Drosophila HyperkineticMutants Have Reduced Sleep and Impaired Memory

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Abstract
In mammals, sleep is thought to be important for health, cognition, and memory. Fruit flies share most features of mammalian sleep, and a recent study found thatDrosophilalines carrying loss-of-function mutations inShaker(Sh) are short sleeping, suggesting that the Sh current plays a major role in regulating daily sleep amount. The Sh current is potentiated by a β modulatory subunit coded byHyperkinetic(Hk). Here, we demonstrate that severe loss-of-function mutations ofHkreduce sleep and do so primarily by affecting the Sh current. Moreover, we prove, using a transgenic approach, that a wild-type copy ofHkis sufficient to restore normal sleep. Furthermore, we show that short-sleepingHkmutant lines have a memory deficit, whereas flies carrying a weaker hypomorphicHkallele have normal sleep and normal memory. By comparing six short-sleepingShlines with two normal sleeping ones, we also found that only alleles that reduce sleep also impair memory. These data identify a gene,Hk, which is necessary to maintain normal sleep, and provide genetic evidence that short sleep and poor memory are linked.