The “Night Owl” Gene

People with delayed sleep phase disorder (DSPD) typically cannot fall asleep until 3 a.m. or 4 a.m., or even later. They find it hard to start work or school at conventional times. Because they often cut sleep short, they commonly experience extreme fatigue.

In June Alina Patke, Ph.D., a research associate working with Michael W. Young, Ph.D., and others, reported in Cell that her group had identified a mutation of the human circadian clock gene CRY1 in familial DSPD. CRY1 was quickly dubbed the “night owl” gene.

The mutation makes one of CRY1’s proteins overactive. People with the mutation have a longer than average circadian cycle and markedly delayed sleep.

The researchers found the CRY1 mutation in a 46-year-old woman who had been diagnosed with DSPD on the basis of her sleep logs and laboratory studies of her sleep, hormones, body temperature, and other circadian rhythms. They found the same mutation in other late-to-bed family members, inherited in an autosomal dominant pattern.

DSPD is the most commonly diagnosed circadian rhythm sleep disorder. About 0.1 percent of the population worldwide carries the CRY1 mutation, Young said at a press conference at Rockefeller University on October 2, responding to a reporter’s query about potential practical payoffs from his research.

“We now have ways of thinking about how we might want to attack a medical problem where a gene is hyperactive,” Young said.

The DSPD finding provides the identity of a mutation prevalent in the human population, he added. “It gives us a target to work on. Previously, we didn’t know this was an inherited disorder. I think we’re going to run into this over and over again, not only in this system but in many others.” ■