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Circadian and ultradian rhythms of clock gene expression in the suprachiasmatic nucleus of freely moving mice.

Ono D, Honma K, Honma S - Sci Rep (2015)

Bottom Line: We found robust circadian rhythms in the clock gene expression, the phase-relation of which were the same as those observed ex vivo.Episodic bursts often accompanied activity bouts, but stoichiometric as well as temporal analyses revealed no causality between them.Clock gene expression in the SCN in vivo is regulated by the circadian pacemaker and ultradian rhythms of unknown origin.

View Article: PubMed Central - PubMed

Affiliation: Photonic Bioimaging Section, Research Center for Cooperative Projects, Hokkaido University Graduate School of Medicine, Sapporo, 060-8638, Japan.

ABSTRACT
In mammals, the temporal order of physiology and behavior is primarily regulated by the circadian pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). Rhythms are generated in cells by an auto-regulatory transcription/translation feedback loop, composed of several clock genes and their protein products. Taking advantage of bioluminescence reporters, we have succeeded in continuously monitoring the expression of clock gene reporters Per1-luc, PER2::LUC and Bmal1-ELuc in the SCN of freely moving mice for up to 3 weeks in constant darkness. Bioluminescence emitted from the SCN was collected with an implanted plastic optical fiber which was connected to a cooled photomultiplier tube. We found robust circadian rhythms in the clock gene expression, the phase-relation of which were the same as those observed ex vivo. The circadian rhythms were superimposed by episodic bursts which had ultradian periods of approximately 3.0 h. Episodic bursts often accompanied activity bouts, but stoichiometric as well as temporal analyses revealed no causality between them. Clock gene expression in the SCN in vivo is regulated by the circadian pacemaker and ultradian rhythms of unknown origin.

No MeSH data available.


Stoichiometric relations between episodic burst of bioluminescence and activity bout(a) Temporal relations between the mean activity bout and accompanying bioluminescence (behavior bout reference) are illustrated for each clock gene reporter. (b) Temporal relations between the mean episodic burst of bioluminescence and accompanying behavior activity (bioluminescence episodic reference) are illustrated for each clock gene reporter. The mean values were obtained by adjusting individual times of initial trough or of 0 counts. Values were expressed as mean ± SEM.
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f4: Stoichiometric relations between episodic burst of bioluminescence and activity bout(a) Temporal relations between the mean activity bout and accompanying bioluminescence (behavior bout reference) are illustrated for each clock gene reporter. (b) Temporal relations between the mean episodic burst of bioluminescence and accompanying behavior activity (bioluminescence episodic reference) are illustrated for each clock gene reporter. The mean values were obtained by adjusting individual times of initial trough or of 0 counts. Values were expressed as mean ± SEM.

Mentions: The frequency and size of episodic bursts were examined to characterize episodic bursts of clock gene reporters. Episodic bursts occurred either sporadically or sequentially. In the latter case, bursts overlapped, leading a stepwise increase in bioluminescence that lasted up to several hours. Since most sporadic episodes persisted for approximately one hour, episodic bursts of less than 2 h duration were used for further analyses. A total of 691 episodic bursts were detected during the first 5 circadian cycles under DD for all mice (Per1-luc, n = 342; PER2::LUC, n = 106; Bmal1-ELuc, n = 243). The mean number of episodic bursts per mouse was 42.8 ± 10.8/5 cycles for Per1-luc, 35.3 ± 20.7/5 cycles for PER2::LUC and 34.7 ± 8.0/5 cycles for Bmal1-ELuc. The mean duration of episodic burst was 70.5 ± 7.5 min for Per1-luc, 85.0 ± 5.0 min for PER2::LUC and 75.5 ± 9.5 min for Bmal1-ELuc, respectively. The frequency and the size of episodic burst depended on the circadian phase of respective reporter genes (Fig. 3). The size of episode was expressed as an area under the curve (AUC). AUC was calculated by summing bioluminescence above the baseline. Both the number of episode and AUC of Per1-luc were largest in the late subjective day (CT6-CT12), those of PER2::LUC were in the early subjective night (CT12-CT18), and of Bmal1-ELuc in the early subjective day (CT0-CT6), respectively (p < 0.05, one-way repeated measure ANOVA), where CT12 was defined as the onset of behavior activity in terms of circadian time (CT) which was a time unit divided by a circadian period. The mean interval from the initial trough of a burst to the episodic peak was 25 min, irrespective of reporter gene (Fig. 4).


Circadian and ultradian rhythms of clock gene expression in the suprachiasmatic nucleus of freely moving mice.

Ono D, Honma K, Honma S - Sci Rep (2015)

Stoichiometric relations between episodic burst of bioluminescence and activity bout(a) Temporal relations between the mean activity bout and accompanying bioluminescence (behavior bout reference) are illustrated for each clock gene reporter. (b) Temporal relations between the mean episodic burst of bioluminescence and accompanying behavior activity (bioluminescence episodic reference) are illustrated for each clock gene reporter. The mean values were obtained by adjusting individual times of initial trough or of 0 counts. Values were expressed as mean ± SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508664&req=5

f4: Stoichiometric relations between episodic burst of bioluminescence and activity bout(a) Temporal relations between the mean activity bout and accompanying bioluminescence (behavior bout reference) are illustrated for each clock gene reporter. (b) Temporal relations between the mean episodic burst of bioluminescence and accompanying behavior activity (bioluminescence episodic reference) are illustrated for each clock gene reporter. The mean values were obtained by adjusting individual times of initial trough or of 0 counts. Values were expressed as mean ± SEM.
Mentions: The frequency and size of episodic bursts were examined to characterize episodic bursts of clock gene reporters. Episodic bursts occurred either sporadically or sequentially. In the latter case, bursts overlapped, leading a stepwise increase in bioluminescence that lasted up to several hours. Since most sporadic episodes persisted for approximately one hour, episodic bursts of less than 2 h duration were used for further analyses. A total of 691 episodic bursts were detected during the first 5 circadian cycles under DD for all mice (Per1-luc, n = 342; PER2::LUC, n = 106; Bmal1-ELuc, n = 243). The mean number of episodic bursts per mouse was 42.8 ± 10.8/5 cycles for Per1-luc, 35.3 ± 20.7/5 cycles for PER2::LUC and 34.7 ± 8.0/5 cycles for Bmal1-ELuc. The mean duration of episodic burst was 70.5 ± 7.5 min for Per1-luc, 85.0 ± 5.0 min for PER2::LUC and 75.5 ± 9.5 min for Bmal1-ELuc, respectively. The frequency and the size of episodic burst depended on the circadian phase of respective reporter genes (Fig. 3). The size of episode was expressed as an area under the curve (AUC). AUC was calculated by summing bioluminescence above the baseline. Both the number of episode and AUC of Per1-luc were largest in the late subjective day (CT6-CT12), those of PER2::LUC were in the early subjective night (CT12-CT18), and of Bmal1-ELuc in the early subjective day (CT0-CT6), respectively (p < 0.05, one-way repeated measure ANOVA), where CT12 was defined as the onset of behavior activity in terms of circadian time (CT) which was a time unit divided by a circadian period. The mean interval from the initial trough of a burst to the episodic peak was 25 min, irrespective of reporter gene (Fig. 4).

Bottom Line: We found robust circadian rhythms in the clock gene expression, the phase-relation of which were the same as those observed ex vivo.Episodic bursts often accompanied activity bouts, but stoichiometric as well as temporal analyses revealed no causality between them.Clock gene expression in the SCN in vivo is regulated by the circadian pacemaker and ultradian rhythms of unknown origin.

View Article: PubMed Central - PubMed

Affiliation: Photonic Bioimaging Section, Research Center for Cooperative Projects, Hokkaido University Graduate School of Medicine, Sapporo, 060-8638, Japan.

ABSTRACT
In mammals, the temporal order of physiology and behavior is primarily regulated by the circadian pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). Rhythms are generated in cells by an auto-regulatory transcription/translation feedback loop, composed of several clock genes and their protein products. Taking advantage of bioluminescence reporters, we have succeeded in continuously monitoring the expression of clock gene reporters Per1-luc, PER2::LUC and Bmal1-ELuc in the SCN of freely moving mice for up to 3 weeks in constant darkness. Bioluminescence emitted from the SCN was collected with an implanted plastic optical fiber which was connected to a cooled photomultiplier tube. We found robust circadian rhythms in the clock gene expression, the phase-relation of which were the same as those observed ex vivo. The circadian rhythms were superimposed by episodic bursts which had ultradian periods of approximately 3.0 h. Episodic bursts often accompanied activity bouts, but stoichiometric as well as temporal analyses revealed no causality between them. Clock gene expression in the SCN in vivo is regulated by the circadian pacemaker and ultradian rhythms of unknown origin.

No MeSH data available.