"Cells obey the laws of physics and chemistry," begins a famous biology textbook, and one of the main goals of molecular biology is to link the properties of single molecules to the behavior of cells and the lives of organisms. So it is probably no surprise that an important new discovery about the physical forces that underlie cell division comes from a physics student-turned biologist, using math and a laser microscope. The findings appear in the current issue of the journal Science (Science, 26 July 2003).
Stephan Grill, Joe Howard, Erik Schffer, Ernst Stelzer and Tony Hyman - in a collaboration between the Max-Planck Institute of Molecular Cell Biology and Genetics in Dresden and EMBL in Heidelberg - have done something few scientists have managed: they have counted the number of proteins that help an egg cell divide. This initial division happens in a special way in the roundworm C. elegans, one of biology's most important model organisms.
"The fertilized egg splits into one large and one smaller cell," Grill says. "That difference in size is crucial to the development of the whole roundworm body. Normally people think of cells as dividing into two identical daughters; if they don't, there must be forces at work that create an imbalance. We wanted to map them."
As a PhD student at EMBL, working in the research groups of Tony Hyman and the microscopist Ernst Stelzer, Grill pursued an intriguing lead. A cable-like network of proteins called microtubules tows freshly-copied DNA off to opposing sides of the cell. The identical sets of genetic material are then sealed off in their own cells. Normally the anchors that the tow-lines are attached to, called centrosomes, remain near the center of the cell. But in the roundworm egg, one centrosome wanders off towards the outer rim of the cell. Either it was being pulled th
Contact: Stephan W. Grill