Lineage and development of glial cells II: Microglia

Vocabulary-style flashcards covering core concepts about microglial origin, development, identity, and diverse brain macrophage populations.

Microglia

Brain’s resident macrophages that act as the brain’s immune cells, derived from yolk sac progenitors and maintained by a balance of proliferation and apoptosis.

Yolk sac erythromyeloid progenitors (EMPs)

Early hematopoietic progenitors in the yolk sac that give rise to all macrophage populations, including microglia.

Colonization of the brain by microglia

Direct brain invasion by yolk sac EMPs without a liver relay, occurring earlier than colonization of other organs.

Ramified microglia

Mature microglia with branched processes that surveil the brain parenchyma, especially in grey matter.

Amoeboid microglia

Immature, rounded microglia seen in early postnatal life that gradually become ramified.

PU.1

A master transcription factor essential for macrophage lineage specification and microglial development.

C/EBPs

Family of transcription factors that cooperate with PU.1 to drive macrophage fate.

RUNX1

Transcription factor important for early hematopoietic and macrophage development.

IRF8

Interferon regulatory factor 8; crucial for macrophage lineage development, including microglia.

CSF1

Colony-stimulating factor 1; environmental signal important for microglial development and maintenance.

IL-34

Cytokine that signals through CSF1R and supports microglial survival.

TGFβ

Transforming growth factor beta; essential for shaping and maintaining microglial identity.

SALL1

Transcription factor enriched in microglia, involved in microglial identity (role still being clarified).

SALL3

Transcription factor enriched in microglia, associated with microglial gene regulation.

MEIS3

Transcription factor enriched in microglia, contributing to microglial regulatory networks.

MAFB

Transcription factor enriched in microglia; role in microglial biology is still being investigated.

Immunosurveillance

Ongoing monitoring of the brain environment by microglia, including potential interactions with immune cells.

Antigen presentation to CD4+ T cells

Possible microglial role in presenting antigens to CD4+ T cells as part of CNS immunosurveillance.

Synaptic pruning

Microglial removal of synapses during development, contributing to circuit refinement.

Neuromodulation

Microglial influence on neuronal activity and signaling beyond phagocytosis.

Phagocytosis

Engulfment and digestion of debris, apoptotic cells, and synaptic material by microglia.

Perivascular macrophage

Non-parenchymal brain macrophage located in the perivascular space around blood vessels.

Meningeal macrophage

Macrophages located in the meninges (dura, arachnoid, and pia) involved in CNS immunosurveillance.

Choroid plexus macrophage

Macrophages in the choroid plexus at the blood-CSF barrier.

Dura mater

Outer, tough membrane of the meninges surrounding the brain.

Arachnoid mater

Middle meningeal layer with the subarachnoid space containing CSF.

Pia mater

Innermost meningeal layer closely applied to the brain surface.

Blood–brain barrier (BBB)

Selective barrier formed by brain endothelial cells with astrocyte endfeet that regulates CNS entry of cells and molecules.

Non-parenchymal brain macrophages

Macrophage populations outside the brain parenchyma (e.g., meningeal, perivascular, choroid plexus) distinct from microglia.

Fountains of microglia

Term used to describe clustered microglial activity seen in certain brain regions and during lesions (Rio Hortega).