The NFκB Dif is required for behavioral and molecular correlates of sleep homeostasis in Drosophila

Abstract

The nuclear factor binding the {kappa} light chain in B-cells (NF{kappa}B) is involved in a wide range of cellular processes including development, growth, innate immunity, and sleep. However, efforts have been limited toward understanding how specific NF{kappa}B transcription factors function in sleep. Drosophila fruit flies carry three genes encoding NF{kappa}B transcription factors, Dorsal, Dorsal Immunity Factor (Dif), and Relish. We previously found that loss of the Relish gene from fat body suppressed daily nighttime sleep, and abolished infection-induced sleep. Here we show that Dif regulates daily sleep and recovery sleep following prolonged wakefulness. Mutants of Dif showed reduced daily sleep and suppressed recovery in response to sleep deprivation. Pan-neuronal knockdown of Dif strongly suppressed daily sleep, indicating that in contrast to Relish, Dif functions from the central nervous system to regulate sleep. Based on the distribution of a Dif-associated GAL4 driver, we hypothesized that its effects on sleep were mediated by the pars intercerebralis (PI). While RNAi knock-down of Dif in the PI reduced daily sleep, it had no effect on the recovery response to sleep deprivation. However, recovery sleep was suppressed when RNAi knock-down of Dif was distributed across a wider range of neurons. Induction of the nemuri (nur) antimicrobial peptide by sleep deprivation was suppressed in Dif mutants and pan-neuronal over-expression of nur also suppressed the Dif mutant phenotype. Together, these findings indicate that Dif functions from brain to target nemuri and to promote sleep. Statement of SignificanceNF{kappa}B transcription factors drive inflammatory processes that underly a multitude of human diseases that are accompanied by sleep disturbance. However, genetic studies in mammals that investigate a function of NF{kappa}B in sleep have been limited. Using genetic approaches in the Drosophila fruit fly, we show that the Dif NF{kappa}B, homologous to the Rel family of NF{kappa}Bs in humans, functions from neuronal tissue to regulate daily sleep and to mediate responses to sleep loss. These findings enhance our understanding of the role of a specific NF{kappa}B gene in sleep regulation.