Researchers at the Johns Hopkins University School of Medicine and the National Institutes of Health have discovered a protein in the visual system of mice that plays a significant role in stabilizing the body’s circadian rhythms by regulating the brain’s response to light. The study, published in PLoS Biology, could potentially lead to improved treatments for sleep disorders and jet lag.
Circadian rhythms are biological rhythms that operate on a 24-hour cycle and impact various cyclic behaviors such as sleep, hunger, and body temperature. Disrupting these rhythms can have serious consequences, including an increased risk of cancer, depression, and other medical problems. Light exposure plays a crucial role in training the circadian system, but it has remained unclear how the brain becomes wired to maintain stable circadian rhythms.
To investigate this further, the research team analyzed a database of molecules present during the development of the suprachiasmatic nucleus (SCN), the control center for circadian rhythms in the mouse brain. They identified a cell surface protein called teneurin-3 (Tenm3) that plays a crucial role in the assembly of the visual system circuit and other central nervous system circuits.
Genetically modified mice that lacked Tenm3 exhibited fewer connections between the retina and the SCN, indicating its importance in stabilizing circadian rhythms. However, these mice developed increased connectivity between cells in the core and shell of the SCN. This suggests that Tenm3 helps wire the brain to maintain stable circadian rhythms even in the presence of variable light exposure.
Further experiments revealed that mice lacking Tenm3 adjusted more rapidly to changes in the light/dark cycle compared to mice with intact Tenm3. They also exhibited heightened sensitivity to light cues necessary for setting or resetting the circadian clock.
The findings of this study provide valuable insights into the mechanisms behind circadian rhythm stability and suggest a potential avenue for diagnosing and treating sleep disorders and jet lag in humans. By understanding the role of Tenm3 in the circadian system, researchers may be able to develop targeted treatments in the future.
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