Data from: Genetic redundancy strengthens the circadian clock leading to a narrow entrainment range

Circadian clocks are internal timekeepers present in almost all organisms. Driven by a genetic network of highly conserved structure, they generate self-sustained oscillations that entrain to periodic external signals such as the 24 h light–dark cycle. Vertebrates possess multiple, functionally overlapping homologues of the core clock genes. Furthermore, vertebrate clocks entrain to a range of periods three times as narrow as that of other organisms. We asked whether genetic redundancies play a role in governing entrainment properties and analysed locomotor activity rhythms of genetically modified mice lacking one set of clock homologues. Exposing them to non-24 h light–dark cycles, we found that the mutant mice have a wider entrainment range than the wild types. Spectral analysis furthermore revealed nonlinear phenomena of periodically forced self-sustained oscillators for which the entrainment range relates inversely to oscillator amplitude. Using the forced oscillator model to explain the observed differences in entrainment range between mutant and wild-type mice, we sought to quantify the overall oscillator amplitude of their clocks from the activity rhythms and found that mutant mice have weaker circadian clocks than wild types. Our results suggest that genetic redundancy strengthens the circadian clock leading to a narrow entrainment range in vertebrates.

昼夜节律钟（Circadian Clock）是几乎所有生物体内均存在的内在计时系统。其由结构高度保守的遗传网络驱动，可产生自主持续的振荡，并能通过24小时明暗周期等周期性外部信号实现节律同步。脊椎动物拥有多套功能相互重叠的核心钟基因同源物。此外，脊椎动物节律钟可同步的周期范围仅为其他生物的三分之一。我们探究了遗传冗余是否参与调控节律同步特性，并分析了缺失一套钟基因同源物的基因修饰小鼠的运动活动节律。将这些小鼠暴露于非24小时明暗周期环境后，我们发现突变型小鼠的节律同步范围较野生型更广。频谱分析进一步揭示了周期性受迫自主持续振荡的非线性现象：此类振荡的节律同步范围与振荡振幅呈负相关。我们利用受迫振荡模型解释突变型与野生型小鼠的节律同步范围差异，尝试通过运动活动节律量化其节律钟的整体振荡振幅，结果发现突变型小鼠的昼夜节律钟强度弱于野生型。本研究结果表明，遗传冗余可增强脊椎动物的昼夜节律钟功能，进而使其节律同步范围更窄。