A new genetic tool for studying malaria

19 March 2013

NIMR scientists have successfully applied a conditional recombination system to Plasmodium falciparum. The research is published in Molecular Microbiology.

The malaria parasite shares its life cycle between a vertebrate host and a mosquito vector. It is the haploid asexual blood stages of the malaria parasite, occurring in the vertebrate host, which cause all the pathology associated with malaria. These can be genetically modified by homologous recombination, enabling the functional study of parasite genes that are not essential in this part of the life cycle. However, there is no widely applicable method for conditional mutagenesis of essential asexual blood stage malarial genes and this hinders their functional analysis. There is therefore great interest in developing conditional genetic tools suitable for exogenous control of gene expression in Plasmodium.

Christine Collins (pictured) and Sujaan Das, working in Mike Blackman’s lab in NIMR’s Division of Parasitology, have applied the DiCre conditional recombinase system to Plasmodium falciparum, the causative agent of the most dangerous form of malaria. Together with collaborators at the University of Glasgow, they have shown that DiCre can be used to obtain rapid, highly regulated site-specific recombination in P. falciparum. The system can excise loxP-flanked sequences from a genomic locus with close to 100% efficiency within the time-span of a single erythrocytic growth cycle (~ 48 h). The researchers successfully used the system to recycle the most widely-used drug resistance marker for P. falciparum, human dihydrofolate reductase, in the process producing DiCre-expressing P. falciparum clones that have broad utility for the functional analysis of essential asexual blood-stage parasite genes.

We have shown here that the DiCre system allows rapid, highly regulated and remarkably efficient site-specific recombination within the course of a single erythrocytic growth cycle. The approach will have important applications in other Plasmodium species, including the human pathogen P. knowlesi. We expect the DiCre strategy to have a marked impact on understanding of gene function in the malaria parasite and other apicomplexan pathogens.

Mike Blackman

This is an exciting advance in our capacity to genetically manipulate the human malaria parasite. For the first time we now have the genetic tools to study the function of parasite proteins that play essential roles at critical points in the asexual blood stage malaria life cycle, such as red blood invasion and exit (egress).

Christine Collins

Click image to view at full-size

Asexual blood-stage forms of Plasmodium falciparum growing in human erythrocytes.

Original article

Christine R Collins, Sujaan Das, Eleanor H Wong, Nicole Andenmatten, Robert Stallmach, Fiona Hackett, Jean-Paul Herman, Sylke Müller, Markus Meissner, and Michael J Blackman (2013)

Robust inducible Cre recombinase activity in the human malaria parasite Plasmodium falciparum enables efficient gene deletion within a single asexual erythrocytic growth

Molecular Microbiology Epub ahead of print. Publisher abstract.

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