Constitutive expression and delayed light response of casein kinase I epsilon and I delta mRNAs in the mouse suprachiasmatic nucleus

Casein kinase I is an element of (CKI is an element of) and casein kinase I delta (CKI delta) phosphorylate clock oscillating mPER proteins, and play a key role in the transcription (post)translation feedback loop that genera tes circadian rhythm. In the present study, the expression profiles of CKI is an element of and CKI delta mRNAs were examined in the mice clock center , suprachiasmatic nucleus (SCN), Moderate levels of CKI is an element of an d CKI delta mRNAs were constantly expressed in the SCN in both light,dark a nd constant dark conditions. This finding supports the hypothesis that CKI may form a constant threshold to the nuclear entry of mPER proteins as in t he Drosophila homologue, double-time. Further, we demonstrated that the lig ht exposure at subjective night induced a delayed increase in CKI is an ele ment of and CKI delta mRNAs in the SCN, CKI is an element of and CKI delta proteins may play a role on light-induced phase-shift. (C) 2001 Wiley-Liss, Inc.