Alexis Webb enters a small room at Washington University in St. Louis with walls, floor and ceiling painted dark green, shuts the door, turns off the lights and bends over a microscope in a black box draped with black cloth. Through the microscope, she can see a single nerve cell on a glass cover slip glowing dimly.
The glow tells her the isolated nerve cell is busy keeping time.
Webb, a graduate student in the neuroscience program, working with Erik Herzog, Ph.D., associate professor of biology in Arts & Sciences; Nikhil Angelo, an undergraduate biology major; and James Huettner, Ph.D., associate professor of cell biology and physiology in the School of Medicine, has demonstrated that individual cells isolated from the biological clock can keep daily time all by themselves.
However, by themselves, they are unreliable. The neurons get out of synch and capriciously quit or start oscillating again.
The biological clock, a one-square millimeter area of the brain called the suprachiasmic nucleus, or SCN, just above the roof of the mouth and atop the crossing of the optic nerves, comprises about 20,000 neurons.
These cells, remarkably, contain the machinery to generate daily, or circadian, rhythms in gene expression and electrical activity. But the individual cells are sloppy and must communicate with one another to establish a coherent 24-hour rhythm, says Herzog.
These features make the SCN a flexible clock that can reset to stay in synch in an ever-changing environment. The underlying sloppiness is probably what allows us to adjust to local time when we cross time zones and to vary our sleep cycles with the season, say the WUSTL researchers.
The research is being published the week of Sept. 7 in the online Early Edition of the Proceedings of the National Academy of Sciences.
"We've known for more than 15 years that unicellular organisms like cyanobacteria can keep 24-hour time, and iso
|Contact: Erik Herzog|
Washington University in St. Louis