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."
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