Both research groups published their findings in the October 14, 2004, issue of the journal Nature. Howard Hughes Medical Institute researcher Michael Rosbash at Brandeis University led one group; Franois Rouyer at the Centre National de la Recherche Scientifique in France led the second group. Graduate students Dan Stoleru and Ying Peng of Brandeis were co-lead authors of the Rosbash group's article.

In an accompanying News & Views article in the journal Nature, neurobiologist William J. Schwartz of the University of Massachusetts Medical School, writes, "A truly integrative circadian biology is close at hand, as researchers learn about an adaptable, layered system that has emergent properties at many levels of organization. Drosophila workers, who have been so effective at taking the clock apart, are now succeeding in putting it back together."

Biological clocks in both flies and humans operate on a 24-hour, or circadian (Latin for "about a day"), cycle. In humans, the clock's influence is far-reaching, governing such functions as sleeping and waking, fluid balance, body temperature, cardiac output, and oxygen consumption. In the fruit fly Drosophila, however, the circadian clock has its most overt effect on the fly's level of activity. In both flies and humans, the clocks are circuits of neurons that naturally oscillate with a circadian periodicity. Inside these cells, the molecular components of the clock are "rewound" daily by the effects of light and other stimuli.

According to Rosbash, the central clue to the existence of dual circadian clocks in the fly was the observation that flies have two activity peaks. "It was always intriguing that flies had two peaks of activity, in the morning and evening, with a siesta during t
'"/>

Contact: Jennifer Michalowski
michalow@hhmi.org
301-215-8576
Howard Hughes Medical Institute
13-Oct-2004