Good morning, please save the date in your agendas for next week seminars! See you 29^th April at 12h in Dr Forteza Conference Room

12:00-12:30 Snežana Đorđević Development of Analytical Procedures for Characterization of Novel Polymer-Drug Conjugates (I36 Lab)

The goal of this project is to develop well-defined and validated analytical protocols that ensure the quality of synthesized Polymer-drug conjugates (PDCs) and help to understand their biological output (safety/efficacy), with a focus on liquid chromatography-mass spectrometry (LC-MS), mass spectrometry imaging (MSI), and asymmetric flow field flow fractionation (AF4). To achieve these goals, we implemented the “design of experiment” (DoE) ethos to identify those factors influencing experimental results and demonstrated the feasibility of DoE in simultaneous LC-MS method development to quantify levels of four anticancer drugs in drug release and stability studies involving PDCs. We employed LC-MS methods and drug extraction protocols for three different purposes. First, to enable the identification of metabolites formed during drug release from polyglutamate (PGA)-based conjugates using a disulfide self-immolative linker. We demonstrated that the disulfide bond’s cleavage rate depends on the chemical bond between the linking moiety and drug and the drug’s structural features and ability to form resonance-stabilized structures. Next, we employed the LC-MS methods and linker design study to develop PDC candidates with optimal drug release profiles as part of a clinically translatable combination therapy for pancreatic cancer. Finally, we characterized the PGA-conjugated form of the Rho kinase inhibitor fasudil to treat spinal cord injury (SCI). Conjugation using an optimized redox-dependent self-immolative linker (-SS-) enhanced stability, sustained release, and improved neuroprotective/regenerative activity to provide an overall increase in therapeutic potential in acute and chronic in vivo SCI models. We implemented the AF4 method to characterize crosslinked combination PDCs where dynamic light scattering, and size exclusion chromatography meet their limitations. We examined the influence of PGA within the AF4 channel, which fostered the enhanced interpretation of experimental results obtained from analyzed crosslinked PDCs particles and allowed for tailor-made nanoparticle design. To enhance PDC characterization in the biological environment, we investigated the potential of matrix-assisted laser desorption ionization MSI (MALDI-MSI) to evaluate drug activity/spatial distribution and responses of metastatic breast cancer after treatment with a combination PDC.

Overall, we demonstrated how integrating innovative techniques and quality control of synthesized complex nanosystems with fit-for-purpose analytical methodologies provides the physicochemical characterization required to foster the enhanced translation of PDCs into clinical use.

12:30 Álvaro Ballesteros Developmental Disruption of Erbb4 in Pet1+ Neurons Impairs Serotonergic Sub-System Connectivity and Memory Formation (I66 Lab)

The serotonergic system of mammals innervates virtually all the central nervous system and regulates a broad spectrum of behavioral and physiological functions. In mammals, serotonergic neurons located in the rostral raphe nuclei encompass diverse sub-systems characterized by specific circuitry and functional features. Substantial evidence suggest that functional diversity of serotonergic circuits has a molecular and connectivity basis. However, the landscape of intrinsic developmental mechanisms guiding the formation of serotonergic sub-systems is unclear. Here, we employed developmental disruption of gene expression specific to serotonergic subsets to probe the contribution of the tyrosine kinase receptor ErbB4 to serotonergic circuit formation and function. Through an in vivo loss-of-function approach, we found that ErbB4 expression occurring in a subset of serotonergic neurons, is necessary for axonal arborization of defined long-range projections to the forebrain but is dispensable for the innervation of other targets of the serotonergic system. We also found that Erbb4-deletion does not change the global excitability or the number of neurons with serotonin content in the dorsal raphe nuclei. In addition, ErbB4-deficiency in serotonergic neurons leads to specific behavioral deficits in memory processing that involve aversive or social components. Altogether, our work unveils a developmental mechanism intrinsically acting through ErbB4 in subsets of serotonergic neurons to orchestrate a precise long-range circuit and ultimately involved in the formation of emotional and social memories.