In a more exciting development, the researchers also found a natural genetic variation in tyra-3 that is associated with lawn-leaving. This gene encodes a receptor protein that responds to tyramine, an adrenalinelike hormones derived from the amino acid tyrosine. Like adrenaline, tyramine is an internal signal that regulates the function of neurons expressing its various receptors.
To find out where in the brain the tyra-3 gene is turned on, the researchers engineered strains of worms in which they could observe production of tyra-3. By attaching a fluorescent green marker to the tyra-3 protein, they could easily observe whenever the protein was made. They then traced where the green fluorescence appeared inside the worms and discovered that the tyra-3 receptor is produced in a place that makes intuitive sense: sensory neurons. In these neurons, external cues, such as oxygen levels, can be integrated with internal states, such as hunger. "It's the result you would have gotten if you made it up," Bargmann says, laughing.
The findings show that particular genetic variants lead to specific behaviors in the real worldbut how, exactly, they do this is still mysterious. "We don't have a fix on when tyramine is being made, where it's released, and how it's working to change behavior," Bargmann says.
Figuring that out is the obvious next step. The trouble is, the tools for tracking the brain's chemical messengers in real time don't exist yet. "We'll just have to put our heads down and develop some," she says.
|Contact: Jim Keeley|
Howard Hughes Medical Institute