Bacteria are single-cell organisms that reproduce by dividing in half. Proteins within these cells organize themselves in a number of fascinating ways during this process, including a recently discovered mechanism that makes the mesmerizing pattern of waves, or oscillations, you see in this video. Produced when the protein MinE chases the protein MinD from one end of the cell to the other, such oscillations are thought to center the cell’s division machinery so that its two new “daughter cells” will be the same size.
To study these dynamic patterns in greater detail, Anthony Vecchiarelli purified MinD and MinE proteins from the bacterium Escherichia coli. Vecchiarelli, who at the time was a postdoc in Kiyoshi Mizuuchi’s intramural lab at NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), labeled the proteins with fluorescent markers and placed them on a synthetic membrane, where their movements were then visualized by total internal reflection fluorescence microscopy. The proteins self-organized and generated dynamic spirals of waves: MinD (blue, left); MinE (red, right); and both MinD and MinE (purple, center) .
This Fourth of July, many of you will spread out a blanket and enjoy an evening display of fireworks with their dramatic, colorful bursts. But here’s one pyrotechnic pattern that you’ve probably never seen. In this real-time video, researchers set off some fluorescent fireworks under their microscope lens while making an important basic discovery about how microtubules, the hollow filaments that act as the supportive skeleton of the cell, dynamically assemble during cell division.
The video starts with a few individual microtubule filaments (red) growing linearly at one end (green). Notice the green “comets” that quickly appear, followed by a red trail. Those are new microtubules branching off. This continuous branching is interesting because microtubules were generally thought to grow linearly in animal cells (although branching had been observed a few years earlier in fission yeast and plant cells). The researchers, led by Sabine Petry, now at Princeton University, Princeton, NJ, showed for the first time that not only do new microtubules branch during cell division, but they do so very rapidly, going from a few branches to hundreds in a matter of minutes .
Caption: A model of the human folate receptor (top) and three antifolate drugs used in chemotherapy: aminopterin (left), pemetrexed, and methotrexate (right). Credit: Charles Dann III / Courtesy of Indiana University
Vitamin B9 or folic acid, which is found in dark green leafy vegetables, is essential for cells to grow and divide rapidly—as they do in a growing embryo. This is why women are advised to take folic acid supplements before conception and during pregnancy: inadequate folate raises the risk of brain and spinal cord defects. But while folic acid is key to normal cell growth, rapidly dividing cancer cells also have a tremendous appetite for this vitamin.
Drugs called antifolates have been used for decades in chemotherapy to starve cancer cells of folate, which can help kill the tumor. These drugs have also been used to treat inflammatory diseases like rheumatoid arthritis and Crohn’s disease. But many of these drugs have nasty side effects because they also enter normal healthy cells, depriving them of this essential compound. Continue reading →
The scientists at the IU School of Medicine-Bloomington nicknamed their new microscope the “OMG” for good reason—the images it produces are showstoppers. The DeltaVision OMX imaging system (its official title) is a $1.2 million dollar microscope that can peek inside a cell and image fluorescent proteins in unprecedented detail.
Jane Stout, a researcher in the NIH-funded lab, used the OMG to create this spectacular image that won her first place in the high- and super-resolution microscopy category of the 2012 GE Healthcare Life Sciences Cell Imaging Competition.
What you’re looking at is a cell in the midst of dividing into two identical copies—a process called mitosis. Here, the chromosomes (in blue) are aligned at the cell’s equator. Microtubules (red) from opposite poles of the cell attach to the chromosomes using the kinetochores (green) and pull them to opposite ends of the cell, which then splits in half. But sometimes cells do not divide properly—a common problem in cancer. Understanding the mechanics of cell division could help us correct this process when it goes wrong.
Jane Stout’s prize: her mitosis image will light up a billboard in Times Square in New York City in April. That is a wonderful celebration of science!
NIH support: the National Institute of General Medical Sciences