La défense publique de la thèse de Madame Marie BONNEEL aura lieu le 11 décembre 2020 à 16h par vidéo-conférence, via ce lien.

Promoteur de thèse: Monsieur Patrick FLAMMANG et Madame Elise HENNEBERT (co-promoteur)

Résumé

Marine adhesives and stimuli-responsive tissues are increasingly being studied in a biomimetic context. Sea cucumbers constitute an interesting model organism and a source of inspiration for such studies. The species Holothuria forskali possess Cuvierian tubules, which form an effective defence system thanks to their adhesiveness and toughness. Moreover, the dermis of his body wall in this species is a mutable collagenous tissue (MCT), a connective tissue with the capacity of changing its mechanical properties under nervous control. In this thesis, the instantaneous adhesion system of Cuvierian tubules was investigated with a focus on proteins. A combination of proteomic and transcriptomic analyses, in situ hybridization, immunohistochemistry and in silico analyses allowed the identification of proteins involved in the instantaneous adhesion. Cuvierian tubules mechanical properties were also studied and tensilin, a MCT stiffening protein, was identified and localized in specialized cells of the connective tissue. Cuvierian tubule connective tissue was identified as a new type of MCT, with irreversible stiffening. Finally, tensilin was also studied inside the body wall dermis of this species. Recombinant tensilin production permitted to identify two types of interactions involved in collagen fibrils aggregation and in dermis stiffening. This thesis therefore contributes to the understanding of three molecular mechanisms in the sea cucumber Holothuria forskali: the instantaneous adhesion system of Cuvierian tubules, the involvement of a MCT for the stiffening of these tubules and the study of tensilin and its interaction with collagen fibrils within the body wall dermis.