Abstract
Individuals with Down syndrome (DS), caused by trisomy of chromosome 21 (chr21, T21), are strongly predisposed to Alzheimer's disease (AD), due to triplication of the APP gene, with ∼100% penetrance of AD brain pathology by age 40 and variable onset of dementia thereafter. It remains unclear what role other triplicated genes play in the pathophysiology of DS-associated AD (DS-AD). Using mouse models of DS-AD, we demonstrate that triplication of other chr21 genes has paradoxical effects on learning and memory in DS-AD mice, exacerbating some phenotypes and attenuating others. Spatial transcriptomic analysis revealed genome-wide alterations typified by upregulation of interferon (IFN) signatures and elevated levels of disease-associated microglia with concomitant decreases in neurons in DS-AD animals. Finally, systemic treatment with a JAK inhibitor improved cognition and rescued gene expression changes in DS-AD animals, indicating that IFN may be a driver of pathophysiology in DS-AD that could be amenable to therapeutic intervention.