Neurons usually steal the limelight during discussions on the CNS. Poojashri does her bit to bring glia to the forefront and in this seminar she succeeded well.
She discussed different hypotheses about how microglia might come into the CNS - that they could be mesodermal in origin and enter during early development or that they come from the choroid plexus or that they may be neuroectodermal in origin.
While the primary role of Microglia seems to be surveillance and scavenging, they seem to have roles in extracellular signalling, protection and trophic support, brain development and rewiring, activity dependent structural remodelling, modulation of GABA/Glutamate signalling and even as part of the quadpartite synapse along with pre and post synaptic neurons and astrocytes.
Microglia undergo morphological changes as per its stage of activation: amoeboid(highly motile that home in where needed), ramified, intermediary, primed, reactive and gitter (post phagocytosis - vacuole laden cell).
Microglia have two distinct activated phases - classically activated (M1) via IFN-gamma or TNF where they are neurotoxic and alternatively activated phase (M2) via IL-4 or IL-13 where they are neuroprotective.
In neurodegenerative disorders different toxic factors might activate the microglia (eg: ABeta peptides for Alzheimers, Alpha-synuclein for Parkinsons, Mutant SOD1 in Familiar ALS etc).