other bacteria. Indeed, the molecular factors behind the non-canonical cell biology of B. bacteriovorus are still largely mysterious.
My goal is to tackle this question by unraveling the novel mechanisms that control key processes of the fascinating cell cycle of this bacterium, using a unique combination of quantitative live imaging of predation at the single-cell level, bacterial genetics and molecular biology. Specifically, I aim to (i) uncover how the genetic information is organized, copied and partitioned in a polyploid cell before non-binary division, (i) shed light on factors that polarize the predator cell, and (iii) discover prey envelope features that influence the predation cycle. Because the biology of B. bacteriovorus stands beyond textbook standards, our results will provide mechanistic insight into important biological questions that remained unexplored using “classical” model species. If successful, this project will advance bacterial cell biology, while offering an innovative contribution to the fight against antibiotics-resistant pathogens.
Summary
The model predatory bacterium Bdellovibrio bacteriovorus feeds upon other Gram-negative bacteria, including pathogenic strains. Upon entry inside the periplasmic space of the prey envelope, B. bacteriovorus initiates an exquisite developmental program in which it digests the host resources while ensuring the osmotic stability of its niche. In the periplasm, the predator cell grows as a polyploid filament, before releasing a variable, odd or even number of daughter cells upon a non-binary division event. The progeny is then liberated to hunt for new prey. B. bacteriovorus is now attracting a revived attention as several in vivo models of infection established its promising “living antibiotic” potential. Despite this remarkable lifestyle, the fields of bacterial cell biology and antibiotics research still lack a comprehensive understanding of how this micro-predator thrives inside the envelope of other bacteria. Indeed, the molecular factors behind the non-canonical cell biology of B. bacteriovorus are still largely mysterious.
My goal is to tackle this question by unraveling the novel mechanisms that control key processes of the fascinating cell cycle of this bacterium, using a unique combination of quantitative live imaging of predation at the single-cell level, bacterial genetics and molecular biology. Specifically, I aim to (i) uncover how the genetic information is organized, copied and partitioned in a polyploid cell before non-binary division, (i) shed light on factors that polarize the predator cell, and (iii) discover prey envelope features that influence the predation cycle. Because the biology of B. bacteriovorus stands beyond textbook standards, our results will provide mechanistic insight into important biological questions that remained unexplored using “classical” model species. If successful, this project will advance bacterial cell biology, while offering an innovative contribution to the fight against antibiotics-resistant pathogens.
Max ERC Funding
1 499 688 €
Duration
Start date: 2019-01-01, End date: 2023-12-31
Project acronym PROCELLDEATH
Project Unraveling the regulatory network of developmental programmed cell death in plants
Researcher (PI) Moritz Karl Nowack
Host Institution (HI) VIB
Call Details Starting Grant (StG), LS3, ERC-2014-STG
Summary Programmed cell death (PCD) is a fundamental biological process that actively terminates a cell’s vital functions by a well-ordered sequence of events. In both animals and plants, various types of PCD are crucial for development, health, and the responses to various stresses. Despite their importance, only little is known about PCD processes and their molecular control in plants. Still, an intricate regulatory network must exist that renders specific plant cell types competent to initiate and execute PCD at precisely determined developmental stages. I recently established a powerful developmental PCD model system in Arabidopsis thaliana, based on a PCD process occurring during root cap development. This root cap model has the potential to revolutionize existing concepts of plant PCD, as it combines a precisely predictable PCD process in easily accessible cells on the root periphery with the abundance of resources available for Arabidopsis research. Exploiting the root cap system will enable me to tackle unresolved fundamental questions about the regulation of developmental PCD in plants: How do cells acquire PCD competency during differentiation? Which signals trigger PCD execution at just the right moment? What are the actual mechanisms that disrupt the vital functions of a plant cell? I will obtain answers to these questions through a comprehensive strategy combining complementary approaches, taking advantage of cell-type specific transcriptomics, forward and reverse genetics, advanced live-cell imaging, biochemistry, and computational modeling. Our unpublished data point to the existence of a common core mechanism controlling PCD not only in the root cap, but also in other vital organs including the vasculature, anthers, or developing seeds. Thus, this project will not only be significant to advance our knowledge on PCD as a general developmental mechanism in plants, but also to generate new leads to tap the so far underexploited potential of PCD in agriculture.
Summary
Programmed cell death (PCD) is a fundamental biological process that actively terminates a cell’s vital functions by a well-ordered sequence of events. In both animals and plants, various types of PCD are crucial for development, health, and the responses to various stresses. Despite their importance, only little is known about PCD processes and their molecular control in plants. Still, an intricate regulatory network must exist that renders specific plant cell types competent to initiate and execute PCD at precisely determined developmental stages. I recently established a powerful developmental PCD model system in Arabidopsis thaliana, based on a PCD process occurring during root cap development. This root cap model has the potential to revolutionize existing concepts of plant PCD, as it combines a precisely predictable PCD process in easily accessible cells on the root periphery with the abundance of resources available for Arabidopsis research. Exploiting the root cap system will enable me to tackle unresolved fundamental questions about the regulation of developmental PCD in plants: How do cells acquire PCD competency during differentiation? Which signals trigger PCD execution at just the right moment? What are the actual mechanisms that disrupt the vital functions of a plant cell? I will obtain answers to these questions through a comprehensive strategy combining complementary approaches, taking advantage of cell-type specific transcriptomics, forward and reverse genetics, advanced live-cell imaging, biochemistry, and computational modeling. Our unpublished data point to the existence of a common core mechanism controlling PCD not only in the root cap, but also in other vital organs including the vasculature, anthers, or developing seeds. Thus, this project will not only be significant to advance our knowledge on PCD as a general developmental mechanism in plants, but also to generate new leads to tap the so far underexploited potential of PCD in agriculture.
Max ERC Funding
1 499 746 €
Duration
Start date: 2015-04-01, End date: 2020-03-31
Project acronym PyroPop
Project Mechanisms and regulation of inflammasome-associated programmed cell death
Researcher (PI) Mohamed Lamkanfi
Host Institution (HI) UNIVERSITEIT GENT
Call Details Consolidator Grant (CoG), LS3, ERC-2015-CoG
Summary Programmed cell death is essential for homeostasis, and its deregulation contributes to human disease. Inflammasome-induced pyroptosis of infected macrophages contributes to host defense against infections, but the concomitant release of inflammatory danger signals and leaderless cytokines is detrimental in chronic inflammatory diseases. The central hypothesis of the PyroPop ERC Consolidator project is that inflammasomes are cytosolic platforms that couple pathogen sensing to multiple programmed cell death modes. This is based on our preliminary data showing that inflammasomes can be triggered to switch from inflammatory pyroptosis to programmed necrosis and non-inflammatory apoptosis. This suggests that the (patho)physiological outcomes of inflammasome activation may be modulated for therapeutic purposes. However, the molecular machinery and effector mechanisms of pyroptosis, inflammasome-induced apoptosis and programmed necrosis are virtually unknown. My objectives are (i) to explore the cleavage events and subcellular dynamics of pyroptosis by proteomics and high-resolution time-lapse microscopy; (ii) to clarify the molecular mechanisms of pyroptosis and inflammasome-controlled cell death switching; and (iii) to address how inflammasome-associated cell death modes impact on anti-bacterial host defense and chronic inflammatory pathology in vivo through the identification of pyroptosis-selective biomarkers and clinical analysis of pyroptosis-deficient mouse models. The central hypothesis in this regard is that inflammasome-mediated secretion of leaderless cytokines (such as IL-1β and IL-18) and danger signals may be mechanistically coupled to pyroptosis, but not apoptosis induction. By clarifying the mechanisms of inflammasome-controlled programmed cell death, this project may set the path for the development of an entirely novel class of inflammation-modulating therapies that are based on converting inflammatory pyroptosis into non-inflammatory apoptosis.
Summary
Programmed cell death is essential for homeostasis, and its deregulation contributes to human disease. Inflammasome-induced pyroptosis of infected macrophages contributes to host defense against infections, but the concomitant release of inflammatory danger signals and leaderless cytokines is detrimental in chronic inflammatory diseases. The central hypothesis of the PyroPop ERC Consolidator project is that inflammasomes are cytosolic platforms that couple pathogen sensing to multiple programmed cell death modes. This is based on our preliminary data showing that inflammasomes can be triggered to switch from inflammatory pyroptosis to programmed necrosis and non-inflammatory apoptosis. This suggests that the (patho)physiological outcomes of inflammasome activation may be modulated for therapeutic purposes. However, the molecular machinery and effector mechanisms of pyroptosis, inflammasome-induced apoptosis and programmed necrosis are virtually unknown. My objectives are (i) to explore the cleavage events and subcellular dynamics of pyroptosis by proteomics and high-resolution time-lapse microscopy; (ii) to clarify the molecular mechanisms of pyroptosis and inflammasome-controlled cell death switching; and (iii) to address how inflammasome-associated cell death modes impact on anti-bacterial host defense and chronic inflammatory pathology in vivo through the identification of pyroptosis-selective biomarkers and clinical analysis of pyroptosis-deficient mouse models. The central hypothesis in this regard is that inflammasome-mediated secretion of leaderless cytokines (such as IL-1β and IL-18) and danger signals may be mechanistically coupled to pyroptosis, but not apoptosis induction. By clarifying the mechanisms of inflammasome-controlled programmed cell death, this project may set the path for the development of an entirely novel class of inflammation-modulating therapies that are based on converting inflammatory pyroptosis into non-inflammatory apoptosis.
Max ERC Funding
1 997 915 €
Duration
Start date: 2017-01-01, End date: 2021-12-31
Project acronym Sperm-Egg Phusion
Project Unexpected connections between a phagocytic machinery and mammalian fertilization
Researcher (PI) Kodimangalam Sethurama Sarma RAVICHANDRAN
Host Institution (HI) VIB VZW
Call Details Advanced Grant (AdG), LS3, ERC-2018-ADG
Summary Fertilization is essential for a species to survive. Mammalian sexual reproduction requires the fusion between the haploid gametes sperm and egg to create a new diploid organism. Although fertilization has been studied for decades, and despite the remarkable recent discoveries of Izumo (on sperm) and Juno (on oocytes) as a critical ligand:receptor pair, due to the structure of Izumo and Juno, it is clear that other players on both the sperm and the oocytes must be involved. While the focus of our laboratory over the years has been in understanding apoptotic cell clearance by phagocytes, we accidentally noted that viable, motile, and fertilization-competent sperm exposes phosphatidylserine (PtdSer). PtdSer is a phospholipid normally exposed during apoptosis and functions as an ‘eat-me’ signal for phagocytosis. Further, masking this PtdSer on sperm inhibits fertilization in vitro. Based on additional exciting preliminary data, in this ERC proposal, we will test the hypothesis that PtdSer on viable sperm and the complementary PtdSer receptors on oocytes are key players in mammalian fertilization. We will test this at a molecular, biochemical, cellular, functional, and genetic level. From the sperm perspective — we will ask how does PtdSer changes during sperm maturation, and what molecular mechanisms regulate the exposure of PtdSer on viable sperm. From the oocyte perspective — we will test the genetic relevance of different PtdSer receptors in fertilization. From the PtdSer perspective — we will test PtdSer induces novel signals within oocytes. By combining the tools and knowledge from field of phagocytosis with tools from spermatogenesis/fertilization, this proposal integrates fields that normally do not intersect. In summary, we believe that these studies are innovative, timely, and will identify new players involved in mammalian fertilization. We expect the results of these studies to have high relevance to both male and female reproductive health and fertility.
Summary
Fertilization is essential for a species to survive. Mammalian sexual reproduction requires the fusion between the haploid gametes sperm and egg to create a new diploid organism. Although fertilization has been studied for decades, and despite the remarkable recent discoveries of Izumo (on sperm) and Juno (on oocytes) as a critical ligand:receptor pair, due to the structure of Izumo and Juno, it is clear that other players on both the sperm and the oocytes must be involved. While the focus of our laboratory over the years has been in understanding apoptotic cell clearance by phagocytes, we accidentally noted that viable, motile, and fertilization-competent sperm exposes phosphatidylserine (PtdSer). PtdSer is a phospholipid normally exposed during apoptosis and functions as an ‘eat-me’ signal for phagocytosis. Further, masking this PtdSer on sperm inhibits fertilization in vitro. Based on additional exciting preliminary data, in this ERC proposal, we will test the hypothesis that PtdSer on viable sperm and the complementary PtdSer receptors on oocytes are key players in mammalian fertilization. We will test this at a molecular, biochemical, cellular, functional, and genetic level. From the sperm perspective — we will ask how does PtdSer changes during sperm maturation, and what molecular mechanisms regulate the exposure of PtdSer on viable sperm. From the oocyte perspective — we will test the genetic relevance of different PtdSer receptors in fertilization. From the PtdSer perspective — we will test PtdSer induces novel signals within oocytes. By combining the tools and knowledge from field of phagocytosis with tools from spermatogenesis/fertilization, this proposal integrates fields that normally do not intersect. In summary, we believe that these studies are innovative, timely, and will identify new players involved in mammalian fertilization. We expect the results of these studies to have high relevance to both male and female reproductive health and fertility.
Max ERC Funding
2 499 375 €
Duration
Start date: 2019-10-01, End date: 2024-09-30
Project acronym T-Rex
Project Clathrin-mediated endocytosis in plants: mechanistic insight into the TPLATE REcycling compleX and its interplay with AP-2
Researcher (PI) Daniel Joseph G Van Damme
Host Institution (HI) VIB VZW
Call Details Consolidator Grant (CoG), LS3, ERC-2015-CoG
Summary Cells communicate with the outside world through proteins anchored in their plasma membrane and hereto constantly adjust their plasma membrane (PM) proteome. In this adjustment process, removing proteins from the PM mainly occurs through clathrin-mediated endocytosis (CME). Mechanistically however, this process remains poorly understood in plants.
A recent study from my group has shown that, in contrast to other model systems, plant CME involves two early endocytic adaptor protein complexes: the evolutionary conserved Adaptor Protein 2 complex (AP-2) and the newly identified TPLATE complex (TPC). In the same study, we also show that both complexes have overlapping but also independent functions in driving CME in plants, implying that plants use additional ways to recognize membrane proteins (cargo) for internalization.
In this project I will use an integrative approach to unravel the early steps of CME in plants. Specifically, I will address the following biological questions:
- Is the evolutionary retention of the TPC in plants causal to specific cargo recognition? (WP1)
- What are the spatio-temporal dynamics of TPC and CME effectors at the plasma membrane? (WP2)
- How does acute removal of TPC subunits affect complex recruitment and CME? (WP3)
- How is the TPC organized at the structural level? (WP4)
- Which interactions occur and can we couple subunit/domain structures to functionality? (WP5)
To answer these questions, I will combine state-of-the art proteomics with highly dynamic multi-color live cell imaging and structural biology.
The overall objective is to gain a deep mechanistic insight into the developmentally essential process of CME in plants. This will enable me to specifically specifically modulate the abundance of plasma membrane proteins involved in nutrient uptake, toxin avoidance, cell wall formation and hormone and defence responses. Understanding TPC-dependent CME will also provide insight into evolutionary aspects of endocytosis.
Summary
Cells communicate with the outside world through proteins anchored in their plasma membrane and hereto constantly adjust their plasma membrane (PM) proteome. In this adjustment process, removing proteins from the PM mainly occurs through clathrin-mediated endocytosis (CME). Mechanistically however, this process remains poorly understood in plants.
A recent study from my group has shown that, in contrast to other model systems, plant CME involves two early endocytic adaptor protein complexes: the evolutionary conserved Adaptor Protein 2 complex (AP-2) and the newly identified TPLATE complex (TPC). In the same study, we also show that both complexes have overlapping but also independent functions in driving CME in plants, implying that plants use additional ways to recognize membrane proteins (cargo) for internalization.
In this project I will use an integrative approach to unravel the early steps of CME in plants. Specifically, I will address the following biological questions:
- Is the evolutionary retention of the TPC in plants causal to specific cargo recognition? (WP1)
- What are the spatio-temporal dynamics of TPC and CME effectors at the plasma membrane? (WP2)
- How does acute removal of TPC subunits affect complex recruitment and CME? (WP3)
- How is the TPC organized at the structural level? (WP4)
- Which interactions occur and can we couple subunit/domain structures to functionality? (WP5)
To answer these questions, I will combine state-of-the art proteomics with highly dynamic multi-color live cell imaging and structural biology.
The overall objective is to gain a deep mechanistic insight into the developmentally essential process of CME in plants. This will enable me to specifically specifically modulate the abundance of plasma membrane proteins involved in nutrient uptake, toxin avoidance, cell wall formation and hormone and defence responses. Understanding TPC-dependent CME will also provide insight into evolutionary aspects of endocytosis.
Max ERC Funding
1 998 813 €
Duration
Start date: 2016-07-01, End date: 2021-06-30
Project acronym TORPEDO
Project Understanding the molecular mechanisms controlling the orientation of plant cell divisions
Researcher (PI) Bert DE RYBEL
Host Institution (HI) VIB VZW
Call Details Starting Grant (StG), LS3, ERC-2016-STG
Summary Due to the presence of a rigid cell wall, plant cells are fixed within their tissue context and cannot move relative to each other during development. Plants thus need to rely on directed cell elongation and cell division to generate a full three-dimensional (3D) structure. Controlling cell division orientations relative to the tissue axis is therefore the fundamental basis for 3D growth. In the root, plant cells are organised in cell files and undergo two main types of cell division to allow directional growth: anticlinal cell divisions (AD, adding cells within a cell file) and periclinal cell divisions (PD, creating new cell files, organs and tissues). Understanding the mechanisms that control cell division orientation is a key question in developmental biology and the main focus of this application.
PDs are challenging to study as they only occur sporadically and typically in the most inner tissues of the root. I recently constructed a powerful system to induce strong, fast and homogenous PDs in any tissue type. I therefore now have the perfect tool at hands to tackle the fundamental question of how plants control the orientation of its cell divisions by:
1. Understanding the cellular events that occur prior to PD using a set of complementary techniques.
2. Identifying novel downstream components that translate the known genetic triggers for PD into changes in cell division orientation by performing an unbiased genetic screen.
3. Determining the developmental specificity and convergence of the known genetic pathways capable of inducing PD through studying their transcriptional targets in an ectopic tissue context.
4. Establishing a cell-culture based system for genetic and high throughput chemical perturbation studies of cell division orientation.
I thus aim to perform a global and comprehensive study of cell division orientation, a process crucial for 3D growth in general and vascular development in specific.
Summary
Due to the presence of a rigid cell wall, plant cells are fixed within their tissue context and cannot move relative to each other during development. Plants thus need to rely on directed cell elongation and cell division to generate a full three-dimensional (3D) structure. Controlling cell division orientations relative to the tissue axis is therefore the fundamental basis for 3D growth. In the root, plant cells are organised in cell files and undergo two main types of cell division to allow directional growth: anticlinal cell divisions (AD, adding cells within a cell file) and periclinal cell divisions (PD, creating new cell files, organs and tissues). Understanding the mechanisms that control cell division orientation is a key question in developmental biology and the main focus of this application.
PDs are challenging to study as they only occur sporadically and typically in the most inner tissues of the root. I recently constructed a powerful system to induce strong, fast and homogenous PDs in any tissue type. I therefore now have the perfect tool at hands to tackle the fundamental question of how plants control the orientation of its cell divisions by:
1. Understanding the cellular events that occur prior to PD using a set of complementary techniques.
2. Identifying novel downstream components that translate the known genetic triggers for PD into changes in cell division orientation by performing an unbiased genetic screen.
3. Determining the developmental specificity and convergence of the known genetic pathways capable of inducing PD through studying their transcriptional targets in an ectopic tissue context.
4. Establishing a cell-culture based system for genetic and high throughput chemical perturbation studies of cell division orientation.
I thus aim to perform a global and comprehensive study of cell division orientation, a process crucial for 3D growth in general and vascular development in specific.
Max ERC Funding
1 499 938 €
Duration
Start date: 2017-02-01, End date: 2022-01-31
