The Alk receptor tyrosine kinase regulates Sparkly, a novel activity regulating neuropeptide precursor in theDrosophilaCNS

Numerous roles for the Alk receptor tyrosine kinase have been described inDrosophila, including functions in the central nervous system (CNS), however the molecular details are poorly understood. To gain mechanistic insight, we employed Targeted DamID (TaDa) transcriptional profiling to identify targets of Alk signaling in the larval CNS. TaDa was employed in larval CNS tissues, while genetically manipulating Alk signaling output. The resulting TaDa data were analysed together with larval CNS scRNA-seq datasets performed under similar conditions, identifying a role for Alk in the transcriptional regulation of neuroendocrine gene expression. Further integration with bulk/scRNA-seq and protein datasets from larval brains in which Alk signaling was manipulated, identified a previously uncharacterizedDrosophilaneuropeptide precursor encoded byCG4577as an Alk signaling transcriptional target.CG4577, which we namedSparkly (Spar),is expressed in a subset of Alk-positive neuroendocrine cells in the developing larval CNS, including circadian clock neurons. In agreement with our TaDa analysis, overexpression of theDrosophilaAlk ligand Jeb resulted in increased levels of Spar protein in the larval CNS. We show that Spar protein is expressed in circadian (Clock) neurons, and flies lacking Spar exhibit defects in sleep and circadian activity control. In summary, we report a novel activity regulating neuropeptide precursor gene that is regulated by Alk signaling in theDrosophilaCNS.