Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Selfish gene may undermine genome police

05.03.2013
Biologists have been observing the “selfish” genetic entity segregation distorter (SD) in fruit flies for decades. Its story is a thriller among molecules, in which the SD gene destroys maturing sperm that have a rival chromosome. A new study reveals a tactic that gives SD’s villainy an extra edge.

For a bunch of inanimate chemical compounds, the nucleic and amino acids caught up in the infamous “selfish” segregation distorter (SD) saga have put on quite a soap opera for biologists since the phenomenon was discovered in fruit flies 50 years ago. A new study, a highlight in the March issue of the journal Genetics, provides the latest plot twist.


A subcellular life and death struggle
Healthy spermatids (maturing sperm) of a fly, left, are decimated in a setting dominated by a “segregation distorter,” right. A runaway snippet of code that rapidly copies itself helps target spermatids for fatal attacks. Credit: Reenan lab/Brown University

In TV listings the series would be described this way: “A gene exploits a rival gene’s excesses, sabotaging any sperm that bear a rival’s chromosome.” The listing is not an exaggeration except for ascribing malicious intent to strings of biochemicals. When male flies make their sperm, the SD gene (call it “A”) manages to rig meiosis — the specialized cell division that makes sex cells — so that maturing sperm that bear chromosomes with the susceptible allele (call that one “a”) end up defective and discarded. They never even leave the testes.

It is murder of a sort. Similar selfish systems occur in mammals, including humans.

In the Genetics study conducted at Brown University, scientists uncover new clues about how the SD gene might be gaming the system against “a.” It’s a plot so fiendish, only an aggregation of genetic bases could evolve it. It also deepens biologists’ understanding of an instance in which life violates a fundamental balance predicted by the father of genetics, Gregor Mendel.

“Mendel’s first law is that different alleles of a gene will segregate,” said Robert Reeenan, professor of biology and the study’s senior author. “If we have two alleles — big A and little a — then Mendel says 50 percent of the sperm at random will get the big A and 50 percent of the sperm will get the little a. But some SD (A) alleles are so strong they pretty much kill off all the non-SD (a) chromosomes.

“This is a real cheater, a real stinker,” Reenan said. “Most genes, like most people, are good upstanding citizens, but some genes want to hog all the resources, hog all the benefit.”

The SD backstory

What makes the “a” allele susceptible to SD’s subterfuge is the number of copies it harbors of a runaway snippet of genetic code called Responder. A few copies of Responder are no problem, but hundreds of copies make “a” susceptible. Some alleles have thousands of copies and only one in a thousand survives.

Genomes try to root out parasites like Responder by creating and dispatching proteins into the nucleus and the cytoplasm. These police proteins are armed with “police sketches” of the parasites in the form of small RNA transcripts.

The new plot twist

It struck Reenan and lead author Selena Gell that this policing system — because it targets self-copiers like Responder — might somehow have a role in the SD saga. They decided to find out by purposely perturbing the system.

In the experiments described in Genetics, Reenan and Gell show that engineered mutations in the police gene named Aubergine (others on the force in the experiments are called Piwi, Squash, and Zucchini) amplify SD chromosomes’ success in eliminating Responder-laden sperm, compared to that of SD chromosomes without Aubergine’s help. The results show that this police system suppresses Responder, and therefore SD. It also means that if SD somehow can upset the policing system, it can have a field day.

“We’re the first to have experimentally shown that mutations in the system can modify the degree of distortion,” Reenan said. “We used homologous recombination to knock in a mutation specifically on the SD chromosome to compromise Aubergine, and that’s exactly what we saw: the chromosome became more selfish.”

Reenan and Gell did not go so far as to determine whether known SD-promoting genes called Enhancer of SD, Stabilizer of SD, and Modifier of SD act by interfering with Aubergine or its buddies on the force, but Reenan said that is among the next things his group will look into.

In the meantime, he reflects, it may not be entirely fair for biologists to label SD as “selfish” and not Responder as well. As an out-of-control self-repeater in the genome, Responder is surely no prize, and SD performs something of a service by taking it out when it can.

The whole story is really a clash of the selfish. “Humans, flies, all of us have been attacked for millennia by selfish genetic elements that want to make as many copies as possible,” Reenan said.

Sometimes, as in SD flies, there are no apparent ill effects, but when the selfish genes come in the form of viruses or other kinds of transposons, there can be trouble. So investigating the tactics of selfish genes is not merely the stuff of biological soap operas.

Gell, who was supported by a National Science Foundation Predoctoral Fellowship during the research, is now a postdoctoral scholar at Harvard University.

Editors: Brown University has a fiber link television studio available for domestic and international live and taped interviews, and maintains an ISDN line for radio interviews. For more information, call (401) 863-2476.

David Orenstein | EurekAlert!
Further information:
http://www.brown.edu

Further reports about: Little Brown Bats Responder SELFISH amino acid chromosomes

More articles from Life Sciences:

nachricht Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory

nachricht How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>