Genetic dissection of physiological properties of local interneurons in the Drosophila larval visual circuit
Authors: Hsueh-Ling Chen; Anna Grigsby-Brown; Aidan Dermady; Quan Yuan
Affiliation: National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD
Keywords: q. vision; m. CNS
Animals continually modify their behaviors in response to the changing environment. Understanding the molecular and circuit basis of how the nervous system modifies its function to adjust behavioral output is an active topic in the neurobiology field. The Drosophila larval visual circuit serves as a suitable system to study this fundamental question. Composed of only twelve photoreceptors (PRs) to detect visual stimuli, one pair of visual local interneurons (VLNs) to modulate the signals, and nine visual projection neurons (VPNs) to transfer the filtered information to higher brain regions, larvae employ a simple visual circuit for a variety of behaviors. Specifically, recent connectome and functional imaging analyses revealed these VLNs, which have been identified as one cholinergic (cha-IOLP) and one glutamatergic (glu-IOLP), synaptically interact with each other as well as receive neuromodulatory input from serotonergic and octopaminergic neurons, suggesting their potential role as plastic components in the circuit for internal or external signals to modulate visual information and impact behavior. Our previous study suggests that excitatory and inhibitory inputs into the VLNs are mediated by glutamatergic and cholinergic signaling. To better understand how visual signals are processed and modulated at the level of VLNs, we aim to evaluate the interactions between these two antagonizing pathways within larval VLNs. First, to identify the neurotransmitter receptors expressed in each VLN, we performed a comprehensive survey on acetylcholine receptors (AChRs) and glutamate receptors (GluRs) using endogenously-tagged GAL4 and LexA lines. Our preliminary results offered an overview of the combinatory expression of nicotinic AChR (nAChR) subunits and muscarinic AChRs (mAChRs) as well as that of ionotropic and metabotropic GluRs in larval VLNs. Second, to validate the screen results, we are performing immunostaining and genetic manipulations, in combination with physiological and behavioral tests. Our results will provide molecular insights into how sensory information is computed and transmitted within a sensory circuit and help us identify specific cellular and molecular components targeted by developmental and activity-dependent regulatory mechanisms.