The phase-shifting effect of bright light exposure on circadian rhythmicity in the human transcriptome

Eleven healthy human subjects were enrolled in a 6-day simulated shift work protocol. Blood samples were collected during the two 24-hour measurement periods. Blood samples were collected every 4 hours during both measurement periods. Subjects entered the lab on Day 1. At the start of Day 2, the first 24-hour measurement period was started. Subjects slept according to their habitual sleep/wake schedule, followed by a 16-hour constant posture procedure. On days 3-6, the sleep period was delayed by 10 hours. Participants in the control group were exposed to dim light throughout the waking periods; participants in the bright group were exposed to bright light (~6,000lux) for 8 hours during the waking period. Following the third night on this schedule, subjects underwent another 24-hour measurement period. During both measurement periods, blood samples were collected and PBMCs were isolated. mRNA was extracted, labelled, and hybridized to microarrays. A total of 141 samples were collected from 11 subjects spread across two 24-hour measurement periods