College of Liberal Arts and Sciences at Iowa State University

Simple division

A group of Iowa State scientists has discovered a new subcellular stucture
While she was a graduate student at Yale University, Kristen Johansen generated an antibody as part of her graduate work.

While the antibody did not turn out to be useful for her dissertation project, she noticed that it nevertheless displayed an intriguing staining pattern in the cell, causing her to save it, hoping to one day learn more about what this antibody was recognizing

Now the associate professor of zoology and genetics at Iowa State has been able to answer this question.

"When I came to ISU we began to look at its staining pattern more closely and found hints of nuclear spindle structure," she said. "But the key to being able to visualize how this structure reorganizes during the cell cycle was the exquisite detail obtained using the high-resolution confocal microscope at Iowa State's Image Analysis Facility," she said.

That technology (a high-resolution microscope employing four lasers along with three-dimensional reconstruction techniques) has enabled Johansen and her research group to identify a new spindle-like structure that is made from proteins in the nucleus.

Scientists have long known that a spindle-like structure formed by microtubules (polymerized tubulin) from the cytoplasm (outside the nucleus) plays an important role in how chromosomes are equally divided into two daughter cells during cell division. Yet there are many unknowns about how the microtubule spindle functions. For example, it is unclear how this spindle forms or how it functions to pull chromosomes apart.

"Coordinated molecular interactions between the microtubule spindle and the new nuclear spindle structure have the potential to provide the answers to many of these questions," Johansen says. "As best we can tell, this new spindle is actually the first of the two spindle structures to form. Later as the microtubule spindle takes shape it co-aligns with the nuclear spindle.

"It was very serendipitous that we were able to discover this protein," Johansen continued. "Scientists have had clues such a structure existed for the past 20 years but have not been able to find it. We were lucky to have found an antibody that gave us the tool to molecularly clone and characterize it and we needed the technology that provided the higher resolution that could reveal the significance of this structure."

By better understanding the steps of normal cell division, like spindle formation, the Iowa State group hopes to provide new insights into what happens during abnormal cell divisions of cancer. The group includes graduate students Diana Walker, Dong Wang, Ye Jin, Uttama Rath, and Yanming Wang as well as Jorgen Johansen, professor of zoology and genetics.

"By identifying and characterizing a new cell structure essential for cell division, alternative therapies for cancer may be developed that target this new spindle to stop cell division in cancer," Kristen Johansen said.

The findings of the research, which was supported by the National Science Foundation, appeared in the Dec. 25 issue of The Journal of Cell Biology and was featured on the cover.