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Published on: September 28, 2017
Constant light disrupts the developing mouse biological clock
Hidenobu Ohta1, Amanda C Mitchell, Douglas G McMahon
1Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA.
Insights
Constant light disrupts infant circadian clocks. Cyclic lighting is crucial for developing biological clocks, suggesting it
Area of Science:
- Chronobiology
- Developmental biology
- Neuroscience
Background:
- The mammalian suprachiasmatic nucleus (SCN) acts as the central biological clock, regulating daily physiological and behavioral rhythms.
- Infant circadian clock development is sensitive to light, raising concerns about artificial lighting in Neonatal Intensive Care Units (NICUs).
- Millions of low-birth-weight infants are annually exposed to constant artificial light in hospital nurseries.
Purpose of the Study:
- To investigate the disruptive effects of constant light (LL) on the developing biological clock in a mouse model.
- To determine if cyclic lighting conditions are necessary for proper circadian clock organization during development.
Main Methods:
- Utilized a circadian reporter transgenic mouse model for real-time gene expression imaging of the SCN.
- Exposed developing mice to constant light (LL) conditions.
- Compared circadian clock organization under LL versus cyclic lighting conditions.
Main Results:
- Constant light (LL) exposure demonstrated both acute and long-term disruptive effects on the developing biological clock.
- Cyclic lighting conditions were found to be critical for coordinating molecular circadian mechanisms during development.
- LL exposure impaired the proper organization of the central biological clock.
Conclusions:
- Constant light exposure negatively impacts the development and organization of the mammalian circadian clock.
- Cyclic lighting is essential for the proper maturation of circadian mechanisms in developing organisms.
- Cyclic light conditions in NICUs are likely optimal for supporting healthy circadian development in human infants.
Abstract:
The central biological clock of the brain, contained within the suprachiasmatic nuclei (SCN) of mammals, orchestrates an orderly "internal day" of physiology and behavior. The developing biological clock begins to respond to light at an early stage and a particular concern in humans is whether light exposure has disruptive effects on the developing biological clock of infants exposed to constant lighting conditions in neonatal intensive care units (NICUs). Worldwide, eighteen million, or 14%, of newborns estimated to be of low birth weight, are exposed to artificial lighting environments in hospital nurseries annually. Here, we have tested whether constant light (LL) exposure disrupts the developing biological clock of mice, using a circadian reporter transgenic mouse model in which the organization of the central biological clock can be assayed by real-time gene expression imaging. We now find that LL has both acute and long-term disruptive effects on developing biological clocks and that cyclic lighting conditions are critical for developing circadian clocks to coordinate their molecular circadian mechanisms. This suggests that, from the perspective of developing circadian organization in humans, cyclic light conditions in NICUs are likely to be most appropriate for infants.
