Circadian clocks provide a mechanism that allows organisms to anticipate environmental rhythms, like light-dark cycles. Nematostella vectensis, an estuarine sea anemone, has a surprising degree of overlap in genomic complexity with vertebrates, including circadian clock genes. These genes are predicted to serve a similar role in driving circadian patterns in sea anemones, but we have not worked out the exact mechanism they use.

In this study, we utilize next-generation sequencing to investigate the time-course transcriptional profiles of animals over 3 days, to dissociate true circadian gene expression vs. photo-responsiveness, by exposing animals to regular light-dark cycles for one month, then abruptly removing the light cue. Hypothesized ‘clock’ genes were rhythmic in the presence of light-dark cycles; however, several of these genes lost their characteristic oscillation after 1 or 2 days in the dark, suggesting lack of endogenous circadian regulation. One would expect a truly circadian gene to continue to cycle in the absence of light, however our results indicate either: 1) the hypothesized ‘clock’ genes simply respond directly to light cues, which implies they are not circadian, or 2) a circadian regulator resides in specific cell types, and the expression signal is too dampened when measuring in the whole animal.

Whitney Leach, Doctoral Candidate, The Reitzel Laboratory, University of North Carolina at Charlotte

Read the full article here: https://onlinelibrary.wiley.com/doi/abs/10.1111/mec.15163