Identifying the role of the ocular immune response in age-related sleep disturbances

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Project Summary Sleep is a conserved function across evolution that is critical for maintaining health and promoting longevity. With age, there are declines in sleep quality that often precede, and are associated with, the onset of disease. However, the mechanisms responsible for sleep senescence are unclear. In both humans and the fruit fly, Drosophila melanogaster, endogenous circadian clocks that set 24h rhythms in sleep and activity are influenced by light input received from the eye. However, with age, there are declines in vision and a dampening of circadian rhythms. Concomitant with this decline, is a chronic activation of the immune system. A central regulator of the immune response is the transcription factor Nuclear Factor Kappa-B (NF-κB), which in both flies and mammals coordinates the response to bacterial pathogens and damage signals. Using a bioinformatics approach in Drosophila, we identified that genes regulated by NF-κB show elevated expression in the photoreceptor cells with age. With this observation in mind, we tested the hypothesis that changes that occur in the eye with age drive sleep senescence. We found that inhibiting the NF-κB homolog, relish, in the photoreceptor cells maintains total sleep time and sleep consolidation with age, suggesting that increases in the ocular immune response drives sleep senescence. Furthermore, we have identified that housing flies in constant darkness suppresses the expression of NF-κB-regulated genes in the fly head, indicating that NF-κB activity is regulated by light. This proposal builds on these preliminary findings with two specific aims. In Aim#1, we will identify genes that are regulated by NF-κB in the eye and that drive sleep senescence. To accomplish this, we have compiled a list of genes whose expression is significantly changed in the photoreceptors with age, and with loss of relish. We will inhibit each of these candidate genes in the photoreceptors and identify genes whose loss-of-function sleep phenotype mimics the effect of relish. In Aim #2, we will firmly establish whether light and the phototransduction signaling cascade promotes NF-κB activity in the photoreceptors. For this, we will use an existing luciferase-based genetic reporter for NF-κB that we can express in the photoreceptor cells. Using the powerful genetic tools available to Drosophila, we will be able to test whether genes involved in the phototransduction signaling cascade affect NF-κB luciferase reporter activity, allowing us to pinpoint the mechanism through which light regulates NF-κB. Ultimately, this work will reveal the mechanism through which eye aging affects sleep senescence, and will identify conserved genetic targets that may be modulated in mammals for preserving sleep quality with age.