CLOCK evolved in cnidaria to synchronize internal rhythms with diel environmental cues
Year: 2024
Type: preprint
Abstract: The circadian clock enables anticipation of the day/night cycle in animals ranging from cnidarians to mammals. Circadian rhythms are generated through a transcription-translation feedback loop (TTFL or pacemaker) with CLOCK as a conserved positive factor in animals. However, the functional evolutionary origin and mechanism of action of CLOCK in basal animals are unknown. In the cnidarian Nematostella vectensis, pacemaker genes transcription including NvClk (the Clock ortholog) appears arrhythmic under constant light conditions, questioning the role of NvCLK. Utilizing CRISPR/Cas9, we generated a NvClk allele mutant (NvClk1), revealing circadian behavior loss in constant light conditions (LL and DD) while a 24-hour rhythm was maintained under light-dark condition (LD). Transcriptomics showed distinct rhythmic genes in wild-type (WT) genes in LD compared to DD. The LD NvClk1-/- showed comparable numbers of rhythmic genes, whereas they were greatly reduced in DD. Furthermore, the LD NvClk1-/- showed alterations of temporal pacemaker genes expression, affecting their potential interactions. Additionally, differential expression of non-rhythmic genes associated with cell division and neuronal differentiation was observed. These findings suggest that while the light-responsive pathway can partially compensate for circadian clock disruption, the Clock gene has evolved in cnidarians to maintain 24-hour rhythmic physiology and behavior in constant conditions.
Source: eLife
Institution: Bar-Ilan University
Language: English
Subfield: Endocrine and Autonomic Systems
Field: Neuroscience
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,500
Awards: G4223123264, G4853542560
OpenAlex ID: W4394844659