Genetic dissection of neural circuit anatomy underlying feeding behavior in Drosophila: distinct classes of hugin-expressing neurons.

The hugin gene of Drosophila encodes a neuropeptide with homology to mammalian neuromedin U. The hugin-expressing neurons are localized exclusively to the subesophageal ganglion of the central nervous system and modulate feeding behavior in response to nutrient signals. These neurons send neurites to the protocerebrum, the ventral nerve cord, the ring gland, and the pharynx and may interact with the gustatory sense organs. In this study, we have investigated the morphology of the hugin neurons at a single-cell level by using clonal analysis. We show that single cells project to only one of the four major targets. In addition, the neurites of the different hugin cells overlap in a specific brain region lateral to the foramen of the esophagus, which could be a new site of neuropeptide release for feeding regulation. Our study reveals novel complexity in the morphology of individual hugin neurons, which has functional implication for how they coordinate feeding behavior and growth.