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Circadian Clock

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Charlotte Wit

on 27 June 2013

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Transcript of Circadian Clock

The comparison of Per2::luc expression rhythms in SCN cells between short and long photoperiod
Introduction
The circadian clock
Hypothesis
Results
Discussion
Circadian rhythms
The SCN
Seasonal changes
Gene expression in the SCN
Circadian feedback loop
Motivation
Per2 as representation of circadian rhythmicity

Where do seasonal changes occur in the SCN?

Synchronization may be important for health
Method
Per2::luc mice
luciferase + luciferin = light reaction
Bioluminescence rhythm
Seasonal changes
Analysis
Whole SCN slices
Single cell analysis
Per2::luc bioluminescence rhythms
Period
Peak time
Synchrony
Amplitude
Summer = long light in the day / long photoperiod (LP)

Winter = short light in the day / short photoperiod (SP)
Light exposure

Reproduction

Winter depression
Seasonal changes affect the compression of Per2 gene expression. In Short Photoperiod we expect a narrow phase distribution, in Long Photoperiod a broader distribution and less synchronization between single neurons.
Conclusions
Regions within the SCN
Rostral
Central
Caudal
Measure differences in separate regions
of the SCN in summer and winter conditions
Changing light intensity of luminescence in SCN neurons
Rostral, Central, Caudal
6 groups
Image Pro Plus
Stacks
Matlab
Charlotte Wit

Bachelor Internship MCB Neurophysiology
Whole SCN
Single Neuron
1
2
Synchrony and Amplitude
Thank you for listening
Questions?
Longer day length shifts the peak time relative to time lights off
(as well when calculated for time lights on)
Caudal region of the SCN exhibits a higher synchrony between cells and a higher amplitude rhythm.
Short photoperiod is related to a high amplitude rhythm as well as high synchrony, where Long photoperiod has more dispersion of single cell oscillations, has a broader peak time distribution and a lower amplitude.
High synchrony (in SP) a sign of better entrainment?
High synchrony (in SP) a sign of better health?
Reference: Intrinsic Regulation of Spatiotemporal Organization within the Suprachiasmatic Nucleus
Jennifer A. Evans, Tanya L. Leise, Oscar Castanon-Cervantes, Alec J. Davidson

Synchrony between cells depends on variance
Amplitude between first through and peak
Method: Evans et al. (2011)
Output signal for peripheral clocks
Amplitude a good measurement for synchonization?
We went around the (biological) clock
Bronson et al. (2009)
Sack et al. (1990)
http://www.nature.com/nature/journal/v418/n6901/images/nature00965-f4.2.jpg
Other studies have shown that winter conditions compress behavior, MUA and Per1 gene expression rhythms, and summer conditions decompress these factors.
Steinlechner (2002), Rohling et al. (2007), Naito (2008)
Other studies have shown rostrocaudal differences in SCN slices in peak time, peak width, amplitude, phase range and brightness
Hazlerigg et al. (2005), Evans et al. (2011), Sellix et al. (2012)
We expect spatial differences in Per2 gene expression between rostral and caudal slices. Not only on a whole SCN level, but also in single neuron oscillations.
"Synchrony” occurs when neurons share the same
circadian period, but not necessarily the same phase.

Quintero et al., (2003); Yamaguchi et al., (2003); Schaap et al., 2003); Aton et al., (2005); Aton and Herzog (2007)
Sosniyenko et al., (2009)
Peak time distribution peak 1
Long Photoperiod Short Photoperiod
Peak time distribution all cells peak 1
Peak time distribution per group
Period distribution of period 1 per group
Full transcript