One day, we might sue our grandparents for their bad habits. Why? Because certain behaviours can impart changes to our genome that can cause disease. And those changes can be passed down to future generations.
That means that our parent’s bad eating may impact your metabolism, for instance.
Journalist Bill Blakemore and three scientists gathered at the NYU’s Skirball centre for the Arts on Saturday May 30 to discuss this emerging field of research — called epigenetics — at the World Science Festival in New York last week.
Epigenetics doesn’t exactly refer to changes to our genes, but rather how our genes are used by our cells.
Small changes to the genome can impact if a gene is “turned on” and used to make a protein, and how much of the protein is made. While each cell contains a full set of genes, they all express those genes in different amounts, which gives them different traits.
New research suggests that outside factors like our behaviours, habits, and environments can also turn genes on and off in our cells, changing the way they act over time.
But, on the upside, we are starting to understand how these changes impact cancer, and improving treatment using that information.
Understanding our traits
Epigenetic research has been fuelled in part by research on identical twins. Twins have the same DNA, but often end up with slightly different traits and diseases. As they grow older, they even seem to look less and less similar.
“So the implication is, as you walk through life, as you have your unique experiences through that lifespan, your epigenetic changes are mirroring those experiences,” said scientist Frances Champagne, of Columbia University.
Epigenetic changes are well studied in plants, where they play an important role in environmental adaptation to severe drought. During droughts some plants survive thanks to specific epigenetic changes. Those can then pass that epigenetic change on to the next generation.
These changes aren’t completely permanent. If the next two or three generations don’t experience another drought, the genome returns to baseline.
Passing on traits
Even if the changes are temporary, they can still have tremendous effects on one’s offspring, even in humans.
Studies show that people who live through times of crisis — such as the Holocaust, China’s Cultural Revolution, and even 9/11 — leave imprints on their genes that they then risk passing on to their children. Even when the children of trauma survivors are raised in normal, stress-free environments, they still show abnormal hormone levels and display symptoms of mental disorders like PTSD.
“There is more and more evidence that grandparental even great-grandparental environmental exposures can impact you,” Champagne said.
The right timing
But, there is no need to stress over stress all the time. Scientists believe we are more susceptible to passing these epigenetic traits during specific periods in our lives.
The time from conception through childbirth is a particularly important time for parents to avoid stress if they don’t want to pass on nervous traits to their children.
“It’s really the mothers when they are pregnant or the fathers when they are conceiving,” Issa said. “There are periods of time when we have to be much more careful about our genome than other periods of time.”
One of the most startling experiments was done by Randy Jirtle, now a scientist at the University of Wisconsin. In an experiment published in the August 2003 edition of Molecular Cell Biology, Jirtle and his colleagues bred pairs of genetically identical agouti mice — so called because they suffering from a genetic defect that leaves them fat, yellow, and at high risk for disease.
Then they supplemented the diets some of the pregnant female agouti mice with nutrients such as choline and folate. Supplementing the diet seemed to suppress the effects of the agouti gene in many of the offspring so much that agouti mouse twins could look incredibly different and have very different risks for obesity and disease.
“What is wonderful about [Jirtle’s study] is that you can see it,” Champagne said. “We’ve got a yellow obese mouse, and a brown mouse. They are genetically identical but clearly not the same.”
A lifelong process
That being said, epigenetic changes can occur after an animal leaves the womb. Champagne found that rat pups shown more affection from their mothers in the first few weeks of their lives were much better at dealing with stress later on in their lives.
This evidence matches studies in other species as well.
“In primates there is evidence that abuse leaves lasting epigenetic changes, even in human brains,” Champagne said.
But there’s also hope these epigenetic changes can be selectively reversed, and that that reversal could treat disease.
Jean-Pierre Issa, a researcher from Temple University, gives epigenetically active drugs to patients suffering from lung cancer. The cancerous cells have very different epigenomic characteristics than normal healthy tissue.
“I like to tell people that these are like bookmarks, and if we simply reconfigure the bookmarks, then there is a different instruction program,” Issa said. “And we can see that in cancers, there is a very different instruction program.”
With treatment the researchers have actually erased the epigenetic signature of the cancer from the patients’ bodies, causing the cancers to slowly disappear. After the epigenetic treatment, the cancerous cells just stop growing and behave like normal cells and those that cannot simply die.
Issa and his colleagues have seen this treatment work in hundreds of patients.
“This is different from the war on cancer. This is diplomacy on cancer,” Issa said. “What we are trying to do is we are trying to change the instruction program of these cells to remind the cells how they should behave.”
Four of these persuasive drugs are already approved by the FDA and about 100,000 people already take them.
“Now everybody understands that [cancer] is as much if not more epigenetic than genetic,” Issa said. “And we have had to convince doctors that we could actually develop therapies based on this. And we have proof of principle. Many patients alive today who would not be alive today were it not for these drugs. 10 years from now, we’ll know a lot more.”
Watch the video of the entire discussion here for more information:
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