Figure 1. Per1 plays a more important role than Per2 and Per3 in sustaining retinal and SCN molecular rhythms and the Period genes have divergent effects on retinal and SCN circadian period.

(A – L) Representative PER2::LUC or Per1::luc bioluminescence traces recorded from WT and Per1−/−, Per2−/− and Per3−/− retinal and SCN explants. Retinal explants were prepared (on Day 0) and cultured in neurobasal media in 5% CO₂ at 37°C for 24 h, and subsequently changed to medium 199 and transferred to the LumiCycle (on Day 1). A media change occurred on Day 8. Raw traces are shown for PER2::LUC rhythms, whereas baseline-corrected (polynomial order = 6) traces are shown for retinal Per1::luc rhythms since retinal Per1::luc bioluminescence signals experienced a substantial decrease in the first several days in culture. (M – P) Tissue specific effects of Period gene knockout on rhythmic power and circadian period. * = p<0.05, ** = p<0.01, *** = p<0.001.