CCHamide-2 Is an Orexigenic Brain-Gut Peptide in Drosophila

The neuroendocrine peptides CCHamide-1 and -2, encoded by the genes ccha1 and -2, are produced by endocrine cells in the midgut and by neurons in the brain of Drosophila melanogaster. Here, we used the CRISPR/Cas9 technique to disrupt the ccha1 and -2 genes and identify mutant phenotypes with a focus on ccha-2 mutants. We found that both larval and adult ccha2 mutants showed a significantly reduced food intake as measured in adult flies by the Capillary Feeding (CAFE) assay (up to 72% reduced food intake compared to wild-type). Locomotion tests in adult flies showed that ccha2 mutants had a significantly reduced locomotor activity especially around 8 a.m. and 8 p.m., where adult Drosophila normally feeds (up to 70% reduced locomotor activity compared to wild-type). Reduced larval feeding is normally coupled to a delayed larval development, a process that is mediated by insulin. Accordingly, we found that the ccha2 mutants had a remarkably delayed development, showing pupariation 70 hours after the pupariation time point of the wild-type. In contrast, the ccha-1 mutants were not developmentally delayed. We also found that the ccha2 mutants had up to 80% reduced mRNA concentrations coding for the Drosophila insulin-like-peptides-2 and -3, while these concentrations were unchanged for the ccha1 mutants. From these experiments we conclude that CCHamide-2 is an orexigenic peptide and an important factor for controlling developmental timing in Drosophila.