Résumés disponibles (91) :

DERNAIKA Racha (UMR CNRS 8161 éq. 03 - Fabrice SONCIN)
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@mail :  rdernayka@gmail.com      tél. :  03 20 87 11 20


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Titre de la communication :
Role of egfl7 in the formation of normal and tumor blood vessels.
Auteurs (et leurs adresses) de la communication :
Racha Dernaika UMR8161 CNRS/Université Lille 2/Institut de Biologie de Lille – 1 rue du Pr. Calmette – 59021 Lille cedex, France
Résumé de la communication :
The egfl7 gene is expressed by blood vessel endothelial cells of the developing embryo and early endothelial progenitors (Soncin et al. 2003). In adults,egfl7 expression is down-regulated and its expression resumes during angiogenesis,such as in tumors.Egfl7 is a 29 kDa secreted protein which regulates smooth muscle cell migration (Soncin et al.2003) and vascular elastogenesis through its interaction with lysyl oxidases (Lelièvre et al. 2008). Furthermore, Egfl7 promotes tumor escape from immunity by repressing the expression of lymphocyte adhesion molecules by endothelial cells,such as ICAM-I,VCAM-I,and E-selectin,thus regulating the infiltration of immune cells within the tumor (Delfortrie et al.2011).
The functions of egfl7 in vivo are still not fully understood. The knock-down of egfl7 in zebrafish results in a disruption of vascular tube formation (Parker et al.2004). On the other hand,gene inactivation approaches in mice have been hampered by the concomitant inactivation of the miR126 locus which is itself important for vascular formation. We generated a gene inactivation approach in order to abolish egfl7 expression in mice without affecting the miR-126 locus and to study egfl7 roles in vivo. Our objectives are to thoroughly analyze the phenotype induced by the inactivation of the egfl7 gene on the development and the maturation of normal and tumor blood vessels in mice.
Genotyping of egfl7+/+, egfl7+/- and egfl7-/- mice is done by PCR, RT-qPCR is used to measure egfl7,miR126 and miR126* expression levels,to validate the knock-out strategy and to measure candidate gene expression levels. Immunohistochemistry is used to visualize blood vessels of various mouse organs using antibodies against CD31,SMA,ICAM1,VCAM1... Angiogenesis in vivo is induced by the Matrigel plug assay,vessel permeability is followed by Lectin-FITC/Dextran-Texas Red injection. Tumor angiogenesis is induced by injection of Lewis Lung Carcinoma cells subcutaneously in mice. Mouse embryos are analyzed at different stages of development to check for growth retardation defects in the egfl7 -/- mice.
Our data show a loss of 50% of egfl7 expression in egfl7+/- mice and its absence in egfl7-/- mice. The levels of miR126 and miR126* are unaffected in all three genotypes, validating our gene inactivation approach. Blood vessels which form in the Matrigel plugs implanted in egfl7-/- mice are abnormal and dilated.The vascular network formed in tumors is more abundant in egfl7-/- mice,and show larger and leakier vessels.Moreover,tumor vessels in egfl7-/- mice express higher levels of Icam-1 and Vcam-1.Tumor growth is also faster in egfl7 -/- mice when compared to WT animals.
Taken together,our results suggest that egfl7 plays a critical role in physiological as well as pathological angiogenesis.The dilated and leaky vessels observed suggest a role of egfl7 in the maturation of blood vessels. We are currently analyzing the molecular mechanisms by which egfl7 mediates these effects.

DERNAIKA Racha (UMR CNRS 8161 éq. 03 - Fabrice SONCIN)