The presence of a microglial proliferative response with neurodegeneration is also supported by microarray analysis correlating clinical scores of incipient Alzheimer’s disease with the expression ofCebpaandSpi1(PU.1), key transcription factors controlling microglial lineage commitment and proliferation (Blalocket al., 2004). Here, SPI1 is linked to early-onset autosomal dominant Alzheimer disease.