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Microenvironment and platelet formation: mechanobiological aspects

Research unit

UMR_S 949 - Biologie et pharmacologie des plaquettes sanguines : hémostase, thrombose, transfusion (BPPS)
10, rue Spielmann - BP 36 67065 Strasbourg Cedex

Group

Name: Biologie de la thrombopoièse

Group leader: LANZA François - francois.lanza@efs.sante.fr

Group leader's phone: 0388212525

Website: Visit website

Group organization:
- Chercheurs: 6
- ITA: 5
- Doctorants: 2
- Post-Docs: 1
- Autres: 5

Publications of the team linked to the topic (3 last years):
1) Pertuy F, Eckly A, Weber J, Proamer F, Rinckel JY, Lanza F, Gachet C, Leon C. Myosin IIA is critical for organelle distribution and f-actin organization in megakaryocytes and platelets. Blood 2014; 128:1261-1269
2) Badirou I, Pan J, Souquere S, Legrand C, Pierron G, Wang A, Eckly A, Roy A, Gachet C, Vainchenker W, Chang Y and Leon C. Distinct localizations and roles of non-muscle myosin II during proplatelet formation and platelet release. J Thromb Haemost. 2015; 13: 851-859.
3) Pertuy F, Aguilar A, Strassel C, Eckly A, Freund JN, Duluc I, Gachet C, Lanza F and Leon C. Broader expression of the mouse platelet factor 4-cre transgene beyond the megakaryocyte lineage. J Thromb Haemost 2015; 13: 115-125.

About PhD

PhD Director: LEON Catherine - catherine.leon@efs.sante.fr

Phone: 0388212525

Junior advisor: non

Co-tutely: non

Co-Director: non

About PhD topic :

Title: Microenvironment and platelet formation: mechanobiological aspects

Project: Background: Blood platelets play a vital role in ensuring bleeding arrest. Patients treated by chemotherapy, or presenting with trauma or quantitative or qualitative platelet abnormalities, which are responsible for hemorrhages, require platelet transfusions. Platelets are produced by megakaryocytes following a process of differentiation from hematopoietic stem cells in the bone marrow. During the maturation phase, megakaryocytes elaborate a complex network of intracellular membranes that will become the membranes of the future platelets.
Bone marrow is a complex milieu which combines stromal and hematopoietic cells, as well as extracellular matrix. Thus, bone marrow behaves as a soft and highly dynamic tissue, with an uninterrupted flow of cells that migrate to the bloodstream. Contact between cells and adhesions to the extracellular matrix generate local physical constraints that necessarily affect the differentiating cells. Our previous observations in 3D culture have shown that the megakaryocytes exhibit a different morphology (modification of the intracellular membrane network) and ability to form platelets according to the stiffness of the surrounding environment.

Thesis project: We will address the issues of 1) whether the modification of the megakaryocyte morphology is a prerequisite to the formation of proplatelets in vivo; 2) what is the mechanotransduction responsible for the remodeling of these internal membranes; 3) what are the extracellular signals that will trigger this remodeling and thus promote the initiation of proplatelets.
We will investigate i) the morphology of megakaryocytes in the process of proplatelet extension; ii) the impact of 3D culture in hydrogels of known rigidity, covalently functionalized or not with matrix proteins (collagens, RGDS). Such gels are commercially available; iii) the importance of adhesions to the extracellular matrix within the stroma or with the sinusoid vessels, using mouse models devoid of the matrix protein receptor integrins on their megakaryocytes. These mice are available in the lab.

Technical approaches: i) techniques for isolation and culture of murine hematopoietic stem cells; ii) immunofluorescence of cells and tissues and observation by confocal microscopy; iii) electron microscopy to visualize the ultrastructure of megakaryocytes differentiated in vitro or in the mouse bone marrow.

Expected outcome: Breakthrough into the poorly investigated field of mechanobiology in megakaryocyte differentiation with the aim of identifying new pathways that could be targeted to improve in vitro platelet production.

Wished skills: A solid theoretical knowledge in the field of cell biology. Knowledge in fluorescence. Skills in cell culture under sterile conditions. Precision and motivation. Being able to work with mice.

Expertises which will be acquired during the training: Expertise in the fields of stem cell biology, stem cells differentiation, culture in 3 dimensions, immunostaining techniques on cells or tissues, imaging microscopy techniques (confocal microscopy, electron microscopy, videomicroscopy of living tissue).