Since you say you won't look at links, here's just one of so many stories on epigenetics (from our national broadcaster, the ABC, at http://www.abc.net.au/catalyst/stories/s1900723.htm):
You are what you eat…but science suggests you’re also what your grandmother ate.
We’ve always known that the genes of our ancestors are passed on through generations, but could they pass on something more than just their genes?
In 2000 the human genome was finally mapped and scientists had cracked our genetic code.
But they didn’t bargain on discovering a hidden array of switches that can be turned on, or off, not only by what our bodies experience, but also by what our predecessors got up to.
This discovery has opened a brave new world of medical research and has implications for the development of treatments for many diseases including cancer.
Narration: We’ve always known the genes of our ancestors can be passed on through generations, but could they pass on something more then just their genes.
Could the effects of my grandfather’s lifestyle, or my grandmother’s diet, somehow have been passed down to me?
Not through their genes, but through something beyond their genes – something known as epigenetics.
Dr Jeff Craig: Epigenetics literally means above genetics and epigenetics refers to the beacons that are on top of the DNA
Dr Catherine Suter: It’s all about what genes are on, and what genes are off.
Dr Jeff Craig: I think it is up there with the DNA code.
Dr Maryanne Demasi: Epigenetic changes are like tags or beacons on our DNA. They can switch our genes on, or off, just like a light switch. Now the significance of this is huge
Narration: These switches can actually control the way our genes behave.
They can affect everything - from our emotional well being, to how much we eat and even the diseases we develop.
Dr Jeff Craig has been studying the causes and effects of epigentic changes in children.
Dr Maryanne Demasi: So Jeff, what information can this slide give us?
Dr Jeff Craig: Well this shows a micro array of the whole human genome. And what it shows is spots of DNA which basically act like traffic lights. The green lights are where genes are on, and the red lights are where genes are off.
Narration: Most of us know a little about DNA – or our genetic blueprint.
DNA consists of a long strand of four sub units known as A, G, C & T. Our genes are basically a long string of letters and it’s the way those letters are arranged that make us unique individuals.
Dr Jeff Craig: The DNA code is very important because the ordering of the letters tell you about the ordering of the amino acids that make the proteins.
Narration: Proteins are the building blocks of life. They make every living cell in our body, from those of our vital organs to our hair and our fingernails.
Identical twins like Imogen and Tennille have the same DNA, the same ordering of the letters.
But despite that, only one of these identical twins was struck down by leukaemia, a devastating cancer usually caused by a genetic mutation.
Dr Maryanne Demasi: When was this taken?
Tennille Purton: At kindi.
Dr Maryanne Demasi: Why’s that your favourite photo?
Heather Purton: I think it was about four to five weeks before her fifth birthday. And like all kids she was a bit off colour, she was pale, lethargic and I thought she had a bug.
I certainly didn’t expect someone to come back and say she has leukaemia.
Dr Jeff Craig: With Imogen and Tennille, Imogen did not show a typical leukaemia associated gene splicing event as usually happens in high proportion of leukaemias and that is why we think she may have had an epigenetic change.
Narration: In other words, Imogen’s cancer wasn’t caused by a genetic mutation, but by another mechanism that switched off an important gene that suppresses cancer.
Fortunately for Tennille, that same gene remained switched on – and she showed no sign of the disease. We had hoped many of these phenomena about genes and their role in disease, would be explained by mapping the human genome.
But they weren’t.
Dr Jeff Craig: After the human genome project we looked at the number of genes that were found, 30,000. It’s not really much more than a fruit fly and we thought, where is the complexity?
What makes human bodies complex?
Narration: Experts now believe that complexity might be due to epigenetics – those tags or beacons that sit upon our DNA.
But what causes them to appear? And can they be inherited by future generations?
Recent research shows epigenetic tags can be caused by any number of environmental influences – such as smoking, pesticides, stress and even diet.
Doctors Jennifer Cropley and Catherine Suter are at the forefront of epigenetic research into diet, and obesity.
Dr Jennifer Cropley: And here are the mice.
Dr Maryanne Demasi: Oh wow. So why are they all different colours?
Dr Jennifer Cropley: They are actually genetically identical. They are all twins, but they don’t look the same.
And it’s due the action of a particular gene, a single gene. All of the mice have this gene, but in some of the mice the gene is switched on, some switched off. An in this guy, the gene is switched off.
Now this little girl over here. She’s identical in every way only she’s yellow, and that’s because the gene is switched on in this mouse. But unfortunately for her, the gene has another effect.
Dr Jennifer Cropley: And so this is what she is going to look like an about three months time.
Dr Maryanne Demasi: Oh gosh she’s large isn’t she .. is she eating too much.
Dr Jennifer Cropley: She most certainly has. Same gene that cause the mice to turn this beautiful yellow colour also makes them overeat and so they get obesity and type 2 diabetes. It’s an almost perfect model of type 2 diabetes in people.
Narration: Incredibly, just one gene was controlling coat colour, and obesity. But what’s even more incredible is that the mother’s diet can determine whether the gene is switched on, or off.
Dr Jennifer Cropley: We found if we gave her a dietary supplement she was more likely to give birth to brown mice, that is, the diabetes gene had been switched off.
Dr Maryanne Demasi: So will this mouse then pass on an epigenetic tag to the next generation?
Dr Jennifer Cropley: Yes, she will.
Dr Maryanne Demasi: So what your saying is a grandma’s diet can actually effect two generations on?
Dr Jennifer Cropley: That’s right.
Narration: So if epigenetic changes can be inherited in mice, what about in humans.
Catherine Suter and colleagues at St Vincents Hospital found an epigenetic mark involved in cancer was passed on. It was an incredible breakthrough for medical research.
Narration: Well, the answer is yes. But the problem is, at the moment epigenetic drugs are not selective. They are not capable of targeting just one gene.
Dr Catherine Suter: We don’t know what the rules are. What we do know is that genes are on and off depending on certain proteins and chemical tags that are attached to the DNA.
Narration: Perhaps in the future, we’ll be able to wipe of those chemical tags inherited from our ancestors.
And our own children might be able to selectively erase the epigenetic memories shaped by our lifestyles.
Epigenetics Laboratory, Murdoch Childrens Research Institute
