Nanodynamic Imaging of Leukemic Cell Adhesion

Type d’annonce: Proposition – Thèses

Description de la proposition:

DOC2AMU is a European COFUND interdisciplinary PhD project.

Cell junctions play a key role in the integrity of biological tissues, via Cell Adhesion Molecules (CAMs).
In particular, in the bone marrow, interactions between hematopoietic and stromal cells allow the
mutual transmission of signals involved in the development and homeostasis of both cell types. This
crosstalk also involves adhesion mechanisms, with a major impact on the physiology of
hematopoietic and stromal cells (development, maintenance, proliferation). Partner I (A. Sergé & M.
Aurrand-Lions, Leuko/Stromal Interactions team, CRCM) is specialized in these interactions,
especially for integrins and Junctional Adhesion Molecules (JAMs, De Grandis et al. Cell Mol Life Sci
2015). In physiological context, the team reported contacts between JAM-C-expressing
hematopoietic stem cells and JAM-B-expressing stromal cells (Arcangeli et al. Blood 2011). These
interactions are deeply revised in tumor context. Preliminary data show that JAM-C-mediated
adhesion of leukemic stem cell (LSC) to the stroma is involved in Cell-Adhesion-Mediated Drug
Resistance (CAM-DR), suggesting that JAM-C constitutes a potential therapeutic target in leukemia.

Recent advances in optical nanoscopy completely revisited the classic pattern of static adhesion
structures in cells (Rossier et al. Nat Cell Biol 2012; Paszek et al. Nature 2014). Major players, such as
integrins and their adapters, are tightly regulated by association/dissociation mechanisms,
modulated according to pathophysiological conditions and signals received by the cell. Brief episodes
of confinement or colocalization can reveal molecular events leading to cellular pathway activation.
Hence, discrete events can lead to critical outcomes, thanks to non-linear amplification, as often
reported in cell signaling. Moreover, integrin-mediated adhesion to collagen, a major component of
the extracellular matrix (ECM), is profoundly implicated in tumor evolution. Analysis of molecular
trajectories with our homemade software MTT (Serge et al. Nat Met 2008; Rouger et al. JoVE 2012)
in combination with simultaneous monitoring on the fine distribution of collagen in the close
environment of the living cell will identify interactions during the onset and stabilization of leukemic
cells/stroma contacts. Ultra-resolved imaging will document the role of CAMs in the dynamic
establishment of cell/cell and cell/ECM adhesion in real time. We will notably study cells weakly or
strongly expressing JAM-C, to assess the impact of blocking antibodies in LSC/stroma interaction.

Simultaneous visualization of collagen fibers and CAM dynamics requires developing a specific,
multi-modal imaging system on live cells. Partner II (S. Monneret, biophotonics group, Fresnel
Institute) will conduct such an instrumental development thanks to its expertise both in nanoscopy
(Bon et al. Nature Comm. 2015) and in phase imaging (development of a now commercially available
phase imaging system in close collaboration with a SME). Partner II already proposed a fluorescence/
phase bimodal microscope (Bon et al. JBO 2012) and more recently a modality particularly adapted
to enhance real-time visualization of collagen fibers (Aknoun et al. Opt Exp 2014). In this project, we
propose to improve the system so as to combine single molecule fluorescence imaging in the visible
wavelengths range, with both phase and intensity imaging in the infrared (IR) range. Indeed, cancer
cells exhibit remarkable IR signatures through collagen and lipids, especially in IR wavelengths, which
could be exploited. Partner III, First Light Imaging, is a company that provides world fastest cameras
with single-molecule sensitivity, initially developed for astronomy. We plan to integrate this new
generation of cameras into the phase imaging system. EMCCD has already been integrated for
nonlinear phase imaging (Berto et al. PRL 2012). We will use it either in 2D, plating cells on coated
coverslips, or in 3D, cultivating cells within collagen spheroids, to obtain more physiological cell

Co direction with Michel Aurrand-Lions (CRCM) and Serge Monneret (Fresnel Institute)

Further description:

Proposé par: Arnauld Sergé
Laboratoire/Institution: Cancer Research Centre of Marseille (CRCM) Inserm U 1068 / Fresnel Institute, CNRS UMR 7249
Adresse: 27 bd Lei Roure, CS 30059, Marseille, 13273, France
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