Casein kinase-1-epsilon (CK1epsilon) and circadian photic responses in hamsters

Circadian rhythms rely on the interaction of highly conserved transcription-translation loops. Casein kinase I epsilon (CK1epsilon) post-transcriptionally regulates circadian rhythms by phosphorylating clock genes, and the tau mutation, an arginine to cysteine substitution at residue 128, results in a short circadian period, abnormal entrainment to light cycles, and potentiated resetting responses to light. Each of these effects could be attributed to changes in the regulation of the core molecular circadian loops. We now demonstrate that the mutation results in a heightened sensitivity to light, suggesting that CK1epsilon also regulates the photic entrainment pathway.