RNAi-based screen for pigmentation in Drosophila melanogaster reveals regulators of brain dopamine and sleep.

The dopaminergic system has been extensively studied for its role in behavior in animals as well as human neuropsychiatric and neurological diseases. However, we still know little about how dopamine levels are tightly regulated in vivo . To identify novel regulators of dopamine, we utilized Drosophila melanogaster cuticle pigmentation as a readout, where dopamine is a precursor to melanin. We measured dopamine from genes known to be critical for cuticle pigmentation and performed an RNAi-based screen to identify new regulators of pigmentation. We found 153 potential pigmentation genes, which were enriched for conserved homologs and disease- associated genes as well as developmental signaling pathways and mitochondria-associated proteins. From 35 prioritized candidates, we found 10 caused significant reduction in head dopamine levels and one caused an increase. Two genes, clueless and mask (multiple ankyrin repeats single KH domain), upon knockdown, reduced dopamine levels in the brain. Further examination suggests that Mask regulates the transcription of the rate-limiting dopamine synthesis enzyme, tyrosine hydroxylase , and its knockdown causes dopamine-dependent sleep phenotypes. In summary, by studying genes that affect cuticle pigmentation, a phenotype seemingly unrelated to the nervous system, we were able to identify several genes that affect dopamine metabolism as well as a novel regulator of behavior.