Abstract
The circadian clock ensures that behavioral and physiological processes occur at appropriate times during the 24-hour day/night cycle, and is regulated at both the cellular and organismal levels. To identify pathways acting on intact animals, we performed a small molecule screen using a luminescent reporter of molecular circadian rhythms in zebrafish larvae. We identified both known and novel pathways that affect circadian period, amplitude and phase. Several drugs identified in the screen did not affect circadian rhythms in cultured cells derived from luminescent reporter embryos or in established zebrafish and mammalian cell lines, suggesting they act via mechanisms absent in cell culture. Strikingly, using drugs that promote or inhibit inflammation, as well as a mutant that lacks microglia, we found that inflammatory state affects circadian amplitude. These results demonstrate a benefit of performing drug screens using intact animals and provide novel targets for treating circadian rhythm disorders.
Highlights
Circadian rhythms help ensure that physiological processes and behaviors occur at appropriate times during the 24-hour day/night cycle
Previous study described transgenic zebrafish in which the promoter for the period[3] gene regulates expression of firefly luciferase (Tg(per3:luc)), and showed that this line accurately reports molecular circadian rhythms in zebrafish larvae[13]. To test whether this line could be used to screen for small molecules that affect molecular circadian rhythms, we asked whether compounds that affect the circadian clock in cell culture induce similar effects in zebrafish larvae
These results indicate that Tg(per3:luc) larvae can be used to report drug-induced changes in molecular circadian rhythms, and that phenotypes observed in mammalian cells can be observed in zebrafish larvae
Summary
Circadian rhythms help ensure that physiological processes and behaviors occur at appropriate times during the 24-hour day/night cycle. Most small molecule screens use in vitro or cell culture assays to identify drugs that bind a specific target or affect a specific process These screens do not recreate the complex environment of whole animals and likely fail to identify some mechanisms that regulate the process under study. To overcome these limitations, we and others have used intact zebrafish as a vertebrate model system for small molecule screens[9]. We and others have used intact zebrafish as a vertebrate model system for small molecule screens[9] This approach combines the in vivo relevance of whole-animal assays with moderate-throughput, low-cost drug screening. These results reveal an unexpected role for the immune system in regulating the circadian clock
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
