Precision of a Mammalian Circadian Clock

Sharma, Vijay Kumar; Chandrashekaran, M. K.

doi:10.1007/s001140050628

Cited by 18 publications

(7 citation statements)

References 7 publications

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“…Several earlier studies reported correlation of circadian period with rhythm precision (a measure of intercycle period stability). They suggested that precision of circadian rhythms is high when the circadian period is closer to 24 h and decreases as period deviates from 24 h, but mostly at the organismal level and within the pacemaker SCN neurons [37][38][39][40][41][42]. In addition, we find that long circadian periods are largely noise driven as compared to short periods.…”

Section: Precision Of Circadian Rhythm Decreases With Increasing Periodmentioning

confidence: 56%

“…Reports by Aschoff [ 37 ] as well as Pittendrigh and Daan [ 38 ] led the latter to hypothesize that circadian rhythms are most stable as the endogenous period (τ) approaches 24 h, whereas deviation of τ from 24 h leads to reduction in rhythm stability and provided an evolutionary reasoning for such a hypothesis. This observation of rhythm stability being the lowest at a particular τ has since been substantiated by studies on various species [ 39 , 41 , 42 ], including the pacemaker SCN neurons [ 40 ], but others have reported either weak or absence of such trends [ 52 , 53 ]. To assess whether such correlation is observed mostly at the level of organisms and central pacemaker neurons or is a general property even for peripheral oscillator cells, we measured the intercycle variation in period across our clonal populations.…”

Section: Discussionmentioning

confidence: 80%

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Heritable gene expression variability and stochasticity govern clonal heterogeneity in circadian period

2020

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A ubiquitous feature of the circadian clock across life forms is its organization as a network of cellular oscillators, with individual cellular oscillators within the network often exhibiting considerable heterogeneity in their intrinsic periods. The interaction of coupling and heterogeneity in circadian clock networks is hypothesized to influence clock's entrainability, but our knowledge of mechanisms governing period heterogeneity within circadian clock networks remains largely elusive. In this study, we aimed to explore the principles that underlie intercellular period variation in circadian clock networks (clonal period heterogeneity). To this end, we employed a laboratory selection approach and derived a panel of 25 clonal cell populations exhibiting circadian periods ranging from 22 to 28 h. We report that a single parent clone can produce progeny clones with a wide distribution of circadian periods, and this heterogeneity, in addition to being stochastically driven, has a heritable component. By quantifying the expression of 20 circadian clock and clock-associated genes across our clone panel, we found that inheritance of expression patterns in at least three clock genes might govern clonal period heterogeneity in circadian clock networks. Furthermore, we provide evidence suggesting that heritable epigenetic variation in gene expression regulation might underlie period heterogeneity.

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Section: Precision Of Circadian Rhythm Decreases With Increasing Periodmentioning

confidence: 56%

Section: Discussionmentioning

confidence: 80%

Heritable gene expression variability and stochasticity govern clonal heterogeneity in circadian period

2020

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“…Since accuracy or precision of circadian clocks in assessing time in the local environment is likely to be closely related to fitness, it is critical to study its genetic variability in natural populations. Previous studies on wild-type animals with different clock periods reported a correlation between precision and circadian period (Pittendrigh and Daan, 1976; Sharma and Chandrashekaran, 1999); however, such a correlation was not seen in mutant strains of animals with distinctly different periods (Bittman, 2012). …”

Section: Introductionmentioning

confidence: 80%

“…The stability of circadian timekeeping in the face of fluctuating internal as well as external environments is likely to confer organisms with adaptive advantages (Daan, 2000). Therefore, precision of circadian clocks, which is key to their functioning as reliable timekeepers, is believed to be under the influence of selection pressures of the environment (Sharma and Chandrashekaran, 1999; Clodong et al, 2007). …”

Section: Introductionmentioning

confidence: 99%

Selection for narrow gate of emergence results in correlated sex-specific changes in life history of Drosophila melanogaster

2014

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Since the ability to time rhythmic behaviours in accordance with cyclic environments is likely to confer adaptive advantage to organisms, the underlying clocks are believed to be selected for stability in timekeeping over evolutionary time scales. Here we report the results of a study aimed at assessing fitness consequences of a long-term laboratory selection for tighter circadian organisation using fruit fly Drosophila melanogaster populations. We selected flies emerging in a narrow window of 1 h in the morning for several generations and assayed their life history traits such as pre-adult development time, survivorship, adult lifespan and lifetime fecundity. We chose flies emerging during the selection window (in the morning) and another window (in the evening) to represent adaptive and non-adaptive phenotypes, respectively, and examined the correlation of emergence time with adult fitness traits. Adult lifespan of males from the selected populations does not differ from the controls, whereas females from the selected populations have significantly shorter lifespan and produce more eggs during their mid-life compared to the controls. Although there is no difference in the lifespan of males of the selected populations, whether they emerge in morning or evening window, morning emerging females live slightly shorter and lay more eggs during the mid-life stage compared to those emerging in the evening. Interestingly, such a time of emergence dependent difference in fitness is not seen in flies from the control populations. These results, therefore, suggest reduced lifespan and enhanced mid-life reproductive output in females selected for narrow gate of emergence, and a sex-dependent genetic correlation between the timing of emergence and key fitness traits in these populations.

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“…Furthermore, findings from some studies show association between circadian period close to 24 h and higher precision, suggesting that stability in circadian entrainment contributes to the evolution of circadian clocks in the face of cyclic fluctuations in nature [18]–[20]. To critically examine this, we carried out a laboratory selection study, where we imposed selection for adult emergence in a narrow window of time.…”

Section: Introductionmentioning

confidence: 99%

Stability of Adult Emergence and Activity/Rest Rhythms in Fruit Flies Drosophila melanogaster under Semi-Natural Condition

Kannan

Varma

et al. 2012

PLoS ONE

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Here we report the results of a study aimed at examining stability of adult emergence and activity/rest rhythms under semi-natural conditions (henceforth SN), in four large outbred fruit fly Drosophila melanogaster populations, selected for emergence in a narrow window of time under laboratory (henceforth LAB) light/dark (LD) cycles. When assessed under LAB, selected flies display enhanced stability in terms of higher amplitude, synchrony and accuracy in emergence and activity rhythms compared to controls. The present study was conducted to assess whether such differences in stability between selected and control populations, persist under SN where several gradually changing time-cues are present in their strongest form. The study revealed that under SN, emergence waveform of selected flies was modified, with even more enhanced peak and narrower gate-width compared to those observed in the LAB and compared to control populations in SN. Furthermore, flies from selected populations continued to exhibit enhanced synchrony and accuracy in their emergence and activity rhythms under SN compared to controls. Further analysis of zeitgeber effects revealed that enhanced stability in the rhythmicity of selected flies under SN was primarily due to increased sensitivity to light because emergence and activity rhythms of selected flies were as stable as controls under temperature cycles. These results thus suggest that stability of circadian rhythms in fruit flies D. melanogaster, which evolved as a consequence of selection for emergence in a narrow window of time under weak zeitgeber condition of LAB, persists robustly in the face of day-to-day variations in cycling environmental factors of nature.

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Precision of a Mammalian Circadian Clock

Cited by 18 publications

References 7 publications

Heritable gene expression variability and stochasticity govern clonal heterogeneity in circadian period

Heritable gene expression variability and stochasticity govern clonal heterogeneity in circadian period

Selection for narrow gate of emergence results in correlated sex-specific changes in life history of Drosophila melanogaster

Stability of Adult Emergence and Activity/Rest Rhythms in Fruit Flies Drosophila melanogaster under Semi-Natural Condition

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