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Etude de l'implication des acides sialiques dans la régulation de la fusion myoblastique

Abstract : Myogenesis is a physiological process which includes the proliferation, the differentiation and the fusion of myoblasts in order to form myotubes and then muscular fibers. These mechanisms are regulated by the MRF (Myogenic Regulatory Factors) and Pax3 and Pax7 proteins which are members of the Pax protein family. The balance between Pax7 and MyoD is the determining factor of the cell fate determination and the entry in differentiation. The myoblasitc fusion requires the presence of glycans on cell surface proteins. We demonstrated that during C2C12 cell differentiation, takes place a decrease of α2,6 sialylation associated with a decrease of gene expression coding for ST6Gal I. We have used the C2C12 myoblastic cell line to analyse the modifications of α2,6 sialylation and its impact on the expression of Pax7 during cell differentiation. For this purpose, we have created C2C12 clones which expressed shRNA against st6gal1. These cells show a slowdown proliferation, a severe decrease of Pax7 expression and an earlier entry in differentiation. The glycanic structures modified during myoblast differentiation were identified by lectinoblotting and mass spectrometry: the sialylated bi-fucosylated N-glycans are the most impacted by the decrease of α2,6 sialylation. The earlier fusion of the clones st6gal1- leads to a decrease of the amount of the reserve cells (Pax7+/MyoD-). The extinction of Pax7 expression during differentiation is due to the decrease of the activation of Notch pathway. The KD of st6gal1 inactivates Smad2/3 pathway associated with the cell proliferation and it activates the Akt pathway which favors the cell fusion. We can conclude that α2,6 sialylation is required for C2C12 proliferation and it contributes to Pax7 activation.
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Caroline Vergé. Etude de l'implication des acides sialiques dans la régulation de la fusion myoblastique. Médecine humaine et pathologie. Université de Limoges, 2019. Français. ⟨NNT : 2019LIMO0054⟩. ⟨tel-02476606⟩

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