Present address: Novartis Pharma AG, Basel, Switzerland.
The circadian cycle of mPER clock gene products in the suprachiasmatic nucleus of the Siberian hamster encodes both daily and seasonal time
Article first published online: 24 DEC 2001
European Journal of Neuroscience
Volume 12, Issue 8, pages 2856–2864, August 2000
How to Cite
Nuesslein-Hildesheim, B., O'brien, J. A., Ebling, F. J. P., Maywood, E. S. and Hastings, M. H. (2000), The circadian cycle of mPER clock gene products in the suprachiasmatic nucleus of the Siberian hamster encodes both daily and seasonal time. European Journal of Neuroscience, 12: 2856–2864. doi: 10.1046/j.1460-9568.2000.00173.x
This work was conducted whilst M.H.H. was a Sabbatical visitor at MRC Laboratory of Molecular Biology.
- Issue published online: 24 DEC 2001
- Article first published online: 24 DEC 2001
- Received 13 March 2000, revised 9 May 2000, accepted 10 May 2000
- pars tuberalis;
- Period gene;
The circadian clock in the hypothalamic suprachiasmatic nuclei (SCN) regulates the pattern of melatonin secretion from the pineal gland such that the duration of release reflects the length of the night. This seasonally specific endocrine cue mediates annual timing in photoperiodic mammals. The aim of this study was to investigate how changes in photoperiod influence the cyclic expression of recently identified clock gene products (mPER and mTIM) in the SCN of a highly seasonal mammal, the Siberian hamster (Phodopus sungorus). Immunocytochemical studies indicate that the abundance of both mPER1 and mPER2 (but not mTIM) in the SCN exhibits very pronounced, synchronous daily cycles, peaking approximately 12 h after lights-on. These rhythms are circadian in nature as they continue approximately under free-running conditions. Their circadian waveform is modulated by photoperiod such that the phase of peak mPER expression is prolonged under long photoperiods. mPER1 protein is also expressed in the pars tuberalis of Siberian hamsters. In hamsters adapted to long days, the expression of mPER1 is elevated at the start of the light phase. In contrast, there is no clear elevation in mPER1 levels in the pars tuberalis of hamsters held on short photoperiods. These results indicate that core elements of the circadian clockwork are sensitive to seasonal time, and that encoding and decoding of seasonal information may be mediated by the actions of these transcriptional modulators.