Neuroscience

Gene drive - take the wheel against malaria

Scientists are coming closer and closer to the dreams of genetic engineering just about

anything for any purpose. Now we can drive those dreams home by engineering mosquitos in

order to eliminate malaria, one of the biggest health and economic threats faced by

developing nations.

The new tool – known as the gene drive – lets us genetically modify entire species.

Recently, scientists have used it to modify mosquitos in order to eliminate the spread of

diseases like malaria and dengue fever.

Though a gene drive would only work with organisms that reproduce quickly (not with

humans), we can harness its power to combat diseases spread by insects, control invasive

species, or even eliminate herbicide-resistance.

And it might be one of the most powerful technologies we've ever had.

Biologists Ethan Bier and Valentino Gantz at the University of California San Diego and

Anthony James at the University of California Irvine have used the tool to engineer mosquitos

that can't transmit malaria to humans. If we genetically modified a group of mosquitos this

way and added them to the wild, they would spread their anti-malaria gene to others. Over

time, we can prevent mosquitos from spreading the disease to humans and slowly eliminate

malaria completely.

The scientists showed the gene drive method works efficiently in male and female mosquitos

for a great deal of genetic possibilities at specific targets in the genome.

The technology works by using endonucleases, biological catalysts for speeding up chemical

reactions of DNA, to cut specific genes in our DNA of our genome. Then, the drive gene we

want gets copied into the genome, and, when the DNA repairs itself, it copies the drive gene.

By controlling which genes are cut and copied, scientists can change our genetic makeup.

With gene drive, we insert genes on both chromosomes for two individuals within a

population, then, when those two individuals sexually reproduce, the gene will be on both

chromosomes in each offspring. This way, we can add the modified organisms of the gene

drive to populations so that, over time, the genes will be found in all individuals in the

population.

The scientists' success came from the use of the new genome-editing system CRISPR-Cas9

(pronounced “crisper cas nine”). CRISPR, short for “clustered regularly interspaced short

palindromic repeats,” uses the parts of DNA that have short repetitions sequences that are

spaced our between genes, as the name would suggest. The Cas9 protein is an

endonuclease used by bacteria to edit DNA, and, when the researchers sent the Cas9 into

cells, they were able to modify an organism's DNA at any location.

In recent years, CRISPR-Cas9 has shown promising results by using sections of RNA, a

modified form of DNA, to target locations in DNA sequences to be added, changed or

removed. It has already been used to modify mosquitos, fruit flies, yeast, and even

unfertilized human embryos.

Though we can't use gene drives on humans, the power and success of CRISPR-Cas9 has

caused scientists to raise concerns about the safety of the gene drive technology. If we have

so much control over biology, then who should be able to control the genetics of other

organisms? If we can permanently eradicate certain disease and protect populations, how

should we maintain an ecologically healthy environment?

There are also difficulties in implementing gene drives. Unlike, for example, genetically

modifying food, it's not easy to keep engineered organisms from spreading outside of a

designated field or area. The gene drive may have unintended impacts as it is carried out on

the population or its surroundings.

Scientists need to figure out the best ways to proceed as efficiently and carefully as possible.

Since mosquitos are detrimental to our health and not absolutely necessary, modifying

mosquitos isn't so controversial.

But given the sheer potential that lies in our genome and our power to change almost

anything about our biological structure, we need to ask ourselves the important questions that

will shape our future. The potential to help or hurt lie in the hands of these new technologies,

and the way we use them will carry powerful impacts on the future. Scientists, policymakers,

ethicists, and other professionals will have to work together to decide how transparent

practices should be, how much we should experiment and, ultimately, what we should do.

How much power is it right to have over Mother Nature?

A gene drive isn't just an Uber ride, but a full-fledged road trip.

Gantz, V., Jasinskiene, N., Tatarenkova, O., Fazekas, A., Macias, V., Bier, E., & James, A. (2015). Highly efficient Cas9-mediated gene drive for population modification of the malaria vector mosquito Proceedings of the National Academy of Sciences, 112 (49) DOI: 10.1073/pnas.1521077112

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