A regulatory variant of the human tryptophan hydroxylase-2 gene biases amygdala reactivity

Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in the synthesis of serotonin (5–HT), a key modulator of mood and affect. Thus, the identification of genetic variation contributing to functional changes in TPH enzymatic activity is of great interest in determining the biological pathways underpinning individual differences in emotional behaviors and risk for psychiatric disorders, including depression, anxiety, and suicidality. Recent molecular and cellular studies have revealed the existence of a second TPH isoform, tryptophan hydroxylase-2 (TPH2), exclusively expressed in the murine brain. 1