Microglia Maintain Homeostatic Conditions in the Developing Rostral Migratory Stream

Area of Science:

• Neuroscience
• Developmental Biology
• Cell Biology

Background:

• The rostral migratory stream (RMS) is a critical pathway for neuroblast migration in the early postnatal brain.
• The developing RMS lacks the mature structural support found in later stages, suggesting other factors regulate neuroblast movement.

Purpose of the Study:

• To investigate the role of microglia in regulating the environment for neuroblast migration within the developing RMS.
• To determine if microglia influence neuroblast survival and migration dynamics in the early postnatal RMS.

Main Methods:

• Utilized CX3CR-1 GFP-reporter mice to visualize microglia and track neuroblasts (tdTomato, DsRed).
• Administered microglia ablation for short (3-day) and longer (14-day) periods postnatally.
• Assessed neuroblast proliferation (BrdU), migration distance, apoptosis (CC3, DCX), and RMS morphology.

Main Results:

• Microglia in the early RMS exhibit ameboid morphology and associate with migrating neuroblasts.
• Short-term microglia ablation did not affect neuroblast density or migration.
• Long-term microglia depletion resulted in increased neuroblast apoptosis, a wider RMS, and altered lateral ventricle patency.

Conclusions:

• Microglia actively regulate the developing RMS environment, expressing markers associated with active phagocytosis and signaling (CD68, CLEC7A, MERTK, IGF-1).
• Microglia are essential for maintaining neuroblast population health and supporting permissive conditions for migration in the early postnatal RMS.
• Disruption of microglia function negatively impacts neuroblast survival and the structural integrity of the developing RMS.