Now a research team led by Phong Tran, PhD, Assistant Professor of Cell and Developmental Biology at the University of Pennsylvania School of Medicine, has the answer: Both.
The findings, published online this week in the journal Current Biology by co-senior authors Tran and Matthieu Piel of the Institut Curie, Paris, combine genetics, live-cell imaging, and microfluidics technology. They were able to force normally rod-shaped yeast cells to grow within tiny curved channels. Using the channels, they made rod-shaped cells deform into curved-shaped mutant cells and conversely, curved-shaped cells straighten out into a rod. The surprising finding: as the cells bend, they reorganize their cytoskeleton, and as they reorganize their internal skeletons, the cells further adjust their shape.
Cell shape gone awry has been implicated in some forms of cancer. In the future, one potential implication of Tran's findings is that it might be possible to rescue certain disease states via squeezing or otherwise applying mechanical pressure to tissues or organs. But that, he concedes, is “completely science fiction on my part.” Instead, he says at this point this study is pure, basic research. “It was just a cool experiment.”
The findings point to a type of feedback loop. “The cytoskeleton changes the shape of the cell and the shape of the cell also changes the organization of the cytoskeleton,” he says. “In fact they feed back on each other, so any perturbation on one system will change the other, and visa versa.”The results validate a common belief among cell biologists, says Tran – that to cause a cell to form a branching projection, such as filopodia or dendrite, or new shape, simply adjust the cytoskeleton accordingly, and the shape will follow suit.
"Our demonstration is a conclusive and direct demonstration of that theory because we used normally rod-shaped cells, as opposed to indirect proof of the concept using mutant cell shapes,” he says.
At least five cellular components are required for making changes to the organization of the cytoskeleton and therefore the shape of a cell: microtubules, actin filaments, the cell membrane, and two protein complexes. Microtubules are hollow protein pipes that arrange themselves in bundles down the long axis of the cell. As they extend from the cell center towards the periphery, they carry with them one of the protein complexes, so that when they finally dock with a protein receptor at the cell membrane, the effect is to deliver the complex to the desired growth point. What follows is a cascade of events: This complex recruits the second protein complex, which in turn recruits the protein actin. Filaments of actin from this site bring the transport machinery necessary for new cell membrane to extend in the intended direction – generally, further along the long axis of the cell.
Essentially, what Tran's team, led by technician Courtney Terenna, found was that if normal yeast cells are forced to bend, their microtubules can no longer reach the old tip of the cell and so form new growth tips. Conversely, they also found that mutant yeast cells normally grow bent or round, if forced to grow in straight channels, will adopt cytoskeletal structures that are the normal rod-shape.
This, says Tran, could in theory partially explain why some cells from mouse knock-outs, when grown in two-dimensional tissue culture, have more severe problems than when grown in a three-dimensional animal. The researchers surmise that the three-dimensional architecture of a tissue inside a living organ rescues cytoskeletal abnormalities that otherwise arise in an artificial two-dimensional construct.
The study stems from an international collaboration between the microfluidics experts in Piel's group and the biology experts in Tran's. Co-first authors Terenna and Tatyana Makushok, a graduate student in Piel's group, funded by a Human Frontier Science Program (HFSP), an international organization funded by various countries, traveled to Paris and Philadelphia, respectively, to learn their counterpart's secrets so they could then proceed independently.
Now Tran's group is working to address several questions that arise from this research. First, how long can mutant cells maintain their wild-type phenotype once they are removed from the physical constraints of the microfluidic channel? How do the two protein complexes work together to affect cell shape? And, what effects do other environmental variables, such as temperature, have on cytoskeletal dynamics?
Tran’s lab is funded by the National Institutes of Health, the American Cancer Society, and the HFSP.
This release and related images can be found at: http://www.uphs.upenn.edu/news/News_Releases/2008/11/cytoskeleton-cell-shape.html
PENN Medicine is a $3.6 billion enterprise dedicated to the related missions of medical education, biomedical research, and excellence in patient care. PENN Medicine consists of the University of Pennsylvania School of Medicine (founded in 1765 as the nation's first medical school) and the University of Pennsylvania Health System.
Penn's School of Medicine is currently ranked #4 in the nation in U.S.News & World Report's survey of top research-oriented medical schools; and, according to most recent data from the National Institutes of Health, received over $379 million in NIH research funds in the 2006 fiscal year. Supporting 1,700 fulltime faculty and 700 students, the School of Medicine is recognized worldwide for its superior education and training of the next generation of physician-scientists and leaders of academic medicine.
The University of Pennsylvania Health System (UPHS) includes its flagship hospital, the Hospital of the University of Pennsylvania, rated one of the nation’s top ten “Honor Roll” hospitals by U.S.News & World Report; Pennsylvania Hospital, the nation's first hospital; and Penn Presbyterian Medical Center. In addition UPHS includes a primary-care provider network; a faculty practice plan; home care, hospice, and nursing home; three multispecialty satellite facilities; as well as the Penn Medicine at Rittenhouse campus, which offers comprehensive inpatient rehabilitation facilities and outpatient services in multiple specialties.
Karen Kreeger | Newswise Science News
At last, butterflies get a bigger, better evolutionary tree
16.02.2018 | Florida Museum of Natural History
New treatment strategies for chronic kidney disease from the animal kingdom
16.02.2018 | Veterinärmedizinische Universität Wien
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).
Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
16.02.2018 | Information Technology
16.02.2018 | Health and Medicine
16.02.2018 | Physics and Astronomy