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Wegener C, Amatobi KM, Ozbek-Unal AG, Fekete A. Circadian Control of Lipid Metabolism. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024. [PMID: 38874889 DOI: 10.1007/5584_2024_810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2024]
Abstract
To ensure optimum health and performance, lipid metabolism needs to be temporally aligned to other body processes and to daily changes in the environment. Central and peripheral circadian clocks and environmental signals such as light provide internal and external time cues to the body. Importantly, each of the key organs involved in insect lipid metabolism contains a molecular clockwork which ticks with a varying degree of autonomy from the central clock in the brain. In this chapter, we review our current knowledge about peripheral clocks in the insect fat body, gut and oenocytes, and light- and circadian-driven diel patterns in lipid metabolites and lipid-related transcripts. In addition, we highlight selected neuroendocrine signaling pathways that are or may be involved in the temporal coordination and control of lipid metabolism.
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Affiliation(s)
- Christian Wegener
- Neurobiology and Genetics, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg, Germany.
| | - Kelechi M Amatobi
- Neurobiology and Genetics, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg, Germany
| | - Ayten Gizem Ozbek-Unal
- Pharmaceutical Biology, Julius-von-Sachs-Institute, Biocenter, University of Würzburg, Würzburg, Germany
| | - Agnes Fekete
- Pharmaceutical Biology, Julius-von-Sachs-Institute, Biocenter, University of Würzburg, Würzburg, Germany
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2
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Cruz LNPD, Teles-de-Freitas R, Resck MEB, Fonseca ABDA, Padilha KP, Farnesi LC, Araripe LO, Bruno RV. Light and dark cycles modify the expression of clock genes in the ovaries of Aedes aegypti in a noncircadian manner. PLoS One 2023; 18:e0287237. [PMID: 37856474 PMCID: PMC10586701 DOI: 10.1371/journal.pone.0287237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 06/02/2023] [Indexed: 10/21/2023] Open
Abstract
Circadian oscillators (i.e., circadian clocks) are essential to producing the circadian rhythms observed in virtually all multicellular organisms. In arthropods, many rhythmic behaviors are generated by oscillations of the central pacemaker, specific groups of neurons of the protocerebrum in which the circadian oscillator molecular machinery is expressed and works; however, oscillators located in other tissues (i.e., peripheral clocks) could also contribute to certain rhythms, but are not well known in non-model organisms. Here, we investigated whether eight clock genes that likely constitute the Aedes aegypti clock are expressed in a circadian manner in the previtellogenic ovaries of this mosquito. Also, we asked if insemination by conspecific males would alter the expression profiles of these clock genes. We observed that the clock genes do not have a rhythmic expression profile in the ovaries of virgin (VF) or inseminated (IF) females, except for period, which showed a rhythmic expression profile in ovaries of IF kept in light and dark (LD) cycles, but not in constant darkness (DD). The mean expression of seven clock genes was affected by the insemination status (VF or IF) or the light condition (LD 12:12 or DD), among which five were affected solely by the light condition, one solely by the insemination status, and one by both factors. Our results suggest that a functional circadian clock is absent in the ovaries of A. aegypti. Still, their differential mean expression promoted by light conditions or insemination suggests roles other than circadian rhythms in this mosquito's ovaries.
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Affiliation(s)
| | - Rayane Teles-de-Freitas
- Laboratório de Biologia Molecular de Insetos, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro- RJ, Brazil
| | - Maria Eduarda Barreto Resck
- Laboratório de Biologia Molecular de Insetos, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro- RJ, Brazil
| | | | - Karine Pedreira Padilha
- Laboratório de Biologia Molecular de Insetos, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro- RJ, Brazil
| | - Luana Cristina Farnesi
- Laboratório de Biologia Molecular de Insetos, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro- RJ, Brazil
| | - Luciana Ordunha Araripe
- Laboratório de Biologia Molecular de Insetos, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro- RJ, Brazil
| | - Rafaela Vieira Bruno
- Laboratório de Biologia Molecular de Insetos, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro- RJ, Brazil
- Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular (INCT-EM), CNPq, Rio de Janeiro- RJ, Brazil
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3
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Zhao J, Warman G, Cheeseman J. The Development and Decay of the Circadian Clock in Drosophila melanogaster. Clocks Sleep 2020; 1:489-500. [PMID: 33089181 PMCID: PMC7445846 DOI: 10.3390/clockssleep1040037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Accepted: 11/15/2019] [Indexed: 12/28/2022] Open
Abstract
The way in which the circadian clock mechanism develops and decays throughout life is interesting for a number of reasons and may give us insight into the process of aging itself. The Drosophila model has been proven invaluable for the study of the circadian clock and development and aging. Here we review the evidence for how the Drosophila clock develops and changes throughout life, and present a new conceptual model based on the results of our recent work. Firefly luciferase lines faithfully report the output of known clock genes at the central clock level in the brain and peripherally throughout the whole body. Our results show that the clock is functioning in embryogenesis far earlier than previously thought. This central clock in the fly remains robust throughout the life of the animal and only degrades immediately prior to death. However, at the peripheral (non-central oscillator level) the clock shows weakened output as the animal ages, suggesting the possibility of the breakdown in the cohesion of the circadian network.
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Affiliation(s)
- Jia Zhao
- Department of Anaesthesiology, School of Medicine, Faculty of Medical and Health Sciences, The University of Auckland, Auckland 1142, New Zealand; (J.Z.); (G.W.)
| | - Guy Warman
- Department of Anaesthesiology, School of Medicine, Faculty of Medical and Health Sciences, The University of Auckland, Auckland 1142, New Zealand; (J.Z.); (G.W.)
| | - James Cheeseman
- Department of Anaesthesiology, School of Medicine, Faculty of Medical and Health Sciences, The University of Auckland, Auckland 1142, New Zealand; (J.Z.); (G.W.)
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4
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Zhao J, Warman GR, Cheeseman JF. The functional changes of the circadian system organization in aging. Ageing Res Rev 2019; 52:64-71. [PMID: 31048031 DOI: 10.1016/j.arr.2019.04.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Revised: 04/14/2019] [Accepted: 04/24/2019] [Indexed: 01/12/2023]
Abstract
The circadian clock drives periodic oscillations at different levels of an organism from genes to behavior. This timing system is highly conserved across species from insects to mammals and human beings. The question of how the circadian clock is involved in the aging process continues to attract more attention. We aim to characterize the detrimental impact of aging on the circadian clock organization. We review studies on different components of the circadian clock at the central and periperal levels, and their changes in aged rodents and humans, and the fruit fly Drosophila. Intracellular signaling, cellular activity and intercellular coupling in the central pacemaker have been found to decline with advancing age. Evidence of degradation of the molecular clockwork reflected by clock gene expression in both central and peripheral oscillators due to aging is inadequate. The findings on age-associated molecular and functional changes of peripheral clocks are mixed. We conclude that aging can affect the circadian clock organization at various levels, and the impairment of the central network may be a fundamental mechanism of circadian disruption seen in aged species.
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Zhao J, Warman GR, Stanewsky R, Cheeseman JF. Development of the Molecular Circadian Clock and Its Light Sensitivity in Drosophila Melanogaster. J Biol Rhythms 2019; 34:272-282. [PMID: 30879378 DOI: 10.1177/0748730419836818] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The importance of the circadian clock for the control of behavior and physiology is well established but how and when it develops is not fully understood. Here the initial expression pattern of the key clock gene period was recorded in Drosophila from embryos in vivo, using transgenic luciferase reporters. PERIOD expression in the presumptive central-clock dorsal neurons started to oscillate in the embryo in constant darkness. In behavioral experiments, a single 12-h light pulse given during the embryonic stage synchronized adult activity rhythms, implying the early development of entrainment mechanisms. These findings suggest that the central clock is functional already during embryogenesis. In contrast to central brain expression, PERIOD in the peripheral cells or their precursors increased during the embryonic stage and peaked during the pupal stage without showing circadian oscillations. Its rhythmic expression only initiated in the adult. We conclude that cyclic expression of PERIOD in the central-clock neurons starts in the embryo, presumably in the dorsal neurons or their precursors. It is not until shortly after eclosion when cyclic and synchronized expression of PERIOD in peripheral tissues commences throughout the animal.
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Affiliation(s)
- Jia Zhao
- Department of Anaesthesiology, School of Medicine, University of Auckland, Auckland, 1142 New Zealand
| | - Guy Robert Warman
- Department of Anaesthesiology, School of Medicine, University of Auckland, Auckland, 1142 New Zealand
| | - Ralf Stanewsky
- Institute for Neuro- and Behavioral Biology, Westfälische Wilhelms University, 48149 Münster, Germany
| | - James Frederick Cheeseman
- Department of Anaesthesiology, School of Medicine, University of Auckland, Auckland, 1142 New Zealand
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6
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Fropf R, Zhou H, Yin JCP. The clock gene period differentially regulates sleep and memory in Drosophila. Neurobiol Learn Mem 2018; 153:2-12. [PMID: 29474956 PMCID: PMC6064670 DOI: 10.1016/j.nlm.2018.02.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 01/20/2018] [Accepted: 02/19/2018] [Indexed: 11/21/2022]
Abstract
Circadian regulation is a conserved phenomenon across the animal kingdom, and its disruption can have severe behavioral and physiological consequences. Core circadian clock proteins are likewise well conserved from Drosophila to humans. While the molecular clock interactions that regulate circadian rhythms have been extensively described, additional roles for clock genes during complex behaviors are less understood. Here, we show that mutations in the clock gene period result in differential time-of-day effects on acquisition and long-term memory of aversive olfactory conditioning. Sleep is also altered in period mutants: while its overall levels don't correlate with memory, sleep plasticity in different genotypes correlates with immediate performance after training. We further describe distinct anatomical bases for Period function by manipulating Period activity in restricted brain cells and testing the effects on specific aspects of memory and sleep. In the null mutant background, different features of sleep and memory are affected when we reintroduce a form of the period gene in glia, lateral neurons, and the fan-shaped body. Our results indicate that the role of the clock gene period may be separable in specific aspects of sleep or memory; further studies into the molecular mechanisms of these processes suggest independent neural circuits and molecular cascades that mediate connections between the distinct phenomena.
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Affiliation(s)
- Robin Fropf
- Neuroscience Training Program, 1300 University Ave., University of Wisconsin-Madison, Madison, WI 53706, United States.
| | - Hong Zhou
- Laboratory of Genetics, 3434 Genetics/Biotechnology, 425 Henry Mall, University of Wisconsin-Madison, Madison, WI 53706, United States.
| | - Jerry C P Yin
- Laboratory of Genetics, 3434 Genetics/Biotechnology, 425 Henry Mall, University of Wisconsin-Madison, Madison, WI 53706, United States; Department of Neurology, School of Medicine and Public Health, University of Wisconsin-Madison, 1685 Highland Ave., Madison, WI 53706, United States.
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7
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Franco DL, Frenkel L, Ceriani MF. The Underlying Genetics of Drosophila Circadian Behaviors. Physiology (Bethesda) 2018; 33:50-62. [PMID: 29212892 DOI: 10.1152/physiol.00020.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 09/20/2017] [Accepted: 09/25/2017] [Indexed: 01/22/2023] Open
Abstract
Life is shaped by circadian clocks. This review focuses on how behavioral genetics in the fruit fly unveiled what is known today about circadian physiology. We will briefly summarize basic properties of the clock and focus on some clock-controlled behaviors to highlight how communication between central and peripheral oscillators defines their properties.
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Affiliation(s)
- D Lorena Franco
- Departamento de Física Médica, Centro Atómico Bariloche and Instituto Balseiro, CONICET, San Carlos de Bariloche, Río Negro, Argentina; and
| | - Lia Frenkel
- Laboratorio de Genética del Comportamiento, Fundación Instituto Leloir (FIL)-Instituto de Investigaciones Bioquímicas-IIBBA-CONICET, Buenos Aires, Argentina
| | - M Fernanda Ceriani
- Laboratorio de Genética del Comportamiento, Fundación Instituto Leloir (FIL)-Instituto de Investigaciones Bioquímicas-IIBBA-CONICET, Buenos Aires, Argentina
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Reflections on contributing to "big discoveries" about the fly clock: Our fortunate paths as post-docs with 2017 Nobel laureates Jeff Hall, Michael Rosbash, and Mike Young. Neurobiol Sleep Circadian Rhythms 2018; 5:58-67. [PMID: 31236512 PMCID: PMC6584674 DOI: 10.1016/j.nbscr.2018.02.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 02/23/2018] [Accepted: 02/23/2018] [Indexed: 11/20/2022] Open
Abstract
In the early 1980s Jeff Hall and Michael Rosbash at Brandeis University and Mike Young at Rockefeller University set out to isolate the period (per) gene, which was recovered in a revolutionary genetic screen by Ron Konopka and Seymour Benzer for mutants that altered circadian behavioral rhythms. Over the next 15 years the Hall, Rosbash and Young labs made a series of groundbreaking discoveries that defined the molecular timekeeping mechanism and formed the basis for them being awarded the 2017 Nobel Prize in Physiology or Medicine. Here the authors recount their experiences as post-docs in the Hall, Rosbash and Young labs from the mid-1980s to the mid-1990s, and provide a perspective of how basic research conducted on a simple model system during that era profoundly influenced the direction of the clocks field and established novel approaches that are now standard operating procedure for studying complex behavior. 2017 Nobel Prize awarded to Hall, Rosbash and Young for circadian clock mechanisms. Work on fruit flies in the 1980s and 1990s were key to deciphering clock mechanisms. Authors recount their experiences as postdocs in the Hall, Rosbash and Young labs. The broad impacts of basic research on fruit fly clock genes.
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Suszczynska A, Kaniewska MM, Bebas P, Giebultowicz JM, Kotwica-Rolinska J. Circadian regulation of caterpillar feeding and growth. JOURNAL OF INSECT PHYSIOLOGY 2017; 101:113-122. [PMID: 28733238 DOI: 10.1016/j.jinsphys.2017.07.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 07/07/2017] [Accepted: 07/17/2017] [Indexed: 06/07/2023]
Abstract
Circadian clocks orchestrate many physiological processes in adult organisms. For example, rhythmic feeding behavior is regulated by the central clock in the nervous system in coordination with metabolic rhythms, which in turn depend mostly on peripheral clocks localized in many tissues. Disruption of the circadian clock leads to metabolic dysregulation both in mammals and in the model insect Drosophila melanogaster. Circadian coordination of feeding and metabolism has been studied mainly in adult insects and not in larval stages, which are dramatically different from adults in species with complete full metamorphosis. The goal of this study was to determine whether feeding and metabolism in lepidopteran larvae are subject to circadian regulation. We show that cotton leafworm caterpillars, Spodoptera littoralis, display rhythmic feeding behavior and that circadian clock genes are expressed in two peripheral tissues, the midgut and fat body. Even though both tissues display rhythmic circadian clock gene expression, the main component of the clock, per, is arrhythmic in the gut and rhythmic in the fat body. In both tissues, the presence of rhythmic physiological processes was observed, which suggested that metabolism is already driven by the circadian clock in the insect's juvenile stages.
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Affiliation(s)
- Agnieszka Suszczynska
- Department of Animal Physiology, Institute of Zoology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Magdalena Maria Kaniewska
- Department of Animal Physiology, Institute of Zoology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Piotr Bebas
- Department of Animal Physiology, Institute of Zoology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | | | - Joanna Kotwica-Rolinska
- Department of Animal Physiology, Institute of Zoology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
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10
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Zhao X, Bergland AO, Behrman EL, Gregory BD, Petrov DA, Schmidt PS. Global Transcriptional Profiling of Diapause and Climatic Adaptation in Drosophila melanogaster. Mol Biol Evol 2016; 33:707-20. [PMID: 26568616 PMCID: PMC5009998 DOI: 10.1093/molbev/msv263] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Wild populations of the model organism Drosophila melanogaster experience highly heterogeneous environments over broad geographical ranges as well as over seasonal and annual timescales. Diapause is a primary adaptation to environmental heterogeneity, and in D. melanogaster the propensity to enter diapause varies predictably with latitude and season. Here we performed global transcriptomic profiling of naturally occurring variation in diapause expression elicited by short day photoperiod and moderately low temperature in two tissue types associated with neuroendocrine and endocrine signaling, heads, and ovaries. We show that diapause in D. melanogaster is an actively regulated phenotype at the transcriptional level, suggesting that diapause is not a simple physiological or reproductive quiescence. Differentially expressed genes and pathways are highly distinct in heads and ovaries, demonstrating that the diapause response is not uniform throughout the soma and suggesting that it may be comprised of functional modules associated with specific tissues. Genes downregulated in heads of diapausing flies are significantly enriched for clinally varying single nucleotide polymorphism (SNPs) and seasonally oscillating SNPs, consistent with the hypothesis that diapause is a driving phenotype of climatic adaptation. We also show that chromosome location-based coregulation of gene expression is present in the transcriptional regulation of diapause. Taken together, these results demonstrate that diapause is a complex phenotype actively regulated in multiple tissues, and support the hypothesis that natural variation in diapause propensity underlies adaptation to spatially and temporally varying selective pressures.
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Affiliation(s)
- Xiaqing Zhao
- Department of Biology, University of Pennsylvania
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12
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Kobelková A, Závodská R, Sauman I, Bazalová O, Dolezel D. Expression of clock genes period and timeless in the central nervous system of the Mediterranean flour moth, Ephestia kuehniella. J Biol Rhythms 2015; 30:104-16. [PMID: 25637625 DOI: 10.1177/0748730414568430] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Homologous circadian genes are found in all insect clocks, but their contribution to species-specific circadian timing systems differs. The aim of this study was to extend research within Lepidoptera to gain a better understanding of the molecular mechanism underlying circadian clock plasticity and evolution. The Mediterranean flour moth, Ephestia kuehniella (Pyralidae), represents a phylogenetically ancestral lepidopteran species. We have identified circadian rhythms in egg hatching, adult emergence, and adult locomotor activity. Cloning full-length complementary DNAs and further characterization confirmed one copy of period and timeless genes in both sexes. Both per and tim transcripts oscillate in their abundance in E. kuehniella heads under light-dark conditions. PER-like immunoreactivity (PER-lir) was observed in nuclei and cytoplasm of most neurons in the central brain, the ventral part of subesophageal complex, the neurohemal organs, the optic lobes, and eyes. PER-lir in photoreceptor nuclei oscillated during the day with maximal intensity in the light phase of the photoperiodic regime and lack of a signal in the middle of the dark phase. Expression patterns of per and tim messenger RNAs (mRNAs) were revealed in the identical location as the PER-lir was detected. In the photoreceptors, a daily rhythm in the intensity of expression of both per mRNA and tim mRNA was found. These findings suggest E. kuehniella as a potential lepidopteran model for circadian studies.
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Affiliation(s)
- Alena Kobelková
- Institute of Entomology, Biology Centre CAS Ceske Budejovice, Czech Republic Faculty of Science, University of South Bohemia, Ceske Budejovice, Czech Republic
| | - Radka Závodská
- Institute of Entomology, Biology Centre CAS Ceske Budejovice, Czech Republic Faculty of Science, University of South Bohemia, Ceske Budejovice, Czech Republic Faculty of Education, University of South Bohemia, Ceske Budejovice, Czech Republic
| | - Ivo Sauman
- Institute of Entomology, Biology Centre CAS Ceske Budejovice, Czech Republic Faculty of Science, University of South Bohemia, Ceske Budejovice, Czech Republic
| | - Olga Bazalová
- Institute of Entomology, Biology Centre CAS Ceske Budejovice, Czech Republic Faculty of Science, University of South Bohemia, Ceske Budejovice, Czech Republic
| | - David Dolezel
- Institute of Entomology, Biology Centre CAS Ceske Budejovice, Czech Republic Faculty of Science, University of South Bohemia, Ceske Budejovice, Czech Republic
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Yao Z, Shafer OT. The Drosophila circadian clock is a variably coupled network of multiple peptidergic units. Science 2014; 343:1516-20. [PMID: 24675961 DOI: 10.1126/science.1251285] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Daily rhythms in behavior emerge from networks of neurons that express molecular clocks. Drosophila's clock neuron network consists of a diversity of cell types, yet is modeled as two hierarchically organized groups, one of which serves as a master pacemaker. Here, we establish that the fly's clock neuron network consists of multiple units of independent neuronal oscillators, each unified by its neuropeptide transmitter and mode of coupling to other units. Our work reveals that the circadian clock neuron network is not orchestrated by a small group of master pacemakers but rather consists of multiple independent oscillators, each of which drives rhythms in activity.
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Affiliation(s)
- Z Yao
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
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Di Cara F, King-Jones K. How clocks and hormones act in concert to control the timing of insect development. Curr Top Dev Biol 2013; 105:1-36. [PMID: 23962837 DOI: 10.1016/b978-0-12-396968-2.00001-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
During the last century, insect model systems have provided fascinating insights into the endocrinology and developmental biology of all animals. During the insect life cycle, molts and metamorphosis delineate transitions from one developmental stage to the next. In most insects, pulses of the steroid hormone ecdysone drive these developmental transitions by activating signaling cascades in target tissues. In holometabolous insects, ecdysone triggers metamorphosis, the remarkable remodeling of an immature larva into a sexually mature adult. The input from another developmental hormone, juvenile hormone (JH), is required to repress metamorphosis by promoting juvenile fates until the larva has acquired sufficient nutrients to survive metamorphosis. Ecdysone and JH act together as key endocrine timers to precisely control the onset of developmental transitions such as the molts, pupation, or eclosion. In this review, we will focus on the role of the endocrine system and the circadian clock, both individually and together, in temporally regulating insect development. Since this is not a coherent field, we will review recent developments that serve as examples to illuminate this complex topic. First, we will consider studies conducted in Rhodnius that revealed how circadian pathways exert temporal control over the production and release of ecdysone. We will then take a look at molecular and genetic data that revealed the presence of two circadian clocks, located in the brain and the prothoracic gland, that regulate eclosion rhythms in Drosophila. In this context, we will also review recent developments that examined how the ecdysone hierarchy delays the differentiation of the crustacean cardioactive peptide (CCAP) neurons, an event that is critical for the timing of ecdysis and eclosion. Finally, we will discuss some recent findings that transformed our understanding of JH function.
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Affiliation(s)
- Francesca Di Cara
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
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Abstract
Although circadian rhythms in mammalian physiology and behavior are dependent upon a biological clock in the suprachiasmatic nuclei (SCN) of the hypothalamus, the molecular mechanism of this clock is in fact cell autonomous and conserved in nearly all cells of the body. Thus, the SCN serves in part as a "master clock," synchronizing "slave" clocks in peripheral tissues, and in part directly orchestrates circadian physiology. In this chapter, we first consider the detailed mechanism of peripheral clocks as compared to clocks in the SCN and how mechanistic differences facilitate their functions. Next, we discuss the different mechanisms by which peripheral tissues can be entrained to the SCN and to the environment. Finally, we look directly at how peripheral oscillators control circadian physiology in cells and tissues.
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Affiliation(s)
- Steven A Brown
- Institute of Pharmacology and Toxicology, 190 Winterthurerstrasse, 8057 Zürich, Switzerland.
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Circadian rhythms in the morphology of neurons in Drosophila. Cell Tissue Res 2011; 344:381-9. [DOI: 10.1007/s00441-011-1174-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Accepted: 04/13/2011] [Indexed: 12/13/2022]
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Sellix MT, Menaker M. Circadian clocks in the ovary. Trends Endocrinol Metab 2010; 21:628-36. [PMID: 20599392 PMCID: PMC2949464 DOI: 10.1016/j.tem.2010.06.002] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Revised: 06/01/2010] [Accepted: 06/02/2010] [Indexed: 11/22/2022]
Abstract
Clock gene expression has been observed in tissues of the hypothalamic-pituitary-gonadal (HPG) axis. Whereas the contribution of hypothalamic oscillators to the timing of reproductive biology is well known, the role of peripheral oscillators like those in the ovary is less clear. Circadian clocks in the ovary might play a role in the timing of ovulation. Disruption of the clock in ovarian cells or desynchrony between ovarian clocks and circadian oscillators elsewhere in the body may contribute to the onset and progression of various reproductive pathologies. In this paper, we review evidence for clock function in the ovary across a number of species and offer a novel perspective into the role of this clock in normal ovarian physiology and in diseases that negatively affect fertility.
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Affiliation(s)
| | - Michael Menaker
- Corresponding Author: PO Box 400328, University of Virginia, Charlottesville, VA 22904, , Phone: 434-982-5767, Fax: 434-982-5626
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Ruiz S, Rickert C, Berger C, Technau GM, Cantera R. Spatio-temporal pattern of cells expressing the clock genes period and timeless and the lineages of period expressing neurons in the embryonic CNS of Drosophila melanogaster. Gene Expr Patterns 2010; 10:274-82. [DOI: 10.1016/j.gep.2010.06.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 05/31/2010] [Accepted: 06/04/2010] [Indexed: 11/26/2022]
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Abstract
Circadian clocks organize behavior and physiology to adapt to daily environmental cycles. Genetic approaches in the fruit fly, Drosophila melanogaster, have revealed widely conserved molecular gears of these 24-h timers. Yet much less is known about how these cell-autonomous clocks confer temporal information to modulate cellular functions. Here we discuss our current knowledge of circadian clock function in Drosophila, providing an overview of the molecular underpinnings of circadian clocks. We then describe the neural network important for circadian rhythms of locomotor activity, including how these molecular clocks might influence neuronal function. Finally, we address a range of behaviors and physiological systems regulated by circadian clocks, including discussion of specific peripheral oscillators and key molecular effectors where they have been described. These studies reveal a remarkable complexity to circadian pathways in this "simple" model organism.
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Affiliation(s)
- Ravi Allada
- Department of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208, USA.
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20
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Abstract
Eclosion is the stage in development when the adult insect emerges from the shell of its old cuticle. The sequence of behaviors necessary for eclosion is coordinated by an integrated system of hormones and is activated by hormones that relay developmental readiness. The circadian clock, which controls the timing of behaviors such as the rest: activity rhythm of adult insects, also controls eclosion timing. A number of groups are actively investigating the mechanisms by which the circadian clock restricts or gates eclosion to a particular time of day. Data from these studies are beginning to reveal details of the molecular and physiological basis of the eclosion rhythm.
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Affiliation(s)
- Edith M Myers
- Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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Paranjpe DA, Anitha D, Joshi A, Sharma VK. Multi-Oscillatory Control of Eclosion and Oviposition Rhythms inDrosophila melanogaster: Evidence from Limits of Entrainment Studies. Chronobiol Int 2009; 21:539-52. [PMID: 15470953 DOI: 10.1081/cbi-200026463] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The eclosion and oviposition rhythms of flies from a population of Drosophila melanogaster maintained under constant conditions of the laboratory were assayed under constant light (LL), constant darkness (DD), and light/dark (LD) cycles of 10:10h (T20), 12:12h (T24), and 14:14h (T28). The mean (+/- 95% confidence interval; CI) free-running period (tau) of the oviposition rhythm was 26.34 +/- 1.04h and 24.50 +/- 1.77h in DD and LL, respectively. The eclosion rhythm showed a tau of 23.33 +/- 0.63 h (mean +/- 95% CI) in DD, and eclosion was not rhythmic in LL. The tau of the oviposition rhythm in DD was significantly greater than that of the eclosion rhythm. The eclosion rhythm of all 10 replicate vials entrained to the three periodic light regimes, T20, T24, and T28, whereas the oviposition rhythm of only about 24 and 41% of the individuals entrained to T20 and T24 regimes, respectively, while about 74% of the individuals assayed in T28 regimes showed entrainment. Our results thus clearly indicate that the tau and the limits of entrainment of eclosion rhythm are different from those of the oviposition rhythm, and hence this reinforces the view that separate oscillators may regulate these two rhythms in D. melanogaster.
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Affiliation(s)
- Dhanashree A Paranjpe
- Chronobiology Laboratory, Evolutionary and Organismal Biology Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
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Veleri S, Wülbeck C. Unique Self-Sustaining Circadian Oscillators Within the Brain ofDrosophila melanogaster. Chronobiol Int 2009; 21:329-42. [PMID: 15332440 DOI: 10.1081/cbi-120038597] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
In Drosophila circadian rhythms persist in constant darkness (DD). The small ventral Lateral Neurons (s-LNv) mainly control the behavioral circadian rhythm in consortium with the large ventral Lateral Neurons (l-LNv) and dorsal Lateral Neurons (LNd). It is believed that the molecular oscillations of clock genes are the source of this persistent behavior. Indeed the s-LNv, LNd, Dorsal Neurons (DN)-DN2 and DN3 displayed self-sustained molecular oscillations in DD both at RNA and protein levels, except the DN2 oscillates in anti-phase. In contrast, the l-LNv and DN1 displayed self-sustained oscillations at the RNA level, but protein oscillations quickly dampened. Having self-sustained and dampened molecular oscillators together in the DN groups suggested that they play different roles. However, all DN groups seemed to contribute together to the light-dark (LD) behavioral rhythm. The LD entrainment of LN oscillators is achieved through Rhodopsin (RH) and Cryptochrome (CRY). CRY's expression in all DN groups implicates also its role in LD entrainment of DN, like in DN1. However, mutations in cry and glass that did not inflict LD synchronization of the DN2, DN3 oscillator implicate the existence of a novel photoreceptor at least in DN3.
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Affiliation(s)
- Shobi Veleri
- Institut für Zoologie, Universität Regensburg, Regensburg, Germany.
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Kotwica J, Larson MK, Bebas P, Giebultowicz JM. Developmental profiles of PERIOD and DOUBLETIME in Drosophila melanogaster ovary. JOURNAL OF INSECT PHYSIOLOGY 2009; 55:419-425. [PMID: 19223210 DOI: 10.1016/j.jinsphys.2009.01.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Revised: 01/20/2009] [Accepted: 01/23/2009] [Indexed: 05/27/2023]
Abstract
The clock protein PERIOD (PER) displays circadian cycles of accumulation, phosphorylation, nuclear translocation and degradation in Drosophila melanogaster clock cells. One exception to this pattern is in follicular cells enclosing previtellogenic ovarian egg chambers. In these cells, PER remains high and cytoplasmic at all times of day. Genetic evidence suggest that PER and its clock partner TIMELESS (TIM) interact in these cells, yet, they do not translocate to the nucleus. Here, we investigated the levels and subcellular localization of PER in older vitellogenic follicles. Cytoplasmic PER levels decreased in the follicular cells at the onset of vitellogenesis (stage 9). Interestingly, PER was observed in the nuclei of some follicular cells at this stage. PER signal disappeared in more advanced (stage 10) vitellogenic follicles. Since the phosphorylation state of PER is critical for the progression of circadian cycle, we investigated the status of PER phosphorylation in the ovary and the expression patterns of DOUBLETIME (DBT), a kinase known to affect PER in the clock cells. DBT was absent in previtellogenic follicular cells, but present in the cytoplasm of some stage 9 follicular cells. DBT was not distributed uniformly but was present in patches of adjacent cells, in a pattern resembling PER distribution at the same stage. Our data suggest that the absence of dbt expression in the follicular cells of previtellogenic egg chambers may be related to stable and cytoplasmic expression of PER in these cells. Onset of dbt expression in vitellogenic follicles coincides with nuclear localization of PER protein.
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Affiliation(s)
- Joanna Kotwica
- Department of Zoology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA
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Houl JH, Ng F, Taylor P, Hardin PE. CLOCK expression identifies developing circadian oscillator neurons in the brains of Drosophila embryos. BMC Neurosci 2008; 9:119. [PMID: 19094242 PMCID: PMC2628352 DOI: 10.1186/1471-2202-9-119] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Accepted: 12/18/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Drosophila circadian oscillator is composed of transcriptional feedback loops in which CLOCK-CYCLE (CLK-CYC) heterodimers activate their feedback regulators period (per) and timeless (tim) via E-box mediated transcription. These feedback loop oscillators are present in distinct clusters of dorsal and lateral neurons in the adult brain, but how this pattern of expression is established during development is not known. Since CLK is required to initiate feedback loop function, defining the pattern of CLK expression in embryos and larvae will shed light on oscillator neuron development. RESULTS A novel CLK antiserum is used to show that CLK expression in the larval CNS and adult brain is limited to circadian oscillator cells. CLK is initially expressed in presumptive small ventral lateral neurons (s-LNvs), dorsal neurons 2 s (DN2s), and dorsal neuron 1 s (DN1s) at embryonic stage (ES) 16, and this CLK expression pattern persists through larval development. PER then accumulates in all CLK-expressing cells except presumptive DN2s during late ES 16 and ES 17, consistent with the delayed accumulation of PER in adult oscillator neurons and antiphase cycling of PER in larval DN2s. PER is also expressed in non-CLK-expressing cells in the embryonic CNS starting at ES 12. Although PER expression in CLK-negative cells continues in ClkJrk embryos, PER expression in cells that co-express PER and CLK is eliminated. CONCLUSION These data demonstrate that brain oscillator neurons begin development during embryogenesis, that PER expression in non-oscillator cells is CLK-independent, and that oscillator phase is an intrinsic characteristic of brain oscillator neurons. These results define the temporal and spatial coordinates of factors that initiate Clk expression, imply that circadian photoreceptors are not activated until the end of embryogenesis, and suggest that PER functions in a different capacity before oscillator cell development is initiated.
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Affiliation(s)
- Jerry H Houl
- Center for Research on Biological Clocks, Department of Biology, Texas A&M University, 3258 TAMU, College Station, TX 77843, USA.
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Hao Zheng, Ng F, Yixiao Liu, Hardin PE. Spatial and circadian regulation of cry in Drosophila. J Biol Rhythms 2008; 23:283-95. [PMID: 18663236 DOI: 10.1177/0748730408318566] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In Drosophila, cryptochrome (cry) encodes a blue-light photoreceptor that mediates light input to circadian oscillators and sustains oscillator function in peripheral tissues. The levels of cry mRNA cycle with a peak at approximately ZT5, which is similar to the phase of Clock (Clk) mRNA cycling in Drosophila. To understand how cry spatial and circadian expression is regulated, a series of cry-Gal4 trans-genes containing different portions of cry upstream and intron 1 sequences were tested for spatial and circadian expression. In fly heads, cry upstream sequences drive constitutive expression in brain oscillator neurons, a novel group of nonoscillator cells in the optic lobe, and peripheral oscillator cells in eyes and antennae. In contrast, cry intron 1 drives rhythmic expression in eyes and antennae, but not brain oscillator neurons. These results demonstrate that intron 1 is sufficient for high-amplitude cry mRNA cycling, show that cry upstream sequences are sufficient for expression in brain oscillator neurons, and suggest that cry spatial and circadian expression are regulated by different elements.
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Affiliation(s)
- Hao Zheng
- Department of Biology and Center for Research on Biological Clocks, Texas A&M University, College Station, TX 77843-3258, USA
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26
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Wen CJ, Lee HJ. Mapping the cellular network of the circadian clock in two cockroach species. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2008; 68:215-231. [PMID: 18618766 DOI: 10.1002/arch.20236] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The German cockroach, Blattella germanica, and the double-striped cockroach, B. bisignata, are sibling species with a similar period sequence but a distinctive circadian rhythm in locomotion. The cell distribution of immunoreactivity (ir) against three clock-related proteins, Period (PER), Pigment Dispersing Factor (PDF), and Corazonin (CRZ), was compared between the species. The PER-ir cells tend to form clusters and are sprayed out in the central nervous system. Three major PER-ir cells are located in the optic lobes, which are the sites of the major circadian clock. They are interconnected with PER-ir axon bundles. Interestingly, the potential output signal of the circadian clock, PDF, is co-localized with PER in all three groups of cells. However, only two CRZ-ir cells and their axons are found in the optic lobes and they are not co-localized with PER-ir or PDF-ir cells and axons. Since only one circadian rhythm is expressed in locomotion, the time signals from both major clocks in optic lobes are coupled by connection with PDF-ir axons. A group of 3-4 PER-ir cells in the protocerebrum display typical characteristics of neurosecretary cells. In addition, there are numerous, small PER-ir and PDF-ir co-localized cells in the pars intercerebralis (PI), which have direct connections with the neurohemoorgan, corpora cardiaca, through PER-ir and PDF-ir axons. Based on these findings, the cellular connection shows a circadian control through the endocrine route. For the rest of central nervous system, only a few PER-ir and PDF-ir cells or axons are detected. This finding implies the circadian clock for locomotion is not located in subesophageal ganglion, thoracic or abdominal ganglia, but may use other neural messengers to pass on circadian signals. Since the overall distribution pattern of the clock cells are the same for B. germanica and B. bisignata, the possible explanation for the different expressions of locomotion between the species depends on genes downstream of per, pdf, and crz.
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Affiliation(s)
- Chih-Jen Wen
- Department of Entomology, National Taiwan University, Taipei, Taiwan
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27
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Rush BL, Murad A, Emery P, Giebultowicz JM. Ectopic CRYPTOCHROME renders TIM light sensitive in the Drosophila ovary. J Biol Rhythms 2007; 21:272-8. [PMID: 16864647 DOI: 10.1177/0748730406290416] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The period (per) and timeless (tim) genes play a central role in the Drosophila circadian clock mechanism. PERIOD (PER) and TIMELESS (TIM) proteins periodically accumulate in the nuclei of pace-making cells in the fly brain and many cells in peripheral organs. In contrast, TIM and PER in the ovarian follicle cells remain cytoplasmic and do not show daily oscillations in their levels. Moreover, TIM is not light sensitive in the ovary, while it is highly sensitive to this input in circadian tissues. The mechanism underlying this intriguing difference is addressed here. It is demonstrated that the circadian photoreceptor CRYPTOCHROME (CRY) is not expressed in ovarian tissues. Remarkably, ectopic cry expression in the ovary is sufficient to cause degradation of TIM after exposure to light. In addition, PER levels are reduced in response to light when CRY is present, as observed in circadian cells. Hence, CRY is the key component of the light input pathway missing in the ovary. However, the factors regulating PER and TIM levels downstream of light/cry action appear to be present in this non-circadian organ.
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Affiliation(s)
- Brandy L Rush
- Department of Zoology, Oregon State University, Corvallis, OR 97331, USA
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28
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Hall JC, Chang DC, Dolezelova E. Principles and problems revolving around rhythm-related genetic variants. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2007; 72:215-232. [PMID: 18419279 DOI: 10.1101/sqb.2007.72.039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Much of what is known about the regulation of circadian rhythms has stemmed from the induction, recognition, or manufacture of genetic variants. Such investigations have been especially salient in chronobiological analyses of Drosophila. Many starting points for elucidation of rhythmic processes operating in this insect entailed the isolation of mutants or the design of engineered gene modifications. Various features of the principles and practices associated with the genetic approach toward understanding clock functions, and chronobiologically related ones, are discussed from perspectives that are largely genetic as such, although intertwined with certain neurogenetic and molecular-genetic concerns when appropriate. Key themes in this treatment connect with the power and problems associated with multiply mutant forms of rhythm-related genes, with the opportunistic or problematical aspects of multigenic variants that are in play (sometimes surprisingly), and with a question as to how forceful chronogenetic inferences have been in terms of elucidating the mechanisms of circadian pacemaking.
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Affiliation(s)
- J C Hall
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454, USA
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29
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Benito J, Zheng H, Ng FS, Hardin PE. Transcriptional feedback loop regulation, function, and ontogeny in Drosophila. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2007; 72:437-44. [PMID: 18419302 PMCID: PMC2866010 DOI: 10.1101/sqb.2007.72.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Drosophila circadian oscillator is composed of interlocked period/timeless (per/tim) and Clock (Clk) transcriptional feedback loops. These feedback loops drive rhythmic transcription having peaks at dawn and dusk during the daily cycle and function in the brain and a variety of peripheral tissues. To understand how the circadian oscillator keeps time and controls metabolic, physiological, and behavioral rhythms, we must determine how these feedback loops regulate rhythmic transcription, determine the relative importance of the per/tim and Clk feedback loops with regard to circadian oscillator function, and determine how these feedback loops come to be expressed in only certain tissues. Substantial insight into each of these issues has been gained from experiments performed in our lab and others and is summarized here.
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Affiliation(s)
- J Benito
- Department of Biology, Texas A&M University, College Station, Texas 77843-3258, USA
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30
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Hess NK, Singer PA, Trinh K, Nikkhoy M, Bernstein SI. Transcriptional regulation of the Drosophila melanogaster muscle myosin heavy-chain gene. Gene Expr Patterns 2006; 7:413-22. [PMID: 17194628 PMCID: PMC2002476 DOI: 10.1016/j.modgep.2006.11.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2006] [Accepted: 11/20/2006] [Indexed: 11/21/2022]
Abstract
We show that a 2.6kb fragment of the muscle myosin heavy-chain gene (Mhc) of Drosophila melanogaster (containing 458 base pairs of upstream sequence, the first exon, the first intron and the beginning of the second exon) drives expression in all muscles. Comparison of the minimal promoter to Mhc genes of 10 Drosophila species identified putative regulatory elements in the upstream region and in the first intron. The first intron is required for expression in four small cells of the tergal depressor of the trochanter (jump) muscle and in the indirect flight muscle. The 3'-end of this intron is important for Mhc transcription in embryonic body wall muscle and contains AT-rich elements that are protected from DNase I digestion by nuclear proteins of Drosophila embryos. Sequences responsible for expression in embryonic, adult body wall and adult head muscles are present both within and outside the intron. Elements important for expression in leg muscles and in the large cells of the jump muscle flank the intron. We conclude that multiple transcriptional regulatory elements are responsible for Mhc expression in specific sets of Drosophila muscles.
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Affiliation(s)
| | | | | | | | - Sanford I. Bernstein
- * Corresponding author. Tel.: +1-619-594-5629; fax: +1-619-594-5676; E-mail address:
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Fahrenkrug J, Georg B, Hannibal J, Hindersson P, Gräs S. Diurnal rhythmicity of the clock genes Per1 and Per2 in the rat ovary. Endocrinology 2006; 147:3769-76. [PMID: 16675517 DOI: 10.1210/en.2006-0305] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Circadian rhythms are generated by endogenous clocks in the central brain oscillator, the suprachiasmatic nucleus, and peripheral tissues. The molecular basis for the circadian clock consists of a number of genes and proteins that form transcriptional/translational feedback loops. In the mammalian gonads, clock genes have been reported in the testes, but the expression pattern is developmental rather than circadian. Here we investigated the daily expression of the two core clock genes, Per1 and Per2, in the rat ovary using real-time RT-PCR, in situ hybridization histochemistry, and immunohistochemistry. Both Per1 and Per2 mRNA displayed a statistically significant rhythmic oscillation in the ovary with a period of 24 h in: 1) a group of rats during proestrus and estrus under 12-h light,12-h dark cycles; 2) a second group of rats representing a mixture of all 4 d of the estrous cycle under 12-h light,12-h dark conditions; and 3) a third group of rats representing a mixture of all 4 d of estrous cycle during continuous darkness. Per1 mRNA was low at Zeitgeber time 0-2 and peaked at Zeitgeber time 12-14, whereas Per2 mRNA was delayed by approximately 4 h relative to Per1. By in situ hybridization histochemistry, Per mRNAs were localized to steroidogenic cells in preantral, antral, and preovulatory follicles; corpora lutea; and interstitial glandular tissue. With newly developed antisera, we substantiated the expression of Per1 and Per2 in these cells by single/double immunohistochemistry. Furthermore, we visualized the temporal intracellular movements of PER1 and PER2 proteins. These findings suggest the existence of an ovarian circadian clock, which may play a role both locally and in the hypothalamo-pituitary-ovarian axis.
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Affiliation(s)
- Jan Fahrenkrug
- Department of Clinical Biochemistry, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark.
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32
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Abstract
Daily rhythms in behavior, physiology and metabolism are controlled by endogenous circadian clocks. At the heart of these clocks is a circadian oscillator that keeps circadian time, is entrained by environmental cues such as light and activates rhythmic outputs at the appropriate time of day. Genetic and molecular analyses in Drosophila have revealed important insights into the molecules and mechanisms underlying circadian oscillator function in all organisms. In this review I will describe the intracellular feedback loops that form the core of the Drosophila circadian oscillator and consider how they are entrained by environmental light cycles, where they operate within the fly and how they are thought to control overt rhythms in physiology and behavior. I will also discuss where work remains to be done to give a comprehensive picture of the circadian clock in Drosophila and likely many other organisms.
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Affiliation(s)
- Paul E Hardin
- Department of Biology and Biochemistry, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5001, USA.
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33
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Chang DC. Neural circuits underlying circadian behavior in Drosophila melanogaster. Behav Processes 2006; 71:211-25. [PMID: 16414209 DOI: 10.1016/j.beproc.2005.12.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2005] [Revised: 10/02/2005] [Accepted: 12/11/2005] [Indexed: 12/11/2022]
Abstract
Circadian clocks include control systems for organizing daily behavior. Such a system consists of a time-keeping mechanism (the clock or pacemaker), input pathways for entraining the clock, and output pathways for producing overt rhythms in behavior and physiology. In Drosophila melanogaster, as in mammals, neural circuits play vital roles in all three functional subdivisions of the circadian system. Regarding the pacemaker, multiple clock neurons, each with cell-autonomous pacemaker capability, are coupled to each other in a network. The outputs of different sets of clock neurons in this network combine to produce the normal bimodal pattern of locomotor activity observed in Drosophila. Regarding input, multiple sensory modalities (including light, temperature, and pheromones) use their own circuitry to entrain the clock. Regarding output, distinct circuits are likely involved for controlling the timing of eclosion and for generating the locomotor activity rhythms. This review summarizes work on all of these circadian circuits, and discusses the broader utility of studying the fly's circadian system.
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Affiliation(s)
- Dennis C Chang
- Department of Biology, Brandeis University, 415 South Street, MS-008, Waltham, MA 02454, USA.
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34
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Alvarez JD, Sehgal A. The thymus is similar to the testis in its pattern of circadian clock gene expression. J Biol Rhythms 2005; 20:111-21. [PMID: 15834108 DOI: 10.1177/0748730404274078] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The molecular basis for the circadian clock in mammals consists of a number of genes and proteins that form transcription-translation feedback loops. These loops result in a 24-h rhythm in the expression of mRNA and protein levels. Although the anatomical site of the central circadian clock is the SCN of the hypothalamus, all of the circadian clock genes are expressed in tissues other than the brain. Moreover, cyclic gene and protein expression occurs in most of these tissues. The best known exception to this rule is the testis, which shows constant rather than cyclic expression of circadian clock genes. Indeed, the testis of multiple animal species displays constant circadian clock gene expression. In recent work, the authors showed that the thymus is similar to the testis in that expression of circadian clock genes is either constant over a 24-h period or cycles with a dampened amplitude, depending on which gene is examined. In the current study, they extend and confirm their findings regarding noncyclic circadian clock gene and protein expression in the testis and the thymus. More important, they also show that expression of these genes in both testis and thymus does not depend on the transcriptional activator, CLOCK, which is necessary for cyclic gene expression in the SCN and in other tissues. These results extend the molecular similarities between the thymus and the testis and suggest that similar mechanisms are at work for regulating expression of circadian clock genes in both tissues. One commonality between these 2 organs is that they are composed primarily of differentiating cells. The authors hypothesize that the circadian clock is not operational in immature, differentiating cells. Possibly, the clock starts in mature cells upon receipt of an initiating signal.
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Affiliation(s)
- J D Alvarez
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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35
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Light-dependent PER-like proteins in the cephalic ganglia of an apterygote and a pterygote insect species. Histochem Cell Biol 2005; 123:407-18. [DOI: 10.1007/s00418-004-0728-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/27/2004] [Indexed: 11/26/2022]
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36
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Abstract
The chronobiological system of Drosophila is considered from the perspective of rhythm-regulated genes. These factors are enumerated and discussed not so much in terms of how the gene products are thought to act on behalf of circadian-clock mechanisms, but with special emphasis on where these molecules are manufactured within the organism. Therefore, with respect to several such cell and tissue types in the fly head, what is the "systems meaning" of a given structure's function insofar as regulation of rest-activity cycles is concerned? (Systematic oscillation of daily behavior is the principal overt phenotype analyzed in studies of Drosophila chronobiology). In turn, how do the several separate sets of clock-gene-expressing cells interact--or in some cases act in parallel--such that intricacies of the fly's sleep-wake cycles are mediated? Studying Drosophila chrono-genetics as a system-based endeavor also encompasses the fact that rhythm-related genes generate their products in many tissues beyond neural ones and during all stages of the life cycle. What, then, is the meaning of these widespread gene-expression patterns? This question is addressed with regard to circadian rhythms outside the behavioral arena, by considering other kinds of temporally based behaviors, and by contemplating how broadly systemic expression of rhythm-related genes connects with even more pleiotropic features of Drosophila biology. Thus, chronobiologically connected factors functioning within this insect comprise an increasingly salient example of gene versatility--multi-faceted usages of, and complex interactions among, entities that set up an organism's overall wherewithal to form and function. A corollary is that studying Drosophila development and adult-fly actions, even when limited to analysis of rhythm-systems phenomena, involves many of the animal's tissues and phenotypic capacities. It follows that such chronobiological experiments are technically demanding, including the necessity for investigators to possess wide-ranging expertise. Therefore, this chapter includes several different kinds of Methods set-asides. These techniques primers necessarily lack comprehensiveness, but they include certain discursive passages about why a given method can or should be applied and concerning real-world applicability of the pertinent rhythm-related technologies.
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Affiliation(s)
- Jeffrey C Hall
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454, USA
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37
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Beaver LM, Rush BL, Gvakharia BO, Giebultowicz JM. Noncircadian regulation and function of clock genes period and timeless in oogenesis of Drosophila melanogaster. J Biol Rhythms 2004; 18:463-72. [PMID: 14667147 DOI: 10.1177/0748730403259108] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Circadian clock genes are ubiquitously expressed in the nervous system and peripheral tissues of complex animals. While clock genes in the brain are essential for behavioral rhythms, the physiological roles of these genes in the periphery are not well understood. Constitutive expression of the clock gene period was reported in the ovaries of Drosophila melanogaster; however, its molecular interactions and functional significance remained unknown. This study demonstrates that period (per) and timeless (tim) are involved in a novel noncircadian function in the ovary. PER and TIM are constantly expressed in the follicle cells enveloping young oocytes. Genetic evidence suggests that PER and TIM interact in these cells, yet they do not translocate to the nucleus. The levels of TIM and PER in the ovary are affected neither by light nor by the lack of clock-positive elements Clock (Clk) and cycle (cyc). Taken together, these data suggest that per and tim are regulated differently in follicle cells than in clock cells. Experimental evidence suggests that a novel fitness-related phenotype may be linked to noncircadian expression of clock genes in the ovaries. Mated females lacking either per or tim show nearly a 50% decline in progeny, and virgin females show a similar decline in the production of mature oocytes. Disruption of circadian mechanism by either the depletion of TIM via constant light treatment or continuous expression of PER via GAL4/UAS expression system has no adverse effect on the production of mature oocytes.
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Affiliation(s)
- L M Beaver
- Department of Zoology, Oregon State University, Corvallis, OR 97331, USA
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38
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Závodská R, Sauman I, Sehnal F. The cycling and distribution of PER-like antigen in relation to neurons recognized by the antisera to PTTH and EH in Thermobia domestica. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2003; 33:1227-1238. [PMID: 14599495 DOI: 10.1016/j.ibmb.2003.06.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The cephalic nervous system of the firebrat contains antigens recognized by antisera to the clock protein period (PER), the prothoracicotropic hormone (PTTH) and the eclosion hormone (EH). The content of the 115 kDa PER-like antigen visualized on the western blots fluctuates in diurnal rhythm with a maximum in the night. The oscillations entrained in a 12:12 h light/dark (LD) cycle persist in the darkness and disappear in continuous light. They are detected by immunostaining in 14 pairs of the protocerebral neurons and are extreme in four suboesophageal neurons and two cells in each corpus cardiacum that contain PER only during the night phase. No circadian fluctuations occur in three lightly stained perikarya of the optic lobe. Five cell bodies located in each brain hemisphere between the deuto-and the tritocerebrum retain weak immunoreactivity under constant illumination. In all cells, the staining is confined to the cytoplasm and never occurs in the cell nuclei. The cells containing PER-like material do not react with the anti-PTTH and anti-EH antisera, which recognize antigens of about 50 and 20 kDa, respectively. The anti-PTTH antiserum stains in each brain hemisphere seven neurons in the protocerebrum, eight in the optic lobe, and 3-5 in the posterior region of the deutocerebrum. The antiserum to EH reacts in each hemisphere with just two cells located medially to the mushroom bodies. No cycling of the PTTH-like and EH-like antigens was detected.
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Affiliation(s)
- Radka Závodská
- Faculty of Pedagogy, University of South Bohemia, Jeronýmova 10, 37115 Ceské Budejovice, Czech Republic
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Helfrich-Förster C. The neuroarchitecture of the circadian clock in the brain of Drosophila melanogaster. Microsc Res Tech 2003; 62:94-102. [PMID: 12966496 DOI: 10.1002/jemt.10357] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Neuroethologists try to assign behavioral functions to certain brain centers, if possible down to individual neurons and to the expression of specific genes. This approach has been successfully applied for the control of circadian rhythmic behavior in the fruit fly Drosophila melanogaster. Several so-called "clock genes" are expressed in specific neurons in the lateral and dorsal brain where they generate cell-autonomous molecular circadian oscillations. These clusters are connected with each other and contribute differentially to the control of behavioral rhythmicity. This report reviews the latest work on characterizing individual circadian pacemaker neurons in the fruit fly's brain that control activity and pupal eclosion, leading to the questions by which neuronal pathways they are synchronized to the external light-dark cycle, and how they impose periodicity on behavior.
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Hall JC. Genetics and molecular biology of rhythms in Drosophila and other insects. ADVANCES IN GENETICS 2003; 48:1-280. [PMID: 12593455 DOI: 10.1016/s0065-2660(03)48000-0] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Application of generic variants (Sections II-IV, VI, and IX) and molecular manipulations of rhythm-related genes (Sections V-X) have been used extensively to investigate features of insect chronobiology that might not have been experimentally accessible otherwise. Most such tests of mutants and molecular-genetic xperiments have been performed in Drosophila melanogaster. Results from applying visual-system variants have revealed that environmental inputs to the circadian clock in adult flies are mediated by external photoreceptive structures (Section II) and also by direct light reception chat occurs in certain brain neurons (Section IX). The relevant light-absorbing molecuLes are rhodopsins and "blue-receptive" cryptochrome (Sections II and IX). Variations in temperature are another clock input (Section IV), as has been analyzed in part by use of molecular techniques and transgenes involving factors functioning near the heart of the circadian clock (Section VIII). At that location within the fly's chronobiological system, approximately a half-dozen-perhaps up to as many as 10-clock genes encode functions that act and interact to form the circadian pacemaker (Sections III and V). This entity functions in part by transcriptional control of certain clock genes' expressions, which result in the production of key proteins that feed back negatively to regulate their own mRNA production. This occurs in part by interactions of such proteins with others that function as transcriptional activators (Section V). The implied feedback loop operates such that there are daily variations in the abundances of products put out by about one-half of the core clock genes. Thus, the normal expression of these genes defines circadian rhythms of their own, paralleling the effects of mutations at the corresponding genetic loci (Section III), which are to disrupt or apparently eliminate clock functioning. The fluctuations in the abundance of gene products are controlled transciptionally and posttranscriptionally. These clock mechanisms are being analyzed in ways that are increasingly complex and occasionally obscure; not all panels of this picture are comprehensive or clear, including problems revolving round the biological meaning or a given features of all this molecular cycling (Section V). Among the complexities and puzzles that have recently arisen, phenomena that stand out are posttranslational modifications of certain proteins that are circadianly regulated and regulating; these biochemical events form an ancillary component of the clock mechanism, as revealed in part by genetic identification of Factors (Section III) that turned out to encode protein kinases whose substrates include other pacemaking polypeptides (Section V). Outputs from insect circadian clocks have been long defined on formalistic and in some cases concrete criteria, related to revealed rhythms such as periodic eclosion and daily fluctuations of locomotion (Sections II and III). Based on the reasoning that if clock genes can regulate circadian cyclings of their own products, they can do the same for genes that function along output pathways; thus clock-regulated genes have been identified in part by virtue of their products' oscillations (Section X). Those studied most intensively have their expression influenced by circadian-pacemaker mutations. The clock-regulated genes discovered on molecular criteria have in some instances been analyzed further in their mutant forms and found to affect certain features of overt whole-organismal rhythmicity (Sections IV and X). Insect chronogenetics touches in part on naturally occurring gene variations that affect biological rhythmicity or (in some cases) have otherwise informed investigators about certain features of the organism's rhythm system (Section VII). Such animals include at least a dozen insect species other than D. melanogaster in which rhythm variants have been encountered (although usually not looked for systematically). The chronobiological "system" in the fruit fly might better be graced with a plural appellation because there is a myriad of temporally related phenomena that have come under the sway of one kind of putative rhythm variant or the other (Section IV). These phenotypes, which range well beyond the bedrock eclosion and locomotor circadian rhythms, unfortunately lead to the creation of a laundry list of underanalyzed or occult phenomena that may or may not be inherently real, whether or not they might be meaningfully defective under the influence of a given chronogenetic variant. However, such mutants seem to lend themselves to the interrogation of a wide variety of time-based attributes-those that fall within the experimental confines of conventionally appreciated circadian rhythms (Sections II, III, VI, and X); and others that consist of 24-hr or nondaily cycles defined by many kinds of biological, physiological, or biochemical parameters (Section IV).
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Affiliation(s)
- Jeffrey C Hall
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454, USA
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Hendricks JC. Invited review: Sleeping flies don't lie: the use of Drosophila melanogaster to study sleep and circadian rhythms. J Appl Physiol (1985) 2003; 94:1660-72; discussion 1673. [PMID: 12626480 DOI: 10.1152/japplphysiol.00904.2002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
During the past century, flies thoroughly proved their value as an animal model for the study of the genetics of development and basic cell processes. During the past three decades, they have also been extensively used to study the genetics of behavior. For both circadian rhythms and for sleep, flies are helping us to understand the genetic mechanisms that underlie these complex behaviors. Since 1971, discoveries in the fly have led the way to a number of significant discoveries, establishing a mechanistic framework that is now known to be conserved in the mammalian clock. The highlights of this history are described. For sleep, the use of the fly as a model is relatively new, that is, only within the past 2 yr. Nonetheless, studies have already established that two transcription factors alter rest and rest homeostasis. The implications of these advances for the future of sleep research are summarized.
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Affiliation(s)
- Joan C Hendricks
- Center for Sleep and Respiratory Neurobiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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Závodská R, Sauman I, Sehnal F. Distribution of PER protein, pigment-dispersing hormone, prothoracicotropic hormone, and eclosion hormone in the cephalic nervous system of insects. J Biol Rhythms 2003; 18:106-22. [PMID: 12693866 DOI: 10.1177/0748730403251711] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Investigations performed on adult insects revealed that putative components of the central pacemaker, the protein Period (PER) and the pigment-dispersing hormone (PDH), are immunocytochemically detectable in discrete sets of brain neurons throughout the class of Insecta, represented by a bristletail, mayfly, damselfly, 2 locust species, stonefly, 2 bug species, goldsmith beetle, caddisfly, honeybee, and 2 blowfly species. The PER-positive cells are localized in the frontal protocerebrum and in most species also in the optic lobes, which are their only location in damselfly and goldsmith beetle. Additional PER-positive cells occur in a few species either in the deuto- and tritocerebrum or in the suboesophageal ganglion. The PER staining was always confined to the cytoplasm. The PDH immunoreactivity consistently occurs in a cluster of perikarya located frontoventrally at the proximal edge of the medulla. The mayfly and both locust species possess additional PDH neurons in 2 posterior cell clusters at the proximal edge of the medulla, and mayfly, waterstrider, and 1 of the blowfly species in the central brain. PDH-positive fibers form a fanlike arrangement over the frontal side of the medulla. Two or just 1 bundle of PDH-positive fibers run from the optic lobe to the protocerebrum, with collaterals passing over to the contralateral optic lobe. Antisera to the prothoracicotropic (PTTH) and the eclosion (EH) hormones, which in some insects regulate the molting and ecdysis rhythms, respectively, typically react with a few neurons in the frontal protocerebrum. However, the PTTH-positive neurons of the mayfly and the damselfly and the EH-positive neurons of the caddisfly are located in the suboesophageal ganglion. No PTTH-like antigen was detected in locusts, and no EH-like antigens were detected in the damselfly, stonefly, locusts, and the honeybee. There are no signs of co-localization of the PER-, PDH-, PTTH-, and EH-like antigens in identical neurons.
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Affiliation(s)
- Radka Závodská
- Faculty of Pedagogy, University of South Bohemia, Jeronýmova 10, 371 15 Ceské Budĕjovice, Czech Republic
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Myers EM, Yu J, Sehgal A. Circadian control of eclosion: interaction between a central and peripheral clock in Drosophila melanogaster. Curr Biol 2003; 13:526-33. [PMID: 12646138 DOI: 10.1016/s0960-9822(03)00167-2] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Drosophila melanogaster display overt circadian rhythms in rest:activity behavior and eclosion. These rhythms have an endogenous period of approximately 24 hr and can adjust or "entrain" to environmental inputs such as light. Circadian rhythms depend upon a functioning molecular clock that includes the core clock genes period and timeless (reviewed in and ). Although we know that a clock in the lateral neurons (LNs) of the brain controls rest:activity rhythms, the cellular basis of eclosion rhythms is less well understood. We show that the LN clock is insufficient to drive eclosion rhythms. We establish that the prothoracic gland (PG), a tissue required for fly development, contains a functional clock at the time of eclosion. This clock is required for normal eclosion rhythms. However, both the PG clock function and eclosion rhythms require the presence of LNs. In addition, we demonstrate that pigment-dispersing factor (PDF), a neuropeptide secreted from LNs, is necessary for the PG clock and eclosion rhythms. Unlike other clocks in the fly periphery, the PG is similar to mammalian peripheral oscillators because it depends upon input, including PDF, from central pacemaker cells. This is the first report of a peripheral clock necessary for a circadian event.
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Affiliation(s)
- Edith M Myers
- The Department of Neuroscience, 232 Stemmler Hall, University of Pennsylvania, Philadelphia, PA 19104, USA
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Giebultowicz JM. Peripheral clocks and their role in circadian timing: insights from insects. Philos Trans R Soc Lond B Biol Sci 2001; 356:1791-9. [PMID: 11710986 PMCID: PMC1088555 DOI: 10.1098/rstb.2001.0960] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Impressive advances have been made recently in our understanding of the molecular basis of the cell-autonomous circadian feedback loop; however, much less is known about the overall organization of the circadian systems. How many clocks tick in a multicellular animal, such as an insect, and what are their roles and the relationships between them? Most attempts to locate clock-containing tissues were based on the analysis of behavioural rhythms and identified brain-located timing centres in a variety of animals. Characterization of several essential clock genes and analysis of their expression patterns revealed that molecular components of the clock are active not only in the brain, but also in many peripheral organs of Drosophila and other insects as well as in vertebrates. Subsequent experiments have shown that isolated peripheral organs can maintain self-sustained and light sensitive cycling of clock genes in vitro. This, together with earlier demonstrations that physiological output rhythms persist in isolated organs and tissues, provide strong evidence for the existence of functionally autonomous local circadian clocks in insects and other animals. Circadian systems in complex animals may include many peripheral clocks with tissue-specific functions and a varying degree of autonomy, which seems to be correlated with their sensitivity to external entraining signals.
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Affiliation(s)
- J M Giebultowicz
- Department of Entomology, Oregon State University, Corvallis, OR 97331-29 07, USA.
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Allada R, Emery P, Takahashi JS, Rosbash M. Stopping time: the genetics of fly and mouse circadian clocks. Annu Rev Neurosci 2001; 24:1091-119. [PMID: 11520929 DOI: 10.1146/annurev.neuro.24.1.1091] [Citation(s) in RCA: 232] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Forward genetic analyses in flies and mice have uncovered conserved transcriptional feedback loops at the heart of circadian pacemakers. Conserved mechanisms of posttranslational regulation, most notably phosphorylation, appear to be important for timing feedback. Transcript analyses have indicated that circadian clocks are not restricted to neurons but are found in several tissues. Comparisons between flies and mice highlight important differences in molecular circuitry and circadian organization. Future studies of pacemaker mechanisms and their control of physiology and behavior will likely continue to rely on forward genetics.
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Affiliation(s)
- R Allada
- Department of Neurobiology, Evanston, IL 60208, USA.
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Abstract
Much of our current understanding of how circadian rhythms are generated is based on work done with Drosophila melanogaster. Molecular mechanisms used to assemble an endogenous clock in this organism are now known to underlie circadian rhythms in many other species, including mammals. The genetic amenability of Drosophila has led to the identification of some genes that encode components of the clock (so-called clock genes) and others that either link the clock to the environment or act downstream of it. The clock provides time-of-day cues by regulating levels of specific gene products such that they oscillate with a circadian rhythm. The mechanisms that synchronize these oscillations to light are understood to some extent. However, there are still large gaps in our knowledge, in particular with respect to the mechanisms used by the clock to control overt rhythms. It has, however, become clear that in addition to the brain clock, autonomous or semi-autonomous clocks occur in peripheral tissues where they confer circadian regulation on specific functions.
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Affiliation(s)
- J A Williams
- Howard Hughes Medical Institute, Department of Neuroscience, University of Pennsylvania Medical School, Philadelphia, Pennsylvania 19104, USA.
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Martinek S, Inonog S, Manoukian AS, Young MW. A role for the segment polarity gene shaggy/GSK-3 in the Drosophila circadian clock. Cell 2001; 105:769-79. [PMID: 11440719 DOI: 10.1016/s0092-8674(01)00383-x] [Citation(s) in RCA: 434] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Tissue-specific overexpression of the glycogen synthase kinase-3 (GSK-3) ortholog shaggy (sgg) shortens the period of the Drosophila circadian locomotor activity cycle. The short period phenotype was attributed to premature nuclear translocation of the PERIOD/TIMELESS heterodimer. Reducing SGG/GSK-3 activity lengthens period, demonstrating an intrinsic role for the kinase in circadian rhythmicity. Lowered sgg activity decreased TIMELESS phosphorylation, and it was found that GSK-3 beta specifically phosphorylates TIMELESS in vitro. Overexpression of sgg in vivo converts hypophosphorylated TIMELESS to a hyperphosphorylated protein whose electrophoretic mobility, and light and phosphatase sensitivity, are indistinguishable from the rhythmically produced hyperphosphorylated TIMELESS of wild-type flies. Our results indicate a role for SGG/GSK-3 in TIMELESS phosphorylation and in the regulated nuclear translocation of the PERIOD/TIMELESS heterodimer.
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Affiliation(s)
- S Martinek
- Laboratory of Genetics and National Science Foundation Science and Technology Center for Biological Timing, The Rockefeller University, New York, NY 10021, USA
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Lyons LC, Darlington TK, Hao H, Houl J, Kay SA, Hardin PE. Specific sequences outside the E-box are required for proper per expression and behavioral rescue. J Biol Rhythms 2000; 15:472-82. [PMID: 11106064 DOI: 10.1177/074873040001500604] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A 69 bp circadian regulatory sequence (CRS) upstream of the per gene is sufficient to drive circadian transcription, mediate proper spatial expression, and rescue behavioral rhythmicity in per01 flies. Within the CRS, an E-box is required for transcriptional activation by two basic-helix-loop-helix (bHLH) PERARNT-SIM (PAS) transcription factors, dCLOCK (dCLK) and CYCLE (CYC). To define sequences within the CRS that are required for spatial expression, circadian expression, and behavioral rhythmicity, a series of mutants that alter blocks of 3 to 12 nucleotides across the entire CRS were used to drive lacZ or per expression in vivo. As expected, the E-box within the CRS is necessary for high-level expression and behavioral rhythmicity, but sequences outside the E-box are also required for transcriptional activation, proper spatial expression, and behavioral rhythmicity. These results indicate that the dCLK-CYC target site extends beyond the E-box and that factors other than dCLK and CYC modulate per transcription.
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Affiliation(s)
- L C Lyons
- Department of Biology and Biochemistry, University of Houston, TX, USA
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Darlington TK, Lyons LC, Hardin PE, Kay SA. The period E-box is sufficient to drive circadian oscillation of transcription in vivo. J Biol Rhythms 2000; 15:462-71. [PMID: 11106063 DOI: 10.1177/074873040001500603] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The minimum element from the Drosophila period promoter capable of driving in vivo cycling mRNA is the 69 bp circadian regulatory sequence (CRS). In cell culture, an 18 bp E-box element from the period promoter is regulated by five genes that are involved in the regulation of circadian expression in flies. This E-box is a target for transcriptional activation by bHLH-PAS proteins dCLOCK (dCLK) and CYCLE (CYC), this activation is inhibited by PERIOD (PER) and TIMELESS (TIM) together, and inhibition of dCLK/CYC by PER and TIM is blocked by CRYPTOCHROME (CRY) in the presence of light. Here, the same 18 bp E-box region generated rhythmic expression of luciferase in flies under both light-dark cycling and constant conditions. Flies heterozygous for the Clke(jrk) mutation maintained rhythmic expression from the E-box although at a lower level than wild type. Homozygous mutant Clk(jrk) animals had drastically lowered and arrhythmic expression. In a per01 background, expression from the E-box was high and not rhythmic. Transcription mediated by the per E-box was restricted to the same spatial pattern as the CRS. The per E-box DNA element and cognate binding proteins can confer per-like temporal and spatial expression. This demonstrates in vivo that the known circadian genes that form the core of the circadian oscillator in Drosophila integrate their activities at a single DNA element.
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Affiliation(s)
- T K Darlington
- Department of Cell Biology and NSF Center for Biological Timing, The Scripps Research Institute, La Jolla, CA 92037, USA
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van Esseveldt KE, Lehman MN, Boer GJ. The suprachiasmatic nucleus and the circadian time-keeping system revisited. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2000; 33:34-77. [PMID: 10967353 DOI: 10.1016/s0165-0173(00)00025-4] [Citation(s) in RCA: 212] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Many physiological and behavioral processes show circadian rhythms which are generated by an internal time-keeping system, the biological clock. In rodents, evidence from a variety of studies has shown the suprachiasmatic nucleus (SCN) to be the site of the master pacemaker controlling circadian rhythms. The clock of the SCN oscillates with a near 24-h period but is entrained to solar day/night rhythm by light. Much progress has been made recently in understanding the mechanisms of the circadian system of the SCN, its inputs for entrainment and its outputs for transfer of the rhythm to the rest of the brain. The present review summarizes these new developments concerning the properties of the SCN and the mechanisms of circadian time-keeping. First, we will summarize data concerning the anatomical and physiological organization of the SCN, including the roles of SCN neuropeptide/neurotransmitter systems, and our current knowledge of SCN input and output pathways. Second, we will discuss SCN transplantation studies and how they have contributed to knowledge of the intrinsic properties of the SCN, communication between the SCN and its targets, and age-related changes in the circadian system. Third, recent findings concerning the genes and molecules involved in the intrinsic pacemaker mechanisms of insect and mammalian clocks will be reviewed. Finally, we will discuss exciting new possibilities concerning the use of viral vector-mediated gene transfer as an approach to investigate mechanisms of circadian time-keeping.
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Affiliation(s)
- K E van Esseveldt
- Graduate School Neurosciences Amsterdam, Netherlands Institute for Brain Research, Meibergdreef 33, 1105 AZ ZO, Amsterdam, The Netherlands
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