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The algebra of sleepiness: investigating the interaction of homeostatic (S) and circadian (C) processes in sleepiness using linear metrics” Vrije Universiteit Brussel KU Leuven

Olivier Mairesse, Joeri Hofmans, Daniel Neu, Armando Luis Dinis De Oliveira, Raymond Cluydts, Peter Theuns
The present studies were conducted to contribute to the debate on the interaction between circadian (C) and homeostatic (S) processes in models of sleep regulation. The Two-Process Model of Sleep Regulation assumes a linear relationship between processes S and C. However, recent elaborations of the model, based on data from forced desynchrony studies, suggest a nonlinear interaction between both processes. Whether this interaction is due to an ...

Interaction between photoperiod and variation in circadian rhythms in tomato Ghent University Flanders Institute for Biotechnology

Yanli Xiang, Thomas Sapir, Pauline Rouillard, Marina Ferrand, JM Jiménez-Gómez
Background: Many biological processes follow circadian rhythmicity and are controlled by the circadian clock. Predictable environmental changes such as seasonal variation in photoperiod can modulate circadian rhythms, allowing organisms to adjust the timing of their biological processes to the time of the year. In some crops such as rice, barley or soybean, mutations in circadian clock genes have altered photoperiod sensitivity, enhancing their ...

Placental circadian pathway methylation and in utero exposure to fine particle air pollution Hasselt University KU Leuven

Tim NAWROT, Nelly SAENEN, Julie SCHENK, Bram JANSSEN, Valeria Motta, Letizia Tarantini, Bianca COX, Wouter Lefebvre, Charlotte Vanpoucke, Cristina Maggioni, et al.
In mammals, a central clock maintains the daily rhythm in accordance with the external environment. At the molecular level, the circadian rhythm is maintained by epigenetic regulation of the Circadian pathway. Here, we tested the role of particulate matter with an aerodynamic diameter <= 2.5 mu m (PM2.5) exposure during gestational life on human placental Circadian pathway methylation, as an important molecular target for healthy development. ...

A systematic survey in Arabidopsis thaliana of transcription factors that modulate circadian parameters Institute of Tropical Medicine

Shigeru Hanano, Ralf Stracke, Marc Jakoby, Thomas Merkle, Malgorzata Domagalska, Bernd Weisshaar, Seth J Davis

BACKGROUND: Plant circadian systems regulate various biological processes in harmony with daily environmental changes. In Arabidopsis thaliana, the underlying clock mechanism is comprised of multiple integrated transcriptional feedbacks, which collectively lead to global patterns of rhythmic gene expression. The transcriptional networks are essential within the clock itself and in its output pathway.

RESULTS: Here, to expand ...

Altered circadian profiles in attention-deficit/hyperactivity disorder Vrije Universiteit Brussel Ghent University University of Antwerp

Lindita Imeraj, Edmund Sonuga-Barke, Inge Antrop, Herbert Roeyers, Roeljan Wiersema, Sarah Bal, Dirk Deboutte

Disruptions in the sleep-wake cycle and the circadian system have been found in a wide range of psychiatric disorders and are generally correlated with clinical severity and diminished quality of life. Emerging evidence suggests similar disturbances may be found in attention-deficit/hyperactivity disorder (ADHD). Here we review the available literature on across the day fluctuations in ADHD-related processes in terms of; (i) time of day ...

XAP5 circadian timekeeper regulates ethylene responses in aerial tissues of Arabidopsis Ghent University

Cory T Ellison, Filip Vandenbussche, Dominique Van Der Straeten, Stacey L Harmer
The phytohormone ethylene differentially regulates plant architecture and growth in both a light-and nutrient-dependent fashion. The modulation of plant development by ethylene in response to both external and internal signals can also generate tissue-specific differential responses. Here, we report that XAP5 CIRCADIAN TIMEKEEPER (XCT) is involved in blue light-dependent ethylene responses in the aerial tissues of Arabidopsis (Arabidopsis ...

Histone H2B monoubiquitination is required to reach maximal transcript levels of circadian clock genes in Arabidopsis Ghent University

Kristiina Himanen, Magdalena Woloszynska, Tommaso M Boccardi, Steven De Groeve, Hilde Nelissen, Leonardo Bruno, Marnik Vuylsteke, Maria Van Lijsebettens
Previously, we identified HISTONE MONOUBIQUITINATION1 (HUB1) as an unconventional ubiquitin E3 ligase that is not involved in protein degradation but in the histone H2B modification that is implicated in transcriptional activation in plants. HUB1-mediated regulation of gene expression played a role in periodic and inducible processes such as the cell cycle, dormancy, flowering time and defense responses. Here, we determined the effects of the ...

Glia on a Mission Their Role in Sleep and Circadian Rhythms as Connectors KU Leuven

Joana Dopp
Sleep, an omnipresent behaviour spanning the animal kingdom, is mostly investigated from a behavioural and cell network perspective. Since rest-states are observed also in animals with different organizations of the nervous system, questions arise as to whether we can find molecular correlates of sleep at a smaller unit: an individual cell, and if such correlates are different depending on the cell's identity. Through a comprehensive and ...

Timekeeping in the gastrointestinal tract: circadian regulation of ghrelin secretion and feeding by the clock gen Bmal1 KU Leuven

Jorien Laermans
The daily rotation of the earth around its axis creates a recurring succession of day and night with a period of 24 hours. As a consequence, life on earth is subjected to cyclical and therefore predictable changes in environmental conditions. In order to anticipate these daily events and fine-tune physiology to the varying demands of activity and rest, virtually all organisms have developed an internal timekeeping system. Circadian rhythms, ...