DOCTORS could soon use a DNA chip to find out in less than a day whether
people near the site of a nuclear accident have been exposed to radiation. When
accidents happen, like that at the Tokaimura nuclear plant in Japan last year,
there is no way for hospitals to quickly find out how much radiation people have
received鈥攊nformation that is critical in deciding what treatment they
require.
Sally Amundson and her colleagues from the National Institutes of Health near
Washington DC knew that cells activate various genes to kick-start repairs
following radiation damage and reasoned that the activity of these genes, as
measured by the amount of RNA they produce, might provide an accurate measure of
exposure.
They irradiated white cells and used a red dye to label DNA copies of the RNA
produced. They then repeated the procedure with non-irradiated cells, and
labelled the DNA green. Then they mixed the two together and washed them over a
chip containing fragments of DNA from 7000 genes arranged in a grid. The DNA
copies of RNA stick to their matching partner, so genes more active in
irradiated cells show up red, less active ones green, and those with unchanged
activity yellow.
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Amundson and colleagues chose the six genes consistently activated by
radiation and put DNA fragments from these genes onto a smaller chip, which they
tested using blood cells from six people. In every case, irradiated cells turned
red, and untreated cells yellow. 鈥淏y using different genes we could conceivably
get bands of how much dose has been received,鈥� says Amundson, who plans to test
the chip on patients undergoing radiotherapy.
