Trans-Seq maps a selective mammalian retinotectal synapse instructed by Nephronectin.

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Understanding mammalian neural circuit wiring is crucial for neuroscience.
• The long-range connectivity from retinal ganglion cell (RGC) types to brain neurons is largely unknown.
• Existing knowledge of retinal circuits is rich, but mapping RGCs to downstream targets requires advanced techniques.

Purpose of the Study:

• To develop an integrated approach, Trans-Seq, for mapping RGCs to superior collicular (SC) circuits.
• To classify SC neuron types innervated by genetically defined RGC types.
• To identify molecular determinants for selective synaptic targeting in the visual system.

Main Methods:

• Developed Trans-Seq, combining fluorescent anterograde trans-synaptic tracer (WGA-mCherry) with single-cell RNA sequencing.
• Applied Trans-Seq to map RGCs to SC circuits in mice.
• Validated predicted neuronal connections using genetic labeling, electrophysiology, and retrograde tracing.

Main Results:

• Classified SC neuron types receiving input from genetically defined RGC types.
• Predicted and validated a novel connection from alphaRGCs to Nephronectin-positive wide-field neurons (NPWFs).
• Identified Nephronectin and Integrin α8β1 as key molecules mediating selective synaptic choice.

Conclusions:

• Trans-Seq is an effective method for mapping RGC to SC circuit connectivity.
• Discovered a specific αRGC to NPWF connection mediated by the Nephronectin/Integrin α8β1 pathway.
• The Trans-Seq approach is broadly applicable for discovering post-synaptic circuits from defined pre-synaptic neurons.