1. Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS-INSERM-ULP, 1 rue Laurent Fries, 67404 Illkirch Cédex, CU de Strasbourg, France
2. These authors contributed equally to this work

Correspondence to: Paolo Sassone-Corsi Correspondence and requests for materials should be addressed to P. S.-C. (e-mail: Email: paolosc@titus.u-strasbg.fr).

Abstract

The expression of clock genes in vertebrates is widespread and not restricted to classical clock structures^{1, 2}. The expression of the Clock gene in zebrafish shows a strong circadian oscillation in many tissues in vivo and in culture, showing that endogenous oscillators exist in peripheral organs³. A defining feature of circadian clocks is that they can be set or entrained to local time, usually by the environmental light–dark cycle^{4, 5}. An important question is whether peripheral oscillators are entrained to local time by signals from central pacemakers such as the eyes or are themselves directly light-responsive. Here we show that the peripheral organ clocks of zebrafish are set by light–dark cycles in culture. We also show that a zebrafish-derived cell line contains a circadian oscillator, which is also directly light entrained.

1. Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS-INSERM-ULP, 1 rue Laurent Fries, 67404 Illkirch Cédex, CU de Strasbourg, France
2. These authors contributed equally to this work

Correspondence to: Paolo Sassone-Corsi Correspondence and requests for materials should be addressed to P. S.-C. (e-mail: Email: paolosc@titus.u-strasbg.fr).