STUDY ON TIAR, G3BP AND TTP, AS MOLECULAR MARKERS OF STRESS GRANULES, IN SOLITARY AND COLONIAL ASCIDIANS: ROLE IN INNATE IMMUNITY AND DEVELOPMENT

The initial aim of my Ph.D. thesis was to study some well known mammalian molecular markers of SGs, i.e. TIAR, G3BP and TTP, in ascidians from the Lagoon of Venice during stress conditions and to assess their role in immune responses mediated by circulating immunocytes. I chose C. robusta as representative of solitary ascidians, and B. schlosseri as representative of colonial ascidians, which are considered reliable model organisms in toxicological and developmental studies. I induced stress conditions in C. robusta by exposing animals to some heavy metals (Cu, Zn, Fe and Cd). Instead, in B. schlosseri, I focused on the oxidative stress which naturally occurs during the TO of the blastogenetic cycle, due to the massive activity of apoptotic cell clearance by phagocytes in resorbing old zooids, which allows the renewal of the colony by generation change. I mainly analyzed tiar, g3bp and ttp transcriptions in the above conditions. Only for tiar, core component of SGs, I also studied the expression of the relative protein during the colonial blastogenetic cycle and the effect of its knockdown on non-embryonic development. The obtained results highlighted that the above markers are not only important to regulate stress responses, probably by forming SGs, but they are also important to regulate processes such as cell proliferation and differentiation, germ cell development and stem cell homeostats, which, in B. schlosseri, allow the progression of the blastogenetic cycle. In addition, I studied another colonial ascidian, the Japanese species B. primigenus, to better understand the importance of the above genes in control of non-embryonic development and gametogenesis. I also decided to extent my research on embryogenesis of C. robusta, to achieve the second aim of my Ph.D., i.e., to ascertain if tiar, g3bp and ttp can also have a role in the regulation of early developmental stages under both physiological and stress (metal exposure) conditions, also by evaluating the effect of their knockout on normal embryonic development.