Clock mRNA expression patterns in the chick pineal gland under experimental jet lag
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1
University of Pécs, Department of Anatomy, Hungary
Circadian biological clocks help organisms to anticipate changes in the environment occuring on a regular 24-hour rhythmic basis. If the daily pattern of environmental exposure such as light/dark periodicity becomes unusual (e.g. jet lag), it may perturb many physiological processes by resetting the circadian clock.
Shift-workers have a higher risk for metabolic syndrome, a condition which developes also in clock -/- mice. To collect data on the transcriptional changes of clock gene under unusual light/dark conditions, we examined the 24h mRNA expression patterns of clock in the chicken pineal model exposed acutely to reversed light/dark conditions.
White Leghorn chickens were kept under 14h light/10h dark control environment (lights on at 6:00). In our in vivo experiments, chickens were placed under reversed light/dark conditions (lights on at 20:00), where pineal glands were collected every 4 hours (n=3). We carried out in vitro experiments in our perifusion system: chicken pineal glands were placed in 6 chambers (n=3 glands/chamber), which were then collected every 4 hours beginning at 18:00 next day. For mRNA measurements, we optimized a semiquantitative RT-PCR method.
Under control LD conditions, clock expression peaked at 2:00 in vivo and at 22:00 in vitro. Compared to control, under in vivo reversed light/dark conditions, we measured between 22:00 and 6:00 higher mRNA contents in the first cycle, but lower in the second cycle. Under in vitro reversed light/dark conditions, we detected between 10:00 and 14:00 higher mRNA contents if compared to control data.
Night-time peaks of clock mRNA amounts in the control group suggest a darkness-related activation of the clock gene. This is supported by our data collected under reversed light/dark conditions: in vivo the nighttime activation is diminished under illumination, and in vitro a daytime activation is seen under darkness. We have found differences in the 24h mRNA patterns between the first and the second reversed cycles in vivo, but also between in vivo and in vitro data. Both suggest that unexpected night-time illumination may rapidly reset the regulation of clock transcription via neurohumoral signals and signalling pathways which may be different from those working under normal, entrained conditions.
Keywords:
comparative endocrinology
Conference:
25th Conference of the European Comparative Endocrinologists, Pécs, Hungary, 31 Aug - 4 Sep, 2010.
Presentation Type:
Conference Presentation
Topic:
Comparative endocrinology
Citation:
Bódis
G,
Kommedal
S,
Matkovits
A,
Csernus
V and
Nagy
AD
(2010). Clock mRNA expression patterns in the chick pineal gland under experimental jet lag.
Front. Endocrinol.
Conference Abstract:
25th Conference of the European Comparative Endocrinologists.
doi: 10.3389/conf.fendo.2010.01.00013
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Received:
26 Aug 2010;
Published Online:
29 Aug 2010.
*
Correspondence:
Dr. Gergely Bódis, University of Pécs, Department of Anatomy, Pécs, Hungary, bouwdeesh@gmail.com