The National Geographic confirms what we've all suspected: that people who are ready to go in the early morning are definitely not like the rest of us. A group of people who have familial advanced sleep phase syndrome (FASPS),a dominant inheirited disorder, have their sleep/wake cycles (part of a "circadian rhythm) out of sync with normal people. They get sleepy in the early evening and wake back up in the wee hours. Scientists at UCSF report in Nature this week that people with this disorder express a mutant form of the enzyme casein kinase I-delta. The mutant enzyme has reduced activity, and affects the processing of a second protein called PER2, which is important for circadian rhythms. When this mutant enzyme was introduced into mice, the mice showed several disruptions of their daily activities. Their overall activity was lower compared to mice without the mutant enzyme. Also, when kept in continuous dark (so that the internal clock cannot be reset by the sight of daytime) their activity showed a shorter daily rhythm. Finally, when light and dark cues were restored, mice with the mutant enzyme had difficulty entraining their daily schedules back to the cues. Thus the presence of the altered enzyme, specified by the human genetic mutation, is sufficient to affect circadian rhythms.
I just know that Coturnix at Circadiana will have something to say about this paper, so I will link to him when it's up!
UPDATE, April 17: Lots more mutants over at Circadiana