Regulation of Drosophila feeding, growth, and development: linking neural precursor identity to functional significance. Amy L. Gresser, Brian Gebelein. Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH.

   The regulation of animal growth requires the interaction of neuronal, hormonal, and metabolic pathways. One key factor in characterizing growth regulation is the ability to link the development of discrete cell populations to their later functional roles. In this study, we show that an enhancer of the rhomboid serine protease, a catalyst for epidermal growth factor secretion, acts in bilaterally symmetric cell clusters in the Drosophila embryonic head. Lineage tracing reveals that these cells give rise to a subset of deutocerebral CNS neurons as well as to the hypopharyngeal sensory organ, a largely uncharacterized neural structure of unknown function. Targeted ablation of the cells results in impaired larval growth, delayed pupation, and pupal lethality. To better ascertain the nature of the growth defect, we used a variety of feeding assays to show that ablated larvae are capable of locating, ingesting, and clearing food. Importantly, however, we observed that while feeding rates for starved control and ablated larvae are initially similar, ablated larvae subsequently exhibit a rapid decrease in feeding that that could suggest an abnormal sense of satiety. In total, our studies reveal that this rhomboid enhancer serves as a valuable tool for labeling and ablating the precursors of two distinct neural structures and that at least one of these structures plays an essential role in the regulation of feeding behavior, animal growth, and viability.