Slicing chromosomes leads to new insights into cel...( ANN ARBOR Mich.By using ultrafast la...)

ANN ARBOR, Mich.By using ultrafast laser pulses to slice off pieces of chromosomes and observe how the chromosomes behave, biomedical engineers at the University of Michigan have gained pivotal insights into mitosis, the process of cell division.

Their findings could help scientists better understand genetic diseases, aging and cancer.

Cells in plants, fungi, and animalsincluding those in the human bodydivide through mitosis, during which the DNA-containing chromosomes separate between the resulting daughter cells. Forces in a structure called the mitotic spindle guide the replicated chromosomes to opposing sides as one cell eventually becomes two.

"Each cell needs the right number of chromosomes. It's central to life in general and very important in terms of disease," said Alan Hunt, an associate professor in the Department of Biomedical Engineering and an author of a paper describing these findings published in Current Biology.

"One of the really important fundamental questions in biology is how do chromosomes get properly segregated when cells divide. What are the forces that move chromosomes around during this process? Where do they come from and what guides the movements?"

Hunt's results validate the theory that "polar ejection forces" are at play. Scientists had hypothesized that the direction and magnitude of these forces might provide physical cues guiding chromosome movements. In this capacity, polar ejection forces would play a central role separating chromosomes in dividing cells, but no one had established a direct link until now.

Polar ejection forces are thought to arise out of the interaction between protein motors on the arms of chromosomes that push against cells' microtubules. Microtubules are long, thin tubes that form a central component of the cytoskeleton and the mitotic spindle. They serve as intracellular structural supports and as railways along which molecular motors move c
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