Genetics play a strong part in the development of attention-deficit/hyperactivity disorder (ADHD), but the path from a gene to risk for the disorder has remained a black box to researchers.. A new study suggests how the risk gene ADGRL3 (LPHN3) might work. ADGRL3 encodes the protein latrophilin 3, which regulates communication between brain cells. According to the study, a common variation of the gene associated with ADHD disrupts its ability to regulate gene transcription - the formation of mRNA from DNA that leads to expression of the gene.