Biology subjects

Anquez, F.

Publications and source records attributed to Anquez, F..

5 recordsLinked to original sources

bioRxiv2024

Spatial self-organization of cancer stem cell niches revealed by live single-cell imaging

Phenotypic plasticity is a major factor of tumor heterogeneity and treatment resistance. In particular, cancer stem cells (CSCs) represent a small subpopulation within tumors with self-renewal and tumor-forming capabilities. Understanding reprogramming, maintenance, and lineage properties of CSCs requires dedicated tools to disentangle the respective influences of phenotypic inheritance and cell-cell interactions. Here we set up ultra-wide field microscopy of breast cancer cell lines expressing a stemness fluorescent reporter for several days. The fluorescent reporter distinguishes three phenotypes: cancer stem cells (CSCs), cancer differentiated cells (CDCs) and intermediate/transiting cancer cells (iCCs). Spatial statistics indicate significant zonation, aka phenotypic niches, with CSC clustering near each other but away from CDCs. Surprisingly, single cell time series reveal spontaneous reprogramming events from CDC to CSC even in unperturbed populations. We identify that such transitions are prone to arise during the cell cycle. Moreover, lineage analysis shows that the phenotype is partially inherited from ancestor cells. However, such heredity is not sufficient to explain the spatial properties of the cell population, which also depend on cell-cell interactions. Indeed, we identified that phenotypic transitions of cancer cells are influenced by the phenotypic state of neighboring cells. Reprogramming into CSCs is respectively promoted and inhibited by the presence of CSCs and CDCs in the neighborhood. Altogether, our results disentangle how phenotypic inheritance and intercellular interactions orchestrate the spatio-temporal self-organization of cancer cell heterogeneity, maintaining a subpopulation of CSCs within niches.

systems biology↗

bioRxiv2022

Quantitative modeling of pentose phosphate pathway response to oxidative stress reveals a cooperative regulatory strategy

Living cells use signaling and regulatory mechanisms to adapt to environmental stresses. In the case of oxidative stress due for instance to hydrogen peroxide exposure, the adaptation response relies on co-regulation of enzymes in both glycolysis and pentose phosphate pathways (PPP), so as to support PPP-dependent NADPH and redox homeostasis. To understand the regulatory logic underlying early oxidative stress response, available metabolomics and 13C fluxomics dataset are used to infer a probabilistic ensemble of kinetic models. Model ensemble properties of parameter distributions, transient dynamics, dose-response curves and loss-of-function phenotypes all highlights significant and cooperative effects of allosteric regulations of G6PD, PGI and GAPD in early oxidative response. Indeed, efficient flux rerouting into PPP is shown to require dose-dependent coordination between upregulated G6PD enzyme and increased G6P metabolite, the latter requiring fine-tuned inhibition of upper and lower glycolytic enzymes. This set of allosteric regulation also combines negative and positive feedback loops in a subtle manner prone to generate paradoxical perturbation phenotypes for instance related to 6PGD modulation.

systems biology↗

bioRxiv2020

Measuring adaptation dynamics to hydrogen peroxide in single human cells using fluorescent reporters

We developed an experimental methodology to monitor response dynamics of single human cells to hydrogen peroxide. Our approach is based on fluidic control of both magnitude and time-evolution of the external perturbation, and on high-throughput imaging of intracellular fluorescent redox reporters. We applied step stimulus to MCF7 cells with hydrogen peroxide concentration in the range of 10 to 500M. First, our data highlights dynamic adaptation of Reactive Oxygen Species (ROS) scavenging system at several time scales. Nicotinamide Adenine Dinucleotide Phosphate (NADPH) level is rapidly restored within 10 min after a transient decrease, while glutathione (GSH) redox potential is slowly driven back toward pre-stimulus level (within one hour). Extra-cellular glucose is necessary for adaptation of both NADPH level and GSH system. Second, our results also reveal large cell-to-cell variability in the dynamic response to external ROS. Our experimental approach is readily usable to monitor other cellular redox systems such as thioredoxins. As response-heterogeneity can lead to fractional killing, we finally discuss how our methodology can be an opportunity to link dynamics of ROS scavenging and cellular fate such as cell death.

cell biology↗

bioRxiv2019

Protein Level Variability Determines Phenotypic Heterogeneity in Proteotoxic Stress Response

Cell-to-cell variability in stress response is a bottleneck for the construction of accurate and predictive models that could guide clinical diagnosis and treatment of diseases as for instance cancers. Indeed such phenotypic heterogeneity can lead to fractional killing and persistence of a subpopulation of cells resistant to a given treatment. The heat shock response network plays a major role in protecting the proteome against several types of injuries. We combine high-throughput measurements and mathematical modeling to unveil the molecular origin of the phenotypic variability in the heat shock response network. Although the mean response coincides with known biochemical measurements, we found a surprisingly broad diversity in single cell dynamics with a continuum of response amplitudes and temporal shapes for several stimuli strengths. We theoretically predict that the broad phenotypic heterogeneity is due to network ultrasensitivity together with variations in the expression level of chaperons controlled by heat shock factor 1. We experimentally confirm this prediction by mapping the response amplitude to concentrations chaperons and heat shock factor 1 expression level.

systems biology↗

bioRxiv2017

Generation And Attenuation Of Variability In A Bacterial Signalling Network Revealed By Single-Cell FRET

We present in vivo single-cell FRET measurements in the Escherichia coli chemotaxis system that reveal pervasive signaling variability, both across cells in isogenic populations and within individual cells over time. We quantify cell-to-cell variability of adaptation, ligand response, as well as steady-state output level, and analyze the role of network design in shaping this diversity from gene expression noise. In the absence of changes in gene expression, we find that single cells demonstrate strong temporal fluctuations. We provide evidence that such signaling noise can arise from at least two sources: (i) stochastic activities of adaptation enzymes, and (ii) receptor-kinase dynamics in the absence of adaptation. We demonstrate that under certain conditions, (ii) can generate giant fluctuations that drive signaling activity of the entire cell into a stochastic two-state switching regime. Our findings underscore the importance of molecular noise, arising not only in gene expression but also in protein networks.

systems biology↗