Life time—circadian clocks,mitochondria and metabolism

A functional circadian clock has long been considered a selective advantage. Accumulating evidence shows that the clock coordinates a variety of physiological processes in order to schedule them to the optimal time of day and thus to synchronize metabolism to changes in external conditions. In mitochondria, both metabolic and cellular defense mechanisms are carefully regulated. Abnormal clock function, might influence mitochondrial function, resulting in decreased fitness of an organism.     

Life time—circadian clocks, mitochondria and metabolism

A functional circadian clock has long been considered a selective advantage. Accumulating evidence shows that the clock coordinates a variety of physiological processes in order to schedule them to the optimal time of day and thus to synchronize metabolism to changes in external conditions. In mitochondria, both metabolic and cellular defense mechanisms are carefully regulated. Abnormal clock function, might influence mitochondrial function, resulting in decreased fitness of an organism.     

Life time-circadian clocks, mitochondria and metabolism

A functional circadian clock has long been considered a selective advantage. Accumulating evidence shows that the clock coordinates a variety of physiological processes in order to schedule them to the optimal time of day and thus to synchronize metabolism to changes in external conditions. In mitochondria, both metabolic and cellular defense mechanisms are carefully regulated. Abnormal clock function, might influence mitochondrial function, resulting in decreased fitness of an organism.     

Commentary: the year in circadian rhythms

The circadian clock orchestrates intrinsic timing in most organisms and controls a large variety of physiological and metabolic programs. In my presentation "The Year in Circadian Rhythms" at the Endocrine Society meeting (San Diego, June 2010) I reviewed some of the recent spectacular developments of the field. The exceptional interest that circadian rhythms have suscitated during the past two decades has caused a remarkable increase in the number of researchers and of committed resources dedicated to the field. This has also generated the promise of potentially novel pharmacological strategies. Indeed, specific molecular pathways of circadian regulation have been recently linked to endocrine and metabolic control, as well as cell cycle and proliferation. Importantly, circadian gene expression involves an important proportion of cellular genes, underscoring the role played by dynamic mechanisms of chromatin remodeling. This suggests that the circadian machinery could have evolved as a privileged molecular interface between cellular metabolism and epigenetic control.     

高等植物中SWI/SNF染色质重塑研究的新进展

染色质重塑是真核生物表观遗传调控的重要方式．通过对染色质物理结构的调节,染色质重塑在高等动植物干细胞的自我更新及分化、器官和个体发育以及肿瘤发生等多种生物学过程中发挥重要作用．近年来,高等动植物染色质重塑方面的研究已经成为表观遗传学研究领域的热点．本综述总结近年来有关高等动植物染色质重塑的重要研究报道,介绍了染色质重塑的结构机制、分析比较了高等动植物染色质重塑复合体的组成及其生物学功能的多样性,并着重综述了高等植物SWI/SNF染色质重塑复合体各组分在调控植物发育与逆境生长等方面的功能,以期为今后植物中染色质重塑的研究提供启示．     

Lamarck rises from his grave: parental environment‐induced epigenetic inheritance in model organisms and humans

Organisms can change their physiological/behavioural traits to adapt and survive in changed environments. However, whether these acquired traits can be inherited across generations through non‐genetic alterations has been a topic of debate for over a century. Emerging evidence indicates that both ancestral and parental experiences, including nutrition, environmental toxins, nurturing behaviour, and social stress, can have powerful effects on the physiological, metabolic and cellular functions in an organism. In certain circumstances, these effects can be transmitted across several generations through epigenetic (i.e. non‐DNA sequence‐based rather than mutational) modifications. In this review, we summarize recent evidence on epigenetic inheritance from parental environment‐induced developmental and physiological alterations in nematodes, fruit flies, zebrafish, rodents, and humans. The epigenetic modifications demonstrated to be both susceptible to modulation by environmental cues and heritable, including DNA methylation, histone modification, and small non‐coding RNAs, are also summarized. We particularly focus on evidence that parental environment‐induced epigenetic alterations are transmitted through both the maternal and paternal germlines and exert sex‐specific effects. The thought‐provoking data presented here raise fundamental questions about the mechanisms responsible for these phenomena. In particular, the means that define the specificity of the response to parental experience in the gamete epigenome and that direct the establishment of the specific epigenetic change in the developing embryos, as well as in specific tissues in the descendants, remain obscure and require elucidation. More precise epigenetic assessment at both the genome‐wide level and single‐cell resolution as well as strategies for breeding at relatively sensitive periods of development and manipulation aimed at specific epigenetic modification are imperative for identifying parental environment‐induced epigenetic marks across generations. Considering their diverse epigenetic architectures, the conservation and prevalence of the mechanisms underlying epigenetic inheritance in non‐mammals require further investigation in mammals. Interpretation of the consequences arising from epigenetic inheritance on organisms and a better understanding of the underlying mechanisms will provide insight into how gene–environment interactions shape developmental processes and physiological functions, which in turn may have wide‐ranging implications for human health, and understanding biological adaptation and evolution.     

The coupling of epigenome replication with DNA replication

In multicellular organisms, each cell contains the same DNA sequence, but with different epigenetic information that determines the cell specificity. Semi-conservative DNA replication faithfully copies the parental nucleotide sequence into two DNA daughter strands during each cell cycle. At the same time, epigenetic marks such as DNA methylation and histone modifications are either precisely transmitted to the daughter cells or dynamically changed during S-phase. Recent studies indicate that in each cell cycle, many DNA replication related proteins are involved in not only genomic but also epigenomic replication. Histone modification proteins, chromatin remodeling proteins, histone variants, and RNAs participate in the epigenomic replication during S-phase. As a consequence, epigenome replication is closely linked with DNA replication during S-phase.     

Perfect timing: epigenetic regulation of the circadian clock

In mammals, higher order chromatin structures are critical for downsizing the genome (packaging) so that the nucleus can be small. The adjustable density of chromatin also regulates gene expression, thus this post-genetic molecular mechanism is one of the routes by which phenotype is shaped. Phenotypes that arise without a concomitant mutation of the underlying genome are termed epigenetic phenomena. Here we discuss epigenetic phenomena from histone and DNA modification as it pertains to the dynamic regulatory processes of the circadian clock. Epigenetic phenomena certainly explain some regulatory aspects of the mammalian circadian oscillator.     

CHD7对发育和疾病的表观遗传调控研究进展

染色质重塑是指染色质通过其结构的动态变化影响基因组DNA的可接近性,进而影响DNA复制、转录、修复和重组的过程,属于表观遗传调控。染色质域解旋酶DNA结合蛋白7(CHD7)是一种ATP依赖的染色质重塑酶,能够调控发育过程中多种重要转录因子,广泛参与众多生理过程。本文对CHD7在发育和疾病当中的表观遗传调控作用进行简要概述。