Embryonic stem cells 'should be dead'
Sylvia Pag Westphal, Boston

19:00 30 June 04

When a young researcher recently took a closer look at embryonic stem cells,
he made an astonishing finding: according to his results, the vigorously
growing cells he was looking at should have been dead or dying.

"I didn't anticipate this," says Thomas Zwaka, who works in the
lab of James
Thomson at the Wisconsin National Primate Research Center in Madison.

Zwaka had tested the embryonic stem cells (ESCs) for the presence of enzymes
called caspases, proteins that chew up the cell from within. Their presence
is usually considered a sure sign that cells are undergoing programmed
suicide, or apoptosis - the body's way of getting rid of damaged or
redundant cells.

"That's when I ran into the most confusing result," he says. Although the
cells had high levels of caspase activity, few of them were actually dying,
he told a recent stem-cell meeting in Boston.

To double-check his results, Zwaka looked for, and found, two other signs of
cell suicide: the presence of a chewed-up protein called PARP-1, which is
abundant in suicidal cells, and the shutting down of the power factories in
cells, the mitochondria, indicated by the depolarisation of their membranes.

Zwaka speculates that the process of self-renewal may have evolved alongside
cell death, and some of the processes may be the same.

The fact that signs thought to be characteristic of cell suicide appear in
cells that are not dying might force a lot of researchers to re-examine
their work, says stem-cell researcher Margaret Goodell from the Baylor
College of Medicine in Houston, Texas. "I think it is potentially incredibly
exciting."

>From NewScientist
http://www.newscientist.com/news/news.jsp?id=ns99996096

Posted by
Robert Karl Stonjek.
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