Scientists studying the fruitfly Drosophila have traced the path of olfactory signals beginning with chemical receptors in the mouth, which set off neurons that signal the antennal lobe of the central nervous system. From here, the electrical stimulation zooms toward the so-called mushroom body, a mushroom-shaped cluster of neurons involved in olfactory processing. Less is known about the gustatory signals, which begin both in the mouth and in the pharynx and aim toward the subesophageal ganglion region of the fly's brain. How olfactory and gustatory signals influence feeding patterns remains murky.
In a new study, Michael Pankratz and Christoph Melcher used genetic analysis to gain insight into the adult and larval neural networks that use taste information to regulate eating. Specifically, they found that several types of neurons responsible for coordinating taste signals express the gene hugin (hug), a gene linked to abnormal eating activity and expressed in only the subesophageal ganglion. By altering hug expression, the researchers uncovered the gene's behavioral influence: hug-expressing neurons influence a fly's decision to sample new food sources. The researchers also proposed that hug proteins play a role in hormone-triggered growth, an important consequence of adequate feeding.
To begin their investigation, Melcher and Pankratz analyzed the DNA from flies with abnormal eating behavior. One group of these flies shared a mutant klumpfuss (klu) gene, normally responsible for encoding a protein transcription factor. Because neural transcription factors control production levels of other neural proteins, the researchers used DNA microarray