EXPRESSION PROFILING REVEALS A POSITIVE REGULATION BYMPER2 ON CIRCADIAN RHYTHM OF CYTOTOXICITY RECEPTORS:LY49C AND NKG2D

摘要

The mammalian circadian gene, mPer2, an indispensable component of the mamma-lian circadian clock, not only modulates endogenous circadian rhythms but also playsa crucial role in regulating innate immune function. Previously, we showed thatmPer2 plays a crucial role in regulating cytotoxic response. To investigate the molecu-lar mechanism for mPer2-controlled cytotoxic response, in the present study we con-ducted mRNA expression for 11 genes participating in cytotoxicity regulation inwild-type (WT) and mPer2 knockout (mPer2~(-/-))mice bone marrow, that is,Dap-10,Ly49C, Ly491, Rac 1 , Mapk1 , Map2k1, Nkg2d, Shp-1, Pak 1 , Pik3ca, and Vav1 . ThemRNA levels of Ly49C (p < 0.001), Ly49I (p = 0.039), and Nkg2d (p = 0.038) weresignificantly downregulated in mPer2~(-/-)mice. Time-dependence of expression pro-filing was then conducted for four core clock genes (Perl , Bmall , Clock, Rev-erba), andsix out of these 11 cytotoxic regulation genes (Ly49C, Ly49I, Mapk1 , Nkg2d, Shp-1,Pik3ca) in WT and mPer2~(-/-)entrained in light/dark (LD) or dark/DD) cycles.Consistently, circadian oscillations were observed for Perl , Rev-erba, Ly49C, andNkg2d in WT mice under LD and DD cycles. However, these rhythmic expressionswere either disrupted or dampened in mPer2~(-/-)mice. Comparison of geneexpression between WT and mPer2~(-/-)mice showed thatmPer2knockout had system-atically downregulated the mRNA expression of two cytotoxicity regulators, Ly49Cand Nkg2d. FACS analysis further confirmed that the circadian expression of thesegenes was not due to the daily difference in cell numbers of NK, N KT, or T cells inbone marrow. Taken together, our results reveal that mPer2 is a critical clock com-ponent in modulating circadian rhythms in bone marrow. Furthermore, it impliesthat Ly49C and Nkg2d are two clock-controlled genes that may play an important role in mediating mPer2-controlled cytotoxic response.