The presence of reactive microglia and astrocytes is a common observation in Alzheimer's disease brain. Microglia are present within the numerous beta-amyloid containing neuritic plaques, whereas reactive astrocytes usually surround the plaque perimeter. These glial cells express and secrete numerous neurotrophic and neurotoxic factors that contribute to the etiology of the disease. The molecular mechanisms that dictate glial cell activation and subsequent alternative gene expression are currently unknown. In the present study we determine that activated microglia in AD brain express the FAC1 protein, a developmentally regulated gene product, while astrocytes fail to express significant levels of FAC1 protein. Since FAC1 is a putative DNA binding protein, expression in microglia during AD suggests that FAC1 participates in the regulation of alternative gene expression.