Figure 2.

Signals from astrocytes promote synapse formation and elimination: (a) neurons without astrocytes form less synaptic neurotransmitter vesicle; (b) astrocytes promote the maturation of both pre- and postsynaptic elements of the synapse; (c) reactive astrocytes upregulate expression of the complement component C1q in neurons, leading to elimination by astrocyte-mediated phagocytosis.