Castellana Stefano, Mazza Tommaso, Capocefalo Daniele, Genov Nikolai, Biagini Tommaso, Fusilli Caterina, Scholkmann Felix, Relógio Angela, Hogenesch John B, Mazzoccoli Gianluigi
Bioinformatics Unit, IRCCS "Casa Sollievo della Sofferenza", San Giovanni Rotondo, Italy.
Institute for Theoretical Biology (ITB), Charité - Universitätsmedizin Berlin and Humboldt University of Berlin, Berlin, Germany.
Front Physiol. 2018 Aug 23;9:1178. doi: 10.3389/fphys.2018.01178. eCollection 2018.
In living organisms, biological clocks regulate 24 h (circadian) molecular, physiological, and behavioral rhythms to maintain homeostasis and synchrony with predictable environmental changes, in particular with those induced by Earth's rotation on its axis. Harmonics of these circadian rhythms having periods of 8 and 12 h (ultradian) have been documented in several species. In mouse liver, harmonics of the 24-h period of gene transcription hallmarked genes oscillating with a frequency two or three times faster than circadian periodicity. Many of these harmonic transcripts enriched pathways regulating responses to environmental stress and coinciding preferentially with subjective dawn and dusk. At this time, the evolutionary history of genes with rhythmic expression is still poorly known and the role of length-of-day changes due to Earth's rotation speed decrease over the last four billion years is totally ignored. We hypothesized that ultradian and stress anticipatory genes would be more evolutionarily conserved than circadian genes and background non-oscillating genes. To investigate this issue, we performed broad computational analyses of genes/proteins oscillating at different frequency ranges across several species and showed that ultradian genes/proteins, especially those oscillating with a 12-h periodicity, are more likely to be of ancient origin and essential in mice. In summary, our results show that genes with ultradian transcriptional patterns are more likely to be phylogenetically conserved and associated with the primeval and inevitable dawn/dusk transitions.
在生物体中，生物钟调节24小时（昼夜节律）的分子、生理和行为节律，以维持体内平衡并与可预测的环境变化同步，特别是与地球自转轴旋转引起的变化同步。在几个物种中已记录到这些昼夜节律的8小时和12小时周期（超日节律）的谐波。在小鼠肝脏中，基因转录24小时周期的谐波标记了那些以比昼夜节律周期快两到三倍的频率振荡的基因。许多这些谐波转录本丰富了调节对环境应激反应的途径，并且优先与主观黎明和黄昏一致。此时，具有节律性表达的基因的进化历史仍然知之甚少，并且在过去四十亿年中由于地球自转速度降低导致的日长变化的作用完全被忽视。我们假设超日节律和应激预期基因比昼夜节律基因和背景非振荡基因在进化上更保守。为了研究这个问题，我们对几个物种中在不同频率范围内振荡的基因/蛋白质进行了广泛的计算分析，结果表明超日节律基因/蛋白质，特别是那些以12小时周期振荡的基因/蛋白质，更有可能起源古老且对小鼠至关重要。总之，我们的结果表明，具有超日节律转录模式的基因在系统发育上更有可能保守，并且与原始且不可避免的黎明/黄昏转变相关。
