Dozing Off With Drosophila: The Effect of Disrupted Circadian Rhythms and Sleep Disturbance on Mortality, Mood, and Addiction

Abstract

Many environmental factors can disrupt sleep and circadian rhythms, yet the consequences of such disruptions are poorly understood. The main goals of this project were to study the effects of disrupted circadian rhythms and sleep disturbance on Drosophila melanogaster’s: (1) lifespan, (2) depression-like behaviors, and (3) propensity to consume caffeine-containing media. Three experimental groups were used: controls, Circadian Dysfunction (CD), and Sleep Disturbance (SD). Circadian disruption (CD): used flies with Tim01 mutation, which eliminates circadian behavioral rhythms. Sleep disturbance (SD): used flies subjected to hourly light exposure and manual mechanical disruption, for 48 hours. To assess the effect on lifespan, the percent of flies surviving over time, within each group, was calculated. Impaired geotaxis, or loss of climbing motivation, was assessed as a measure of a depression-like state. Preference for caffeine-containing food was evaluated using a choice chamber where caffeine enriched, and regular media were presented to flies. Group differences were analyzed with survival curves. Chi-square tests were used for the categorical variables. Survival curve analysis showed that Flies with the timeless gene mutation ( tim01) have a significantly shorter lifespan than controls. Geotaxis was not significantly impaired by sleep disturbance, but it was negatively affected by circadian dysfunction. Both the Circadian Dysfunction and Sleep Disturbance groups showed a preference for caffeine-containing food, after 72 hours of exposure to it, although the Circadian Dysfunction group was much more affected than the Sleep Disturbance group. Sleep and circadian disturbances can negatively influence physical and mental wellbeing and the accompanying molecular mechanisms, as well as disrupted brain physiology, must be studied. It is critical to identify and minimize social and environmental disruptors of such biological rhythms.