PhotoResearchers from the University of Tsukuba recently published a study in the Proceedings of the National Academy of Sciences entitled, “A single phosphorylation site of SIK3 regulates daily sleep amounts and sleep need in mice.”

The scientists found that a mutation in a single amino acid plays a large role in the amount of sleep needed in mice on a daily basis -- an area that had been largely under researched prior to the study. Sleepiness, and the amount of sleep organisms need, as well as the variations in sleep patterns has been a mystery for a long time. Now, the researchers have uncovered a key finding in the field.

Based on the study, the researchers found that changing this amino acid affects not only the mice’s sleeping patterns, but also their alertness when awake.

“The findings were particularly interesting in that this mutation affected the periods of sleep lacking rapid-eye-movement, the largely non-dreaming part of sleep, while rapid-eye-movement sleep was largely unchanged,” said researcher Masashi Yanagisawa in a statement.

The study

Using mice as test subjects, the researchers created a mutation in the SIK3 protein.

From there, the team evaluated the ways the mutated protein affected the mice’s sleep patterns, brain activity during waking and sleeping hours, alertness when awake, and time spent asleep and awake.

The study found that adjusting the 551st amino acid of the SIK3 protein produced the greatest effect on the mice’s sleeping patterns. In short, the mutation made them sleep more. At times of the night when the mice were usually active, the change in the amino acid found them sleeping for more extended periods of time. Despite the increased sleep, much of the mice’s sleep under the mutated protein was found to be non-dreaming sleep.

“This showed that SIK3 is involved in very specific sleep-related regulatory mechanisms,” Yanagisawa added.

Effect on human sleep patterns  

In looking at the way the molecular composition affected the mutated protein, the researchers were able to draw conclusions that could affect future research on human sleeping patterns.

“The features of this amino acid in this protein are evolutionarily conserved across the animal kingdom, so these findings are also relevant to studies on sleep in humans,” said lead author Takato Honda.

Honda referenced individuals with idiopathic hypersomnia -- a sleep condition that makes people excessively tired during the day and has great difficulty being woken up (both of which without clear explanation). Because the mice in the study experienced similar symptoms, Honda is confident that the research can help provide answers.


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