scholarly journals mir-276a strengthens Drosophila circadian rhythms by regulating timeless expression

2016 ◽  
Vol 113 (21) ◽  
pp. E2965-E2972 ◽  
Author(s):  
Xiao Chen ◽  
Michael Rosbash
Keyword(s):  
Circadian Rhythms ◽  
Molecular Clock ◽  
Posttranscriptional Regulation ◽  
Clock Gene ◽  
Constant Darkness ◽  
Transcription Activator ◽  
Behavioral Rhythms ◽  
Culture Cells ◽  
Tissue Culture Cells ◽  
The Central Nervous System

Circadian rhythms in metazoan eukaryotes are controlled by an endogenous molecular clock. It functions in many locations, including subsets of brain neurons (clock neurons) within the central nervous system. Although the molecular clock relies on transcription/translation feedback loops, posttranscriptional regulation also plays an important role. Here, we show that the abundant Drosophila melanogaster microRNA mir-276a regulates molecular and behavioral rhythms by inhibiting expression of the important clock gene timeless (tim). Misregulation of mir-276a in clock neurons alters tim expression and increases arrhythmicity under standard constant darkness (DD) conditions. mir-276a expression itself appears to be light-regulated because its levels oscillate under 24-h light–dark (LD) cycles but not in DD. mir-276a is regulated by the transcription activator Chorion factor 2 in flies and in tissue-culture cells. Evidence from flies mutated using the clustered, regularly interspaced, short palindromic repeats (CRISPR) tool shows that mir-276a inhibits tim expression: Deleting the mir-276a–binding site in the tim 3′ UTR causes elevated levels of TIM and ∼50% arrhythmicity. We suggest that this pathway contributes to the more robust rhythms observed under light/dark LD conditions than under DD conditions.

scholarly journals Long-term in vivo recording of circadian rhythms in brains of freely moving mice

2018 ◽  
Vol 115 (16) ◽  
pp. 4276-4281 ◽  
Author(s):  
Long Mei ◽  
Yanyan Fan ◽  
Xiaohua Lv ◽  
David K. Welsh ◽  
Cheng Zhan ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Clock Gene ◽  
Constant Darkness ◽  
Behavioral Rhythms ◽  
Clock Gene Expression ◽  
Hippocampal Ca1 ◽  
Freely Moving ◽  
Term Monitoring

Endogenous circadian clocks control 24-h physiological and behavioral rhythms in mammals. Here, we report a real-time in vivo fluorescence recording system that enables long-term monitoring of circadian rhythms in the brains of freely moving mice. With a designed reporter of circadian clock gene expression, we tracked robust Cry1 transcription reporter rhythms in the suprachiasmatic nucleus (SCN) of WT, Cry1−/−, and Cry2−/− mice in LD (12 h light, 12 h dark) and DD (constant darkness) conditions and verified that signals remained stable for over 6 mo. Further, we recorded Cry1 transcriptional rhythms in the subparaventricular zone (SPZ) and hippocampal CA1/2 regions of WT mice housed under LD and DD conditions. By using a Cre-loxP system, we recorded Per2 and Cry1 transcription rhythms specifically in vasoactive intestinal peptide (VIP) neurons of the SCN. Finally, we demonstrated the dynamics of Per2 and Cry1 transcriptional rhythms in SCN VIP neurons following an 8-h phase advance in the light/dark cycle.

scholarly journals Phase-dependent resetting of the adrenal clock by ACTH in vitro

2014 ◽  
Vol 306 (6) ◽  
pp. R387-R393 ◽  
Author(s):  
J. Marina Yoder ◽  
Megan Brandeland ◽  
William C. Engeland
Keyword(s):  
Circadian Rhythms ◽  
Molecular Clock ◽  
Clock Gene ◽  
External Environment ◽  
Phase Delay ◽  
Melanocyte Stimulating Hormone ◽  
Circadian Time ◽  
Acth Receptor ◽  
Acth Fragments

The adrenal cortex has a molecular clock that generates circadian rhythms in glucocorticoids, yet how the clock is synchronized to the external environment is unknown. Using mPER2::Luciferase (mPER2Luc) knockin mice, in which luciferase is rhythmically expressed under the control of the mouse Per2 clock gene, we hypothesized that ACTH transmits entrainment signals to the adrenal. Adrenal explants were administered ACTH at different phases of the mPER2Luc rhythm. Treatment with ACTH 1–39 produced a phase delay that was phase-dependent, with a maximum at circadian time (CT)18; ACTH did not alter the period or amplitude of the rhythm. Forskolin produced a parallel response, suggesting that the phase delay was cAMP-mediated. The response to ACTH was concentration-dependent and peptide-specific. Pulse administration (60 min) of ACTH 1–39 also produced phase delays restricted to late CTs. In contrast to ACTH 1–39, other ACTH fragments, including α-melanocyte-stimulating hormone, which do not activate the melanocortin 2 (MC2/ACTH) receptor, had no effect. The finding that ACTH in vitro phase delays the adrenal mPER2luc rhythm in a monophasic fashion argues for ACTH as a key resetter, but not the sole entrainer, of the adrenal clock.

scholarly journals Neuron-specific knockouts indicate the importance of network communication to Drosophila rhythmicity

2019 ◽  
Author(s):  
M Schlichting ◽  
MM Diaz ◽  
J Xin ◽  
M Rosbash
Keyword(s):  
Gene Expression ◽  
Circadian Rhythms ◽  
Intercellular Communication ◽  
Clock Gene ◽  
Feedback Loops ◽  
Neuronal Firing ◽  
Network Communication ◽  
Constant Darkness ◽  
Circadian Period ◽  
Clock Gene Expression

AbstractAnimal circadian rhythms persist in constant darkness and are driven by intracellular transcription-translation feedback loops. Although these cellular oscillators communicate, isolated mammalian cellular clocks continue to tick away in darkness without intercellular communication. To investigate these issues in Drosophila, we assayed behavior as well as molecular rhythms within individual brain clock neurons while blocking communication within the ca. 150 neuron clock network. We also generated CRISPR-mediated neuron-specific circadian clock knockouts. The results point to two key clock neuron groups: loss of the clock within both regions but neither one alone has a strong behavioral phenotype in darkness; communication between these regions also contributes to circadian period determination. Under these dark conditions, the clock within one region persists without network communication. The clock within the famous PDF-expressing s-LNv neurons however was strongly dependent on network communication, likely because clock gene expression within these vulnerable sLNvs depends on neuronal firing or light.

Role of suprachiasmatic nuclei in circadian and light-entrained behavioral rhythms of lizards

2000 ◽  
Vol 279 (6) ◽  
pp. R2121-R2131 ◽  
Author(s):  
Cristiano Bertolucci ◽  
Valeria Anna Sovrano ◽  
Maria Chiara Magnone ◽  
Augusto Foà
Keyword(s):  
Circadian Rhythms ◽  
Constant Temperature ◽  
Locomotor Behavior ◽  
Functional Similarity ◽  
Daily Rhythm ◽  
Constant Darkness ◽  
Suprachiasmatic Nuclei ◽  
Podarcis Sicula ◽  
Behavioral Rhythms

To establish whether the suprachiasmatic nuclei (SCN) of the Ruin lizard ( Podarcis sicula) play a role in entrainment of circadian rhythms to light, we examined the effects of exposure to 24-h light-dark (LD) cycles on the locomotor behavior of lizards with SCN lesions. Lizards became arrhythmic in response to complete SCN lesion under constant temperature and constant darkness (DD), and they remained arrhythmic after exposure to LD cycles. Remnants of SCN tissue in other lesioned lizards were sufficient to warrant entrainment to LD cycles. Hence, the SCN of Ruin lizards are essential both to maintain locomotor rhythmicity and to mediate entrainment of these rhythms to light. We also asked whether light causes expression of Fos-like immunoreactivity (Fos-LI) in the SCN. Under LD cycles, the SCN express a daily rhythm in Fos-LI. Because Fos-LI is undetectable in DD, the rhythm seen in LD cycles is caused by light. We further showed that unilateral SCN lesions in DD induce dramatic period changes. Altogether, the present data support the existence of a strong functional similarity between the SCN of lizards and the SCN of mammals.

scholarly journals Dissection of central clock function in Drosophila through cell-specific CRISPR-mediated clock gene disruption

2019 ◽  
Author(s):  
Rebecca Delventhal ◽  
Meghan Pantalia ◽  
Reed M. O’Connor ◽  
Matthew Ulgherait ◽  
Han X. Kim ◽  
...  
Keyword(s):  
Locomotor Activity ◽  
Circadian Rhythms ◽  
Molecular Clock ◽  
Gene Disruption ◽  
Clock Gene ◽  
Distributed Network ◽  
Circadian Activity ◽  
Clock Proteins ◽  
Central Clock ◽  
Circadian Behavior

AbstractIn Drosophila, ~150 neurons expressing molecular clock proteins regulate circadian behavior. Sixteen of these clock neurons secrete the neuropeptide Pdf and have been called “master pacemakers” because they are essential for circadian rhythms. A subset of Pdf+ neurons (the morning oscillator) regulates morning activity and communicates with other non-Pdf+ neurons, including a subset called the evening oscillator. It is assumed that the molecular clock in Pdf+ neurons is required for these functions. To test this, we developed and validated Gal4-UAS based CRISPR tools for cell-specific disruption of key molecular clock components, period and timeless. While loss of the molecular clock in both the morning and evening oscillators eliminates circadian locomotor activity, the molecular clock in either oscillator alone is sufficient for circadian locomotor activity. This suggests that clock neurons do not act in a hierarchy but as a distributed network to regulate circadian activity.

Circadian rhythms in the absence of the clock gene Bmal1

Science ◽  
2020 ◽  
Vol 367 (6479) ◽  
pp. 800-806 ◽  
Author(s):  
Sandipan Ray ◽  
Utham K. Valekunja ◽  
Alessandra Stangherlin ◽  
Steven A. Howell ◽  
Ambrosius P. Snijders ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Transcriptional Regulation ◽  
Transcription Factors ◽  
Circadian Rhythms ◽  
Molecular Clock ◽  
Knockout Mice ◽  
Clock Gene ◽  
Skin Fibroblasts ◽  
Temperature Cycles ◽  
Ets Family

Circadian (~24 hour) clocks have a fundamental role in regulating daily physiology. The transcription factor BMAL1 is a principal driver of a molecular clock in mammals. Bmal1 deletion abolishes 24-hour activity patterning, one measure of clock output. We determined whether Bmal1 function is necessary for daily molecular oscillations in skin fibroblasts and liver slices. Unexpectedly, in Bmal1 knockout mice, both tissues exhibited 24-hour oscillations of the transcriptome, proteome, and phosphoproteome over 2 to 3 days in the absence of any exogenous drivers such as daily light or temperature cycles. This demonstrates a competent 24-hour molecular pacemaker in Bmal1 knockouts. We suggest that such oscillations might be underpinned by transcriptional regulation by the recruitment of ETS family transcription factors, and nontranscriptionally by co-opting redox oscillations.

scholarly journals Neuron-specific knockouts indicate the importance of network communication to Drosophila rhythmicity

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Matthias Schlichting ◽  
Madelen M Díaz ◽  
Jason Xin ◽  
Michael Rosbash
Keyword(s):  
Gene Expression ◽  
Circadian Rhythms ◽  
Intercellular Communication ◽  
Clock Gene ◽  
Feedback Loops ◽  
Neuronal Firing ◽  
Network Communication ◽  
Constant Darkness ◽  
Circadian Period ◽  
Clock Gene Expression

Animal circadian rhythms persist in constant darkness and are driven by intracellular transcription-translation feedback loops. Although these cellular oscillators communicate, isolated mammalian cellular clocks continue to tick away in darkness without intercellular communication. To investigate these issues in Drosophila, we assayed behavior as well as molecular rhythms within individual brain clock neurons while blocking communication within the ca. 150 neuron clock network. We also generated CRISPR-mediated neuron-specific circadian clock knockouts. The results point to two key clock neuron groups: loss of the clock within both regions but neither one alone has a strong behavioral phenotype in darkness; communication between these regions also contributes to circadian period determination. Under these dark conditions, the clock within one region persists without network communication. The clock within the famous PDF-expressing s-LNv neurons however was strongly dependent on network communication, likely because clock gene expression within these vulnerable sLNvs depends on neuronal firing or light.

Interruption of the rat circadian clock by short light-dark cycles

2003 ◽  
Vol 284 (5) ◽  
pp. R1255-R1259 ◽  
Author(s):  
Setsuo Usui ◽  
Terue Okazaki ◽  
Yoshiko Honda
Keyword(s):  
Locomotor Activity ◽  
Circadian Rhythms ◽  
Circadian Clock ◽  
Constant Darkness ◽  
Sprague Dawley ◽  
Light Stimulation ◽  
Behavioral Rhythms ◽  
Light Pulses ◽  
Sprague Dawley Rats

Ninety male Sprague-Dawley rats were exposed to 1:1-h light-dark (LD1:1) cycles for 50–90 days, and then they were released into constant darkness (DD). During LD1:1 cycles, behavioral rhythms were gradually disintegrated, and circadian rhythms of locomotor activity, drinking, and urine 6-sulfatoxymelatonin excretion were eventually abolished. After release into DD, 44 (49%) rats showed arrhythmic behavior for >10 days. Seven (8%) animals that remained arrhythmic for >50 days in DD were exposed to brief light pulses or 12:12-h light-dark cycles, and then they restored their circadian rhythms. These results indicate that the circadian clock was stopped, at least functionally, by LD1:1 cycles and was restarted by subsequent light stimulation.

Cytoplasmic Tubules in Cells Infected with Laryngotracheitis Virus

1969 ◽  
Vol 27 ◽  
pp. 376-377
Author(s):  
A. M. Watrach
Keyword(s):  
Tissue Culture ◽  
Small Proportion ◽  
Chicken Embryo ◽  
Culture Cells ◽  
Tissue Culture Cells ◽  
Morphologic Characteristics ◽  
Infectious Laryngotracheitis ◽  
Laryngotracheitis Virus ◽  
In Cells

During a study of the development of infectious laryngotracheitis (LT) virus in tissue culture cells, unusual tubular formations were found in the cytoplasm of a small proportion of the affected cells. It is the purpose of this report to describe the morphologic characteristics of the tubules and to discuss their possible association with the development of virus.The source and maintenance of the strain of LT virus have been described. Prior to this study, the virus was passed several times in chicken embryo kidney (CEK) tissue culture cells.

Sulfhydryl bond formation is a prerequisite for proper cycling of centrosomes and chromosomes in mammalian tissue culture cells

1993 ◽  
Vol 51 ◽  
pp. 342-343
Author(s):  
Heide Schatten ◽  
Neidhard Paweletz ◽  
Ron Balczon
Keyword(s):  
Tissue Culture ◽  
Cell Cycle Progression ◽  
Group Formation ◽  
Sulfhydryl Group ◽  
Mammalian Tissue ◽  
Mitotic Chromosomes ◽  
Microtubule Network ◽  
Culture Cells ◽  
Tissue Culture Cells ◽  
Transmission Electron

To study the role of sulfhydryl group formation during cell cycle progression, mammalian tissue culture cells (PTK2) were exposed to 100¼M 2-mercaptoethanol for 2 to 6 h during their exponential phase of growth. The effects of 2-mercaptoethanol on centrosomes, chromosomes, microtubules, membranes and intermediate filaments were analyzed by transmission electron microscopy (TEM) and by immunofluorescence microscopy (IFM) methods using a human autoimmune antibody directed against centrosomes (SPJ), and a mouse monoclonal antibody directed against tubulin (E7). Chromosomes were affected most by this treatment: premature chromosome condensation was detected in interphase nuclei, and the structure in mitotic chromosomes was altered compared to control cells. This would support previous findings in dividing sea urchin cells in which chromosomes are arrested at metaphase while the centrosome splitting cycle continues. It might also support findings that certairt-sulfhydryl-blocking agents block cyclin destruction. The organization of the microtubule network was scattered probably due to a looser organization of centrosomal material at the interphase centers and at the mitotic poles.

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