SPI1 encodes PU.1, a central transcription factor in microglial development and activation, and has a genome-wide significant genic association with AD in the IGAP GWAS (rs3740688 Odds Ratio 0.92 Meta p = 5.4 × 10−13), comprising 35,274 Alzheimer’s disease cases and 59,163 controls4. The gene discussed is SPI1; the disease is early-onset autosomal dominant Alzheimer disease.