The physiological period length of the human circadian clock In Vivo is directly proportional to period in human fibroblasts

Lucia Pagani, Ekaterina A. Semenova, Ermanno Moriggi, Victoria L. Revell, Lisa M. Hack, Steven W. Lockley, Josephine Arendt, Debra J. Skene, Fides Meier, Jan Izakovic, Anna Wirz-Justice, Christian Cajochen, Oksana J. Sergeeva, Sergei V. Cheresiz, Konstantin V. Danilenko, Anne Eckert, Steven A. Brown

Research output: Contribution to journalArticlepeer-review

69 Scopus citations


Background: Diurnal behavior in humans is governed by the period length of a circadian clock in the suprachiasmatic nuclei of the brain hypothalamus. Nevertheless, the cell-intrinsic mechanism of this clock is present in most cells of the body. We have shown previously that for individuals of extreme chronotype ("larks" and "owls"), clock properties measured in human fibroblasts correlated with extreme diurnal behavior. Methodology/Principal Findings: In this study, we have measured circadian period in human primary fibroblasts taken from normal individuals and, for the first time, compared it directly with physiological period measured in vivo in the same subjects. Human physiological period length was estimated via the secretion pattern of the hormone melatonin in two different groups of sighted subjects and one group of totally blind subjects, each using different methods. Fibroblast period length was measured via cyclical expression of a lentivirally delivered circadian reporter. Within each group, a positive linear correlation was observed between circadian period length in physiology and in fibroblast gene expression. Interestingly, although blind individuals showed on average the same fibroblast clock properties as sighted ones, their physiological periods were significantly longer. Conclusions/Significance: We conclude that the period of human circadian behaviour is mostly driven by cellular clock properties in normal individuals and can be approximated by measurement in peripheral cells such as fibroblasts. Based upon differences among sighted and blind subjects, we also speculate that period can be modified by prolonged unusual conditions such as the total light deprivation of blindness.

Original languageEnglish (US)
Article numbere13376
JournalPloS one
Issue number10
StatePublished - 2010
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General


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