Genetic targeting of astrocytes associated with specific neuronal circuit in adult Drosophila

Astrocytes are the major glial population of the brain and have been associated with a vast number of functions. To probe this diversity and to reach a similar level of understanding about astrocyte physiology that we have about neurons, we need genetic tools to target specific astrocytic subpopulations. In Drosophila, we are restricted to using driver lines that drive expression in astrocytes throughout the brain. To target specific astrocytes, we have optimized the genetic tool TRACT (and refer to it as astro-TRACT), allowing effector expression specifically in local astrocytes of a given neuronal circuit. We analyzed specificity, sensitivity and reproducibility of the tool across various MB split-Gal4 drivers. We found that the number of pre-synapses correlates positively with the success of the tool. Applying the tool to characterize morphology of individual astrocytes revealed that local astrocytes around MB medial compartments project into the ellipsoid body. Astro-TRACT will be a valuable resource to investigate both mechanistic astrocyte-neuron signaling and functional and structural astrocytic diversity across the adult Drosophila brain.