Reassessing the involvement of the CREB pathway in the circadian clock of Drosophila melanogaster.

Circadian clocks are ubiquitous in almost all organisms on Earth and many key genes are highly conserved among species. In the mammalian suprachiasmatic nucleus, the cAMP response element binding protein (CREB) pathway is known to play a crucial role in conveying light-input to the transcription of clock genes. The fruit fly Drosophila melanogaster also expresses two Creb proteins, CrebA and CrebB, which have been associated with the circadian clock. For example, Drosophila Creb has been suggested to constitute a molecular link between neuronal excitability and clock gene transcription. In this study we subjected flies with clock cell specific CrebA or CrebB mutations to circadian behavioral and bioluminescence assays. Surprisingly, we found that neither loss of CrebA or CrebB did affect free-running locomotor behavior, rhythmic period oscillations in clock neurons, or light-dependent synchronization. In conclusion our findings question the conserved circadian role of the Creb pathway in Drosophila and encourage further studies to elucidate its potential function within insect circadian clocks.