Researchers have identified a protein key to the development of a type of brain cell believed to play a role in disorders like Alzheimer’s and Parkinson’s diseases and used the discovery to grow the neurons from stem cells for the first time. The stem-cell-derived norepinephrine neurons of the type found in a part of the human brain called the locus coeruleus may enable research into many psychiatric and neurodegenerative diseases and provide a tool for developing new ways to treat them.