Control of Sleep-Wake Cycles in Drosophila

Abstract

Inter-oscillator communication modulates and sustains the circadian locomotor rhythms in flies and rodent animal models. In Drosophila, the multioscillator network that controls sleep-wake cycles includes about 150 clock neurons. A subset of lateral neurons (LNs) expressing the Pigment-dispersing factor (PDF) appears to act as a master clock in constant darkness (DD). In light-dark (LD) cycles, flies show a bimodal distribution of their activity, and the PDF-expressing LNs play a major role in the control of the morning bout of activity. In contrast, a subset of PDF-negative LNs can generate evening activity in the absence of other functional oscillators. How these oscillators interact in a fully functional network to shape the sleep-wake cycle remains debated. The PDF neurons strongly influence the PDF-negative ones in DD and, to a lesser extent, in LD. The extent of hierarchy depends on environmental conditions and the way the dominance of PDF neurons is exerted on the different types of PDF-negative neurons is unclear. The recent discovery of light-and temperature-dependent oscillators in the dorsal neurons (DNs) sheds new light on the circuits that control the Drosophila diurnal behavior and its adaptation to environmental changes.

A Circadian Clock in the Blood-Brain Barrier Regulates Xenobiotic Efflux

“…It is interesting that flies use non-cell autonomous mechanisms to drive a rhythm of BBB permeability, and fits with the idea that clocks localize to specific cell populations in Drosophila and control behavior/physiology through circuits (Chatterjee and Rouyer, 2016; Guo et al, 2014; Liang et al, 2017). However, given that one class of Drosophila BBB cells contains clocks, these findings still raise the question of why clocks and transporters localize to different cell types.…”

Automated analysis of long-term grooming behavior in Drosophila using a k-nearest neighbors classifier

“…The appearance of repeating patterns raised the possibility that external light-dark (LD) cycles alone or in combination with internal programs could be exerting temporal control over several of these behavioral outputs, including grooming. Indeed, environmental light-dark cycles through influence on the circadian clock are known to drive rhythmic changes in fly sleep and wake durations and within the awake state, feeding, and locomotor activities ( Chatterjee and Rouyer, 2016 ; Pfeiffenberger et al, 2010 ). That these rhythms persisted in the absence of LD cycles is generally considered to be strong support for clock control of these behaviors.…”

“…To test the independence of rhythms, we performed a series of ‘shuffling experiments’ using well-established ( Allada and Chung, 2010 ; Chatterjee and Rouyer, 2016 ) rhythmicities of wakefulness and locomotion as metrics ( Figure 4F ). In brief, we took data from Figure 4E in which grooming, locomotion and wakefulness have LD-driven ~24 hr rhythms ( Figure 4F , left and power spectra) and computationally randomized the grooming time-series such that it lost rhythmicity ( Figure 4F , right).…”

Reconfiguration of a Multi-oscillator Network by Light in the Drosophila Circadian Clock

“…Circadian clocks align our physiology and behavior to the 24h day-night cycles that are imposed by the rotation of the earth. The daily rhythm in rest-activity behavior is sculpted by a coupled multi-oscillator system that is located in the brain of both insects [1, 6, 7] and mammals [2, 8]. The circadian clock functions to anticipate daily environmental changes.…”

“…Fruit flies are crepuscular animals displaying morning and evening peaks of activity in light-dark cycles. The circadian clock that underlies this bimodal activity rhythm resides in 150 clock neurons that comprise a series of brain oscillators [1, 7, 23]. Among those, morning and evening oscillators were defined as the small ventral lateral neurons (s-LNvs) that express the Pigment-dispersing factor (PDF) neuropeptide (LN MO ) and the four CRY-positive, PDF-negative lateral neurons (3 LNds and 5 th s-LNv = LN EO ), respectively [15, 24–26].…”