Linking enhancers to disease Enhancers are genomic regions that regulate gene expression, sometimes in a cell-dependent manner. However, most of our knowledge of human brain cell–type enhancers derives from studies of bulk human brain tissue. Nott et al. examined chromatin and promoter activity in cell nuclei isolated from human brains. Genetic variants associated with brain traits and disease showed cell-specific patterns of enhancer enrichment. These data indicate that Alzheimer's disease is regulated by genetic variants within microglial cells, whereas psychiatric diseases tend to affect neurons. Science , this issue p. 1134