New way to tackle malaria parasite gene

A new genome-editing technique can disrupt a single malaria parasite gene with a success rate of up to 100 per cent in just a few weeks, MIT scientists have found.
The technique, called CRISPR could enable much more rapid gene analysis and boost drug-development efforts.
"Even though we've sequenced the entire genome of Plasmodium falciparum, half of it still remains functionally uncharacterised. That's about 2,500 genes that if only we knew what they did, we could think about novel therapeutics, whether it's drugs or vaccines," said Jacquin Niles, an associate professor of biological engineering at Massachusetts Institute of Technology (MIT).

CRISPR, a gene-editing system devised within the past several years, exploits a set of bacterial proteins that protect microbes from viral infection.
The system includes a DNA-cutting enzyme, Cas9, bound to a short RNA guide strand that is programmed to bind to a specific genome sequence, telling Cas9 where to make its cut.
This approach allows scientists to target and delete any gene by simply changing the RNA guide strand sequence.

As soon as researchers successfully demonstrated that this system could work in cells other than bacteria, Niles started to think about using it to manipulate Plasmodium falciparum.
To test this approach, he and his colleagues tried using CRISPR to disrupt two genes, kahrp and eba-175, that had previously been knocked out in malaria using traditional approaches.

The kahrp gene produces a protein that causes red blood cells, which are normally smooth, to develop a knobby appearance when infected with malaria.
Niles' team was able to disrupt this gene in 100 per cent of parasites treated with the CRISPR system; red blood cells infected by those parasites remained smooth.
With eba-175, which codes for a protein that binds to red blood cell receptors and helps the parasite get into the cells, the researchers disrupted this gene in 50 to 80 per cent of parasites manipulated with the CRISPR system.
"We consider this to be a win. Compared to the efficiency with which P falciparum genetics have been done in the past, even 50 per cent is pretty substantial," Niles said.

For both targets, the researchers demonstrated that they could insert a gene for the protein luciferase, which emits light, in addition to turning off the existing genes.
The research was published in the journal Nature Methods.