Table 1.

Summary of the known major developmental functions of microglia, the ages at which they have been observed, the brain regions in which they have been observed, the major impact of the finding, and the reference associated with the findings. These citations are the basis for the schematic in Figure 1.

Developmental function	Age	Brain area	Notable findings	Reference
Synaptic patterning	P12–15	Hippocampus	CX3CR1, social behavior	Paolicelli et al. (12) and Zhan et al. (62)
	P5–9	Barrel cortex	CX3CR1	Hoshiko et al. (11)
	P5	dLGN of thalamus	C3, activity dependent	Schafer et al. (36)
	P2	POA	Sex difference, PGE2, sex behavior	Lenz et al. (33)
	P30+	Motor cortex	BDNF, motor learning	Parkhurst et al. (52)
	P40	dLGN of thalamus	Second wave of synaptic pruning	Schafer et al. (48)
	P15	Spinal cord and thalamus	IL-33m, sensorimotor behavior	Vainchtein et al. (47)
Cell genesis	P2–5	Ventricular area	IL6, IL1B, TNF, IFNY	Shigemoto-Mogami et al. (37)
Myelinogenesis	P6–22	Corpus callosum, cerebellum	IGF1, Cd11c+	Hagemeyer et al. (32)
	P6–22	Corpus callosum	IGF1, Cd11c+	Wlodarczyk et al. (26)
Cellular phagocytosis	E9.5	Neural tube	Earliest noted microglia function	Kierdorf et al. (4)
	P0-2	Hippocampus	Induce cell death, Cd11b	Wakselman et al. (40)
	E17–P6	Cortical proliferative zones	Phagocytosis of progenitor cells	Cunningham et al. (31)
	P4	Hippocampus	VEGFR1, Nox-2	Lelli et al. (41)
	P2–3	Hippocampus	Sex difference	Nelson et al. (28)
Axon dynamics	E14.5	Striatum	Cr3, Dap12/Tyrobp, Cx3cr1	Squarzoni et al. (38)
	E17.5	Corpus callosum	Dap12	Pont-Lezica et al. (35)
Cell positioning	E18.5	Cortex		Squarzoni et al. (38)
Cell survival	P3–4	Cortex	IGF1, Cx3cr1	Ueno et al. (39)