Multiplexed peroxidase-based electron microscopy labeling enables simultaneous visualization of multiple cell types.

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Electron microscopy (EM) is crucial for neural circuit mapping.
• Identifying specific cell types within EM datasets is a significant challenge.
• Current methods lack the ability to simultaneously visualize multiple genetically defined neuronal populations.

Purpose of the Study:

• To develop a technique for simultaneous multiplexed EM labeling of genetically identified neuronal populations.
• To enable unequivocal definition of synaptic interactions between different cell types.
• To facilitate comprehensive analysis of neural connectivity in the mammalian nervous system.

Main Methods:

• Development of 15 adeno-associated virus constructs and 6 mouse reporter lines for multiplexed EM labeling.
• Utilized dAPEX2, an enhanced ascorbate peroxidase, for improved signal detection.
• Targeted dAPEX2 to distinct subcellular compartments for orthogonal visualization.
• Protocol is compatible with existing EM pipelines.

Main Results:

• Demonstrated proof-of-principle double and triple EM labeling experiments.
• Successfully visualized synaptic connections between primary afferents, descending cortical inputs, and inhibitory interneurons in the spinal cord dorsal horn.
• Achieved simultaneous visualization and distinction of multiple orthogonal reporters under EM.

Conclusions:

• The developed multiplexed peroxidase-based EM labeling system significantly enhances the ability to map neural circuits.
• This technique overcomes major challenges in identifying cell types and defining synaptic interactions in EM datasets.
• Facilitates detailed analysis of neural connectivity, advancing neuroscience research.