A microtubule, part of the cell’s skeleton, builds and deconstructs. Credit: Eva Nogales lab, University of California, Berkeley.
In this animation, tubulin proteins snap into place like Lego blocks to build a microtubule, part of the cell’s skeleton. When construction ends, this long hollow cylinder falls to pieces from its top end. The breakdown is critical for many basic biological processes, including cell division, when rapidly shortening microtubules pull chromosomes into each daughter cell.
Until recently, scientists didn’t know exactly what drove microtubules to fall apart. A research team led by Eva Nogales of the Lawrence Berkeley National Laboratory and the University of California, Berkeley, now has an explanation.
Using high-powered microscopy, the scientists peered into the structure of a microtubule and found how a chemical reaction puts the stacking tubulin proteins under intense strain. The only thing keeping the proteins from springing apart is the pressure from the addition of more tubulin. So when assembly stops, the microtubule deconstructs.
The team also learned that Taxol, a common cancer drug, relieves this tension and allows microtubules to remain intact indefinitely. With microtubules frozen in place, a cancer cell cannot divide and eventually dies.
Because of this research, scientists now better understand both the success behind a common cancer drug and the molecular basis underlying the workings of microtubules.
University of California, Berkeley News Release
A newly designed fluorescent biosensor shows where Rac1, a molecule involved in cancer metastasis, is active in this cell. Warmer colors show greater Rac1 activity. Credit: Yasmin Moshfegh, Albert Einstein College of Medicine.
Most of the more than half-a-million deaths caused by cancer each year in the United States result not from the original tumor but from the spread of cancer to new parts of the body, or metastasis. Cancer cells travel from a primary tumor using invadopodia, foot-like protrusions that break through surrounding connective tissue. Invadopodia are driven by protein filaments that repeatedly grow and disassemble. Exactly what guides this cycle was unclear, but scientists suspected a molecule called Rac1 might be involved. A new tool now sheds light on the details.
Researchers led by Louis Hodgson of Albert Einstein College of Medicine developed a fluorescent biosensor that glows wherever Rac1 is active in a cell, and they used it to study highly invasive breast cancer cells taken from rodents and humans. The scientists observed invadopodia form when Rac1 activity was low and disappear when it was high. They then confirmed their findings when they shut down the gene that encodes Rac1 and saw the invadopodia remain intact indefinitely.
This discovery suggests that targeting Rac1 activity with drugs could stop the spread of cancer cells. But a major hurdle remains: Healthy cells, including those that make up our immune system, also rely on the molecule for normal activity. Researchers must find a way to turn off Rac1 in cancer cells without disrupting its function in the rest of the body.
This work also was funded by NIH’s National Cancer Institute.
Albert Einstein College of Medicine News Release
Neurons activated with red or blue light using algae-derived opsins. Credit: Yasunobu Murata/McGovern Institute for Brain Research at MIT.
The nerve cells, or neurons, lit up in blue and red in this image of mouse brain tissue are expressing algae-derived, light-sensitive proteins called opsins. To control neurons with light, scientists engineer the cells to produce particular opsins, most of which respond to light in the blue-green range. Then they shine light on the cell to activate it. Now, a team of researchers led by Ed Boyden of the Massachusetts Institute of Technology and Gane Ka-Shu Wong of the University of Alberta has discovered an opsin that responds to red light preferentially, enabling them to manipulate two groups of neurons simultaneously with different colors of light and get a more comprehensive look at how those two sets of brain cells interact. Other opsins have shown potential for vision restoration in animal studies, and, because red light causes less damage to tissue than blue-green light, this new opsin might eventually be used for such treatments in humans.
MIT News Release
Blood vessels in a mouse retina visualized using cutting-edge imaging technology. Credit: Tom Deerinck and Mark Ellisman, NCMIR.
For poets and lovers, the eyes are the windows of the soul. For scientists and doctors, blood vessels at the back of the eye are windows into many diseases.
Blood vessel abnormalities can indicate a variety of serious conditions such as atherosclerosis (hardening of the arteries), heart attacks and strokes. But most vessels are buried beneath skin and other tissues, making them difficult to examine without surgery.
There’s one exception—in the eye. Unlike anywhere else in the body, larger vessels on the retina at the back of the eye are directly visible through the pupil, requiring essentially only light and magnifying lenses to view.
These vessels are used to diagnose glaucoma and diabetic eye disease. Because they display characteristic changes in people with high blood pressure, some researchers hope retinal vessels might one day help predict an impending stroke, congestive heart failure or other diseases stemming from dangerously high blood pressure.
The medical importance of retinal vessels piqued the interest of scientists funded by the National Institutes of Health at the National Center for Microscopy and Imaging Research (NCMIR) at the University of California, San Diego, who captured this micrograph image of mouse retinal vessels.
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Viral RNA (red) in an RSV-infected cell. Credit: Eric Alonas and Philip Santangelo, Georgia Institute of Technology and Emory University.
What looks like a colorful pattern produced as light enters a kaleidoscope is an image of a cell infected with respiratory syncytial virus (RSV) illuminated by a new imaging technology. Although relatively harmless in most children, RSV can lead to bronchitis and pneumonia in others. Philip Santangelo of the Georgia Institute of Technology and Emory University, along with colleagues nationwide, used multiply-labeled tetravalent RNA imaging probes (MTRIPS) to observe the entry, assembly and replication of RSV inside a living cell. Once introduced into RSV-plagued cells, the MTRIPS latched onto the viral RNA (in the image, red) without altering the level of infectivity. This led to fluorescent RSV viral particles that let the researchers track the viral RNA in host cells and better understand what the virus was doing. The knowledge gained from this new technique might aid in the development of RSV antiviral drugs and possibly a vaccine. Scientists could also one day use the imaging approach to study other RNA viruses, such as the flu and Ebola.
Georgia Tech News Release