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03.18.2013

DNA from HeLa cells is sequenced

HeLa cells

HeLa cells viewed under a light microscope

Nature magazine reports that a German lab has sequenced the DNA of HeLa cells. Like cells from most tumors, there are multiple copies of many genes. Excerpt:

Previous work showed that HeLa cells, like many tumors, have bizarre, error-filled genomes, with one or more extra copies of many chromosomes. To get a closer look at these alterations, a team led by Lars Steinmetz, a geneticist at the EuropeanMolecular Biology Laboratory in Heidelberg, Germany, sequenced the popular ‘Kyoto’ version of the cell line and compared the sequence with that of a reference human genome. The team’s results are published in G3.

Steinmetz’s team confirmed that HeLa cells contain one extra version of most chromosomes, with up to five copies of some. Many genes were duplicated even more extensively, with four, five or six copies sometimes present, instead of the usual two.  Furthermore, large segments of chromosome 11 and several other chromosomes were reshuffled like a deck of cards, drastically altering the arrangement of the genes.

Without the genome sequence of Lacks’ healthy cells or that of her original tumor, it is difficult to trace the origin of these alterations. Steinmetz points out that other cervical tumors have massive rearrangements on chromosome 11, so the changes in the HeLa cell may have contributed to Lacks’ tumor.

HeLa cells have been the subject of many biological studies as they are easy to culture and replicate very fast. The cells were originally isolated from an African American woman named Henrietta Lacks, and have been cultured for over 60 years. There is also a fascinating book about the origin of these cells called The Immortal Life of Henrietta Lacks.

11.15.2012

telomere length linked to longevity

Telomere length has long been thought to play a role in the death of cells. Our telomeres shorten as we age, and the truncated telomeres have been linked to some diseases. Now research suggests that it increases overall chances of dying soon. From Science News:

To find out, researchers at Kaiser Permanente and the University of California, San Francisco measured telomere length in 110,266 people in northern California. The participants are part of an ongoing project that explores links between genetics and health. This study is the largest ever to examine telomeres’ role in health.

The 10 percent of people with the shortest telomeres had a more than 20 percent higher risk of dying than people with longer telomeres, Catherine Schaefer, an epidemiologist who directs the Kaiser Permanente Research Program on Genes, Environment and Health, reported November 8 at the annual meeting of the American Society of Human Genetics. “It seems as though once your telomeres get critically short, your risk of dying goes up,” she said. The increased death risk is about the same as for people who drink 20 to 30 alcoholic beverages per week or smoke for 20 to 30 years. “It’s a modest increase, but it’s not nothing.”

The study was presented at the American Society of Human Genetics annual meeting.

11.14.2012

how camels survive in the desert

An Arabian Camel

Genomic studies are helping researchers determine what is unique about these dessert dwelling mammals. It turns out it is mostly their metabolism. From Scientific American:

Camels, as ruminants like cattle and sheep, digest food by chewing the cud. But many of the Bactrian genome’s rapidly evolving genes regulate the metabolic pathway, suggesting that what camels do with the nutrients after digestion is a whole different ball game. “It was surprising to me that they had significant difference in the metabolism,” says Kim Worley, a molecular geneticist at Baylor College of Medicine in Houston, Texas. The differences could point to how Bactrians produce and store energy in the desert.

The work shows that camels can withstand massive blood glucose levels owing in part to changes in genes that are linked to type II diabetes in humans. The Bactrians’ rapidly evolving genes include some that regulate insulin signaling pathways, the authors explain. A closer study of how camels respond to insulin may help to unravel how insulin regulation and diabetes work in humans. “I’m very interested in the glucose story,” says Brian Dalrymple, a computational biologist at the Queensland Bioscience Precinct in Brisbane, Australia.

The researchers also identified sections of the genome that could begin to explain why Bactrian camels are much better than humans at tolerating high levels of salt in their bloodstreams. In humans, the gene CYP2J controls hypertension: suppressing it leads to high blood pressure. However, camels have multiple copies of the gene, which could keep their blood pressure low even when they consume a lot of salt, suggest the authors of the latest work.

The study appears in Nature Communications.

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