Roles of Ecdysone signaling in cell survival and epithelium morphogenesis during Drosophila melanogaster development

In Drosophila the steroid hormone ecdysone regulates a wide range of developmental and physiological responses, including reproduction, embryogenesis, postembryonic development and metamorphosis. Drosophila provides an excellent system to address some fundamental questions linked to hormone actions. In fact, the apparent relative simplicity of its hormone signaling pathways taken together with well-established genetic and genomic tools developed to this purpose, defines this insect as an ideal model system for studying the molecular mechanisms through which steroid hormones act. During my PhD research program I’ve analyzed the role of ecdysone signaling to gain insight into the molecular mechanisms through which the hormone fulfills its pleiotropic functions in two different developmental stages: the oogenesis and the imaginal wing disc morphogenesis. To this purpose, I performed a reverse genetic analysis to silence the function of two different genes involved in ecdysone signaling pathway, EcR and ecd.

Tra società informazionale e prosumerismo: il citizen journalism e la partecipazione on line

I temi della ricerca riguardano il rapporto fra avvento del web e la modificazione dei processi di formazione di identità personale e sociale, della percezione dello spazio e del tempo, del prosumerismo digitale e delle varie forme di partecipazione ed associazione. Centrale è stata l’analisi del rapporto fra il Web 2.0 e la trasformazione delle forme di comunicazione a vari livelli, sia personali che sociali. Partendo da una analisi dei contesti socio-economici globali che hanno trasformato la società moderna nella società informazionale, è stato impostato un percorso di ricerca che approfondisse gli attuali criteri di strutturazione della propria identità, alla luce dell’avvento dei social network e delle reti virtuali di comunicazione come strumento preferenziale di socializzazione. La realtà delle reti sociali è stata analizzata in un’ottica di aggregazione spontanea mirata tanto alla comunicazione quanto alla tutela dei consumatori, e le trasformazioni portate dal Web 2.0 sono state la chiave di lettura per ridefinire i parametri della partecipazione dal basso generata dalla rete. Per comprendere la portata di tali trasformazioni nel contesto italiano è stato impostato un paragone tra l’uso del web negli Stati Uniti e in Italia, avendo le recente campagne elettorali dimostrato l’importanza del web nella partecipazione politica bottom-up; il percorso di ricerca ha dunque affrontato una comparazione di due casi, quello italiano e quello statunitense, finalizzato a comprendere l’attuale ruolo dell’utente nelle dinamiche di comunicazione mediatica. Per focalizzare al meglio le trasformazioni sociali generate dalla partecipazione on line è stato infine analizzato il caso del citizen journalism, per misurare, attraverso la metodologia dell’etnografia digitale, l’entità delle trasformazioni in corso. Il portale di giornalismo partecipativo YouReporter è stato il contesto privilegiato dove poter verificare le ipotesi iniziali circa le dinamiche di partecipazione, e il supporto di programmi di elaborazione statistica netnografica ha permesso di destrutturare al meglio tali dinamiche.

The Domon Family of Plant Plasma Membrane B-Type Cytochromes: Heterologous Expression, Biochemical Characterization and Physiological Roles in Vivo

The DOMON domain is a domain widespread in nature, predicted to fold in a β-sandwich structure. In plants, AIR12 is constituted by a single DOMON domain located in the apoplastic space and is GPI-modified for anchoring to the plasma membrane. Arabidopsis thaliana AIR12 has been heterologously expressed as a recombinant protein (recAtAIR12) in Pichia pastoris. Spectrophotometrical analysis of the purified protein showed that recAtAir12 is a cytochrome b. RecAtAIR12 is highly glycosylated, it is reduced by ascorbate, superoxide and naftoquinones, oxidised by monodehydroascorbate and oxygen and insensitive to hydrogen peroxide. The addition of recAtAIR12 to permeabilized plasma membranes containing NADH, FeEDTA and menadione, caused a statistically significant increase in hydroxyl radicals as detected by electron paramagnetic resonance. In these conditions, recAtAIR12 has thus a pro-oxidant role. Interestingly, AIR12 is related to the cytochrome domain of cellobiose dehydrogenase which is involved in lignin degradation, possibly via reactive oxygen species (ROS) production. In Arabidopsis the Air12 promoter is specifically activated at sites where cell separations occur and ROS, including •OH, are involved in cell wall modifications. air12 knock-out plants infected with Botrytis cinerea are more resistant than wild-type and air12 complemented plants. Also during B. cinerea infection, cell wall modifications and ROS are involved. Our results thus suggest that AIR12 could be involved in cell wall modifying reactions by interacting with ROS and ascorbate. CyDOMs are plasma membrane redox proteins of plants that are predicted to contain an apoplastic DOMON fused with a transmembrane cytochrome b561 domain. CyDOMs have never been purified nor characterised. The trans-membrane portion of a soybean CyDOM was expressed in E. coli but purification could not be achieved. The DOMON domain was expressed in P. pastoris and shown to be itself a cytochrome b that could be reduced by ascorbate.

Neuroinflammation and the role of glia: relevance for neurodegenerative and neurosupportive roles

Inflammation is thought to contribute to the pathogenesis of neurodegenerative diseases. Among the resident population of cells in the brain, astroglia have been suggested to actively participate in the induction and regulation of neuroinflammation by controlling the secretion of local mediators. However, the initial cellular mechanisms by which astrocytes react to pro-inflammatory molecules are still unclear. Our study identified mitochondria as highly sensitive organelles that rapidly respond to inflammatory stimuli. Time-lapse video microscopy revealed that mitochondrial morphology, dynamics and motility are drastically altered upon inflammation, resulting in perinuclear clustering of mitochondria. These mitochondrial rearrangements are accompanied by an increased formation of reactive oxygen species and a recruitment of autophagic vacuoles. 24 to 48 hours after the acute inflammatory stimulus, however, the mitochondrial network is re-established. Strikingly, the recovery of a tubular mitochondrial network is abolished in astrocytes with a defective autophagic response, indicating that activation of autophagy is required to restore mitochondrial dynamics. By employing co-cultivation assays we observed that primary cortical neurons undergo degeneration in the presence of inflamed astrocytes. However, this effect was not observed when the primary neurons were grown in conditioned medium derived from inflamed astrocytes, suggesting that a direct contact between astrocytes and neurons mediates neuronal dysfunction upon inflammation. Our results suggest that astrocytes react to inflammatory stimuli by transiently rearranging their mitochondria, a process that involves the autophagic machinery.