Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researcher gives hard thoughts on soft inheritance

09.08.2006
Above and beyond the gene

Organisms, including humans, all inherit DNA from generation to generation, what biologists call hard inheritance, because the nucleotide sequence of DNA is constant and only changes by rare random mutation as it is passed down the generations.

But there also is evidence, especially in plants, that non-genetic factors modifying the DNA can also be inherited. The modifications of the genetic material take the form of small chemical additions to one of the DNA bases and the alternative packaging of the DNA. These so-called epigenetic modifications are known to be important for turning genes on and off during the course of an organism's life, but their importance in controlling inheritance has been debated. Many biologists are skeptical of any form of soft inheritance, where the genetic material is not constant, believing that it is only genetic information - DNA -- that can be passed onto generations.

Now Eric Richards, Ph.D., professor of biology at Washington University in St. Louis, writing in the May issue of Nature Reviews Genetics, analyzes recent and past research in epigenetics and the history of evolution and proposes that epigenetics should be considered a form of soft inheritance, citing examples in both the plant and mammalian kingdoms.

In doing so, he evokes the pre-Darwinian evolutionist Jean-Baptiste Lamarck (1744-1829), a name that evolutionary biologists thought long ago left the stage, and Soviet agronomist T.D. Lysenko. Lamarck, and more recent neo-Lamarckian researchers, believed that the environment plays a key role in a species acquiring inherited characteristics that drive variation and evolution. Lamarck, for instance, believed that shore birds acquired their long legs by constantly stretching their legs to lift themselves out of the water and that generations later that kind of environment gave rise to birds with long legs. Neo-Lamarckian views of evolutionary change stress the importance of the environment in altering inheritance.

"When most biologists hear the name Lamarck or the term soft inheritance, the reaction is, 'Oh my God, here we go again'," Richards says. "But from a molecular biology point of view there is a mechanism to do soft inheritance, and epigenetic inheritance can be construed as a form of soft inheritance. That's all I'm saying. The really heretical thing to say is that the environment could be pushing the epigenetic information in a direction that is beneficial. This is the more extreme variation of soft inheritance that raises the hackles."

Packing DNA

Epigenetic mechanisms leave DNA sequence unaltered but can affect DNA by preventing the expression of genes. Richards cites a study that shows certain epigenetic alleles can be inherited that affect tumor suppressor genes. His own work in plants has often shown epigenetic information can be inherited. The Richards lab specializes in epigenetics, a biological field that deals with information stored "above and beyond the gene," referring to the Greek meaning of the term. A classic epigenetic mechanism is a process known as DNA methylation, a chemical modification of cytosine, one of the four chemical subunits of DNA. Without proper DNA methylation, higher organisms from plants to humans have a host of developmental problems, from dwarfing in plants to certain death in mice.

The next level of gene regulation studied in epigenetics is DNA packaging. DNA is wrapped around proteins similar to the way that thread is wrapped around a spool. Loosely wrapped DNA is more readily accessible and therefore more easily expressed than tightly wrapped DNA, allowing another mechanism for regulation of gene expression. The location of DNA within the nucleus also influences gene expression.

"Epigenetics as soft inheritance in mammals puts us on a slippery slope that many people don't want to visit," Richards says.

'Different strokes' for rat folks

Still, recent studies in mice and rats have fueled the controversy. Richards cited "a whole new world called nutritional epigenomics," where researchers are trying to influence epigenetic information by of all things diet. In a study with mice hybrids, researchers provided pregnant moms with varying levels of folate and B vitamins, to affect DNA methylation.

"The idea was : If you pump these pregnant moms up with these dietary supplements, you might be able to skew the DNA methylation patterns, and thus skew the way the mice come out at the end of the day, and it works,'" Richards says. "In this particular instance that says what you're getting fed in the womb influences your phenotype - physical and physiological attributes. "

Another study showed that early grooming and nurturing of rat pups by rat moms affects methylation of a glucocorticoid receptor gene in the hippocampus in the brain. If the pups get lots of nurturing the glucocorticoid gene gets turned on and expressed early at a critical period, providing pups the beneficial outcome to handle stress later in life. Not enough nurturing and grooming, and the gene never gets turned on. Richards says that whole mechanism appears to be the result of changes in DNA methylation associated with changes in DNA packaging.

"These studies do not demonstrate inheritance between generations, but they do show that the early nutritional environment in the mice and early behavioral environment in the rat studies can change the DNA packaging on the genome, and that that is 'remembered' in the cell divisions that make the rest of the organism, " Richards says. "But this is not from one generation to another. No one has shown that yet.

"To get to the issue of the more extreme variations of soft inheritance, it has to be determined whether the environment can induce an epigenetic change in an organism that can be inherited in subsequent generations. Certainly, nobody has shown that an epigenetically induced beneficial or adaptive change has been inherited. Mechanistically, there is no reason to discount epigenetic inheritance. The biochemical nuts and bolts are there to support it. The big questions to resolve are how many epigenetic changes are induced by the environment, what types of phenotypes result from these changes, and how many of these epigenetic changes are inherited."

Tony Fitzpatrick | EurekAlert!
Further information:
http://www.wustl.edu

More articles from Life Sciences:

nachricht The birth of a new protein
20.10.2017 | University of Arizona

nachricht Building New Moss Factories
20.10.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>