A tiny, freshwater flatworm found in ponds and rivers around the world that has long intrigued scientists for its remarkable ability to regenerate has now added a new wrinkle to biology.
The freshwater flatworm Schmidtea mediterranea lives in southern Europe and Northern Africa is the first animal ever discovered without a crucial structure inside its cells known as the centrosome. (Image credit: UCSF/J.Azimzadeh)
Reporting in the journal Science today, researchers at the University of California, San Francisco (UCSF) and the Stowers Institute for Medical Research in Kansas City, MO, have discovered that the worm lacks a key cellular structure called a “centrosome,” which scientists have considered essential for cell division.
Every animal ever examined, from the mightiest mammals to the lowliest insects, has these centrosomes in their cells.
“This is the first time we’ve found one that didn’t,” said Wallace Marshall, PhD, an associate professor in the Department of Biochemistry & Biophysics at UCSF, who led the research.
The fact that flatworms lack these centrosomes calls into question their purpose, Marshall added. “Clearly we have to rethink what centrosomes are actually doing,” he said.The Necessity of Even Division
A hallmark of cancer, for instance, involves abnormalities in this division. Tumor cells often duplicate extra pieces of DNA. Certain forms of childhood mental retardation are also marked by abnormal divisions, which cause the loss of large pieces of DNA, leading to development problems in certain brain structures.
Centrosomes have been seen as animals’ ultimate evolutionary fix for this problem. Plants and fungi don’t have them, but animals have had centrosomes in their cells, as long as there have been animals. These structures were thought to play a central role in cell division — laying down track-like spindles onto which the cells sort their dividing DNA. Centrosomes were seen as so important to cell division that all animals were assumed to have them.
The discovery that at least one animal doesn’t came quite unexpectedly.
Interested in the basic mechanics of the centrosome, Marshall and UCSF postdoctoral researcher Juliette Azimzadeh, PhD, teamed up with Alejandro Sánchez Alvarado, PhD, a Howard Hughes Medical Institute and Stowers Institute investigator, who has worked with the flatworm Schmidtea mediterranea for several years.Worm Regenerates Without Centrosomes
The original intention of the study Azimzadeh, Marshall and Sánchez Alvarado devised was to see what happened to the worm when it lost its centrosome.
Together they manipulated the flatworm to knock out genes needed to assemble these centrosomes. Without centrosomes the worms should have lost their ability to regenerate normally — or so they thought.
They were amazed to find that losing these structures didn’t affect the worms’ ability to regenerate at all. Then they looked more carefully at the worms and discovered that they never had these centrosomes in the first place.
“It came as a surprise to all of us,” said Sánchez Alvarado. What it means, he said, is that the evolutionary pressure that has maintained these structures in nearly all animals may have very little to do with cell division itself.
“There may be another function for centrosomes that is still obscured,” he said.
The article, “Centrosome Loss in the Evolution of Planarians,” by Juliette Azimzadeh, Mei Lie Wong, Diane Miller Downhour, Alejandro Sánchez Alvarado and Wallace F. Marshall, will be published in Science Express on Jan. 5, 2012.
In addition to UCSF and the Stowers Institute, authors of this paper are affiliated with the University of Utah School of Medicine in Salt Lake City.
The work was supported in part by the Howard Hughes Medical Institute, the W.M. Keck Foundation and the National Institute of General Medical Sciences.
UCSF is a leading university dedicated to promoting health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care.
Jason Socrates Bardi | EurekAlert!
Overlooked molecular machine in cell nucleus may hold key to treating aggressive leukemia
23.04.2019 | Cincinnati Children's Hospital Medical Center
Bacteria use their enemy -- phage -- for 'self-recognition'
23.04.2019 | Chinese Academy of Sciences Headquarters
Researchers led by Francesca Ferlaino from the University of Innsbruck and the Austrian Academy of Sciences report in Physical Review X on the observation of supersolid behavior in dipolar quantum gases of erbium and dysprosium. In the dysprosium gas these properties are unprecedentedly long-lived. This sets the stage for future investigations into the nature of this exotic phase of matter.
Supersolidity is a paradoxical state where the matter is both crystallized and superfluid. Predicted 50 years ago, such a counter-intuitive phase, featuring...
A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter
A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.
Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...
The technology could revolutionize how information travels through data centers and artificial intelligence networks
Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...
Physicists observe how electron-hole pairs drift apart at ultrafast speed, but still remain strongly bound.
Modern electronics relies on ultrafast charge motion on ever shorter length scales. Physicists from Regensburg and Gothenburg have now succeeded in resolving a...
17.04.2019 | Event News
15.04.2019 | Event News
09.04.2019 | Event News
23.04.2019 | Information Technology
23.04.2019 | Earth Sciences
23.04.2019 | Life Sciences