Gene found key to brain chemical

The story of serotonin, a brain chemical associated with depression and anxiety, just became more complicated. German scientists have found that the mouse brain doesn’t use the expected enzyme to create the neurotransmitter.

The previously known serotonin-making enzyme is tryptophan hydroxylase, or TPH. Recently, Diego J. Walther of the Max Delbruck Center for Molecular Medicine in Berlin-Buch and his colleagues created mutant mice that lack this enzyme. Surprisingly, the rodents still made serotonin in their brains. In other tissues, however, the chemical was almost nonexistent.

The investigators soon discovered the explanation–mice have a gene encoding a second form of TPH, as do people. It’s this version of TPH that’s responsible for serotonin synthesis in the brains of mice and, presumably, people, the researchers report in the Jan. 3 Science. The many past efforts to link the original TPH gene to psychiatric disorders now must be reevaluated, Walther and his colleagues suggest.

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