Abstract: We previously reported a circadian reporter knockin mouse line, Per2::Luc, which expresses PER2::LUC fusion proteins and has been widely used for real-time circadian bioluminescence monitoring. To understand in vivo function of Per2 3'-UTR, we generated Per2::LucSV, a modified knockin reporter mouse line where the endogenous Per2 3'-UTR was replaced by an SV40 late poly(A) signal.

Bioluminescence recording and molecular analysis showed robust PER2::LUC rhythms in various tissues with significantly enhanced amplitude compared with those in Per2::Luc. In addition, Per2::LucSV mice also exhibited lengthened free-running periods (~24.0 hr), greater phase delays following light pulse, and enhanced temperature compensation relative to Per2::Luc. Analysis of the Per2 3'-UTR sequence revealed that miR-24, and to a lesser degree miR-30, suppressed PER2 protein translation, and the relief of this inhibition in Per2::LucSV augmented PER2::LUC protein level and oscillatory amplitude.

Together, these studies provide important mechanistic insights into the regulatory roles of miR-24 and PER2 in Per2 expression and core clock function, and establish Per2::LucSV as a valuable in vivo system endowed with enhanced bioluminescence and circadian amplitude.