Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Clawed frog helps Fanconi anemia research make leaps

25.01.2006


OHSU scientists using Xenopus eggs demonstrate Fanconi genes’ importance to DNA duplication, repair



A large, clawed frog is helping Oregon Health & Science University researchers gather a princely sum of knowledge on Fanconi anemia, a rare, genetic, cancer-susceptibility syndrome.

Scientists in the OHSU School of Medicine’s Department of Biochemistry and Molecular Biology are the first to report a new approach using eggs of the African clawed frog, which goes by the Latin name Xenopus laevis, to understand how the Fanconi anemia proteins ensure that DNA is replicated properly, according to a study published this month in the journal Molecular and Cellular Biology.


The international team is led by the OHSU laboratory of Maureen Hoatlin, Ph.D. Using extracts from Xenopus eggs and chemically triggering DNA copying, the team showed that the Fanconi proteins function to prevent accumulation of breaks in DNA strands that arise even during normal replication. Fanconi anemia is thought to be the result of a defect in the Fanconi genes’ ability to repair DNA damage.

Hoatlin said there are many advantages to using the frogs’ eggs, instead of human cells, to study Fanconi anemia.

"In human cells, most of the Fanconi proteins are hard to detect, so you have to grow millions of cells over long periods of time to collect enough to study," she said. "The other problem is that cultured human cells are at all different stages of the cell cycle. The bulk of the cells are not rapidly dividing, and it’s only when cells are dividing that the Fanconi proteins are usually at their highest expression and activity."

In Xenopus eggs, however, Fanconi proteins are stockpiled in preparation for the rapid divisions that occur after fertilization. Plus, the divisions occur at the same time, or synchronously, allowing naturally regulated stages of division to be studied simultaneously.

"It’s very hard to synchronize mammalian cells," Hoatlin added. "Also, unfortunately for Fanconi researchers, methods used to synchronize cells are usually also the ways you might damage the DNA in cells, whereas this system allows us to look at unperturbed replication."

The use of Xenopus eggs as a cell-free system for studying checkpoints in the DNA damage pathway is nothing new. Since the mid-1980s, scientists have been using the BB-sized, black-and-white, bead-like eggs to probe orchestration of the DNA replication process, something not as easily done in mammalian cells.

Since a Xenopus egg isn’t fertilized until after it is laid outside the body of the female frog, it’s in a relative state of suspension until it is fertilized. During this time, when the cell cycle is arrested, scientists can use chemicals and a centrifuge machine to keep its DNA from replicating. This creates a convenient extract rich in all the essential components ready for full replication.

Then, by chemically activating the extract and adding sperm DNA from the male frog, the proteins in the extract unwind the DNA and the replication process is off and running under the watchful eyes of the researchers.

"That’s just the beginning of what we want to do with these extracts to study how the Fanconi proteins work," Hoatlin said. "You can control the extract with chemicals or by removing proteins with specific antibodies. It’s a very powerful system."

In the Molecular and Cellular Biology paper, Hoatlin’s team identified many of the Xenopus versions of the Fanconi genes and found that they were very similar to the human counterparts by sequence and behavior. For example, the Fanconi proteins were drawn to the DNA once the copying process began. By adding a protein called geminin to the extract, which prevents the assembly of protein complexes essential to the beginning steps of replication, the scientists found the Fanconi proteins no longer accumulated on the DNA, even if the DNA was damaged.

The implication, Hoatlin pointed out, is that even if the DNA is damaged, "unless there’s replication, the Fanconi proteins don’t recognize the damage."

"We wanted to develop an approach that would allow us to determine how the Fanconi proteins assemble on replicating DNA and what proteins control the important steps. These extracts give us the tool we need for those experiments," she said. In fact, in the new Molecular and Cellular Biology study, Hoatlin’s lab already found that an important regulator of the cell’s DNA damage-sensing mechanism controls some, but not all, of the Fanconi protein’s arrival on replicating DNA.

Stacie Stone, an OHSU graduate student and co-lead author of the study, believes Hoatlin’s lab, where she has worked with frogs for more than two years, will continue to yield discoveries that may someday lead to a treatment of certain cancers and for Fanconi anemia, a devastating disease that primarily affects children. The lab already joined forces with other labs to isolate several of the dozen genes known to exist in the Fanconi pathway.

"Really, there are not a whole lot of labs using the Xenopus extract approach yet," Stone said. "There are so many experiments we’d like to do now." For example, Alexandra Sobeck, Ph.D., the study’s other co-lead author and a scientist in Hoatlin’s lab, is examining the order of assembly of Fanconi proteins on DNA and how the Fanconi proteins are activated in response to DNA damage.

"What I’m seeing is that Fanconi proteins work together with other important protein complexes," Sobeck added. "Every day is exciting."

Jonathan Modie | EurekAlert!
Further information:
http://www.ohsu.edu

More articles from Life Sciences:

nachricht Not of Divided Mind
19.01.2017 | Hertie-Institut für klinische Hirnforschung (HIH)

nachricht CRISPR meets single-cell sequencing in new screening method
19.01.2017 | CeMM Forschungszentrum für Molekulare Medizin der Österreichischen Akademie der Wissenschaften

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland

19.01.2017 | Earth Sciences

Not of Divided Mind

19.01.2017 | Life Sciences

Molecule flash mob

19.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>