Circadian Rhythm Monitoring in U2OS Cells

Bmal1:luc U2OS and Per2:luc U2OS cells were a gift from Dr. Andrew Liu, University of Memphis (Liu et al., 2008 (link)). U2OS cells were cultured in standard conditions. For bioluminescence recordings, U2OS cells were synchronized by changing medium to “Air Medium” (Hastings et al., 2005 (link)). Bioluminescence assays were performed at 37°C using 12-well and 96-well plates in custom-made bioluminescence recording systems (Cairn Research Ltd) composed of a charge-coupled device (CCD) camera (Andor iKon-M 934) mounted on the top of an Eppendorf Galaxy 170R CO₂ incubator. Bioluminescence data traces were analyzed using a modified version of the R script “CellulaRhythm” (Hirota et al., 2008 (link)).