PICMI-AFM core facility is dedicated to the study of biological samples for nanometric imaging, and/or for the study of their mechanical properties. Before PICMI-AFM creation (2012), there was no AFM biological corefacility in the whole Region Sud and it remains unique to date. Thanks to PICMI-AFM, IRCAN has filled a scientific and technical void. This Imaging core facility is part of the network Microscopie Imagerie Cytométrie Azur (MICA) ), a multi-site, multi-research bodies facility, accredited by GIS IBISA in 2010 (https://univ-cotedazur.fr/mica). The Atomic Force Microscopy (AFM) is based on the physical interaction between the AFM probe and the sample surface.

The probe measures the forces of interaction (attractive or repulsive) with the sample surface, which depend monotonously on the distance.

These measurements can be used for two scientific purposes:

• for imaging, by obtaining 3D images at nanometric resolution
• for studying the mechanical properties of the sample, such as elasticity, by means of what is known as nanoindentation.

The advantages of the technique lie in the almost no sample preparation requirement that leaves the native surface unaltered and in the possibility of performing the experiment in a liquid environment (physiological condition). Besides, AFM is a single molecule technique, so measurements give distributions with a full statistical description and detection of intermediates and rare events.

The high resolution of AFM can be used in a very wide spectrum of applications from cell or tissue imaging to single molecules, not only for topography but also for studying the mechanical properties of biological samples.

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Current Projects

Recent Publications

• The biophysical property of the limbal niche maintains stemness through YAP
  24 avril 2023 par Swarnabh Bhattacharya
  The cell fate decisions of stem cells (SCs) largely depend on signals from their microenvironment (niche). However, very little is known about how biochemical niche cues control cell behavior in vivo. To address this question, we focused on the corneal epithelial SC model in which the SC niche, known as the limbus, is spatially segregated from the differentiation compartment. We report that the unique biomechanical property of the limbus supports the nuclear localization and function of…
• Regulation of the collagen IV network by the basement membrane protein perlecan is crucial for squamous epithelial cell morphogenesis and organ architecture
  7 novembre 2022 par Raphaël Bonche
  All epithelia have their basal side in contact with a specialized extracellular matrix, the basement membrane (BM). During development, the BM contributes to the shaping of epithelial organs via its mechanical properties. These properties rely on two core components of the BM, collagen type IV and perlecan/HSPG2, which both interact with another core component, laminin, the initiator of BM assembly. While collagen type IV supplies the BM with rigidity to constrain the tissue, perlecan…
• Secretion of IL1 by Dedifferentiated Melanoma Cells Inhibits JAK1-STAT3-Driven Actomyosin Contractility of Lymph Node Fibroblastic Reticular Cells
  3 mai 2022 par Christopher Rovera
  Fibroblastic reticular cells (FRC) are immunologically specialized myofibroblasts that control the elasticity of the lymph node, in part through their contractile properties. Swelling of tumor-draining lymph nodes is a hallmark of lymphophilic cancers such as cutaneous melanoma. Melanoma displays high intratumoral heterogeneity with the coexistence of melanoma cells with variable differentiation phenotypes from melanocytic to dedifferentiated states. Factors secreted by melanoma cells promote…
• Targeting Discoidin Domain Receptors DDR1 and DDR2 overcomes matrix-mediated tumor cell adaptation and tolerance to BRAF-targeted therapy in melanoma
  27 décembre 2021 par Ilona Berestjuk
  Resistance to BRAF/MEK inhibitor therapy in BRAF^(V600) -mutated advanced melanoma remains a major obstacle that limits patient benefit. Microenvironment components including the extracellular matrix (ECM) can support tumor cell adaptation and tolerance to targeted therapy; however, the underlying mechanisms remain poorly understood. Here, we investigated the process of matrix-mediated drug resistance (MMDR) in response to BRAF^(V600) pathway inhibition in melanoma. We demonstrate that physical…
• Mechano-induced cell metabolism promotes microtubule glutamylation to force metastasis
  8 juin 2021 par Stéphanie Torrino
  Mechanical signals from the tumor microenvironment modulate cell mechanics and influence cell metabolism to promote cancer aggressiveness. Cells withstand external forces by adjusting the stiffness of their cytoskeleton. Microtubules (MTs) act as compression-bearing elements. Yet how cancer cells regulate MT dynamic in response to the locally constrained environment has remained unclear. Using breast cancer as a model of a disease in which mechanical signaling promotes disease progression, we…
• Fibronectin Extra Domains tune cellular responses and confer topographically distinct features to fibril networks
  2 février 2021 par Georgios Efthymiou
  Cellular fibronectin (FN; also known as FN1) variants harboring one or two alternatively spliced so-called extra domains (EDB and EDA) play a central bioregulatory role during development, repair processes and fibrosis. Yet, how the extra domains impact fibrillar assembly and function of the molecule remains unclear. Leveraging a unique biological toolset and image analysis pipeline for direct comparison of the variants, we demonstrate that the presence of one or both extra domains impacts FN…
• A Feed-Forward Mechanosignaling Loop Confers Resistance to Therapies Targeting the MAPK Pathway in BRAF-Mutant Melanoma
  18 mars 2020 par Christophe A Girard
  Aberrant extracellular matrix (ECM) deposition and stiffening is a physical hallmark of several solid cancers and is associated with therapy failure. BRAF-mutant melanomas treated with BRAF and MEK inhibitors almost invariably develop resistance that is frequently associated with transcriptional reprogramming and a de-differentiated cell state. Melanoma cells secrete their own ECM proteins, an event that is promoted by oncogenic BRAF inhibition. Yet, the contribution of cancer cell-derived ECM…
• Cyclic uniaxial mechanical stretching of cells using a LEGO^® parts-based mechanical stretcher system
  12 décembre 2019 par Etienne Boulter
  Mechanical cues are essential for the regulation of cell and tissue physiology. Hence, it has become an utmost necessity for cell biologists to account for those mechanical parameters when investigating biological processes and they need devices to manipulate cells accordingly. Here, we report a simple mechanical cell-stretching system that can generate uniaxial cyclic mechanical stretch on cells in tissue culture. This system is based upon a low-cost battery-powered uniaxial cyclic mechanical…
• Tracing the cellular dynamics of sebaceous gland development in normal and perturbed states
  31 juillet 2019 par Marianne Stemann Andersen
  The sebaceous gland (SG) is an essential component of the skin, and SG dysfunction is debilitating^(1,2). Yet, the cellular bases for its origin, development and subsequent maintenance remain poorly understood. Here, we apply large-scale quantitative fate mapping to define the patterns of cell fate behaviour during SG development and maintenance. We show that the SG develops from a defined number of lineage-restricted progenitors that undergo a programme of independent and stochastic cell fate…
• Cancer cells induce immune escape via glycocalyx changes controlled by the telomeric protein TRF2
  20 avril 2019 par Julien Cherfils-Vicini
  Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells with strong immunosuppressive activity that promote tumor growth. In this study, we describe a mechanism by which cancer cells control MDSCs in human cancers by upregulating TRF2, a protein required for telomere stability. Specifically, we showed that the TRF2 upregulation in cancer cells has extratelomeric roles in activating the expression of a network of genes involved in the biosynthesis of heparan sulfate proteoglycan,…
• UBTD1 is a mechano-regulator controlling cancer aggressiveness
  27 février 2019 par Stéphanie Torrino
  Ubiquitin domain-containing protein 1 (UBTD1) is highly evolutionary conserved and has been described to interact with E2 enzymes of the ubiquitin-proteasome system. However, its biological role and the functional significance of this interaction remain largely unknown. Here, we demonstrate that depletion of UBTD1 drastically affects the mechanical properties of epithelial cancer cells via RhoA activation and strongly promotes their aggressiveness. On a stiff matrix, UBTD1 expression is…
• Cell metabolism regulates integrin mechanosensing via an SLC3A2-dependent sphingolipid biosynthesis pathway
  20 novembre 2018 par Etienne Boulter
  Mechanical and metabolic cues independently contribute to the regulation of cell and tissue homeostasis. However, how they cross-regulate each other during this process remains largely unknown. Here, we show that cellular metabolism can regulate integrin rigidity-sensing via the sphingolipid metabolic pathway controlled by the amino acid transporter and integrin coreceptor CD98hc (SLC3A2). Genetic invalidation of CD98hc in dermal cells and tissue impairs rigidity sensing and mechanical signaling…
• Analysis of DNA-Protein Complexes by Atomic Force Microscopy Imaging: The Case of TRF2-Telomeric DNA Wrapping
  31 octobre 2018 par Sabrina Pisano
  Atomic force microscopy (AFM) is a non-optical microscopy that enables the acquisition at the nanoscale level of a 3D topographical image of the sample. For 30 years, AFM has been a valuable tool in life sciences to study biological samples in the field of tissue, cellular and molecular imaging, of mechanical properties and of force spectroscopy. Since the early beginnings of the technique, AFM has been extensively exploited as an imaging tool for structural studies of nucleic acids and…
• Tumor-Stroma Mechanics Coordinate Amino Acid Availability to Sustain Tumor Growth and Malignancy
  9 octobre 2018 par Thomas Bertero
  Dysregulation of extracellular matrix (ECM) deposition and cellular metabolism promotes tumor aggressiveness by sustaining the activity of key growth, invasion, and survival pathways. Yet mechanisms by which biophysical properties of ECM relate to metabolic processes and tumor progression remain undefined. In both cancer cells and carcinoma-associated fibroblasts (CAFs), we found that ECM stiffening mechanoactivates glycolysis and glutamine metabolism and thus coordinates non-essential amino…
• Matrix Stiffening and EGFR Cooperate to Promote the Collective Invasion of Cancer Cells
  21 juillet 2018 par Eloise M Grasset
  In squamous cell carcinoma (SCC), tissue invasion by collectively invading cells requires physical forces applied by tumor cells on their surrounding extracellular matrix (ECM). Cancer-related ECM is composed of thick collagen bundles organized by carcinoma-associated fibroblasts (CAF) within the tumor stroma. Here, we show that SCC cell collective invasion is driven by the matrix-dependent mechano-sensitization of EGF signaling in cancer cells. Calcium (Ca^(2+)) was a potent intracellular…
• Dynamics under the Telomeric Bridge
  18 novembre 2017 par Sabrina Pisano
  In this issue of Molecular Cell, Kim et al. (2017) have studied the structure and organization of the shelterin protein complex protecting telomeres in Schizosaccharomyces pombe and humans and discovered an allosteric structural transition that drives the formation of the shelterin complex and participates in telomere length regulation.
• Post-transcriptional gene silencing mediated by microRNAs is controlled by nucleoplasmic Sfpq
  1 novembre 2017 par Silvia Bottini
  There is a growing body of evidence about the presence and the activity of the miRISC in the nucleus of mammalian cells. Here, we show by quantitative proteomic analysis that Ago2 interacts with the nucleoplasmic protein Sfpq in an RNA-dependent fashion. By a combination of HITS-CLIP and transcriptomic analyses, we demonstrate that Sfpq directly controls the miRNA targeting of a subset of binding sites by local binding. Sfpq modulates miRNA targeting in both nucleoplasm and cytoplasm, indicating…
• TRF2-Mediated Control of Telomere DNA Topology as a Mechanism for Chromosome-End Protection
  18 janvier 2016 par Delphine Benarroch-Popivker
  The shelterin proteins protect telomeres against activation of the DNA damage checkpoints and recombinational repair. We show here that a dimer of the shelterin subunit TRF2 wraps ∼ 90 bp of DNA through several lysine and arginine residues localized around its homodimerization domain. The expression of a wrapping-deficient TRF2 mutant, named Top-less, alters telomeric DNA topology, decreases the number of terminal loops (t-loops), and triggers the ATM checkpoint, while still protecting telomeres…
• A higher-order entity formed by the flexible assembly of RAP1 with TRF2
  10 janvier 2016 par Guillaume Gaullier
  Telomere integrity is essential to maintain genome stability, and telomeric dysfunctions are associated with cancer and aging pathologies. In human, the shelterin complex binds TTAGGG DNA repeats and provides capping to chromosome ends. Within shelterin, RAP1 is recruited through its interaction with TRF2, and TRF2 is required for telomere protection through a network of nucleic acid and protein interactions. RAP1 is one of the most conserved shelterin proteins although one unresolved question…
• CD98hc (SLC3A2) loss protects against ras-driven tumorigenesis by modulating integrin-mediated mechanotransduction
  1 octobre 2014 par Soline Estrach
  CD98hc (SLC3A2) is the heavy chain component of the dimeric transmembrane glycoprotein CD98, which comprises the large neutral amino acid transporter LAT1 (SLC7A5) in cells. Overexpression of CD98hc occurs widely in cancer cells and is associated with poor prognosis clinically, but its exact contributions to tumorigenesis are uncertain. In this study, we showed that genetic deficiency of CD98hc protects against Ras-driven skin carcinogenesis. Deleting CD98hc after tumor induction was also…