Period 2: A Regulator of Multiple Tissue-Specific Circadian Functions

The zebrafish represents a powerful model for exploring how light regulates the circadian clock due to the direct light sensitivity of its peripheral clocks, a property that is retained even in organ cultures as well as zebrafish-derived cell lines. Light-inducible expression of the per2 clock gene has been predicted to play a vital function in relaying light information to the core circadian clock mechanism in many organisms, including zebrafish. To directly test the contribution of per2 to circadian clock function in zebrafish, we have generated a loss-of-function per2 gene mutation. Our results reveal a tissue-specific role for the per2 gene in maintaining rhythmic expression of circadian clock genes, as well as clock-controlled genes, and an impact on the rhythmic behavior of intact zebrafish larvae. Furthermore, we demonstrate that disruption of the per2 gene impacts on the circadian regulation of the cell cycle in vivo. Based on these results, we hypothesize that in addition to serving as a central element of the light input pathway to the circadian clock, per2 acts as circadian regulator of tissue-specific physiological functions in zebrafish.

Automated summary

The study demonstrates that the per2 gene in zebrafish plays a tissue-specific role in maintaining rhythmic expression of circadian clock genes and clock-controlled genes, as well as impacting the rhythmic behavior of zebrafish larvae. Additionally, disruption of the per2 gene affects the circadian regulation of the cell cycle in vivo. This suggests that per2 not only acts as a key element in relaying light information to the circadian clock, but also functions as a circadian regulator of tissue-specific physiological functions in zebrafish.