Pyramidal neuron subtype diversity governs microglia states in the neocortex

Area of Science:

• Neuroscience
• Immunology
• Genomics

Background:

• Microglia, the brain's resident immune cells, exist in diverse transcriptional states within various neuronal environments.
• The mechanisms generating these microglial states and their spatial distribution remain unclear.

Purpose of the Study:

• To investigate how local neuronal composition influences microglial density and molecular state acquisition in the mouse somatosensory cortex.
• To map the molecular signatures and spatial distributions of distinct microglial populations and their relationship with pyramidal neuron classes.

Main Methods:

• Single-cell and spatial transcriptomic profiling of the mouse somatosensory cortex.
• Analysis of microglial states in relation to pyramidal neuron classes and cortical layers.
• Experimental manipulation of deep-layer pyramidal neurons to observe microglial state and distribution changes.

Main Results:

• Microglial density and molecular states are determined by the local composition of pyramidal neuron classes.
• Specific microglial states are enriched in particular cortical layers, while others are broadly distributed.
• Altering pyramidal neuron identity reconfigures local homeostatic microglia distribution to match the new neuronal niche.

Conclusions:

• Neuronal diversity fundamentally instructs microglial state acquisition, influencing neuroimmune interactions within cortical circuitry.
• A ligand-receptor atlas reveals rules governing neuron-microglia communication, highlighting the role of neuronal subtypes.