IRF8 defines the epigenetic landscape in postnatal microglia, thereby directing their transcriptome programs

Area of Science:

• Neuroscience
• Immunology
• Epigenetics

Background:

• Microglia are the brain's innate immune cells.
• Transcription factor IRF8 is highly expressed in microglia, but its role in postnatal development is unclear.

Purpose of the Study:

• To investigate the role of IRF8 in postnatal microglia development and function.
• To understand how IRF8 influences the epigenetic landscape and gene expression in microglia.

Main Methods:

• Chromatin immunoprecipitation sequencing (ChIP-seq) to identify IRF8 binding sites.
• Single-cell RNA sequencing (scRNA-seq) and single-cell ATAC-seq (scATAC-seq) for multi-omic analysis.
• Genetic deletion of IRF8 in mouse models, including the 5xFAD Alzheimer's disease model.

Main Results:

• IRF8 binds to enhancers in developing microglia, correlating with increased chromatin accessibility and microglia-specific gene expression.
• Loss of IRF8 leads to a loss of microglial identity and a gain of disease-associated microglia (DAM) signatures.
• IRF8 is essential for establishing microglia-specific DNA methylation patterns.
• IRF8 deletion in 5xFAD mice reduces amyloid-beta plaque interaction, plaque size, and neuronal loss.

Conclusions:

• IRF8 plays a critical role in establishing the epigenetic landscape necessary for postnatal microglia gene expression and identity.
• IRF8 is a key regulator of microglial maturation and function, impacting neuroinflammation and neuroprotection in Alzheimer's disease models.