“Owl” pattern associated with mutation
American and Turkish scientists have discovered a gene variant associated with difficult falling asleep and awakening, which are observed in people-“owls”.
The results are published in the journal Cell.
Cycles of daytime activity and sleep (circadian rhythm) are controlled by “internal clocks” of humans and usually have a roughly 24-hour periodicity associated with the mode of illumination. In “owls” this rhythm is delayed relative to social norms that prevent them to fall asleep at the desired time and makes it difficult to timely spill leads to daytime sleepiness and often interferes with school, work and other life tasks.
Usually, these people diagnosed with the syndrome of delayed sleep phase (SSPS), according to estimates, they are suffering from 0.2 to 10 percent of the population. Several genetic variants associated with this disorder, managed to find members of separate families, but they were not.
To examine this issue, the staff of the Rockefeller and Kornilovskogo universities invited to participate in the experiment of a man with clinically verified diagnosis SSPS and a control subject with normal circadian rhythms. They asked for two weeks to live in a laboratory without any sources of information about the time of day, eat and sleep was allowed at any desired time.
It turned out that the person with SSFS daily cycle lasted approximately 30 minutes longer than normal.
Sleep had come and ended later than in the control subject, the same was observed in relation to diurnal changes in body temperature and production-related circadian rhythms of hormones, primarily melatonin. In people with normal rhythms of melatonin levels on average began to increase in the period from 21:00 to 22:00, and have observed the patient — 2:00 to 3:00.
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Genetic analysis revealed a person with SSFS mutation of the gene CRY1, which encodes a protein cryptochrome CRY1. This protein, sensitive to light blue part of the spectrum regulates the “internal clock”, suppressing the activity of key transcription factors ARNTL (in other animals they are called Clock and Bmal1). Discovered the gene mutation increases its affinity for ARNTL, enhancing their suppression and delaying the cycles of sleep and wakefulness, as well as increasing its amplitude.
Using this data, the researchers asked the family members of the patient to undergo genetic analysis and identified five carriers of the same mutation CRY1. All of them experienced chronic sleep disorders with signs SSFS.
Then, with the assistance of colleagues from the University of Bilkent in Ankara, the researchers found in the Turkish databases, dozens of people with a mutation of CRY1. Contact these people, the researchers found that the presence of mutations clearly associated with sleep disorders, while relatives without the mutation is not observed.
At the last stage of the study, the researchers searched for mutant forms of CRY1 in large genetic databases. According to their calculations, it can occur approximately every 75 person non-Finnish European descent.
In itself detection of “owl” mutations is of no practical use, the researchers note, but it can help in the development of pharmacological treatment SSFS. Currently, the research team plans to work on the effect of CRY1 on metabolism, because circadian rhythms regulate not only sleep, but also food intake, levels of hormones and metabolites.
Earlier, Japanese and American scientists have discovered genes responsible for phases of slow and fast sleep. To do this, they brought more than 8,000 mice with spontaneous mutations.