THE adage that 鈥測ou are what you eat鈥� has taken on a whole new meaning.
Researchers in Germany claim that DNA fed to a mouse can survive digestion and
invade cells throughout its body. Because food contains DNA, this may be a way
for species to acquire genes, they argue.
The surprising results were announced by Walter D枚rfler of the
University of Cologne at the International Congress on Cell Biology in San
Francisco last month. 鈥淲e鈥檙e taking in DNA in food every day,鈥� he says. 鈥淚n my
mind, the question became: why isn鈥檛 DNA incorporated all the time in
补苍颈尘补濒蝉?鈥�
Textbooks say that DNA in food should be digested and destroyed. But
D枚rfler and his student Rainer Schubbert found that when they fed a
bacterial virus called M13 to a mouse, sections of its genetic material about
700 DNA 鈥渓etters鈥� long鈥攍arge enough to contain a gene鈥攕urvived to
emerge in faeces.
Advertisement
The researchers wondered whether a few of these genetic snippets had managed
to penetrate the mouse鈥檚 cells. They took cells from the mice and probed them
with a dye molecule that lights up when it binds to the M13 DNA. The probe lit
up inside cells not only from the intestine, but the spleen, white blood cells
and liver. 鈥淭hey weren鈥檛 hard to find,鈥� says D枚rfler. 鈥淚n some cases as
much as one cell in a thousand had viral DNA.鈥�
Usually the DNA does not stay long inside the cells. After 18 hours, most
cells had somehow ejected the viral intruders. But D枚rfler speculates that
occasionally some foreign DNA may remain.
Other researchers are sceptical. 鈥淚t鈥檚 amazing that this DNA could get all
the way into the blood,鈥� says Rudolf Jaenisch, a geneticist at the Massachusetts
Institute of Technology. He warns that the German team鈥檚 results are 鈥渧ery
preliminary鈥�, and that they have not been able to determine how much DNA is
absorbed by the cells. Jaenisch suspects that the amounts would be so small that
any effect on a cell is minimal.