We propose to investigate how dietary restrictions (DR) affect aging from a new angle by using social insects as models. Aging is a hallmark of most bilateria and most animals balance their reproduction rate against lifespan. Intriguingly, this trade-off is inverted in reproductive individuals (queens) of social insects (termites, ants, bees). Whereas most studies on aging directly manipulate the lifespan, e.g. of mice or worms or other lab-bred animals, we here propose a radically new approach by employing easily accessible and natural extremely long-lived termite queens as models. Their metabolism, response to DR and fertility will be gauged against genomically identical bu infertile and short lived workers, as well as shorter lived and less fecund queen of a closely related termite species. We will sample termite colonies directly from the field, keep them, expose them to DR and measure their fitness and fecundity. We will examine the role of DR during colony development by sampling transcriptomes, analyzing their epigenetic status, their metabolome and endocrine status and performing in-depth molecular analyses of key molecular components that are known to be implicated in regulating aging and fecundity. Using multiple OMICS methods, reverse genetics, hormonal and dietary administration we will be able to disentangle pathways involved in development of queens and measure the impact of energetic metabolic reprogramming on fitness and reproduction status. Expression patterns and spatio-temporal changes of genetic networks will be used to develop a simple state model. In this model, the metabolic status can be used to predict an individual's trajectory of aging and fecundity depending on its epigenetically imprinted background such as it's caste. Our project thus establishes a new model system for studying the relationship between DR, aging and fecundity, in which the latter two are decoupled and comparison of our model to other model organisms will help understand which dependencies and molecular components have universally conserved interaction partners or phenotypic effects. The project is possible only due to the four participants from three continents, with expertise in dietary research, energy metabolism, field research and social insect genomics.

Organ development depends on the integration of local cell-to-cell interactions with long range signalling throughout the body. We will investigate mechanisms by which long-range signalling via the cerebrospinal fluid (CSF) regulate body axis formation and spine curvature. The CSF is produced by the choroid plexus in the brain ventricles and flows down the central canal in the spinal cord. The CSF instructs brain development by delivering age-dependent grow-promoting factors to target cells. CSF circulation also contributes to the curvature of body axis (embryo) and to the spine (juveniles). However, the mechanisms regulating the flow and content of CSF remain poorly understood. Progress has been impeded by a historical lack of tools and challenges inherent to studying fluids in small, developing organisms. The advent of innovative tools and approaches now provides an unprecedented opportunity to overcome previous limitations. The transparency of zebrafish and the accessibility to mouse CSF provide powerful models for testing our driving hypothesis that the physical and biochemical properties of CSF impact body axis formation and spine curvature. We propose an entirely new, interdisciplinary collaboration of three leaders in their field: (1) physicist Francois Gallaire (EPFL, Switzerland), expert in the theory & modelling of complex fluid dynamics; (2) developmental neurobiologist Maria Lehtinen (Boston Children’s, HMS, USA), expert in analysis of the choroid plexus-CSF system; (3) biophysicist Claire Wyart (ICM, France), expert in imaging and sensory physiology in the spinal cord. Our multi-tiered approach will unravel the principal parameters driving CSF composition and flow. We will map CSF flow in the developing fourth ventricle and central canal (Aim 1), elucidate mechanisms regulating protein secretion into the CSF (Aim 2), and investigate mechanisms of active transport of instructive signals along the anteroposterior axis controlling organogenesis (Aim 3). The proposed studies will transform this historically understudied area of neuroscience into a robust field spanning CSF-based signalling in brain and spine. As studies of paracrine signalling and fluid dynamics lag far behind cell-intrinsic studies of signalling, our techniques and concepts should provide a roadmap for future studies of fluid niches throughout the vertebrate body.

Organ development depends on the integration of local cell-to-cell interactions with long range signalling throughout the body. We will investigate mechanisms by which long-range signalling via the cerebrospinal fluid (CSF) regulate body axis formation and spine curvature. The CSF is produced by the choroid plexus in the brain ventricles and flows down the central canal in the spinal cord. The CSF instructs brain development by delivering age-dependent grow-promoting factors to target cells. CSF circulation also contributes to the curvature of body axis (embryo) and to the spine (juveniles). However, the mechanisms regulating the flow and content of CSF remain poorly understood. Progress has been impeded by a historical lack of tools and challenges inherent to studying fluids in small, developing organisms. The advent of innovative tools and approaches now provides an unprecedented opportunity to overcome previous limitations. The transparency of zebrafish and the accessibility to mouse CSF provide powerful models for testing our driving hypothesis that the physical and biochemical properties of CSF impact body axis formation and spine curvature. We propose an entirely new, interdisciplinary collaboration of three leaders in their field: (1) physicist Francois Gallaire (EPFL, Switzerland), expert in the theory & modelling of complex fluid dynamics; (2) developmental neurobiologist Maria Lehtinen (Boston Children’s, HMS, USA), expert in analysis of the choroid plexus-CSF system; (3) biophysicist Claire Wyart (ICM, France), expert in imaging and sensory physiology in the spinal cord. Our multi-tiered approach will unravel the principal parameters driving CSF composition and flow. We will map CSF flow in the developing fourth ventricle and central canal (Aim 1), elucidate mechanisms regulating protein secretion into the CSF (Aim 2), and investigate mechanisms of active transport of instructive signals along the anteroposterior axis controlling organogenesis (Aim 3). The proposed studies will transform this historically understudied area of neuroscience into a robust field spanning CSF-based signalling in brain and spine. As studies of paracrine signalling and fluid dynamics lag far behind cell-intrinsic studies of signalling, our techniques and concepts should provide a roadmap for future studies of fluid niches throughout the vertebrate body.

Plant development and growth are linked to cellular shape changes, which are controlled by genetic programs but also by perception of environmental signals, including mechanical cues. While both genetic regulation and mechanical control of morphogenesis were studied independently, there is a need to explore how cellular shape-associated strain and stress can mechanically regulate gene expression during differentiation. In animals, mechanical stimuli are known effectors of differentiation. They involve propagation of mechanical forces through the cytoskeleton to the nucleus, leading to chromatin remodeling and modification of gene expression. Thus, nuclear envelope proteins that control nuclear shape and transmit forces to chromatin play a key role in rapid triggering of gene expression. In plants, less is known about mechanotransduction from cell surface to the nucleus.
Using a systems biology approach and an interdisciplinary network, we propose to investigate how mechanical cues affecting cellular shaping are sensed at the nuclear envelope to drive chromatin remodeling in Arabidopsis. We will sudy a unique cellular model, the single root hair in an epidermal tissue context, with well-defined morphogenetic programs linked to cytoskeleton and nuclear dynamics. We will analyze root hair formation and growth in WT and mutants affected in either root hair development or nuclear shape. Combining in vivo live imaging and micro-mechanical measurements (rheometry), we will evaluate mechanical properties of cells and nuclei during root hair development and their dependence on cytoskeleton and nuclear dynamics in relation to gene expression. We will also determine how these mechanical, structural and biological properties are modified when a controlled mechanical stress is applied to the root hair cell during development. Our data will highlight proteins involved in mechanosensing, and we will evaluate their interaction with the nuclear envelope network. Live imaging and rheometry data will be correlated to finite element modeling to estimate strain and stress in the system for predicting chromatin remodeling following cellular and nuclear shape changes.
Altogether, this will highlight the molecular networks involved in mechanosensing at the nucleo-cytoplamic interface and reveal how gene expression is robustly regulated during cellular morphogenesis in higher plants.

Plant development and growth are linked to cellular shape changes, which are controlled by genetic programs but also by perception of environmental signals, including mechanical cues. While both genetic regulation and mechanical control of morphogenesis were studied independently, there is a need to explore how cellular shape-associated strain and stress can mechanically regulate gene expression during differentiation. In animals, mechanical stimuli are known effectors of differentiation. They involve propagation of mechanical forces through the cytoskeleton to the nucleus, leading to chromatin remodeling and modification of gene expression. Thus, nuclear envelope proteins that control nuclear shape and transmit forces to chromatin play a key role in rapid triggering of gene expression. In plants, less is known about mechanotransduction from cell surface to the nucleus.
Using a systems biology approach and an interdisciplinary network, we propose to investigate how mechanical cues affecting cellular shaping are sensed at the nuclear envelope to drive chromatin remodeling in Arabidopsis. We will sudy a unique cellular model, the single root hair in an epidermal tissue context, with well-defined morphogenetic programs linked to cytoskeleton and nuclear dynamics. We will analyze root hair formation and growth in WT and mutants affected in either root hair development or nuclear shape. Combining in vivo live imaging and micro-mechanical measurements (rheometry), we will evaluate mechanical properties of cells and nuclei during root hair development and their dependence on cytoskeleton and nuclear dynamics in relation to gene expression. We will also determine how these mechanical, structural and biological properties are modified when a controlled mechanical stress is applied to the root hair cell during development. Our data will highlight proteins involved in mechanosensing, and we will evaluate their interaction with the nuclear envelope network. Live imaging and rheometry data will be correlated to finite element modeling to estimate strain and stress in the system for predicting chromatin remodeling following cellular and nuclear shape changes.
Altogether, this will highlight the molecular networks involved in mechanosensing at the nucleo-cytoplamic interface and reveal how gene expression is robustly regulated during cellular morphogenesis in higher plants.

Plant development and growth are linked to cellular shape changes, which are controlled by genetic programs but also by perception of environmental signals, including mechanical cues. While both genetic regulation and mechanical control of morphogenesis were studied independently, there is a need to explore how cellular shape-associated strain and stress can mechanically regulate gene expression during differentiation. In animals, mechanical stimuli are known effectors of differentiation. They involve propagation of mechanical forces through the cytoskeleton to the nucleus, leading to chromatin remodeling and modification of gene expression. Thus, nuclear envelope proteins that control nuclear shape and transmit forces to chromatin play a key role in rapid triggering of gene expression. In plants, less is known about mechanotransduction from cell surface to the nucleus.
Using a systems biology approach and an interdisciplinary network, we propose to investigate how mechanical cues affecting cellular shaping are sensed at the nuclear envelope to drive chromatin remodeling in Arabidopsis. We will sudy a unique cellular model, the single root hair in an epidermal tissue context, with well-defined morphogenetic programs linked to cytoskeleton and nuclear dynamics. We will analyze root hair formation and growth in WT and mutants affected in either root hair development or nuclear shape. Combining in vivo live imaging and micro-mechanical measurements (rheometry), we will evaluate mechanical properties of cells and nuclei during root hair development and their dependence on cytoskeleton and nuclear dynamics in relation to gene expression. We will also determine how these mechanical, structural and biological properties are modified when a controlled mechanical stress is applied to the root hair cell during development. Our data will highlight proteins involved in mechanosensing, and we will evaluate their interaction with the nuclear envelope network. Live imaging and rheometry data will be correlated to finite element modeling to estimate strain and stress in the system for predicting chromatin remodeling following cellular and nuclear shape changes.
Altogether, this will highlight the molecular networks involved in mechanosensing at the nucleo-cytoplamic interface and reveal how gene expression is robustly regulated during cellular morphogenesis in higher plants.

Plant development and growth are linked to cellular shape changes, which are controlled by genetic programs but also by perception of environmental signals, including mechanical cues. While both genetic regulation and mechanical control of morphogenesis were studied independently, there is a need to explore how cellular shape-associated strain and stress can mechanically regulate gene expression during differentiation. In animals, mechanical stimuli are known effectors of differentiation. They involve propagation of mechanical forces through the cytoskeleton to the nucleus, leading to chromatin remodeling and modification of gene expression. Thus, nuclear envelope proteins that control nuclear shape and transmit forces to chromatin play a key role in rapid triggering of gene expression. In plants, less is known about mechanotransduction from cell surface to the nucleus.
Using a systems biology approach and an interdisciplinary network, we propose to investigate how mechanical cues affecting cellular shaping are sensed at the nuclear envelope to drive chromatin remodeling in Arabidopsis. We will sudy a unique cellular model, the single root hair in an epidermal tissue context, with well-defined morphogenetic programs linked to cytoskeleton and nuclear dynamics. We will analyze root hair formation and growth in WT and mutants affected in either root hair development or nuclear shape. Combining in vivo live imaging and micro-mechanical measurements (rheometry), we will evaluate mechanical properties of cells and nuclei during root hair development and their dependence on cytoskeleton and nuclear dynamics in relation to gene expression. We will also determine how these mechanical, structural and biological properties are modified when a controlled mechanical stress is applied to the root hair cell during development. Our data will highlight proteins involved in mechanosensing, and we will evaluate their interaction with the nuclear envelope network. Live imaging and rheometry data will be correlated to finite element modeling to estimate strain and stress in the system for predicting chromatin remodeling following cellular and nuclear shape changes.
Altogether, this will highlight the molecular networks involved in mechanosensing at the nucleo-cytoplamic interface and reveal how gene expression is robustly regulated during cellular morphogenesis in higher plants.

The human brain gains much of its computational abilities from the trillions of connections made between cells by synapses. Molecular changes in synapses (a process called synaptic plasticity) are considered to underlie learning and memory. An important component of the synapse is the postsynaptic density (PSD). This specialized structure has been studied extensively to understand its function, in particular because >100 neurologic disorders (such as autism spectrum disorder and schizophrenia) have been associated with PSD dysfunction. Information regarding the overall molecular architecture of the PSD, however, is largely incomplete, in part because the PSD is extremely complex, containing hundreds of individual components connected in a dense network. The PSD is also highly dynamic and asymmetrical—two properties that render protein structural analyses challenging. While solving the structure of the entire PSD seems insurmountable, half of the PSD’s mass is composed of only ten classes of linker proteins. We hypothesize that these highly-abundant proteins form a molecular scaffold, a network we term the ‘postsynaptic scaffold’ (PSS). We aim to develop an approach we call the ‘Thermophile-Assisted Postsynaptic Architecture Strategy’ (TAPAS) to solve the PSS structure. Given the delicate nature of proteins, structural biologists like to work with resilient, temperature-resistant proteins that can be obtained from thermophilic organisms. For brain-derived proteins, there is one animal known to be comfortable at temperatures >50 °C: a worm that lives on hydrothermal vents in the Pacific Ocean. We plan to sequence this worm’s genome (Alvinella pompejana) to find the PSS proteins that it shares with humans. We will determine the structures of the thermophilic proteins by X-ray crystallography. As much of the PSS architecture consists of filamentous structures that do not crystallize, we will use cryo-electron microscopy to define these larger structures. Finally, we will integrate several other methods (biochemical, proteomic, bioinformatic and advanced electron tomography methods) to build a model of the overall PSS. Achieving this ambitious goal will inform studies into learning and memory, lead to new treatments for devastating brain disorders, and help explain how the synapse contributes to human cognition.

Epithelial collective cell migration (CCM) is important in biological processes such as organ development, tissue maintenance and tissue repair. CCM usually occurs on curved surfaces such as that found in blood vessel walls and intestinal villi. However, current CCM research are still conducted on flat surfaces. This is due to lack of techniques to fabricate tubular and spherical microstructures resembling that of organs as well as difficulty in observing and measuring the collective dynamic behaviour of cells on these surfaces. Nevertheless, recent studies are beginning to show that cells do behave differently on curved surfaces. However, these studies were mainly focused on single cells, as such, there is limited insight into CCM which involves complex interactions among multiple cells.
Here, we claim that curved surfaces can significantly influence CCM. As such, we propose to systematically study CCM on such surfaces to better understand their underlying mechanisms. Our project will combine distinct but complementary scientific expertises coming from biology, biophysics and engineering. We aim to: 1) Develop novel techniques in fabricating different, well-defined curved geometries such as tubular and spherical surfaces with nano-patterns; 2) Identify biomolecules and proteins involved in CCM on curved surfaces; 3) Develop computational models to perform 3D imaging and analysis so as to better monitor and measure complex tissue dynamics; and 4) Develop a universal theory to better explain and unify experimental observations.
Together, the unique combination of these different approaches will enable us to better understand the fundamental mechanisms and impact of surface curvature on cell behaviour and tissue organization. These will shed light on related biological functions such as in organ development and tissue repair, as well as contributing towards better tissue engineering or regenerative medicine applications.

Epithelial collective cell migration (CCM) is important in biological processes such as organ development, tissue maintenance and tissue repair. CCM usually occurs on curved surfaces such as that found in blood vessel walls and intestinal villi. However, current CCM research are still conducted on flat surfaces. This is due to lack of techniques to fabricate tubular and spherical microstructures resembling that of organs as well as difficulty in observing and measuring the collective dynamic behaviour of cells on these surfaces. Nevertheless, recent studies are beginning to show that cells do behave differently on curved surfaces. However, these studies were mainly focused on single cells, as such, there is limited insight into CCM which involves complex interactions among multiple cells.
Here, we claim that curved surfaces can significantly influence CCM. As such, we propose to systematically study CCM on such surfaces to better understand their underlying mechanisms. Our project will combine distinct but complementary scientific expertises coming from biology, biophysics and engineering. We aim to: 1) Develop novel techniques in fabricating different, well-defined curved geometries such as tubular and spherical surfaces with nano-patterns; 2) Identify biomolecules and proteins involved in CCM on curved surfaces; 3) Develop computational models to perform 3D imaging and analysis so as to better monitor and measure complex tissue dynamics; and 4) Develop a universal theory to better explain and unify experimental observations.
Together, the unique combination of these different approaches will enable us to better understand the fundamental mechanisms and impact of surface curvature on cell behaviour and tissue organization. These will shed light on related biological functions such as in organ development and tissue repair, as well as contributing towards better tissue engineering or regenerative medicine applications.

Epithelial collective cell migration (CCM) is important in biological processes such as organ development, tissue maintenance and tissue repair. CCM usually occurs on curved surfaces such as that found in blood vessel walls and intestinal villi. However, current CCM research are still conducted on flat surfaces. This is due to lack of techniques to fabricate tubular and spherical microstructures resembling that of organs as well as difficulty in observing and measuring the collective dynamic behaviour of cells on these surfaces. Nevertheless, recent studies are beginning to show that cells do behave differently on curved surfaces. However, these studies were mainly focused on single cells, as such, there is limited insight into CCM which involves complex interactions among multiple cells.
Here, we claim that curved surfaces can significantly influence CCM. As such, we propose to systematically study CCM on such surfaces to better understand their underlying mechanisms. Our project will combine distinct but complementary scientific expertises coming from biology, biophysics and engineering. We aim to: 1) Develop novel techniques in fabricating different, well-defined curved geometries such as tubular and spherical surfaces with nano-patterns; 2) Identify biomolecules and proteins involved in CCM on curved surfaces; 3) Develop computational models to perform 3D imaging and analysis so as to better monitor and measure complex tissue dynamics; and 4) Develop a universal theory to better explain and unify experimental observations.
Together, the unique combination of these different approaches will enable us to better understand the fundamental mechanisms and impact of surface curvature on cell behaviour and tissue organization. These will shed light on related biological functions such as in organ development and tissue repair, as well as contributing towards better tissue engineering or regenerative medicine applications.

Epithelial collective cell migration (CCM) is important in biological processes such as organ development, tissue maintenance and tissue repair. CCM usually occurs on curved surfaces such as that found in blood vessel walls and intestinal villi. However, current CCM research are still conducted on flat surfaces. This is due to lack of techniques to fabricate tubular and spherical microstructures resembling that of organs as well as difficulty in observing and measuring the collective dynamic behaviour of cells on these surfaces. Nevertheless, recent studies are beginning to show that cells do behave differently on curved surfaces. However, these studies were mainly focused on single cells, as such, there is limited insight into CCM which involves complex interactions among multiple cells.
Here, we claim that curved surfaces can significantly influence CCM. As such, we propose to systematically study CCM on such surfaces to better understand their underlying mechanisms. Our project will combine distinct but complementary scientific expertises coming from biology, biophysics and engineering. We aim to: 1) Develop novel techniques in fabricating different, well-defined curved geometries such as tubular and spherical surfaces with nano-patterns; 2) Identify biomolecules and proteins involved in CCM on curved surfaces; 3) Develop computational models to perform 3D imaging and analysis so as to better monitor and measure complex tissue dynamics; and 4) Develop a universal theory to better explain and unify experimental observations.
Together, the unique combination of these different approaches will enable us to better understand the fundamental mechanisms and impact of surface curvature on cell behaviour and tissue organization. These will shed light on related biological functions such as in organ development and tissue repair, as well as contributing towards better tissue engineering or regenerative medicine applications.

Cells achieve reproducible outputs while relying on intrinsically stochastic molecular processes. In plants, cell division orientation is accurately predicted before mitosis by a microtubular ring, the preprophase band (PPB), through an unknown mechanism. Using high-throughput microscopy, quantitative image analysis, biomechanics and stochastic modeling, we will investigate how the stochasticity of microtubule (MT) self-organization is used, or filtered out, during PPB formation to sense temporal, geometric and mechanical cues in order to generate a robust placement of cell division planes. In short, we will test whether the PPB acts as a macromolecular mechanosensor. Using statistical mechanics such as Monte Carlo, event-based modeling and mean-field theory, we will assess how stochasticity leads to distinct dynamical states for MT arrays. We will develop biophysical models of dynamic MTs in 3D cells to explore how stochastic MTs self-organize into PPBs and how spatiotemporal cues modulate that process. Using the Arabidopsis shoot apical meristem, we will identify correlations between MT array dynamics, PPB behavior, cell shape, growth and mechanics, cell cycle progression, and cell division plane from statistically representative sample involving hundreds of dividing cells. To challenge the robustness of PPB and cell division in vivo and in silico, we will globally and locally increase variability in these cell parameters with mutants (MT dynamics, wall mechanics, cell cycle, mechanotransduction), inducible lines, mosaics, and micromechanical perturbations. Last, we will unravel the molecular mechanism processing molecular stochasticity to channel cell divisions: we will investigate how the TTP (TON1-TRM-PP2A) complex, a key regulator of PPB formation in connection with the cell cycle, contributes to generate reproducible divisions by monitoring MT self-organization, integrating geometric, mechanical and temporal cues. Implications of this project go beyond cell division robustness: while many cellular pathways are adapted to respond to rapid and discontinuous changes, we expect here to unravel mechanisms managing slow and continuous signals, like shape, growth or tissue-stress. We will also gain insight into the mathematical properties of stochastic extended objects like microtubules, and we will propose a mechanism for cells to perceive directional cues.

Muscles are producing the active forces that enable all our voluntary body movements. The cellular components of muscle are called muscle fibers and are very large cells that can be several centimeters in length in humans. Inside all muscle cells are millions of tiny molecular machines, called sarcomeres that produce the active forces of muscles. These sarcomeres are arrayed in highly regular long chains called myofibrils that span from one muscle end to the other. This arrangement ensures that the force produced by the myofibrils is transmitted to the connected tendons and bones at the muscles ends. The highly regular periodic organization of the myofibrils results in the cross-striated appearance of skeletal muscles under the microscope.
We assembled an international team of researchers from France, USA and Germany to study how myofibrils are built during muscle development. For this we combine two different experimental model systems, the fruit fly Drosophila muscles and human muscle cells generated in vitro from stem cells, together with mathematical modeling of myofibril assembly. Our starting hypothesis is that mechanical forces, which are generated early during muscle development, are an important factor for the polymerization of myofibrils. We will test this hypothesis in fly as well as in human muscles produced in vitro by following the localization of sarcomeric protein components with high-resolution microscopy techniques. We will measure when a sarcomeric protein pattern can be first detected and how this pattern is refined. These data will be used to generate a computer model that can produce periodic sarcomere-like structures that are linked together from homogenous components. We will further measure the strength of mechanical forces present during myofibril formation in fly muscles in vivo and in human muscles in culture. Finally, we aim to modify these forces and to observe the effect of these manipulations on the developing muscles and myofibrils. These data will be used to produce a refined computer model of myofibrillogenesis. Together, our research should lead to a better understanding of how the contractile apparatus of human muscle is built, which could eventually be helpful to treat muscle injuries or aged dependent myopathies.

Understanding how out of single cells functional tissues and organs develop is a major challenge of biology. Recent progress allows us to grow organ-like cell assemblies (organoids) from stem cells in vitro. Organoids offer great potential for studying diseases and development. However, in many cases we do not yet understand how these complex tissues emerge out of progenitor stem cells. A common feature in the initial growth phase of many organoid systems is the formation of a polarized epithelial cyst with a single or multiple internal apical lumen. This initial transition into an epithelial cyst establishes a tissue template that on the one hand enables maintenance of progenitor/stem cells (niche) and on the other hand guides the patterning of differentiated cells into a functional tissue. Our aim is to understand how the interplay between proliferation (cell divisions), polarization (epithelial transition) and differentiation (patterning) leads to self-organization of this epithelial progenitor template and how this structure facilitates correct patterning into functional organoids. To this end, we will systematically control and characterize the early growth phase of two organoid systems (pancreatic and neural tube) using microfabrication and micro-patterning approaches. We will quantify evolution of cell shapes, adhesion and cortical forces, apical-basal polarization and differentiation as a function of initial cell contact patterns. This approach will provide the means to find rules how local cell interactions (cell-cell, cell-matrix, cell-lumen) are connected to tissue growth and differentiation. We will then test sufficiency of the hypothetical rules to generate the observed organoid structures using an in silico mechano-chemical model. Taken together, by dissecting the early growth phase of two organoid systems, we aim to uncover the common rules on how progenitors establish a polarized epithelial template, and how this template is then differentially used to generate organ specific differentiation patterns.

Understanding how out of single cells functional tissues and organs develop is a major challenge of biology. Recent progress allows us to grow organ-like cell assemblies (organoids) from stem cells in vitro. Organoids offer great potential for studying diseases and development. However, in many cases we do not yet understand how these complex tissues emerge out of progenitor stem cells. A common feature in the initial growth phase of many organoid systems is the formation of a polarized epithelial cyst with a single or multiple internal apical lumen. This initial transition into an epithelial cyst establishes a tissue template that on the one hand enables maintenance of progenitor/stem cells (niche) and on the other hand guides the patterning of differentiated cells into a functional tissue. Our aim is to understand how the interplay between proliferation (cell divisions), polarization (epithelial transition) and differentiation (patterning) leads to self-organization of this epithelial progenitor template and how this structure facilitates correct patterning into functional organoids. To this end, we will systematically control and characterize the early growth phase of two organoid systems (pancreatic and neural tube) using microfabrication and micro-patterning approaches. We will quantify evolution of cell shapes, adhesion and cortical forces, apical-basal polarization and differentiation as a function of initial cell contact patterns. This approach will provide the means to find rules how local cell interactions (cell-cell, cell-matrix, cell-lumen) are connected to tissue growth and differentiation. We will then test sufficiency of the hypothetical rules to generate the observed organoid structures using an in silico mechano-chemical model. Taken together, by dissecting the early growth phase of two organoid systems, we aim to uncover the common rules on how progenitors establish a polarized epithelial template, and how this template is then differentially used to generate organ specific differentiation patterns.