Kristen Johansen, Zoology and Genetics, (515) 294-7959
Teddi Barron, News Service, (515) 294-4778
Steve Sullivan, News Service, (515) 294-3720


AMES, Iowa — A group of Iowa State University scientists has discovered a new subcellular structure that improves understanding of how normal cells divide. This discovery could provide insight into the abnormal cell division that occurs in cancer. Their findings appear in the Dec. 25 issue of "The Journal of Cell Biology."

Normal cells in plants and animals divide to replace worn-out or damaged cells and to provide growth. During cell division, chromosomes (collections of genes) are pulled apart and segregated into the nuclei of the two new cells. Genetic material is passed on from cell to cell in this fundamental process.

Scientists have long known that a spindle-like structure from the cytoplasm (material outside the nucleus) plays a vital role in bringing about chromosome movement. Known as the microtubule spindle (because it is made of the protein tubulin), it serves as a scaffold for the chromosomes. The chromosomes line up, separate and migrate to opposite ends of the spindle, which disintegrates. The cell splits and two new cells are formed.

The Iowa State scientists discovered a new and different spindle structure during cell division that is made up of proteins from the nucleus, said Kristen Johansen, associate professor of zoology and genetics.

"This newly discovered nuclear structure is definitely a true spindle and, as best we can tell, it actually is the first of the two spindle structures to form. When a microtubule spindle takes

shape, it co-aligns with a nuclear spindle," said Johansen, who led the research.

The scientists on Johansen's team were Jorgen Johansen, professor of zoology and genetics; and graduate students Diana Walker, Dong Wang, Ye Jin, Uttama Rath and Yanming Wang.

The researchers used a high-resolution microscope and three-dimensional reconstruction techniques to see the spindles form, co-exist and disintegrate.

"There are many unknowns about how the microtubule spindle functions. For example, it's unclear how microtubules manage to pull on the chromosomes or how they align," Johansen said. "Coordinated molecular interactions between the microtubule spindle and the new nuclear spindle structure have the potential to provide answers to many of these questions."

Through better knowledge of the steps of normal cell division, like spindle formation, the Iowa State research opens the door to a new understanding of what takes place during the abnormal cell division of cancer. "When cancer researchers have a better understanding of how to stop cell division in cancerous cells, they could eventually develop new treatments for cancer," Johansen said.

The five-year research was supported by the National Science Foundation.



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