Mapping Neurotransmitter Receptors to Active Synaptic Circuits by Fluorescence Complementation
Thursday, September 15, 2016 — Poster Session III
- P Muthuirulan
- CY Ting
- CH Lee
Mapping synaptic circuits in brain could provide insight into the computation processes that underlie brain functions and pathophysiology of neurological diseases. The overwhelming complexity of neural circuits poses a great challenge to map its connection patterns and synaptic components. To overcome these challenges, we developed a novel receptor-based GRASP method to map neurotransmitter receptors to active synapses. In this method, we attach the neurotransmitter receptors of interest, to the small split-GFP moiety (spGFP11), which reconstitutes with the large split-GFP moiety (spGFP1-10) tethered on synaptic vesicles (syb-spGFP1-10) to form functional GFP in active synapses. We modeled different neurotransmitter receptors with split-GFP tag based on their related crystal structures. By a combination of molecular, histology and genetic approaches, we applied this strategy to map Drosophila motion detection circuits. Our previous electron microscopic reconstruction and single cell transcript profiling studies revealed that the motion-sensitive T4 and T5 neurons expresses distinct combinations of nicotinic and muscarinic cholinoceptors to receive synaptic inputs from different cholinergic transmedulla (Tm) neurons. To map the cholinoceptors to specific synapses, we engineered spGFP11-tagged nicotinic (nAchR-β3) and muscarinic (mAchR-B) receptors based on rational design. These spGFP11-tagged receptors, when expressed in the T4 and T5 neurons, specifically targeted to dendritic terminals. Furthermore, we additively expressed in different Tm neurons syb-spGFP1-10, which reconstituted GFP fluorescence in vivo with spGFP11-tagged cholinoceptors on T4 and T5. With the advance of the CRISPR/Cas9 genome editing technique, we envision this method could be applied effectively to map neurotransmitter receptors to neural circuits of essentially any animal models.