Light entrainment of the circadian clock: identifying natural molecular adaptations

生物钟的光夹带：识别自然分子适应

• 批准号: BB/G02085X/1
• 负责人: Eran Tauber
• 金额: $ 37.42万
• 依托单位: University of Leicester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FG02085X%2F1
• 关键词: Light; entrainment; circadian; clock; identifying

Circadian clocks are molecular pacemakers that drive daily rhythms in physiology, metabolism, behaviour and other process, and are present in diverse range of organism, from cyanobacteria to human. When detached from ambient cues, circadian clock cycle ('freerun') at periods slightly different from 24 hr. This endogenous rhythm is adjusted to the 24 hr solar day by entrainment to various stimuli, primarily light. Modern life introduces situations, such as trans-atlantic flights and shift work, where the circadian rhythm and the external light cycle are too dissimilar to reconcile; accumulating evidence suggests that people exposed repeatedly to such disruptions suffer from wide range of health problems, including 'jetlag', sleep disorders, seasonal depression, and cancer. In the last few decades, a great deal has been learned about the molecular details of the clock. Drosophila has been instrumental in identifying circadian clock genes, which are well conserved in mammals, both in sequence and function. By inducing mutagenesis and screening for Drosophila mutants that show aberrant light response, two proteins were identified to be involved in light transduction: TIMELESS (TIM), which is a circadian light-sensitive core-clock protein, and CRYPTOCHROME (CRY), a dedicated blue-light photoreceptor of the circadian system. These two proteins interact with each other, and light-activated CRY attaches itself to TIM, degrading it rapidly. Our research at the University of Leicester focuses on natural genetic variation related to circadian photo-responsiveness. Rather than inducing random mutations, we aim to understand the clock mechanism by identifying natural variants, or natural clock alleles that have been evolved in different wild populations, serving as molecular adaptations under different light and temperature conditions. In collaboration with CPK and ER at Leicester and the Costa lab at Padova, we have identified a natural polymorphism in Timeless that involves a single-base insertion/deletion, situated between two alternative translation starts. We have found that this polymorphism follows a robust latitudinal cline and is maintained by directional selection. We subsequently tested natural isolates and transformants flies and found that photo-responsiveness is significantly different between flies with the different alleles. This difference was correlated with the variation we have observed in the photoperiodic response of flies with the different alleles suggesting that this polymorphism represents molecular adaptation to cold environments. Recently, another protein named JETLAG (JET) has been identified as being involved in light-induced degradation of TIM. Interestingly, it turns out that the phenotype of jet mutants is only expressed in strains carrying a specific natural tim allele. These discoveries have demonstrated how natural genetic variation modulates light sensitivity of the circadian clock, and how in turn, could the better characterization of natural adaptations lead to a better understanding of the circadian-clock mechanism. The current proposal is aimed at identifying natural variation in clock genes by testing strains derived from wild-populations, using tools of quantitative genetics combined with molecular techniques. We propose to use various genome-wide screens to identify these variations, including Quantitative Trait Loci (QTL) mapping, artificial selection and global expression analysis. Our preliminary QTL screen indicated four genomic regions (QTLs) that show significant contribution to variation in circadian light-sensitivity. By using various deficiency and mutant strains we will carry complementation tests that will allow us to identify the causal sequence variations that account for these variations. The results of this study will allow a better understanding of light entrainment of the clock, and provide candidate genes for studying in mammals, including human.

生物钟是一种分子起搏器，在生理、新陈代谢、行为和其他过程中驱动日常节奏，存在于从蓝藻到人类的各种生物体中。当脱离环境提示时，昼夜时钟周期(‘freerun’)的周期与24小时略有不同。这种内源节律通过对各种刺激(主要是光)的夹带来调节到24小时的太阳日。现代生活中出现了一些情况，比如跨越大西洋的航班和倒班工作，这些情况下的昼夜节律和外部光周期太不相似，无法调和；越来越多的证据表明，反复暴露在这种干扰下的人会患上广泛的健康问题，包括时差、睡眠障碍、季节性抑郁症和癌症。在过去的几十年里，关于钟的分子细节已经了解了很多。果蝇在识别生物钟基因方面发挥了重要作用，这些基因在哺乳动物中非常保守，在序列和功能上都是如此。通过诱导突变和筛选表现出异常光反应的果蝇突变体，两种蛋白质被鉴定参与光转导：TIM是昼夜节律光敏感的核心时钟蛋白，隐花色素(CRY)是昼夜节律系统的专用蓝光感受器。这两种蛋白质相互作用，光激活的CRY附着在Tim上，迅速将其降解。我们在莱斯特大学的研究重点是与昼夜照相反应相关的自然遗传变异。我们的目标不是诱导随机突变，而是通过识别在不同野生种群中进化的自然变异或自然时钟等位基因，作为不同光和温度条件下的分子适应，来了解时钟机制。在与莱斯特的CPK和ER以及Padova的Costa实验室的合作下，我们已经确定了Timless的一个自然多态，它涉及一个单碱基插入/缺失，位于两个可选的翻译开始之间。我们发现，这种多态遵循一个强大的纬度跃变，并通过定向选择保持。我们随后对自然分离株和转基因果蝇进行了测试，发现不同等位基因的果蝇对光的反应能力有显着差异。这种差异与我们观察到的具有不同等位基因的果蝇光周期反应的差异有关，表明这种多态代表了分子对寒冷环境的适应。最近，另一种名为JetLag(JET)的蛋白质被发现与光诱导的TIM降解有关。有趣的是，JET突变体的表型只在携带特定天然TIM等位基因的菌株中表达。这些发现展示了自然遗传变异是如何调节生物钟的光敏感度的，而反过来，更好地描述自然适应如何能够更好地理解生物钟机制。目前的建议旨在通过使用数量遗传学和分子技术相结合的工具，通过测试来自野生种群的菌株来识别时钟基因的自然变异。我们建议使用各种全基因组筛选来识别这些变异，包括数量性状基因座(QTL)定位、人工选择和全局表达分析。我们的初步QTL筛选显示了四个基因组区域(QTL)，它们对昼夜节律光敏感度的变化有显著贡献。通过使用各种缺陷型和突变型菌株，我们将进行互补测试，这将使我们能够识别导致这些变异的因果序列变异。这项研究的结果将使我们更好地了解时钟的光携带，并为包括人类在内的哺乳动物的研究提供候选基因。

项目成果

Natural variation in cryptochrome in wild populations of Drosophila

果蝇野生种群隐花色素的自然变异

• 作者: Eran Tauber (Author)

Is the circadian clock required for seasonal timing?

季节性计时是否需要生物钟？

• 作者: Eran Tauber (Co-Author)

Identification and functional analysis of early gene expression induced by circadian light-resetting in Drosophila.

• DOI: 10.1186/s12864-015-1787-7
• 发表时间: 2015-08-01
• 期刊: BMC genomics
• 影响因子: 4.4
• 作者: Adewoye AB;Kyriacou CP;Tauber E
• 通讯作者: Tauber E

Interspecific studies of circadian genes period and timeless in Drosophila.

• DOI: 10.1016/j.gene.2018.01.020
• 发表时间: 2018-03-30
• 期刊: Gene
• 影响因子: 3.5
• 作者: Noreen S;Pegoraro M;Nouroz F;Tauber E;Kyriacou CP
• 通讯作者: Kyriacou CP

Quantitative trait loci mapping of circadian photosensitivity in Drosophila

果蝇昼夜节律光敏性的数量性状位点定位

• 作者: Eran Tauber (Co-Author)