Silencing DNA: Adding methyl groups to specific spots in the genome can alter the expression of marked genes. The process, known as DNA methylation, is one mechanism of epigenetic change, heritable change that does not alter the sequence of DNA itself. In this image, colored bars represent the bases that make up a strand of DNA, while the green circles represent methylation.
Technology Review
Two new studies show that the effects of a mother's early environment can be passed on to the next generation.
The effects of an animal's environment during adolescence can be passed down to future offspring, according to two new studies. If applicable to humans, the research, done on rodents, suggests that the impact of both childhood education and early abuse could span generations. The findings provide support for a 200-year-old theory of evolution that has been largely dismissed: Lamarckian evolution, which states that acquired characteristics can be passed on to offspring.
"The results are extremely surprising and unexpected," says Li-Huei Tsai, a neuroscientist at MIT who was not involved in the research. Indeed, one of the studies found that a boost in the brain's ability to rewire itself and a corresponding improvement in memory could be passed on. "This study is probably the first study to show there are transgenerational effects not only on behavior but on brain plasticity."
In recent years, scientists have discovered that epigenetic changes--heritable changes that do not alter the sequence of DNA itself--play a major role in development, allowing genetically identical cells to develop different characteristics; epigenetic changes also play a role in cancer and other diseases. (The definition of epigenetics is somewhat variable, with some scientists limiting the term to refer to specific molecular mechanisms that alter gene expression.) Most epigenetic studies have been limited to a cellular context or have looked at the epigenetic effects of drugs or diet in utero. These two new studies are unique in that the environmental change that triggers the effect--enrichment or early abuse--occurs before pregnancy. "Give mothers chemicals, and it can affect offspring and the next generation," says Larry Feig, a neuroscientist at Tufts University School of Medicine, in Boston, who oversaw part of the research. "In this case, [the environmental change] happened way before the mice were even fertile."
In Feig's study, mice genetically engineered to have memory problems were raised in an enriched environment--given toys, exercise, and social interaction--for two weeks during adolescence. The animals' memory improved--an unsurprising finding, given that enrichment has been previously shown to boost brain function. The mice were then returned to normal conditions, where they grew up and had offspring. This next generation of mice also had better memory, despite having the genetic defect and never having been exposed to the enriched environment.
The researchers also looked at a molecular correlate of memory called long-term potentiation, or LTP, a mechanism that strengthens connections between neurons. Environmental enrichment fixed faulty LTP in mice with the genetic defect; the fixed LTP was then passed on to their offspring. The findings held true even when pups were raised by memory-deficient mice that had never had the benefits of toys and social interaction. "When you look at offspring, they still have the defect in the protein, but they also have normal LTP," says Feig. The findings were published today in the Journal of Neuroscience.
"If the findings can be conveyed to human, it means that girls' education is important not just to their generation but to the next one," says Moshe Szyf of McGill University, in Montreal, who was not involved in the research.
In a second study, researchers found that rats raised by stressed mothers that neglected and physically abused their offspring showed specific epigenetic modifications to their DNA. The abused mice grew up to be poor mothers, and appeared to pass down these changes to their offspring.
Worms given life-span-enhancing mutations produce offspring that lack the responsible genes but live longer anyway.
A startup is targeting diseases including cancer using epigenetic approaches.
I was reading an article about "Black-White Gap Widens Faster for High Achievers" and, based on a commentary done by someone named Mikke on the site http://hip.weblogs.hopkins.k12.mn.us/, I belive it would be very interesting to the authors to read the paper and the comment. They are both related with the experiment.
Lamarckian evolution is still Darwinian
Even if Lamarckian evolution happens, it is still hierarchically under Darwinian rule. This is because all the molecular machinery involved in epigenetic changes is still encoded by genes. And all these genes are ultimately under Darwinian "rule".
So epigenetic/Lamarckian changes only serve to temporarily nuance the phenotype.
Think of Darwinian selection as the big brush, which paints 90% of the picture. Then think of the epigenetic changes, as the small, finishing brush that fills in the small details, and brings nuance to the picture.
last year in other magazine, Science News I think.
Basically saying that environment of the genes / cells can activate certain cellular machinery (RNA) in the parent as part of everyday living, i.e. better nutrition or certain bio-chemicals or state of the body.
And, as the article says, this has large consequences on the offspring. This makes sense because we know intuitively and by examples that health of the mother animal or parent plant produce healthier babies / non-stunted or more seed.
Now we see that genes get a jump start depending on state of the parent. Not exactly the same but similar in principle.
This is by no means a setback for Darwinian theory, as I'm sure some will posit. Check, recheck, adjust...it's all the nature of the beast. I have long believed in my gut that Lamarck would eventually regain some cred, but alas, I can find no place where I have said so publicly. Guess I don't have "told you so" bragging rights.
Just for the record, I found it from Feb. of 2007: http://bit.ly/4nZJLL
Darwinism is not synonymous with evolutionary theory. Evolutionary theory has progressed since Darwin and will continue to evolve. The common sort of simple-minded pseudo-scientific dogmatism that believes that all past and future observations are already explained by current theories is a principal impediment to scientific progress. Much more is inherited than a just the sequence of DNA bases. Selection operates on more than one level. Inheirited attributes are not always passive or simple, but may be patterns of coordinated epigenetic response.
I first learned the term "epigenetic" reading "Neural Darwinism - The Theory of Neuronal Group Selection" by Nobelist Gerald Edelman some 20 years ago. Then he wrote of an high-dimensional "epigenetic landscape" with branching paths such that the developing organism's state would roll down one or another branch at each of many forks according to chance and environmental influences. The genetic code is not a fixed linear tape, but rather a library of code which can be called in many different orders and patterns of simultaneous activation. The newer concepts of epigenetics such as methylation patterns add to rather than replace that point of view.
It has long seemed odd to me that girls are born with all the eggs that they will ever have. Each of our cells traces its lineage back to a single cell which developed in our maternal grandmother's womb. The development of our mothers' ova could potentially be affected by the environment of our grandmothers' wombs. I can see no evolutionary reason for this curious arrangement other than to ensure that such influences actually happen.
As everyone should realize as interesting as this is, novel research is often inaccurate or misinterpreted. I would really like to see this research continued and built upon. Until that time it should be treated carefully before we claim too much from it.
How does this differ so much from the studies that support acquired resistant mutations by fruit flies to, say, DDT--which is passed on to offspring? The fact is, genes learn. They memorialize adaptations. One also suspects that an unchanged archival blueprint for genes may exist as well, perhaps in all the so-called latent DNA material. Although it may sound unrelated, Sheldrake's morphic resonance may have a biologic basis in this regard.
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
Our list of the 50 most innovative companies, including the following:
On Twitter
Become a Fan on Facebook
Subscribe to the Feed
BioPhile
1 Comment
It's not Lamarck vs Darwin
We should stop thinking of it (and reporting it) as a fight between the ideas and concepts of Lamarck *versus* Darwin. These are simply two different but complementary methods of increasing the fitness of a line of individuals. Tech Review could help lead us to this new way of thinking by promoting their complementarity rather than their competition.
Reply