Identifying pathways modulating sleep duration: from genomics to transcriptomics

Memory, Sleep, and Tau Function

Memory consolidation related to the hippocampal-cortex connection takes place during sleep. This connection may involve at least two steps- one in the NREM phase of sleep (transmission) and the other in the REM phase (consolidation). In this brief report, we comment on the role of tau protein in these two phases of sleep. The absence of tau decreases δ waves in NREM, whereas the overexpression of modified (phosphorylated and/or mutated) tau alters θ waves in REM.

Sleep behavior is associated with over two-fold decrease of sperm count in a chronotype-specific pattern: path analysis of 667 young men in the MARHCS study

Recent studies have shown that the reduction of sperm count is associated with sleep behaviors, including restricted/excessive sleep duration, late sleep time midpoint, and shift of sleep midpoint time (social jetlag). Chronotype is suggested to regulate sleep behaviors; however, the relationship between chronotype and human sperm count is unknown. The relationship between sleep behaviors and human sperm count, when sleep behaviors as well as chronotype are controlled is also unclear. We performed a path analysis of the data obtained from 667 Chinese men recruited into the MARHCS (Male Reproductive Health in Chongqing College Students) study. Chronotype, sleep duration, sleep time midpoint, and social jetlag were estimated by the Munich Chronotype Questionnaire. Sperm count was measured by computer-aided sperm analysis. The comprehensive relationship between chronotype, all sleep behaviors, and sperm count was tested by path analysis, in which the standardized residual of sperm count was used for adjustment of age, abstinence period, body mass index, tobacco smoking, alcohol drinking, and intake of tea, cola, and coffee. Our major findings are: (1) Chronotype negatively correlated with sleep duration (correlation coefficient (R) = -0.32, P < .001) and positively correlated with sleep midpoint (R = 0.65, P < .001) and social jetlag (R = 0.37, P < .001). (2) Sleep duration (U-shape transformed; R = -0.11, P = .005), sleep midpoint (R = -0.09, P = .021), and social jetlag (R = -0.12, P = .001), respectively, correlated with sperm count in univariate analysis. The relationship between sleep midpoint and sperm count disappeared when social jetlag was controlled. (3) Path analysis showed that chronotype is connected with sperm count through two pathways: via sleep duration (standardized path coefficient = -0.09, 95% CI: -0.17 to -0.01, P = .030) and via social jetlag (standardized path coefficient = -0.09, 95% CI: -0.17 to -0.01, P = .031). For men of earlier, intermediate, and later tertile of chronotype, the sleep-duration-related decrease of sperm count was separately estimated to be 16.3%, 12.8%, and 11.6%, while the social-jetlag-related decrease of sperm count was estimated to be 9.3%, 12.8%, and 19.2%. The total effect of sleep behaviors on sperm count was estimated to be 25.7%, 25.6%, and 30.7%, with an average of 27.4% for men of different chronotypes. The present study showed that men of earlier chronotype were prone to restricted/excessive sleep duration, while men of later chronotype were prone to social jetlag, both of which correlated with reduced sperm count, suggesting that chronotype may modulate the sleep behaviors and exert dual effects on sperm count via different sleep behaviors, leading to a ubiquitous sperm decline. Men of different chronotypes should take care to avoid different types of improper sleep behaviors, so as to prevent such deleterious effect on sperm count.

High-Frequency Neuronal Bursting is Essential for Circadian and Sleep Behaviors in Drosophila

Circadian rhythms have been extensively studied in Drosophila; however, still little is known about how the electrical properties of clock neurons are specified. We have performed a behavioral genetic screen through the downregulation of candidate ion channels in the lateral ventral neurons (LNvs) and show that the hyperpolarization-activated cation current I_h is important for the behaviors that the LNvs influence: temporal organization of locomotor activity, analyzed in males, and sleep, analyzed in females. Using whole-cell patch clamp electrophysiology we demonstrate that small LNvs (sLNvs) are bursting neurons, and that I_h is necessary to achieve the high-frequency bursting firing pattern characteristic of both types of LNvs in females. Since firing in bursts has been associated to neuropeptide release, we hypothesized that I_h would be important for LNvs communication. Indeed, herein we demonstrate that I_h is fundamental for the recruitment of pigment dispersing factor (PDF) filled dense core vesicles (DCVs) to the terminals at the dorsal protocerebrum and for their timed release, and hence for the temporal coordination of circadian behaviors.SIGNIFICANCE STATEMENT Ion channels are transmembrane proteins with selective permeability to specific charged particles. The rich repertoire of parameters that may gate their opening state, such as voltage-sensitivity, modulation by second messengers and specific kinetics, make this protein family a determinant of neuronal identity. Ion channel structure is evolutionary conserved between vertebrates and invertebrates, making any discovery easily translatable. Through a screen to uncover ion channels with roles in circadian rhythms, we have identified the I_h channel as an important player in a subset of clock neurons of the fruit fly. We show that lateral ventral neurons (LNvs) need I_h to fire action potentials in a high-frequency bursting mode and that this is important for peptide transport and the control of behavior.

Better Sleep at Night: How Light Influences Sleep in Drosophila

Sleep-like states have been described in Drosophila and the mechanisms and factors that generate and define sleep-wake profiles in this model organism are being thoroughly investigated. Sleep is controlled by both circadian and homeostatic mechanisms, and environmental factors such as light, temperature, and social stimuli are fundamental in shaping and confining sleep episodes into the correct time of the day. Among environmental cues, light seems to have a prominent function in modulating the timing of sleep during the 24 h and, in this review, we will discuss the role of light inputs in modulating the distribution of the fly sleep-wake cycles. This phenomenon is of growing interest in the modern society, where artificial light exposure during the night is a common trait, opening the possibility to study Drosophila as a model organism for investigating shift-work disorders.

Therapeutic Effect of Berberine on Insomnia Rats by ErbB Signaling Pathway

Background

Insomnia seriously affects people’s health and quality of life. Short-term use of Western drugs may also be harmful. Traditional Chinese medicine has been widely used to treat diseases in world. Therefore, this paper aims to study the therapeutic effect of berberine based on the insomnious rat model.

Material/Methods

The insomnia rat model was established by intragastric administration of caffeine and parachlorophenylalanine (PCPA). Berberine and diazepam were used to treat the established insomnia rats. Then, the pathological changes of insomnia rats were detected. In addition, transcriptome sequencing and data analysis were carried out using rat hippocampus. The expression of key genes was verified by quantitative polymerase chain reaction and western blot.

Results

After 7 days of intragastric administration of berberine, the body weight, memory, and sleep quality of insomnia rats were significantly improved. The key roles of Erbb4, Erbb2, Ar, and Grin2a in berberine treatment were identified. Through the analysis of biological functions and signaling pathways, berberine was shown to play a salutary role through nervous system development and ErbB signaling pathway. Gene-set enrichment analysis (GSEA) results showed that berberine treatment affected more metabolic pathways. Compared with diazepam, berberine can play a faster role, and also improve the overall health level of insomnia rats.

Conclusions

These results suggest that berberine can alleviate insomnia in rats through a neuroprotective effect and improved metabolic level. Berberine has great potential in treatment of insomnia and might have better clinical significance.

Sleep increases chromosome dynamics to enable reduction of accumulating DNA damage in single neurons

Sleep is essential to all animals with a nervous system. Nevertheless, the core cellular function of sleep is unknown, and there is no conserved molecular marker to define sleep across phylogeny. Time-lapse imaging of chromosomal markers in single cells of live zebrafish revealed that sleep increases chromosome dynamics in individual neurons but not in two other cell types. Manipulation of sleep, chromosome dynamics, neuronal activity, and DNA double-strand breaks (DSBs) showed that chromosome dynamics are low and the number of DSBs accumulates during wakefulness. In turn, sleep increases chromosome dynamics, which are necessary to reduce the amount of DSBs. These results establish chromosome dynamics as a potential marker to define single sleeping cells, and propose that the restorative function of sleep is nuclear maintenance.

The molecular genetics of human sleep

It has been known for many years that genetic influences account for some of the individual differences in human sleep parameters, but the underlying molecular mechanisms remain unclear. With major advances of molecular biology and the recognition of heritable sleep behaviors in humans over the past 30 years, a number of genetic variants have been identified to be associated with human sleep timing, duration and quality, both in healthy individuals and under pathological conditions. Some of these variants were further validated and characterized in animal models, shedding light on the mechanism of how these variants likely alter sleep in humans, which may provide new insights into developing more effective treatments to improve human sleep.