Ahna Skop

In Search of the Midbody

As colorful as a Venetian glass bead, a Chinese hamster ovary (CHO) cell hovers on a field of black. Created by professor Ahna Skop's lab at the University of Wisconsin-Madison, the image provides a window into cytokinesis, the process by which a eukaryotic cell divides into two daughter cells.

It's a process depicted in every high-school biology textbook, yet still poorly understood on a molecular level. "Cells are successfully dividing all the time in our bodies, which is a miraculous event," says Skop, "and yet we don't really understand how it happens." Her lab investigates the identity and function of the proteins involved in cell division, hoping to understand how membranes in cytokinesis pinch in and turn one cell into two. Because cell division defects are involved in cancer, miscarriages, and aging-related disorders, the work has broad implications for biomedicine.

Finding the Midbody

For a 2004 paper in Science, Skop and her lab isolated and conducted a proteomic analysis of the midbody, a cellular structure present during cytokinesis at the joint between the two new daughter cells, which mediates the cells' final separation. To isolate the midbody, Skop cultured CHO cells, conducting frequent assays to synchronize cell division and identify the appearance of the midbody. Those assays produced this image, which shows a CHO cell in anaphase, about 45 minutes before the midbody developed. Two sets of chromosomes appear in blue, with the microtubules of the mitotic spindle in green, and the actin of the surrounding cytoskeleton in red.

Building the Image

To create these images, Skop first fixes the cells with methanol and glutaraldehyde. She then stains the cells with anti-tubulin, anti-actin, and a fluorescent dye called DAPI. She takes the prepared cells to her microscope, a Zeiss Axiovert, which runs on one of two microscope-based Mac Pros in her lab. "It's all computerized," says Skop, "so the microscope will not run unless the computer is running it." The computer adjusts light and objectives, and the image outputs to her 30-inch Apple Cinema Display.

Lasers in the microscope scan over the cell, picking up different pixel intensities corresponding to the various stains. Each pixel intensity comes up in a different channel. Skop uses Openlab software created by Improvision, a Mac-only microscope software program, for this part of the process. "It's like Photoshop but it interfaces directly with the microscope," says Skop, "so it's user-friendly in that regard." She adds false color to the image, a different shade for each wavelentgh that the laser records. Finally, the image is post-processed in Adobe Photoshop.

The Power of Sight

Skop says that she was drawn to science because it rewards her visual way of approaching the world. "I realize I understand through seeing," she says, "and cell biology is just that. You often need a way of making these discoveries by seeing." She's also sensitive to the aesthetic power of the images that science reveals—she describes cell division as "just inherently beautiful." She has installed a gallery of microscopy art on the campus at UW-Madison, and founded a C. elegans art show at the international bi-annual meeting of scientists who study the nematode worm. Expanding the realm of the seen, in other words, isn't just a side effect of Skop's job; it's her passion. "To me," she says, "when you look at a DNA band on a gel, that's not life and living. I want to really see it happening."