Re: Emerging science aims to manipulate human DNA

[Guest guest]

>>>

Do the chemicals we ingest today affect our great-grandchildren?

In addition to pesticides, toxicologists are studying chemicals in

plastics, such as phthalates and bisphenol A, to see if they could

enhance our risk of disease by alteringthe epigenome.

>>>

I wish that they would study things that manufacturers add to our

food intentionally like hydrogenated fats, artificial colors, and

preservatives. I think these are of more concern because they are

consumed in greater amounts.

Tony

>

>

> Research on mice might have meaning for many human illnesses

>

> By Saslow

> Washington Post Staff Writer

> Tuesday, December 15, 2009

>

> Two mice. One weighs 20 grams and has brown fur. The other is a hefty 60

> grams with yellow fur and is prone to diabetes and cancer. They're identical

> twins, with identical DNA.

>

> So what accounts for the differences?

>

> It turns out that their varying traits are controlled by a mediator between

> nature and nurture known as epigenetics. A group of molecules that sit atop

> our DNA, the epigenome (which means " above the genome " ) tells genes when to

> turn on and off. Duke University's Randy Jirtle made one of the mice brown

> and one yellow by altering their epigenetics in utero through diet. The

> mother of the brown, thin mouse was given a dietary supplement of folic

> acid, vitamin B12 and other nutrients while pregnant, and the mother of the

> obese mouse was not. (Though the mice had different mothers, they're

> genetically identical as a result of inbreeding.) The supplement " turned

> off " the agouti gene, which gives mice yellow coats and insatiable

> appetites.

>

> " If you look at these animals and realize they're genetically identical but

> at 100 days old some of them are yellow, obese and have diabetes and you

> don't appreciate the importance of epigenetics in disease, there's frankly

> no hope for you, " Jirtle says.

>

> He offers this analogy: The genome is a computer's hardware, and the

> epigenome is the software that tells it what to do.

>

> Epigenomes vary greatly among species, Jirtle explains, so we cannot assume

> that obesity in humans is preventable with prenatal vitamins. But his

> experiment is part of a growing body of research that has some scientists

> rethinking humans' genetic destinies. Is our hereditary fate -- bipolar

> disorder or cancer at age 70, for example -- sealed upon the formation of

> our double helices, or are there things we can do to change it? Are we

> recipients of our DNA, or caretakers of it?

>

> Last year, the National Institutes of Health announced that it would invest

> $190 million to accelerate epigenetic research. The list of illnesses to be

> studied in the resulting grants reveals the scope of the emerging field:

> cancer, Alzheimer's disease, autism, bipolar disorder, schizophrenia,

> asthma, kidney disease, glaucoma, muscular dystrophy and more.

>

> When Jirtle planned his first epigenetics conference in 1998 in Raleigh,

> N.C., epigenetics was such a small field that he worried nobody would come.

> About 160 people attended. Jirtle hosted another conference in 2005; it

> attracted 470.

>

> " It's the flavor of the month, " says Meaney, a brain researcher at

> McGill University in Montreal.

>

> When a gene is turned off epigenetically, the DNA has usually been

> " methylated. " Biologists have known for decades that methylation is involved

> in cell differentiation in utero, making one cell a skin cell, another cell

> a liver cell, and so on. Cell differentiation is also what happens when

> scientists prompt an embryonic stem cell to grow into a specific type of

> cell. But five years ago, when Meaney submitted a paper suggesting that DNA

> methylation happens throughout life in response to environmental changes, he

> was told, " This just can't happen. " (Most DNA methylation occurs prenatally

> and during infancy, puberty and old age, Jirtle says. Research suggests that

> epigenetically, humans are pretty stable during adulthood.)

>

> Duke Department of Medicine researcher Simon described the link

> between DNA methylation and autism in a paper published in October in the

> journal BMC Medicine.

>

> Most genetic studies of autism focus on variations in the DNA sequence

> itself, especially on genes that are missing. and his colleagues

> looked at an oxytocin receptor gene, called OXTR, and found that about 70

> percent of the 119 autistic people in his study had a methylated OXTR; in a

> control group of people without autism, the rate was about 40 percent.

> Oxytocin is a hormone that affects social interaction; difficulty relating

> to others is common for those with autism spectrum disorders.

>

> Because this was only a pilot study, more research is necessary. But

> says methylation-modifying drugs might be a new avenue for treatments. He

> also hopes that his findings will provide a new tool for doctors to diagnose

> autism.

>

> " Methylation has been very hot in the cancer field for a number of years, "

> says. " To find something like this associated with autism is very

> exciting. "

>

> Epigenetic therapy is still very inexact -- " a pretty broad brush, " says

> Jirtle. But oncologists have seen some success in using it against leukemia.

> Azacitidine, sold as Vidaza and used to treat bone-marrow cancer and blood

> disorders, became the first FDA-approved epigenetic drug in 2004. When

> tumor-suppressing genes aren't doing their job, due to a genetic mutation or

> hypermethylation, cancer cells can replicate uncontrollably. But by

> manipulating the epigenetic marks, doctors can get tumor-suppressing genes

> to work again. Toxicologists also have a big stake in epigenetics. A 2005

> study by Washington State University molecular biologist Skinner

> generated buzz with his finding that when a pregnant rat was exposed to high

> doses of pesticides, her offspring plus the next three generations suffered

> from high rates of infertility. (Some scientists have challenged Skinner's

> work because they have not been able to reproduce his results in their

> labs.)

>

> The potential human implications -- do the chemicals we ingest today affect

> our great-grandchildren? -- are tremendous. In addition to pesticides,

> toxicologists are studying chemicals in plastics, such as phthalates and

> bisphenol A, to see if they could enhance our risk of disease by altering

> the epigenome.

>

> Jirtle says that he and his fellow researchers usually discuss epigenetics

> only on the microscopic level, but when he pulls back and looks at the big

> picture, he is awed.

>

> " I've got goose bumps right now talking about it, " he says. " You're looking

> at the book of life, how it's read and how you can change it. "

>