Constitutive expression of the Period1 gene impairs behavioral and molecular circadian rhythms

Rika Numano, Shin Yamazaki, Nanae Umeda, Tomonori Samura, Mitsugu Sujino, Ri Ichi Takahashi, Masatsugu Ueda, Akiko Mori, Kazunori Yamada, Yoshiyuki Sakaki, Shin Ichi T Inouye, Michael Menaker, Hajime Tei

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48 Scopus citations


Three mammalian Period (Per) genes, termed Per1, Per2, and Per3, have been identified as structural homologues of the Drosophila circadian clock gene, period (per). The three Per genes are rhythmically expressed in the suprachiasmatic nucleus (SCN), the central circadian pacemaker in mammals. The phases of peak mRNA levels for the three Per genes in the SCN are slightly different. Light sequentially induces the transcripts of Per1 and Per2 but not of Per3 in mice. These data and others suggest that each Per gene has a different but partially redundant function in mammals. To elucidate the function of Per1 in the circadian system in vivo, we generated two transgenic rat lines in which the mouse Per1 (mPer1) transcript was constitutively expressed under the control of either the human elongation factor-1α (Ef-1α) or the rat neuron-specific enolase (NSE) promoter. The transgenic rats exhibited an ≈0.6-1.0-h longer circadian period than their wild-type siblings in both activity and body temperature rhythms. Entrainment in response to light cycles was dramatically impaired in the transgenic rats. Molecular analysis revealed that the amplitudes of oscillation in the rat Per1 (rPer1) and rat Per2 (rPer2) mRNAs were significantly attenuated in the SCN and eyes of the transgenic rats. These results indicate that either the level of Per1, which is raised by overexpression, or its rhythmic expression, which is damped or abolished in over expressing animals, is critical for normal entrainment of behavior and molecular oscillation of other clock genes.

Original languageEnglish (US)
Pages (from-to)3716-3721
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number10
StatePublished - Mar 7 2006


  • Entrainment
  • Transgenic rats

ASJC Scopus subject areas

  • General


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