The Resonance and Adaptation of Neurospora crassa Circadian and Conidiation Rhyth ms to Short Light-Dark Cycles

Circadian clocks control the physiological and behavioral rhythms to adapt to the environment with a period of ~24 h. However, the influences and mechanisms of the extreme light/dark cycles on the circadian clock remain unclear. We showed that, in Neurospora crassa, both the growth and the microconidia production contribute to adaptation in LD12:12 (12 h light/12 h dark, periodically). Mathematical modeling and experiments demonstrate that in short LD cycles, the expression of the core clock protein FREQUENCY was entrained to the LD cycles when LD > 3:3 while it free ran when T ≤ LD3:3. The conidial rhythmicity can resonate with a series of different LD conditions. Moreover, we demonstrate that the existence of unknown blue light photoreceptor(s) and the circadian clock might promote the conidiation rhythms that resonate with the environment. The ubiquitin E3 ligase FWD-1 and the previously described CRY-dependent oscillator system were implicated in regulating conidiation under short LD conditions. These findings shed new light on the resonance of Neurospora circadian clock and conidiation rhythms to short LD cycles, which may benefit the understandings of both the basic regulatory aspects of circadian clock and the adaptation of physiological rhythms to the extreme conditions.

The E3 ubiquitin ligase adaptor Tango10 links the core circadian clock to neuropeptide and behavioral rhythms

Circadian transcriptional timekeepers in pacemaker neurons drive profound daily rhythms in sleep and wake. Here we reveal a molecular pathway that links core transcriptional oscillators to neuronal and behavioral rhythms. Using two independent genetic screens, we identified mutants of Transport and Golgi organization 10 (Tango10) with poor behavioral rhythmicity. Tango10 expression in pacemaker neurons expressing the neuropeptide PIGMENT-DISPERSING FACTOR (PDF) is required for robust rhythms. Loss of Tango10 results in elevated PDF accumulation in nerve terminals even in mutants lacking a functional core clock. TANGO10 protein itself is rhythmically expressed in PDF terminals. Mass spectrometry of TANGO10 complexes reveals interactions with the E3 ubiquitin ligase CULLIN 3 (CUL3). CUL3 depletion phenocopies Tango10 mutant effects on PDF even in the absence of the core clock gene timeless. Patch clamp electrophysiology in Tango10 mutant neurons demonstrates elevated spontaneous firing potentially due to reduced voltage-gated Shaker-like potassium currents. We propose that Tango10/Cul3 transduces molecular oscillations from the core clock to neuropeptide release important for behavioral rhythms.

Principal Component Analysis of the Social and Behavioral Rhythms Scale in elderly

Background: Changes in social and behavioral rhythms (SBR) in elderly are related to health status. Nevertheless, there is no data on factor analysis of the Brief Social Rhythm Scale (BSRS) an internationally well-known tool in this field. The aim was to analyze, in elderly, the factorial structure of the Italian version of BSRS.Design and Methods: Principal Component Analysis of the BSRS carried out in elderly living at home.Results: Sample of 141 participants (83 Females, 58,9%), aged 72.3±4.8. All the items of the questionnaire were related and could compose a single factor, explaining 56% of variance. A solution adopting two factors, the first (including items 1,2,3,4,9,10), the second (including items 5,6,7,8), covered cumulatively 78.8% of the variance.Conclusion: The study confirms that the BSRS is consistent with the idea for which it was built and can be useful for the study of regularity of SBR in old adults.

Exercise improves long-term social and behavioral rhythms in older adults: Did it play a role during the COVID-19 lockdown?

The study aimed to verify whether exercise training in older adults can improve social behavioral rhythms (SBR) and if any modification is maintained over time. Older adults (n=120) from a previous randomized controlled trial, were randomly allocated to either a moderate-intensity exercise group or a control group. SBR was evaluated at t0, t26, and t48 weeks (during the COVID-19 lockdown), using the brief social rhythms scale (BSRS). Seventy-nine participants completed the follow-up (age 72.3±4.7, women 55.3%). An improvement in the BSRS score was found in the exercise group at 26 weeks (p=0.035) when the exercise program was concluded, and it was maintained at 48 weeks (p=0.013). No improvements were observed in the control group. To conclude, SBR, previously found as a resilience factor in older adults during COVID-19, appear to improve after a moderate 12 weeks exercise program, and the improvement persisted even after stopping exercise during the COVID-19 lockdown.

The effects of dynamic daylight-like light on the rhythm, cognition, and mood of irregular shift workers in closed environment

Shift workers are mostly suffered from the disruption of circadian rhythm and health problems. In this study, we designed proper light environment to maintain stable circadian rhythm, cognitive performance, and mood status of shift workers. We used five-channel light-emitting diodes to build up the dynamic daylight-like light environment. The illuminance, correlated color temperature, and circadian action factor of light were tunable in the ranges of 226 to 678 lx, 2680 to 7314 K, and 0.32 to 0.96 throughout the day (5:30 to 19:40). During the nighttime, these parameters maintained about 200 lx, 2700 K, and 0.32, respectively. In this light environment, three subjects had engaged in shift work for 38 consecutive days. We measured plasma melatonin, activity counts, continuous performance tests, and visual analogue scale on mood to assess the rhythm, cognitive performance, and mood of subjects. After 38-day shift work, the subjects’ peak melatonin concentration increased significantly. Their physiological and behavioral rhythms maintained stable. Their cognitive performance improved significantly after night work, compared with that before night work. Their mood status had no significant change during the 38-day shift work. These results indicated that the light environment was beneficial to maintain circadian rhythm, cognitive performance and mood status during long-term shift work in closed environment.

Timed daily exercise remodels circadian rhythms in mice

Regular exercise is important for physical and mental health. An underexplored and intriguing property of exercise is its actions on the body’s 24 h or circadian rhythms. Molecular clock cells in the brain’s suprachiasmatic nuclei (SCN) use electrical and chemical signals to orchestrate their activity and convey time of day information to the rest of the brain and body. To date, the long-lasting effects of regular physical exercise on SCN clock cell coordination and communication remain unresolved. Utilizing mouse models in which SCN intercellular neuropeptide signaling is impaired as well as those with intact SCN neurochemical signaling, we examined how daily scheduled voluntary exercise (SVE) influenced behavioral rhythms and SCN molecular and neuronal activities. We show that in mice with disrupted neuropeptide signaling, SVE promotes SCN clock cell synchrony and robust 24 h rhythms in behavior. Interestingly, in both intact and neuropeptide signaling deficient animals, SVE reduces SCN neural activity and alters GABAergic signaling. These findings illustrate the potential utility of regular exercise as a long-lasting and effective non-invasive intervention in the elderly or mentally ill where circadian rhythms can be blunted and poorly aligned to the external world.

Social and Behavioral Rhythms as a Marker of Well-being Indicator in Old Adults Living at Home

Social and behavioral rhythms (SBRs) are related to circadian rhythms well known as central points in the pathophysiology of bipolar disorders. The purpose is to verify in elderly people if having functional SBRs correlated with a positive perception of the quality of life (QoL) and health parameters and if there was an association between dysfunctionality of SBRs and Major Depressive Disorder (MDD). Sample: 141 people aged 65 years (58,9%Female). Each subject was submitted to SBRs Scale (in which higher scores show more dysfunctional SRB); SF-12 for QoL; PHQ-9 for depressive symptoms and underwent blood levels essays including cholesterol and triglyceride. The medical documented lifetime diagnosis including Major Depressive Disorder was taken into account. SBRs Scale score correlated inversely with SF-12 score (r=-0.360, p<0.0001) and positively with PHQ9 (r=0.396, p<0.0001). Lifetime MDD medical diagnosis was associated with a higher score at scale on social rhythms (24.811.9 vs 20.18.0, F=15.848, p<0.0001).The study highlighted, for the first time, that SBRs such as sleep, and nutrition have a role in well-being and that dysregulation of SBRs is related to MDD. Further longitudinal studies with a sufficient number of individuals will have to confirm these data and clarify causal links of the association between QoL and SBRs.

Drosophila acquires seconds-scale rhythmic behavior

Detection of the temporal structure of stimuli is crucial for prediction. While perception of interval timing is relevant for immediate behavioral adaptations, it has been scarcely investigated, especially in invertebrates. Here we examined if the fruit fly, Drosophila melanogaster, can acquire rhythmic behavior in the range of seconds. To this end, we developed a novel temporal conditioning paradigm utilizing repeated electric shocks. Combined automatic behavioral annotation and time-frequency analysis revealed that behavioral rhythms continued after cessation of the shocks. Furthermore, we found that aging impaired interval timing. This study thus not only demonstrated the ability of insects to acquire behavioral rhythms of a few seconds, but highlighted a life-course decline of temporal coordination, that is common also in mammals.