Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Acquired Traits Can Be Inherited Via Small RNAs

06.12.2011
Columbia University Medical Center (CUMC) researchers have found the first direct evidence that an acquired trait can be inherited without any DNA involvement. The findings suggest that Lamarck, whose theory of evolution was eclipsed by Darwin’s, may not have been entirely wrong. The study is slated to appear in the December 9 issue of Cell.

“In our study, roundworms that developed resistance to a virus were able to pass along that immunity to their progeny for many consecutive generations,” reported lead author Oded Rechavi, PhD, associate research scientist in biochemistry and molecular biophysics at CUMC. “The immunity was transferred in the form of small viral-silencing agents called viRNAs, working independently of the organism’s genome.”

In an early theory of evolution, Jean Baptiste Larmarck (1744-1829) proposed that species evolve when individuals adapt to their environment and transmit those acquired traits to their offspring. For example, giraffes developed elongated long necks as they stretched to feed on the leaves of high trees, an acquired advantage that was inherited by subsequent generations. In contrast, Charles Darwin (1809-1882) later theorized that random mutations that offer an organism a competitive advantage drive a species’ evolution. In the case of the giraffe, individuals that happened to have slightly longer necks had a better chance of securing food and thus were able to have more offspring. The subsequent discovery of hereditary genetics supported Darwin’s theory, and Lamarck’s ideas faded into obscurity.

However, some evidence suggests that acquired traits can be inherited. “The classic example is the Dutch famine of World War II,” said Dr. Rechavi. “Starving mothers who gave birth during the famine had children who were more susceptible to obesity and other metabolic disorders — and so were their grandchildren.” Controlled experiments have shown similar results, including a recent study in rats demonstrating that chronic high-fat diets in fathers result in obesity in their female offspring.

Nevertheless, Lamarckian inheritance has remained controversial, and no one has been able to describe a plausible biological mechanism, according to study leader Oliver Hobert, PhD, professor of biochemistry and molecular biophysics and a Howard Hughes Medical Institute Investigator at CUMC.

Dr. Hobert suspected that RNA interference (RNAi) might be involved in the inheritance of acquired traits. RNAi is a natural process that cells use to turn down, or silence, specific genes. It is commonly employed by organisms to fend off viruses and other genomic parasites. RNAi works by destroying mRNA, the molecular messengers that carry information coded in a gene to the cell’s protein-making machinery. Without its mRNA, a gene is essentially inactive.

RNAi is triggered by doubled-stranded RNA (dsRNA), which is not found in healthy cells. When dsRNA molecules (for example, from a virus) enter a cell, they are sliced into small fragments, which guide the cell’s RNAi machinery to find mRNAs that match the genetic sequence of the fragments. The machinery then degrades these mRNAs, in effect destroying their messages and silencing the corresponding gene.

RNAi can be also triggered artificially by administering exogenous (externally derived) dsRNA. Intriguingly, the resultant gene-silencing occurs not only in the treated animal, but also in its offspring. However, it was not clear whether this effect is due to the inheritance of RNAs or to changes in the organism’s genome — or whether this effect has any biological relevance.

To look further into these phenomena, the CUMC researchers turned to the roundworm (C. elegans). The roundworm has an unusual ability to fight viruses, which it does using RNAi.

In the current study, the researchers infected roundworms with Flock House virus (the only virus known to infect C. elegans) and then bred the worms in such a way that some of their progeny had nonfunctional RNAi machinery. When those progeny were exposed to the virus, they were still able to defend themselves. “We followed the worms for more than one hundred generations — close to a year — and the effect still persisted,” said Dr. Rechavi.

The experiments were designed so that the worms could not have acquired viral resistance through genetic mutations. The researchers concluded that the ability to fend off the virus was “memorized” in the form of small viral RNA molecules, which were then passed to subsequent generations in somatic cells, not exclusively along the germ line.

According to the CUMC researchers, Lamarckian inheritance may provide adaptive advantages to an animal. “Sometimes, it is beneficial for an organism to not have a gene expressed,” explained Dr. Hobert. “The classic, Darwinian way this occurs is through a mutation, so that the gene is silenced either in every cell or in specific cell types in subsequent generations. While this is obviously happening a lot, one can envision scenarios in which it may be more advantageous for an organism to hold onto that gene and pass on the ability to silence the gene only when challenged with a specific threat. Our study demonstrates that this can be done in a completely new way: through the transmission of extrachromosomal information. The beauty of this approach is that it’s reversible.”

Any therapeutic implications of the findings are a long way off, Dr. Rechavi added. “The basic components of the RNAi machinery exist throughout the animal kingdom, including humans. Worms have an extra component, giving them a much stronger RNAi response. Theoretically, if that component could be incorporated in humans, then maybe we could improve our immunity and even our children’s immunity.”

The CUMC team is currently examining whether other traits are also inherited through small RNAs. “In one experiment, we are going to replicate the Dutch famine in a Petri dish,” said Dr. Rechavi. “We are going to starve the worms and see whether, as a result of starvation, we see small RNAs being generated and passed to the next generation.”

The CUMC team’s paper is entitled, “Transgenerational inheritance of an acquired small RNA-based antiviral response in C. elegans.” The other co-author is Gregory Minevich at CUMC.

This research was supported by the Howard Hughes Medical Institute and Gruss Lipper Fellowship to Oded Rechavi.

The authors declare no financial or other conflicts of interest.

Columbia University Medical Center provides international leadership in basic, pre-clinical and clinical research, in medical and health sciences education, and in patient care. The medical center trains future leaders and includes the dedicated work of many physicians, scientists, public health professionals, dentists, and nurses at the College of Physicians and Surgeons, the Mailman School of Public Health, the College of Dental Medicine, the School of Nursing, the biomedical departments of the Graduate School of Arts and Sciences, and allied research centers and institutions. Established in 1767, Columbia's College of Physicians and Surgeons was the first institution in the country to grant the M.D. degree and is among the most selective medical schools in the country. Columbia University Medical Center is home to the largest medical research enterprise in New York City and State and one of the largest in the United States.

Karin Eskenazi | Newswise Science News
Further information:
http://www.columbia.edu

More articles from Life Sciences:

nachricht Repairing damaged hearts with self-healing heart cells
22.08.2017 | National University Health System

nachricht Biochemical 'fingerprints' reveal diabetes progression
22.08.2017 | Umea University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Cholesterol-lowering drugs may fight infectious disease

22.08.2017 | Health and Medicine

Meter-sized single-crystal graphene growth becomes possible

22.08.2017 | Materials Sciences

Repairing damaged hearts with self-healing heart cells

22.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>