Dr. Lina Ni awarded a grant from the The National Institute of Mental Health (NIMH) to develop functional trans-Tango to identify higher-order neurons with determined functions.

A neural circuit is composed of a population of neurons that are interconnected by synapses and carry out a specific function when activated. Thus, to identify a neural circuit, both the synaptic connections and the functional relevance of each neuron in the circuit must be examined. To date, few methods are available to study these two aspects of a neural circuit simultaneously. In this proposal, this problem will be addressed using a new class of trans-synaptic techniques. Current trans-synaptic techniques enable the labelling of postsynaptic elements of first-order neurons without using driver lines. However, the ability to discriminate the function of each neuron in the circuit and the ability to track higher-order neurons remains lacking. This proposal will use a Drosophila thermosensory system that controls rapid warmth avoidance as a model to demonstrate how a modified trans-synaptic technique can sparsely label both second- and higher-order neurons in a single neural circuit and determine their functional relevance to a specific behavioral response. The expected outcome of this proposal is development of a tool that can (1) sparsely label synaptically interconnected second- and higher-order neurons without using driver lines, and (2) determine the function of labelled neurons. The tool will be able to be readily applied to many other Drosophila neural circuits, where the synaptic connections and the functional relevance of each neuron will be simultaneously identified. Moreover, it has the potential to provide an alternative for labelling mammalian circuits.