Investigation Of Nipped-A And Circadian Clock Genes In Drosophila Circadian Rhythm And Sleep Regulation

Circadian rhythm exists in most organism on the earth,manifest in most aspects of physiology and behavior.The circadian rhythm system is driven by multiple cells in the organism that contain circadian clocks.The disruption of circadian rhythm system leads to a variety of diseases,which seriously affect human health.Psychiatric diseases is one of the diseases most closely related to the disruption of circadian rhythm,but the relationship between psychiatric diseases and the circadian rhythm disruption is unclear.Through genetic screening,we found that TRRAP/Nipped-A,a gene associated with schizophrenia and autism,is involved in determining the period of circadian rhythm in Drosophila.Knocking down Nipped-A in circadian neurons leads to lengthened period of locomotor rhythms in flies,but the action of Nipped-A in circadian neurons is un-known.I employed immunofluorescence assay and demonstrated that knocking down Nipped-A decrease the protein level of core clock genes timless(tim),Par domain pro-tein 1?(Pdp1?)and period(per)in the main pacemaker neruons small ventral lateral(sLNv).Knocking down Nipped-A also decreases the expression of the circadian neu-ropeptide pigment dispersing factor(PDF)in the s LNvs,as well as the complexity of the dorsal projections from these neurons,indicating that Nipped-A also affects the transmission of clock information from s LNvs to downstream targets.These studies uncover the mechanism of how Nipped-A regulates circadian rhythm at the neurobio-logical level,adding to our understanding of circadian rhythm disruption and psychiat-ric disorders.Previous studies have found that the mutations in the human circadian clock gene PERIOD3(PER3)contribute to the development of seasonal affective disorder(SAD).Patients with SAD also experience drowsiness,but the mechanism is unclear.In fruit flies,I found that per,the fly homolog of PER3,modulates sleep under long photoper-iod conditons mimicking summer.Under long photoperiod,flies with per~L mutation sleep longer,and the sleep is more consolidated.Overexpressing per in the s LNvs could rescue the sleep phenotype of per~L flies.Through genetic interaction and pharmacolog-ical experiments,I find that the effect of per~L on sleep is dependent on the blue light photoreceptor cryptochrome(cry)and may be mediated by the GABAergic system.In addition,I also examine the effects of other circadian clock genes on sleep under dif-ferent photoperiod and find that under short photoperiod that mimics winter,flies with cry~b mutation have increased sleep and sleep is more consolidated.Knocking down cry in GABAergic neurons also lead to increased sleep in flies,and pharmacological ex-periments reveal that the effects of cry~b on sleep may be mediated by the GABAergic system.In summary,I find that the circadian clock genes per and cry promote wake-fulness under long and short photoperiod,respectively,and investigate their mecha-nisms at the anatomical and molecular levels.