Detection of Synaptic Proteins in Microglia by Flow Cytometry

Area of Science:

• Neuroscience
• Immunology
• Cell Biology

Background:

• Microglia are key players in synaptic refinement and brain connectivity through in vivo synapse removal.
• Traditional methods like immunofluorescence and confocal microscopy for quantifying synaptic material in microglia are time-consuming and labor-intensive.

Purpose of the Study:

• To develop and validate flow cytometry for quantifying synaptic proteins within microglia.
• To assess microglial synaptic pruning during brain development and in disease models.

Main Methods:

• Flow cytometry was utilized to quantify VGLUT1 protein levels in microglia.
• Analysis was performed on microglia from healthy adult and developing (P15) mouse brains.
• VGLUT1 levels were also quantified in microglia from 5xFAD Alzheimer's disease and TDP-43 conditional knockout mouse models.

Main Results:

• Healthy adult microglia contain detectable levels of VGLUT1.
• VGLUT1 immunoreactivity was more than two-fold higher in microglia from developing brains compared to adults, indicating significant synaptic pruning during development.
• Microglia in 5xFAD mice showed increased VGLUT1 before amyloid pathology onset.
• Conditional deletion of TDP-43 in microglia led to increased VGLUT1, correlating with a hyper-phagocytic phenotype and synaptic loss.

Conclusions:

• Flow cytometry provides an efficient method for quantifying synaptic material within microglia.
• Microglia-mediated synaptic pruning is a prominent process during brain development.
• Microglial synaptic pruning is dysregulated in mouse models of Alzheimer's disease and in conditions with altered microglial phagocytosis.