Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Algae provide new clues to cancer

16.10.2006
A microscopic green alga helped scientists at the Salk Institute for Biological Studies identify a novel function for the retinoblastoma protein (RB), which is known for its role as a tumor suppressor in mammalian cells. By coupling cell size with cell division, RB ensures that cells stay within an optimal size range.

Their findings, which will be published in the October 13 online edition of PLoS Genetics, show that RB blocks cells from dividing before they reach a minimum size and could provide new insights into the origins of cancer.

"Being the right size is very important for cells because their physiology changes quite dramatically when the surface-to-volume ratio changes," explains senior author James Umen, Ph.D., an assistant professor and Hearst Endowment Chair in Salk's Plant Biology Laboratory. "The human body is composed of trillions of cells, each of which must coordinate its growth and division in order to maintain size equilibrium," he adds.

This process is very tightly regulated and any given cell type will always stay within a very narrow size range, but the means by which cell size is determined remain mysterious. In proliferating cells, control mechanisms termed checkpoints are thought to prevent cells from dividing until they reach a specific size, but the nature of the checkpoints has proved difficult to dissect.

... more about:
»Umen »alga »cell cycle »mechanism »reinhardtii

Understanding how cells balance the opposing processes of growth and division in order to achieve size control is more than just a fascinating intellectual pursuit for cell biologists: loss of size control is a hallmark of cancer cells, which exhibit severe defects in regulating growth and division.

"In mammalian cells it is very hard to separate size control from cell cycle control because it is very easy to mess up cell size as an indirect consequence of manipulating cell cycle rates," says Umen.

The tiny single-celled alga Chlamydomonas reinhardtii provided a model organism to study the link between cell size and growth. In nature, the organism is found in fresh and brackish water and in all kinds of soil. Its close relatives have adapted to the harsh conditions found in underwater thermal vents and even to life under the Antarctic ice shelf. In the lab, C. reinhardtii has been used to investigate agricultural, energy-related and medical questions.

Chlamydomonas is particularly well suited as an organism to dissect the control mechanisms behind cell size not only because of its simplicity but due to its peculiar cell cycle: during a prolonged growth phase cells enlarge to many times their original size and then suddenly divide several times in rapid succession. Despite this rapid-fire response, cell division is tightly controlled by a sizing mechanism that ensures daughter cells are never too large or too small.

In the course of earlier work, Umen identified an RB homolog encoded by the mat3 gene in C. reinhardtii and later discovered algal counterparts of other players in the RB pathway in humans and mice. To analyze their function in Chlamydomonas, the Salk team isolated cells with mutations in individual members of the RB signaling pathway – and things immediately started to go wrong.

Explains Umen, "Cells with mutations in the C. reinhardtii RB homolog start dividing prematurely, and continue dividing excessively, producing abnormally small daughter cells. Mutations in the algal versions of two key targets of the RB tumor suppressor have exactly the opposite effect of RB mutations, resulting in abnormally large cells that don't divide when they should." These findings demonstrate that once cells reach a critical size, they need those two RB target proteins to divide on schedule.

"The interesting thing for us is that the whole genetic module has been conserved from algae to plants to humans," says Umen. "It's been controlling cell division for well over a billion years. As multicellular organisms evolved, the RB pathway was co-opted to integrate growth factor signals, but its original purpose in single cells was more fundamental: to couple cell size to cell cycle progression," he adds.

Recently, evidence has emerged that animal cells also have size checkpoints whose nature is still unknown. "Our results open up the possibility that the ancient size control function for the RB pathway we discovered in Chlamydomonas may still be there in animal cells, but was integrated into a larger network that also responds to extracellular input from growth factors. It will be an interesting challenge now to dissect out that function for RB in animal cells," he says.

Gina Kirchweger | EurekAlert!
Further information:
http://www.salk.edu

Further reports about: Umen alga cell cycle mechanism reinhardtii

More articles from Life Sciences:

nachricht Zap! Graphene is bad news for bacteria
23.05.2017 | Rice University

nachricht Discovery of an alga's 'dictionary of genes' could lead to advances in biofuels, medicine
23.05.2017 | University of California - Los Angeles

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

Im Focus: Bacteria harness the lotus effect to protect themselves

Biofilms: Researchers find the causes of water-repelling properties

Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

Innovation 4.0: Shaping a humane fourth industrial revolution

17.05.2017 | Event News

 
Latest News

Scientists propose synestia, a new type of planetary object

23.05.2017 | Physics and Astronomy

Zap! Graphene is bad news for bacteria

23.05.2017 | Life Sciences

Medical gamma-ray camera is now palm-sized

23.05.2017 | Medical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>