Epigenetic Changes in Cancer

Lung cancer close-up MOREDUN ANIMAL HEALTH LTD/SPL / Gettyimages

The study of how covalent marks on DNA and histones are involved in the origin and spread of cancer cells
is also leading to new therapeutic strategies.

Much of the current hype in epigenetics stems from the recognition of its role in human cancer. Yet, intriguingly, the first epigenetic change in human tumors—global genomic DNA hypomethylation—was reported way back in the early 1980s, at about the same time the first genetic mutation in an oncogene was discovered.1 So why the delay in recognizing the importance of epigenetics in cancer?

In the 1980s epigenetics was a fledgling discipline, hampered by methodological limitations, while genetic knowledge of Continue reading

Mom’s blood carries fetus genome

A complete copy of the fetal genome exists in the mother’s blood, suggesting many prenatal diagnoses could be performed noninvasively

[Published 8th December 2010 07:00 PM GMT]

Circulating in the blood of pregnant women is the full genome of their unborn child, according to a study published online today (December 8) in Science Translational Medicine.

Image: Wikimedia commons, Swangerschaft

The results suggest that whole genome sequencing of fetuses may be possible without invasive procedures, and hold implications for the prenatal diagnoses of every genetic disease.

This study provides “a window into the fetal genome,” said reproductive geneticist Diana W. Bianchi of the Mother Infant Research Institute at the Tufts University School of Medicine, who was not involved in the research. “In principle, that means that you could noninvasively prenatally diagnose anything because the sequence is going to be there.”

In 1997, chemical pathologist Dennis Lo of The Chinese University of Hong Kong and his colleagues discovered the presence of fetal DNA in maternal blood. Scientists have since developed noninvasive procedures to prenatally diagnose certain diseases. Down syndrome, for example, results from an abnormal number of chromosomes, and can be detected by searching mother’s blood for disproportionate amounts of DNA from different chromosomes. And genetic diseases inherited from the father may also be detected by searching the mother’s blood for the paternal mutation.

It was unclear, however, if the entire fetal genome was present in the maternal plasma, which would give clinicians more confidence in the tests currently available by limiting the rate of false-negative results. Additionally, it might make it possible to screen for genetic diseases that are caused by genetic mutations inherited from the mother, as well as sequence the entire genome of the unborn child, without subjecting the mother to invasive procedures that carry a small risk of miscarriage.

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Arsenic supports life?

The toxic element might be able to replace phosphorus to support microbial growth, casting doubt on the belief phosphorus is essential to life

A strain of bacteria isolated from a salt lake in California can grow on arsenic, seemingly in lieu of phosphorus in its DNA and other major biomolecules.

Mono Lake, California
Image: Image © 2010 Henry Bortman

The finding, published today (December 2) on the Science Express Web site, throws into doubt the long-held belief that phosphorus is absolutely essential to life, and broadens the range of environments in which scientists might expect to find extraterrestrial organisms.

“This is a surprise,” said biochemist Barry Rosen of Florida International University, who was not involved in the research. “Not just for bacteria but for life in general, arsenic is one of the few elements that is considered to be only toxic and has no role in metabolism.”

It’s “pretty damn surprising,” agreed ecologist James Elser of the Arizona State University, who also did not participate in the study. “I’ve spent my career studying phosphorus limitation, and how organisms use phosphorus, and how nucleic acids always have phosphorus in them, and now there’s this exception. That’s what’s really weird.”

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Aging Ills Reversed in Mice

Scientists Tweak a Gene and Rejuvenate Cells, Raising Hopes for Uses in Humans

By GAUTAM NAIK

Scientists have partially reversed age-related degeneration in mice, an achievement that suggests a new approach for tackling similar disorders in people.

By tweaking a gene, the researchers reversed brain disease and restored the sense of smell and fertility in prematurely aged mice. Previous experiments with calorie restriction and other methods have shown that aspects of aging can be slowed. This appears to be the first time that some age-related problems in animals have actually been reversed.

REGENThe study was published online Sunday in the peer-reviewed journal Nature.

“These mice were equivalent to 80-year-old humans and were about to pass away,” says Ronald DePinho, co-author of the paper and a scientist at Dana-Farber Cancer Institute in Boston. After the experiment, “they were the physiological equivalent of young adults.”

The institute is a teaching affiliate of Harvard Medical School. The first author of the study is Mariela Jaskelioff at Dr. DePinho’s lab.

Although the finding is compelling, it remains to be seen whether the approach can slow the signs and symptoms of aging in people. The latest results were obtained with mice that were specifically altered to age prematurely. And while the animals showed no signs of tumors, there is a risk that the technique could trigger cancer.

The experiment focused on telomerase, an enzyme that makes small units of DNA that seal the tips of chromosomes.

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Age assay for forensics toolkit

A test that tracks declines in T cell byproducts can estimate a person’s age from a blood sample, and may someday help identify victims or perpetrators of crimes 

A smudge of blood at a crime scene may provide enough evidence for investigators to determine the age of criminals or victims, thanks to a new procedure that analyzes the age-related loss of specific DNA molecules in immune cells. 

Blood droplets

The approach is more reliable than other genetic analyses and does not involve the destruction of evidence, forensic molecular biologist Manfred Kayser, whose study was published online today (22 November) in Current Biology, told The Scientist.

T cells must develop different types of surface receptors so that they can recognize and respond to a wide range of foreign pathogens. Inside the thymus, gene segments encoding T-cell receptors rearrange to produce distinct receptors, and as a byproduct, some deleted DNA sequences form circular fragments inside the cell called signal joint TCR excision circles (sjTRECs). As the function of the thymus declines with age, so does the number of sjTRECs.
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“Epigenetics” drives phenotype?

Researchers have identified a possible mechanism by which DNA regions that don’t encode proteins can still determine phenotypic traits such as a person’s height or susceptibility to a particular disease, researchers report online in Science today.

"Epigenetics" drives phenotype?

The scientists found that certain chromatin modifications often considered to be epigenetic — meaning, regulated by factors other than genetic sequence — are in fact determined by a person’s DNA.

Moreover, they found that this chromatin variation is associated with distinct single nucleotide polymorphisms, suggesting that the variation may serve as a platform to enable these SNPs — often found in non-coding regions of DNA — to influence phenotype.

“This is quite novel,” said Emmanouil Dermitzakis, a geneticist at the University of Geneva Medical School, who was not involved in the study. “Epigenetics has been used as a term that is orthogonal to genetics. This study clearly shows it’s not.”

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