Ascertaining cells' synaptic connections and RNA expression simultaneously with barcoded rabies virus libraries.

Area of Science:

• Neuroscience
• Molecular Biology
• Genomics

Background:

• Understanding brain function requires detailed knowledge of synaptic networks and their molecular underpinnings.
• Current methods lack systematic descriptions of neuron-to-neuron connections and their associated gene expression.

Purpose of the Study:

• To introduce SBARRO (Synaptic Barcode Analysis by Retrograde Rabies ReadOut), a novel method for mapping synaptic connectivity.
• To simultaneously profile genome-wide RNA expression in connected neurons.

Main Methods:

• Utilized a barcoded rabies virus for retrograde tracing of monosynaptic connections.
• Employed single-cell RNA sequencing to identify presynaptic partners and their transcriptomes.
• Applied the method to diverse mouse brain cell types in vitro.

Main Results:

• Successfully mapped thousands of directional, monosynaptic relationships in a single experiment.
• Identified cell type-specific differences in presynaptic network size and composition.
• Observed RNA expression patterns suggesting functional synapses are crucial for rabies virus uptake.

Conclusions:

• SBARRO provides a powerful tool for dissecting synaptic organization in neural circuits.
• The method enables simultaneous mapping of neural connectivity and molecular identity.
• This approach opens new avenues for understanding brain circuitry at a molecular level.