PDF(Pubmed)
Abstract：
The circadian clock enables anticipation of the day/night cycle in animals ranging from cnidarians to mammals. Circadian rhythms are generated through a transcription-translation feedback loop (TTFL or pacemaker) with CLOCK as a conserved positive factor in animals. However, CLOCK\'s functional evolutionary origin and mechanism of action in basal animals are unknown. In the cnidarian Nematostella vectensis, pacemaker gene transcript levels, including NvClk (the Clock ortholog), appear arrhythmic under constant darkness, questioning the role of NvCLK. Utilizing CRISPR/Cas9, we generated a NvClk allele mutant (NvClkΔ), revealing circadian behavior loss under constant dark (DD) or light (LL), while maintaining a 24 hr rhythm under light-dark condition (LD). Transcriptomics analysis revealed distinct rhythmic genes in wild-type (WT) polypsunder LD compared to DD conditions. In LD, NvClkΔ/Δ polyps exhibited comparable numbers of rhythmic genes, but were reduced in DD. Furthermore, under LD, the NvClkΔ/Δ polyps showed alterations in temporal pacemaker gene expression, impacting their potential interactions. Additionally, differential expression of non-rhythmic genes associated with cell division and neuronal differentiation was observed. These findings revealed that a light-responsive pathway can partially compensate for circadian clock disruption, and that the Clock gene has evolved in cnidarians to synchronize rhythmic physiology and behavior with the diel rhythm of the earth\'s biosphere.
摘要：
昼夜节律时钟能够预测从刺胞动物到哺乳动物的动物的日/夜周期。昼夜节律是通过转录-翻译反馈回路（TTFL或起搏器）产生的，CLOCK是动物中保守的积极因素。然而,CLOCK在基础动物中的功能进化起源和作用机制尚不清楚。在cnidarianNematostellavectensis中，起搏器基因转录水平，包括NvClk（时钟直向序列），在持续的黑暗中出现心律失常，质疑NvCLK的作用。利用CRISPR/Cas9，我们产生了NvClk等位基因突变体（NvClkΔ），揭示恒定黑暗(DD)或光(LL)下的昼夜节律行为损失，同时在明暗条件（LD）下保持24小时的节律。转录组学分析显示，与DD条件相比，野生型（WT）息肉在LD中具有不同的节律基因。在LD,NvClkΔ/Δ息肉表现出相当数量的节律基因，但在DD中减少。此外，在LD下,NvClkΔ/Δ息肉表现出颞起搏器基因表达的改变，影响他们潜在的互动。此外,观察到与细胞分裂和神经元分化相关的非节律基因的差异表达。这些发现表明，光响应通路可以部分补偿昼夜节律的中断，时钟基因在刺胞动物中进化，使有节奏的生理和行为与地球生物圈的diel节奏同步。
