Featured Research

from universities, journals, and other organizations

Deletion of any single gene provokes mutations elsewhere in the genome

Date:
November 13, 2013
Source:
Johns Hopkins Medicine
Summary:
Researchers report that the deletion of any single gene in yeast cells puts pressure on the organism's genome to compensate, leading to a mutation in another gene. Their discovery, which is likely applicable to human genetics because of the way DNA is conserved across species, could have significant consequences for the way genetic analysis is done in cancer and other areas of research.

Deletion of Gene B causes instability in the genome that is compensated for through a secondary mutation in Gene A.
Credit: Xinchen Teng, courtesy of Molecular Cell

Johns Hopkins researchers report that the deletion of any single gene in yeast cells puts pressure on the organism's genome to compensate, leading to a mutation in another gene. Their discovery, which is likely applicable to human genetics because of the way DNA is conserved across species, could have significant consequences for the way genetic analysis is done in cancer and other areas of research, they say.

Summarized in a report to be published on Nov. 21 in the journal Molecular Cell, the team's results add new evidence that genomes, the sum total of species' genes, are like supremely intricate machines, in that the removal of a single, tiny part stresses the whole mechanism and might cause another part to warp elsewhere to fill in for the missing part.

"The deletion of any given gene usually results in one, or sometimes two, specific genes being 'warped' in response," says J. Marie Hardwick, Ph.D., the David Bodian Professor of Molecular Microbiology and Immunology at the Johns Hopkins Bloomberg School of Public Health and a professor of pharmacology and molecular sciences at the school of medicine. "Pairing the originally deleted gene with the gene that was secondarily mutated gave us a list of gene interactions that were largely unknown before."

Hardwick says the findings call researchers to greater scrutiny in their genetic analyses because they could unwittingly attribute a phenomenon to a gene they mutated, when it is actually due to a secondary mutation.

"This work has the potential to transform the field of cancer genetics," Hardwick says. "We had been thinking of cancer as progressing from an initial mutation in a tumor-suppressor gene, followed by additional mutations that help the cancer thrive. Our work provides hard evidence that a single one of those 'additional mutations' might come first and actively provoke the mutations seen in tumor-suppressor genes. We hope that our findings in yeast will help to identify these 'first' mutations in tumors."

The beauty of working with yeast, Hardwick says, is that it is easy to delete, or "knock out," any given gene. Her team started with a readily available collection of thousands of different yeast strains, each with a different gene knockout.

At their preferred temperature, each of these strains of yeast grows robustly even though they each have a different gene missing. Hardwick's team first asked a fundamental question: Within a given strain of yeast, does each cell have the same genetic sequence as the other cells, as had generally been presumed?

"We know, for example, that within a given tumor, different cells have different mutations or versions of a gene," explains Hardwick. "So it seemed plausible that other cell populations would exhibit a similar genetic diversity."

To test this idea, her team randomly chose 250 single-knockout strains from the thousands of strains in the collection. For each strain, they generated six sub-strains, each derived from a single yeast cell from the "parental batch."

They then put each sub-strain through a "stress test" designed to detect sub-strains with behaviors that varied from the behavior of the parental batch. All of the sub-strains grew indistinguishably without stress, but when the temperature was gradually raised for only a few minutes, some sub-strains died because they could not handle the stress. When the Hardwick team examined their genes, they found that, in addition to the originally knocked-out gene, each of the sub-strains that faltered also had a mutation in another gene, leading the team to conclude that the cells in each strain of the single-gene knockouts do not all share the same genetic sequence.

They then tested all 5,000 of the original single-gene knockout strains to find sub-strains that could overgrow when given low-nutrient food -- a trait that tumor cells often possess. This was another stress test designed to detect differences between the individual cells taken from the parental batches. They identified 749 such knockout strains and showed that their growth differences were often due to secondary mutations.

In total, the team's evidence indicates that 77 percent of all the knockout strains have acquired one or two additional mutations that affect cell survival and/or excessive growth when food is scarce.

Hardwick believes that stressing yeast in other ways may lead to an even higher percentage of double-mutant strains. In fact, she said she believes that "essentially any gene, when mutated, has the power to alter other genes in the genome." Deleting the first gene seems to cause a biological imbalance that is sufficient to provoke additional adaptive genetic changes, she explains.

Furthermore, in all of the strains that they examined, they found that the secondary mutations that appeared after a given knockout were always in the same one or two genes as in their earlier observations. Unexpectedly, Hardwick said, the altered growth of the sub-strains was usually due to the secondary mutations, not the original knockout, and many of those secondary mutations were in genes that are known to be cancer-causing in humans.


Story Source:

The above story is based on materials provided by Johns Hopkins Medicine. Note: Materials may be edited for content and length.


Journal Reference:

  1. Xinchen Teng, Margaret Dayhoff-Brannigan, Wen-Chih Cheng, CatherineE. Gilbert, CierraN. Sing, NicolaL. Diny, SarahJ. Wheelan, MaitreyaJ. Dunham, JefD. Boeke, FernandoJ. Pineda, J.Marie Hardwick. Genome-wide Consequences of Deleting Any Single Gene. Molecular Cell, 2013; DOI: 10.1016/j.molcel.2013.09.026

Cite This Page:

Johns Hopkins Medicine. "Deletion of any single gene provokes mutations elsewhere in the genome." ScienceDaily. ScienceDaily, 13 November 2013. <www.sciencedaily.com/releases/2013/11/131113162535.htm>.
Johns Hopkins Medicine. (2013, November 13). Deletion of any single gene provokes mutations elsewhere in the genome. ScienceDaily. Retrieved August 22, 2014 from www.sciencedaily.com/releases/2013/11/131113162535.htm
Johns Hopkins Medicine. "Deletion of any single gene provokes mutations elsewhere in the genome." ScienceDaily. www.sciencedaily.com/releases/2013/11/131113162535.htm (accessed August 22, 2014).

Share This




More Health & Medicine News

Friday, August 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Drug Used To Treat 'Ebola's Cousin' Shows Promise

Drug Used To Treat 'Ebola's Cousin' Shows Promise

Newsy (Aug. 21, 2014) An experimental drug used to treat Marburg virus in rhesus monkeys could give new insight into a similar treatment for Ebola. Video provided by Newsy
Powered by NewsLook.com
Two US Ebola Patients Leave Hospital Free of the Disease

Two US Ebola Patients Leave Hospital Free of the Disease

AFP (Aug. 21, 2014) Two American missionaries who were sickened with Ebola while working in Liberia and were treated with an experimental drug are doing better and have left the hospital, doctors say on August 21, 2014. Duration: 01:05 Video provided by AFP
Powered by NewsLook.com
Cadavers, a Teen, and a Medical School Dream

Cadavers, a Teen, and a Medical School Dream

AP (Aug. 21, 2014) Contains graphic content. He's only 17. But Johntrell Bowles has wanted to be a doctor from a young age, despite the odds against him. He was recently the youngest participant in a cadaver program at the Indiana University NW medical school. (Aug. 21) Video provided by AP
Powered by NewsLook.com
American Ebola Patients Released: What Cured Them?

American Ebola Patients Released: What Cured Them?

Newsy (Aug. 21, 2014) It's unclear whether the American Ebola patients' recoveries can be attributed to an experimental drug or early detection and good medical care. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins