Single-cell transcript profiling: Towards functional connectomics of Drosophila visual system

Thursday, October 11, 2012 — Poster Session IV
2:00 p.m. – 4:00 p.m.	Natcher Conference Center, Building 45	NICHD	NEURO/BEHAV/SENSYS-13

Authors

• T. Karuppudurai
• C.Y. Ting
• C.H. Lee

Abstract

The Drosophila visual system has served as a model for sensory information processing. Using EM reconstruction, genetic and behavioral approaches, we mapped the synaptic circuits in the peripheral visual ganglion that extract different visual attributes, such as motion and color. However, the resulting circuit diagram provides little information as how visual signals are transformed through these synaptic circuits. To determine the synaptic properties of the identified connections, we developed a single-cell transcript profiling technique to identify neurotransmitters and receptors expressed in specific types of neurons marked by green fluorescent protein (GFP). We found that most neurons in the feed-forward color and motion pathways are connected through excitatory glutamatergic or cholinergic synapses. RNAi-mediated knockdown of the vesicular glutamate transporter (vGlut) in the Dm8 neurons, a key neuron in the color pathway, leads to aberrant green preference. Based on the synaptic circuits and transcript profiles, we propose that the amacrine neuron Dm8 enhances UV light sensitivity by pooling histaminergic inputs from multiple R7 photoreceptors and providing excitatory glutamatergic input to the downstream transmedulla neurons. This approach is generally applicable to other neural circuits to determine synaptic properties in identified connections and to attain a major goal of functional connectomics.

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