C1q Regulates Horizontal Cell Neurite Confinement in the Outer Retina

Area of Science:

• Neuroscience
• Immunology
• Developmental Biology

Background:

• Neuronal development involves eliminating excess processes during circuit maturation.
• The complement cascade protein C1q is implicated in this elimination, but its specific targets are unknown.

Purpose of the Study:

• To investigate the role of C1q in regulating neurite elimination and targeting within neural circuits.
• To determine if C1q mediates cell-specific and subcellular-specific elimination processes.

Main Methods:

• Utilized the murine retina model to study C1q function.
• Examined C1q expression in retinal microglia.
• Assessed horizontal cell morphology and neurite extension in the absence of C1q, C3aR, and CR3.

Main Results:

• Identified C1q as a specific regulator of horizontal cell neurite confinement in the retina.
• Observed that C1q targets both cellular and subcellular neurites, including dendritic and axonal processes.
• Found that C1q expression is limited to retinal microglia, and its absence reduces microglia activation.

Conclusions:

• C1q plays a novel role in cell- and neurite-specific confinement during neural development.
• Microglia-mediated phagocytosis, regulated by C1q, is critical for this confinement process.
• This C1q pathway is independent of C3aR and CR3 signaling in horizontal cells.