Sensors for synaptic Ca2+ and exocytosis. A long-standing goal in neuroscience has been to ‘see’ the Ca2+ that triggers synaptic transmission. The lab recently succeeded in imaging Ca2+ signals and vesicle release in the same synapse in response to a single action potential, by targeting the genetically encoded Ca2+ indicator GCaMP6s and the red-shifted pH-sensitive probe mOrange2 to synaptic vesicles (SVs). The current spatial resolution for Ca2+ signals is at the level of a single synapse (~1 mm). The lab plans to engineer GCaMP6s genetically encoded Ca2+ indicators to improve spatial resolution to a single active zone (~200 nm), to detect the Ca2+ responsible for SV release.
Chemo-optogenetic nanomachines. Extracellular pH impacts on neuronal activity, which is in turn an important determinant of extracellular H+ concentration. By using ex.E2GFP, a membrane-targeted extracellular ratiometric pH indicator exquisitely sensitive to acidic shifts, we recently demonstrated that extracellular synaptic pH shifts take place during epileptic-like activity of neural cultures. This evidence may contribute to the understanding of the physio-pathological mechanisms associated with hyperexcitability in the epileptic brain, and may constitute the basis for the development of innovative therapeutic tools for the treatment of this pathology (Chiacchiaretta et al, 2017). With the aim of employing our tool in vivo, we are presently implementing a chemogenetic, pH-sensitive probe, based on an endogenous light source, i.e. the luciferase enzyme.