Researchers at Massachusetts General Hospital have tested a novel positron emission tomography (PET) radiotracer that reveals gene expression patterns regulated by chromatin-modifying enzymes within the brain in a first in-human study (Wey H-Y et al. Sci Transl Med. 2016;8:351ra106). Alterations in such epigenetic activity has increasingly been associated with the pathophysiology of Alzheimer disease, schizophrenia, depression, addiction, among others. Read more.