Organization of endogenous clocks in insects

2005 ◽  
Vol 33 (5) ◽  
pp. 957-961 ◽  
Author(s):  
C. Helfrich-Förster
Keyword(s):  
Drosophila Melanogaster ◽  
Molecular Mechanisms ◽  
Clock Genes ◽  
Fruit Fly ◽  
Circadian Clocks ◽  
Rhythm Generation ◽  
Similarities And Differences ◽  
The Brain ◽  
Master Clock

Insect and mammalian circadian clocks show striking similarities. They utilize homologous clock genes, generating self-sustained circadian oscillations in distinct master clocks of the brain, which then control rhythmic behaviour. The molecular mechanisms of rhythm generation were first uncovered in the fruit fly Drosophila melanogaster, whereas cockroaches were among the first animals where the brain master clock was localized. Despite many similarities, there exist obvious differences in the organization and functioning of insect master clocks. These similarities and differences are reviewed on a molecular and anatomical level.

The neuronal network of the endogenous clock

e-Neuroforum ◽  
2010 ◽  
Vol 16 (1) ◽  
Author(s):  
Charlotte Förster
Keyword(s):  
Molecular Basis ◽  
Clock Genes ◽  
Fruit Fly ◽  
Biological Processes ◽  
Rhythm Generation ◽  
The Metabolic Syndrome ◽  
Clock Network ◽  
Endogenous Clock ◽  
The Brain

AbstractEndogenous clocks control the rhythm of many biological processes. Malfunction of endogenous clocks in humans can lead to various diseases as sleep disorders, depres­sions, the metabolic syndrome and cancer. All animals have a main clock in the brain. This clock comprises a network of clock neurons that communicate with each other. In each clock neuron, conserved clock genes and pro­teins interact in to generate a molecular os­cillation. The molecular basis of this rhythm generation as well as the anatomy of the neuronal clock network is best investigated in the fruit fly Drosophila melanogaster. In the little fly, clock genes can be shut down in specific clock neurons. Furthermore, specific clock neurons can be electrically silenced and the rhythmic behaviour of such manipulated flies can be studied. A flurry of recent studies has begun to identify the role of specific clock neurons in the clock network, and these find­ings are helping to understand the basic neu­ronal mechanisms of endogenous clocks.

scholarly journals Peripheral Sensory Organs Contribute to Temperature Synchronization of the Circadian Clock in Drosophila melanogaster

2021 ◽  
Vol 12 ◽  
Author(s):  
Rebekah George ◽  
Ralf Stanewsky
Keyword(s):  
Gene Expression ◽  
Drosophila Melanogaster ◽  
Circadian Clock ◽  
Temperature Fluctuations ◽  
Fruit Fly ◽  
Circadian Clocks ◽  
Sensory Cells ◽  
Clock Gene Expression ◽  
External Time ◽  
Peripheral Sensory

Circadian clocks are cell-autonomous endogenous oscillators, generated and maintained by self-sustained 24-h rhythms of clock gene expression. In the fruit fly Drosophila melanogaster, these daily rhythms of gene expression regulate the activity of approximately 150 clock neurons in the fly brain, which are responsible for driving the daily rest/activity cycles of these insects. Despite their endogenous character, circadian clocks communicate with the environment in order to synchronize their self-sustained molecular oscillations and neuronal activity rhythms (internal time) with the daily changes of light and temperature dictated by the Earth’s rotation around its axis (external time). Light and temperature changes are reliable time cues (Zeitgeber) used by many organisms to synchronize their circadian clock to the external time. In Drosophila, both light and temperature fluctuations robustly synchronize the circadian clock in the absence of the other Zeitgeber. The complex mechanisms for synchronization to the daily light–dark cycles are understood with impressive detail. In contrast, our knowledge about how the daily temperature fluctuations synchronize the fly clock is rather limited. Whereas light synchronization relies on peripheral and clock-cell autonomous photoreceptors, temperature input to the clock appears to rely mainly on sensory cells located in the peripheral nervous system of the fly. Recent studies suggest that sensory structures located in body and head appendages are able to detect temperature fluctuations and to signal this information to the brain clock. This review will summarize these studies and their implications about the mechanisms underlying temperature synchronization.

scholarly journals The Kidney Clock Contributes to Timekeeping by the Master Circadian Clock

2019 ◽  
Vol 20 (11) ◽  
pp. 2765 ◽  
Author(s):  
Jihwan Myung ◽  
Mei-Yi Wu ◽  
Chun-Ya Lee ◽  
Amalia Ridla Rahim ◽  
Vuong Hung Truong ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Sleep Disturbances ◽  
The Body ◽  
Circadian Clocks ◽  
Whole Body ◽  
The Hierarchical Structure ◽  
Body Level ◽  
The Brain ◽  
Master Clock

The kidney harbors one of the strongest circadian clocks in the body. Kidney failure has long been known to cause circadian sleep disturbances. Using an adenine-induced model of chronic kidney disease (CKD) in mice, we probe the possibility that such sleep disturbances originate from aberrant circadian rhythms in kidney. Under the CKD condition, mice developed unstable behavioral circadian rhythms. When observed in isolation in vitro, the pacing of the master clock, the suprachiasmatic nucleus (SCN), remained uncompromised, while the kidney clock became a less robust circadian oscillator with a longer period. We find this analogous to the silencing of a strong slave clock in the brain, the choroid plexus, which alters the pacing of the SCN. We propose that the kidney also contributes to overall circadian timekeeping at the whole-body level, through bottom-up feedback in the hierarchical structure of the mammalian circadian clocks.

scholarly journals Drosophila as a Model for Microbiota Studies of Neurodegeneration

2021 ◽  
pp. 1-12
Author(s):  
Fukiko Kitani-Morii ◽  
Robert P. Friedland ◽  
Hideki Yoshida ◽  
Toshiki Mizuno
Keyword(s):  
Gut Microbiota ◽  
Molecular Mechanisms ◽  
Environmental Changes ◽  
Fruit Fly ◽  
Endocrine Regulation ◽  
Nutrient Metabolism ◽  
Host Health ◽  
And Behavior ◽  
The Brain ◽  
Lateral Sclerosis

Accumulating evidence show that the gut microbiota is deeply involved not only in host nutrient metabolism but also in immune function, endocrine regulation, and chronic disease. In neurodegenerative conditions such as Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis, the gut-brain axis, the bidirectional interaction between the brain and the gut, provides new route of pathological spread and potential therapeutic targets. Although studies of gut microbiota have been conducted mainly in mice, mammalian gut microbiota is highly diverse, complex, and sensitive to environmental changes. Drosophila melanogaster, a fruit fly, has many advantages as a laboratory animal: short life cycle, numerous and genetically homogenous offspring, less ethical concerns, availability of many genetic models, and low maintenance costs. Drosophila has a simpler gut microbiota than mammals and can be made to remain sterile or to have standardized gut microbiota by simple established methods. Research on the microbiota of Drosophila has revealed new molecules that regulate the brain-gut axis, and it has been shown that dysbiosis of the fly microbiota worsens lifespan, motor function, and neurodegeneration in AD and PD models. The results shown in fly studies represents a fundamental part of the immune and proteomic process involving gut-microbiota interactions that are highly conserved. Even though the fly’s gut microbiota are not simple mimics of humans, flies are a valuable system to learn the molecular mechanisms of how the gut microbiota affect host health and behavior.

scholarly journals Minireview: Entrainment of the Suprachiasmatic Clockwork in Diurnal and Nocturnal Mammals

Endocrinology ◽  
2007 ◽  
Vol 148 (12) ◽  
pp. 5648-5655 ◽  
Author(s):  
Etienne Challet
Keyword(s):  
Activity Pattern ◽  
Molecular Mechanisms ◽  
Clock Genes ◽  
Light Exposure ◽  
Hormone Secretion ◽  
Receptor Activation ◽  
Active Species ◽  
Voluntary Exercise ◽  
Nocturnal Species ◽  
Master Clock

Daily rhythmicity, including timing of wakefulness and hormone secretion, is mainly controlled by a master clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN clockwork involves various clock genes, with specific temporal patterns of expression that are similar in nocturnal and diurnal species (e.g. the clock gene Per1 in the SCN peaks at midday in both categories). Timing of sensitivity to light is roughly similar, during nighttime, in diurnal and nocturnal species. Molecular mechanisms of photic resetting are also comparable in both species categories. By contrast, in animals housed in constant light, exposure to darkness can reset the SCN clock, mostly during the resting period, i.e. at opposite circadian times between diurnal and nocturnal species. Nonphotic stimuli, such as scheduled voluntary exercise, food shortage, exogenous melatonin, or serotonergic receptor activation, are also capable of shifting the master clock and/or modulating photic synchronization. Comparison between day- and night-active species allows classifications of nonphotic cues in two, arousal-independent and arousal-dependent, families of factors. Arousal-independent factors, such as melatonin (always secreted during nighttime, independently of daily activity pattern) or γ-aminobutyric acid (GABA), have shifting effects at the same circadian times in both nocturnal and diurnal rodents. By contrast, arousal-dependent factors, such as serotonin (its cerebral levels follow activity pattern), induce phase shifts only during resting and have opposite modulating effects on photic resetting between diurnal and nocturnal species. Contrary to light and arousal-independent nonphotic cues, arousal-dependent nonphotic stimuli provide synchronizing feedback signals to the SCN clock in circadian antiphase between nocturnal and diurnal animals.

scholarly journals The neuropeptide allatostatin C from clock-associated DN1p neurons generates the circadian rhythm for oogenesis

2021 ◽  
Vol 118 (4) ◽  
pp. e2016878118
Author(s):  
Chen Zhang ◽  
Ivana Daubnerova ◽  
Yong-Hoon Jang ◽  
Shu Kondo ◽  
Dušan Žitňan ◽  
...  
Keyword(s):  
Clock Genes ◽  
Biological Clock ◽  
Model Organism ◽  
Fruit Fly ◽  
Neural Substrates ◽  
Pacemaker Neurons ◽  
Insulin Producing Cells ◽  
Gonadotrophin Secretion ◽  
Show Evidence ◽  
The Brain

The link between the biological clock and reproduction is evident in most metazoans. The fruit fly Drosophila melanogaster, a key model organism in the field of chronobiology because of its well-defined networks of molecular clock genes and pacemaker neurons in the brain, shows a pronounced diurnal rhythmicity in oogenesis. Still, it is unclear how the circadian clock generates this reproductive rhythm. A subset of the group of neurons designated “posterior dorsal neuron 1” (DN1p), which are among the ∼150 pacemaker neurons in the fly brain, produces the neuropeptide allatostatin C (AstC-DN1p). Here, we report that six pairs of AstC-DN1p send inhibitory inputs to the brain insulin-producing cells, which express two AstC receptors, star1 and AICR2. Consistent with the roles of insulin/insulin-like signaling in oogenesis, activation of AstC-DN1p suppresses oogenesis through the insulin-producing cells. We show evidence that AstC-DN1p activity plays a role in generating an oogenesis rhythm by regulating juvenile hormone and vitellogenesis indirectly via insulin/insulin-like signaling. AstC is orthologous to the vertebrate neuropeptide somatostatin (SST). Like AstC, SST inhibits gonadotrophin secretion indirectly through gonadotropin-releasing hormone neurons in the hypothalamus. The functional and structural conservation linking the AstC and SST systems suggest an ancient origin for the neural substrates that generate reproductive rhythms.

scholarly journals The Fruit Fly Drosophila melanogaster as a Model System to Study Cholesterol Metabolism and Homeostasis

Cholesterol ◽  
2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Ryusuke Niwa ◽  
Yuko S. Niwa
Keyword(s):  
Drosophila Melanogaster ◽  
Steroid Hormones ◽  
Molecular Mechanisms ◽  
Cholesterol Metabolism ◽  
Cholesterol Biosynthesis ◽  
Fruit Fly ◽  
Model System ◽  
Biophysical Properties ◽  
Type C ◽  
Niemann Pick

Cholesterol has long been recognized for its versatile roles in influencing the biophysical properties of cell membranes and for serving as a precursor of steroid hormones. While many aspects of cholesterol biosynthesis are well understood, little is currently known about the molecular mechanisms of cholesterol metabolism and homeostasis. Recently, genetic approaches in the fruit fly, Drosophila melanogaster, have been successfully used for the analysis of molecular mechanisms that regulate cholesterol metabolism and homeostasis. This paper summarizes the recent studies on genes that regulate cholesterol metabolism and homeostasis, including neverland, Niemann Pick type C(NPC) disease genes, and DHR96.

scholarly journals Entrainment of the Drosophila clock by the visual system

2020 ◽  
Vol 15 ◽  
pp. 263310552090370
Author(s):  
Matthias Schlichting
Keyword(s):  
Drosophila Melanogaster ◽  
Visual System ◽  
Clock Synchronization ◽  
Fruit Fly ◽  
Circadian Clocks ◽  
Cyclic Change ◽  
Animal Physiology ◽  
Light Entrainment ◽  
Physiological Evidence ◽  
External Cues

Circadian clocks evolved as an adaptation to the cyclic change of day and night. To precisely adapt to this environment, the endogenous period has to be adjusted every day to exactly 24 hours by a process called entrainment. Organisms can use several external cues, called zeitgebers, to adapt. These include changes in temperature, humidity, or light. The latter is the most powerful signal to synchronize the clock in animals. Research shows that a complex visual system and circadian photoreceptors work together to adjust animal physiology to the outside world. This review will focus on the importance of the visual system for clock synchronization in the fruit fly Drosophila melanogaster. It will cover behavioral and physiological evidence that supports the importance of the visual system in light entrainment.

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