Navigation Links
Does the villainous 'selfish' gene undermine genome's police?
Date:3/5/2013

PROVIDENCE, R.I. [Brown University] 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.

In TV listings the series would be described this way: "A gene exploits a rival gene's excesses, sabotaging any sperm that bear the 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.


'/>"/>

Contact: David Orenstein
david_orenstein@brown.edu
401-863-1862
Brown University
Source:Eurekalert  

Related biology news :

1. Selfish DNA in animal mitochondria offers possible tool to study aging
2. Research!America says house funding levels for FY13 could undermine medical progress
3. Athletic frogs have faster-changing genomes
4. Researchers announce GenomeSpace environment to connect genomic tools
5. Differences in the genomes of related plant pathogens
6. Thirty teams compete to interpret three families genomes
7. The first goat genome sets a good example for facilitating de novo assembly of large genomes
8. Sequencing hundreds of chloroplast genomes now possible
9. FASEB SRC announces conference registration open for: Mobile DNA in Mammalian Genomes
10. Mitochondrial mutations: When the cells 2 genomes collide
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Does the villainous 'selfish' gene undermine genome's police?
(Date:4/3/2017)... 3, 2017  Data captured by IsoCode, ... detected a statistically significant association between the ... treatment and objective response of cancer patients ... predict whether cancer patients will respond to ... well as to improve both pre-infusion potency testing ...
(Date:3/29/2017)...  higi, the health IT company that operates the ... , today announced a Series B investment from ... The new investment and acquisition accelerates higi,s strategy to ... population health activities through the collection and workflow integration ... collects and secures data today on behalf of over ...
(Date:3/24/2017)... -- Research and Markets has announced the addition of ... - Industry Forecast to 2025" report to their offering. ... The Global Biometric Vehicle ... around 15.1% over the next decade to reach approximately $1,580 million ... estimates and forecasts for all the given segments on global as ...
Breaking Biology News(10 mins):
(Date:4/25/2017)... , April 25, 2017 ... has licensed its novel immune-modulating technology to an undisclosed ... and allergy. Tregitopes, pronounced T·rej·itopes, are ... immunoglobulin by EpiVax CEO Annie De Groot ... intravenous immunoglobulin G, an autoimmune disease therapy, Tregitopes ...
(Date:4/24/2017)... ... 24, 2017 , ... It is well established that ligand ... broad application of this cellular target engagement concept to drug discovery has been ... stabilization assays are valuable methods for particular applications, but they can require target-specific ...
(Date:4/21/2017)... ... 2017 , ... The University of Connecticut, in partnership with ... startups through the UConn Innovation Fund. The $1.5 million UConn Innovation Fund was ... , The UConn Innovation Fund provides investments of up to $100,000 to companies ...
(Date:4/21/2017)... ... April 21, 2017 , ... Frederick Innovative ... range of emerging technology-based businesses, recently earned a $77,518 grant from the Rural ... Founded in 2004, FITCI is Frederick’s first incubator. A non-profit corporation, FITCI is ...
Breaking Biology Technology: