GM mosquitoes offer malaria hope

Scientists believe they are closer to
being able to change the DNA of
wild mosquitoes in order to
combat malaria.
In the laboratory, they made a
gene spread from a handful of
mosquitoes to most of the
population in just a few
generations, according toa report
in Nature.
If the right gene can be made to
spread then researchers hope to
reduce the number of cases of
malaria.
Other academics have described the
study as a "major step forward".
The World Health Organisation
estimated that malaria caused
nearly one million deaths in 2008.
Spreading resistance
Research groups have already
created "malaria-resistant
mosquitoes" using techniques such
as introducing genes todisrupt the
malaria parasite's development.
The research, however, has a great
challenge - getting those genes to
spread from the genetically-
modified mosquitoes to the vast
number of wild insects across the
globe.
Unless the gene gives the mosquito
an advantage, the gene will likely
disappear.
Scientists at Imperial College
London and the University of
Washington, in Seattle, believe
they have found a solution.
They inserted a gene into the
mosquito DNA which is very good
at looking after its own interests - a
homing endonuclease called I-SceI.
The gene makes an enzyme which
cuts the DNA in two. The cell's repair
machinery then uses the gene as a
template when repairing the cut.
As a result the homing
endonuclease gene is copied.
It does this in such a way that all
the sperm produced by a male
mosquito carry the gene.
So all its offspring have the gene.
The process is then repeated so the
offspring's offspring have the gene
and so on.
In the laboratory experiments, the
gene was spread to half the caged
mosquitoes in 12 generations.
Defeating malaria
Professor Andrea Crisanti, from the
department of life sciences at
Imperial College London, said: "This
is an exciting technological
development, one which I hope will
pave the way for solutions to many
global health problems.
"At the beginning I was really quite
sceptical and thought it probably
would not work, but the results are
so encouraging that I'm starting to
change my mind."
He said the idea had been proved
in principle and was now working
on getting other genes to spread in
the same way.
He believes it could be possible to
introduce genes which will make
the mosquito target animals rather
than humans, stop the parasite
from multiplying in the insect or
produce all male offspring which do
not transmit malaria.
Professor Janet Hemingway, from
the Liverpool School of Tropical
Medicine, said the work was an
"exciting breakthrough".
She cautioned that the technique
was still some way off being used
against wild mosquitoes and there
were social issues around the
acceptability of using GM
technology.
"This is however a major step
forward providing technology that
may be used in a cost effective
format to drive beneficial genes
through mosquito populations
from relatively small releases," she
added.
Dr Yeya Touré, from the World
Health Organisation, said: "This
research finding is very important
for driving a foreign gene in a
mosquito population. However,
given that it has been
demonstrated in a laboratory cage
model, there is the need to conduct
further studies before it could be
used as a genetic control strategy."