The Mechanism Of Nipped-A And MAN1 In Regulating Drosophila Circadian Rhythm

Many of our behavioral and physiological processes exhibit 24 h rhythms,or circadian rhythms,and disruptions of circadian rhythms are associated with many diseases and disorders.These rhythms are driven by endogenous clocks which,at the molecular level,consist of a series of transcriptional and translational feedback loops.In recent years,accumulating evidence demonstrate that epigenetic modifications also play a crucial role in the circadian system,adding an extra layer of regulation and thus plasticity.Because psychiatric diseases are often accompanied by circadian disruptions,but the molecular underpinnings remain largely unclear.To address this,we screened genes that have been previously reported to be associated with psychiatric diseases and found that TRRAP /Nipped-A,a gene associated with schizophrenia,is involved in circadian rhythm regulation in drosophila.TRRAP is an evolutionarily conserved protein known to function as a histone acetyltransferase(HAT)cofactor by facilitating the recruitment of HAT to chromatin to regulate transcription and DNA repair.Knocking down Nipped-A,the Drosophila homolog of human TRRAP,leads to lengthened period of fly locomotor rhythms.Molecular analysis demonstrates that Nipped-Asets the pace of the clock by increasing the mRNA and protein level of core clock genes timeless(tim)and Par domain protein 1?(Pdp1?).Over-expressing tim or Pdp1? rescues the long period phenotype caused by Nipped-A deficiency,while mutating tim or Pdp1? synergistically enhances the phenotype.Furthermore,we found that Nipped-A promotes the transcription of tim and Pdp1? possibly by facilitating deubiquitylation of histone H2 B via the deubiquitinase NON-STOP.These findings reveal a role for Nipped-A in epigenetic regulation of the clock,and provides a possible explanation for circadian misalignments often observed in schizophrenia patients.Previously,we have shown that inner nuclear membrane protein MAN1 regulates this clock and thus locomotor rhythm in flies,but the mechanism remains unclear.Here we further confirmed previous findings and found that knocking down MAN1 in the pacemaker neurons of adult flies is sufficient for lengthening the period of locomotor rhythm.Molecular analysis reveal that knocking down MAN1 leads to reduced mRNA and protein levels of core clock gene period(per),likely by reducing per transcription.Over-expressing per rescues the long period phenotype caused by MAN1 deficiency whereas per mutation exerts an epistatic effect on MAN1,indicating that MAN1 sets the pace of the clock by targeting per.