[Microglia arise from extra-embryonic yolk sac primitive progenitors]

Area of Science:

• Neuroimmunology
• Hematopoiesis
• Cellular Biology

Context:

• Microglia, the central nervous system's resident macrophages, are vital for brain homeostasis, immune defense, and repair.
• Understanding microglia's origin and homeostasis is critical due to their role in CNS health and disease.
• Existing research shows controversy regarding the precise origin and contribution of embryonic versus postnatal hematopoietic progenitors to the adult microglia pool.

Purpose:

• To investigate the contribution of postnatal hematopoietic progenitors to the adult microglia population in mice.
• To clarify the ontogeny and steady-state homeostasis of microglia within the central nervous system.
• To determine the specific embryonic or postnatal origins of microglia in the adult brain.

Summary:

• This study utilized in vivo lineage tracing in mice to investigate microglial origins.
• Results demonstrate that postnatal hematopoietic progenitors do not significantly contribute to adult microglia homeostasis.
• Adult microglia were found to derive exclusively from primitive hematopoietic progenitors originating before embryonic day 8.

Impact:

• Identifies microglia as an ontogenically distinct population within the broader mononuclear phagocyte system.
• Provides crucial insights into the developmental origins of the brain's primary immune cells.
• Suggests potential therapeutic strategies for brain disorders by focusing on embryonically-derived microglial progenitors.