Circadian rhythms are regulated by changes in daylight cycles, but how and when they first develop is not well understood. Reported this week in the open-access journal PLoS Biology, Maki Kaneko and Gregory Cahill have created a new tool for investigating the components of the circadian clock in vertebrates: a zebrafish that luminesces (glows) in sync with the periodicity of its circadian clock. They find, contrary to earlier studies, that aspects of circadian rhythms are not hardwired into the embryo, but develop in specific stages.
To do this, the researchers created a transgene that places expression of the firefly luciferase gene under the control of the promoter of the zebrafish circadian gene period3 (per3). Each cell of the transgenic fish has one normal copy of the per3 gene and one copy of the period3-luciferase fusion gene (per3-luc). Therefore, whenever per3 expression is normally turned on in a cell, the cell produces Per3 protein and also produces the luciferase protein.
Kaneko and Cahill anticipate that these transgenic zebrafish will be quite useful in examining the molecular machinery of the vertebrate circadian clock. For example, researchers can use the per3-luc transgenic zebrafish in forward genetic screens to identify new molecular regulators of circadian rhythms. What is more, luminescence can be measured quickly and noninvasively, making this animal an ideal candidate for high-throughput screening aimed at iden
Contact: Paul Ocampo
Public Library of Science