Our group studies how cells attach to the extracellular matrix (ECM) and its implications. Cell-ECM adhesions modulate mechanical signals and control growth factor signalling, determining cell survival, differentiation, migration and extravasation. ECMs are organised into fibrillar lattices of varying complexity to which cells attach via specialised membrane receptors, such as integrins, that act as a link to the cytoskeleton. Among the proteins and proteoglycans that make up ECMs, the fibronectin (FN) protein is particularly interesting as it offers multiple cell adhesion motifs and its polymerisation is the initial step for the organisation of the rest of the components of many ECMs, mainly those that promote embryonic development and those transient matrices that allow tissue regeneration and tumour development.
FN is secreted as a soluble dimer and its polymerisation depends on the cell, as only if it binds to integrins and these are activated and stimulate the contractility of the cytoskeleton does it exert traction on the FN allowing it to unfold and self-polymerise. Fibronectin fibres are undergoing continuous remodelling and disruption of this process can lead to fibrosis, arthritis and defects in development and angiogenesis.
In our group, we have generated and analysed different strains of fibronectin-expressing knock-in and conditional knock-in mice with mutations in residues potentially critical for cell adhesion. We are interested in which adhesions are really limiting and how each adhesion influences cell behaviour and ECM secretion, structure, maintenance or stiffness; factors that ultimately determine tissue formation and regeneration. We are using these mice to find out how essential proteins or sequences involved in adhesion are in vivo and to define pathologies caused by their deficiency. Regions of the FN that we consider crucial to its function:
- the RGD motif of the FNIII10 module is the main integrin-binding sequence. FN-RGD adhesion is very complex: it has been said to be the only one that allows the formation of FN polymers; it links two distinct families of integrins:
- the first consisting of Alpha5Beta1 and AlphaIIbBeta3 (exclusive to platelets);
- Alphav-containing dimers, with different, but in many tissues complementary, functions. It has been described that in the first group, adhesion is enhanced, under conditions of increased stress, by the binding of an amino acid sequence, called the synergistic site, which is located in the FNIII9 module.
- the heparin II region (modules FNIII12-14) which on the one hand binds Syndecan-4, another cellular receptor, and on the other hand binds numerous growth factors involved in angiogenesis and cell proliferation, such as the FGF family, the TGFBeta family and the PDGF family. This region has been hypothesised to allow signalling by growth factors in a cooperative manner with RGD adhesion. This region is of particular interest in the area of tissue regeneration.
- Understand how the binding of a5b1 integrins and av-containing integrins, both families with complementary action, is managed in vivo
- Know which factors condition a correct secretion and fibrillogenesis of the FN
- Find out what is the involvement of FN in blood coagulation and thrombus formation and platelet adhesion
- Evaluate the influence of a5b1-mediated mechanical signals on FN adhesion and their relevance to tissue regeneration and cancer
- Study the cooperation of mechanical signals with growth factor signalling.
- Skin wound healing in FN-syn mice
Our hypothesis suggests that the adhesions made by the keratinocyte with FN, which are necessarily mediated by a5ß1 integrins, are weaker. To study this, we are using microprinting of FN-syn lines of different thicknesses and distances that force the cell to withstand more stress.
- Influence of the FN synergistic site on blood coagulation
Using intravital microscopy experiments in mouse cremaster muscle venules after injury, we are studying the speed of clot formation and clot stability in FN-Syn mice.
- FN-syn and FN-Hep II mice and skeletal muscle regeneration
Skeletal muscle regeneration involves the activation of satellite cells. The niche in which satellite cells live greatly increases FN expression when they are activated. We want to find out what role this FN plays
- RGE and osteoarthritis mice
FN-RGE mice express FN that cannot bind a5ß1 integrins, but does bind av class integrins. We are studying how knee cartilage evolves in these mice after injury induction.
- Analysis of FNdeltaRGD mice
We want to find out what are the implications of removing the RGD sequence located in the 10th repeat of type III: 1) can a5ß1 integrins and av class bind to other regions of the FN or are they totally dependent on this sequence? can FN fibrillogenesis occur in the absence of this?
- Tumour development and metastasis in mice expressing FN with inactivated synergistic site
We want to cross a strain of tumour-prone mice with our FN-syn mice and analyse the influence of this mutation on tumour development, migration and metastasis formation of tumour cells.
- COSTELL ROSSELLO, M.MERCEDES
- PDI-Catedratic/a d'Universitat
- ExpandirCOSTELL ROSSELLO, M.MERCEDESPDI-Catedratic/a d'Universitat
Burjassot/Paterna Campus
C/ Doctor Moliner, 50
46100 Burjassot (Valencia)
- COSTELL ROSSELLO, M.MERCEDES
- PDI-Catedratic/a d'Universitat
