If you stay up late and have trouble getting up in the morning, you might be able to blame a gene mutation for this night owl behavior.
Researchers from the U.S. and Turkey have discovered that a variant of the gene CRY1 alters the human circadian clock, which normally dictates when you feel sleepy each night and when you're ready to wake.
Carriers of the gene variant experienced nighttime sleep delays of two to 2.5 hours compared to non-carriers, the team reported Thursday in the U.S. journal Cell.
In a healthy circadian clock, a handful of genes turn on and off over a 24 hour cycle, and the protein made by CRY1 is normally responsible for suppressing some of these genes during certain parts of the cycle.
However, the mutation, first identified in a U.S. patient, made the CRY1 protein more active than usual, keeping other clock genes switched off for a longer period of time, and in turn, stretching the daily cycle by half an hour or more.
Professor Michael Young and colleagues of the Rockefeller University then reached out to other members of the patient's family and discovered five relatives who shared the mutation in CRY1. All of them had a history of persistent sleep problems.
Next, Young collaborated with clinical researchers at Bilkent University to analyze the sleep patterns of six unrelated families in Turkey and were able to confirm that 38 people with the mutation had altered sleep behavior, while none of their relatives without the CRY1 mutation had unusual sleep patterns.
Finally, after scouring larger genetic databases for CRY1 mutations, Young's group calculated that as many as one in 75 people of non-Finnish European descent have at least one copy of the mutation.
“Compared to other mutations that have been linked to sleep disorders in just single families worldwide, this is a fairly impactful genetic change,” Young said in a statement.