Microglial colonization of the developing mouse brain is controlled by both microglial and neural CSF-1

Area of Science:

• Neuroscience
• Developmental Biology
• Immunology

Background:

• Microglia, brain-resident macrophages, are vital for brain development and function.
• The mechanisms governing microglial colonization and proliferation in the developing brain are not fully understood.

Purpose of the Study:

• To investigate the mechanisms controlling microglial colonization and proliferation in the developing mouse forebrain.
• To identify the role of colony-stimulating factor 1 (CSF-1) in microglial development.

Main Methods:

• Conditional inactivation of the colony-stimulating factor 1 (Csf1) gene in mice.
• Analysis of microglial distribution and proliferation patterns in the developing brain.
• Investigation of CSF-1 sources, including neural and intrinsic microglial sources.

Main Results:

• Two distinct waves of microglial proliferation were observed in the developing mouse forebrain.
• Microglial colonization and proliferation are independent of neuronal activity.
• Neural CSF-1, primarily from cortical progenitors and neurons, is crucial for embryonic cortical microglial distribution and proliferation.
• Intrinsic CSF-1 from axon tract-associated microglia (ATM)-like cells supports their sustained proliferation.

Conclusions:

• Microglial development relies on distinct, local, and cell-type-specific sources of CSF-1.
• Understanding these CSF-1-dependent mechanisms is critical for comprehending microglial colonization in both health and disease.