Abstract
Chemical synapses are specialized gaps where neurons transmit signals through neurotransmitter to each other or to non-neuronal cells. To visualize the incidence of functional synaptic transmission, we have modified the GFP reconstitution across synaptic partners (GRASP) and created chimeric trans-synaptic protein probes that are able to label the functional connectivity in Drosophila in previous work. However, our trans-synaptic probes are not sufficient to discriminate whether the signals are observed from the active-neurotransmissions or already established neuron connections. In order to purely detect the synaptic transmission in a dynamic and activity-dependent fashion, we attempt to create a more powerful tool by constructing split-photoconvertible fluorescent protein in the probe design instead of stable GFP. By changing the color of already established neural connections, we are able to see neurons that are still actively transmitting signals. In our work, we adopted the PSmOrange2 to construct the new trans-synaptic probes system. To optimize the probes, we have tested different modifications and confirmed the properties of reconstitution and photoconverting in N2a cell culture system. We are now operating microinjection to create transgenic flies expressing the trans-synaptic probes so that the neurotransmission can be observed in vivo.