Microglia

Microglia

The CNS's resident immune cell, not from neural tube or bone marrow, but from primitive yolk-sac macrophages that colonise the brain at embryonic day 8.5 and stay for life.

Function

Immune surveillance and synaptic pruning. During development, microglia tag weak or inappropriate synapses for elimination via the classical complement cascade: C1q and C3 mark synapses, microglial CR3/CD11b recognises them, phagocytosis removes them.

Morphology

A small cell body with highly ramified, actively motile processes. Two-photon imaging revealed that 'resting' microglia are actually hyperactive surveyors, continuously extending and retracting processes to sample the entire brain parenchyma every few hours.

Specification

  • Receptors: Purinergic (P2RY12); Fractalkine (CX3CR1)
  • Location: Ubiquitous in the CNS parenchyma.
  • Firing: Non-spiking
  • Markers: AIF1/Iba1; CX3CR1; P2RY12; TMEM119; SALL1; C1QA/B/C; TREM2/APOE (disease states)
  • Developmental origin: Yolk sac (Mesoderm)
  • Disease: Alzheimer's GWAS identified TREM2, CR1, CD33, and ABI3 as microglial risk genes, microglia are central drivers, not bystanders. Aberrant complement-mediated synapse pruning is implicated in Alzheimer's and schizophrenia (C4 risk allele).
  • Cell Ontology: CL:0000129

References

  1. Nimmerjahn A, Kirchhoff F, & Helmchen F (2005). Resting microglial cells are highly dynamic surveillants of brain parenchyma in vivo.. Science 308: 1314–1318 PMID 15831717
  2. Stevens B et al. (2007). The classical complement cascade mediates CNS synapse elimination.. Cell 131: 1164–1178 PMID 18083105
  3. Ginhoux F et al. (2010). Fate mapping analysis reveals that adult microglia derive from primitive macrophages.. Science 330: 841–845 PMID 20966214

Loading interactive 3D atlas…