Shedding light on Toxoplasma invasion

Abstract

To date, genome engineering in Toxoplasma gondii has proved difficult owing to inefficient gene targeting. The observation of a mild phenotype in a knockdown experiment always leads to some uncertainty about whether the gene of interest is essential. Now, Andenmatten et al. have used a gene swap approach based on the conditional dimerizable Cre recombinase (DiCre) system to dissect T. gondii gliding motility and host cell invasion. Replacing components of the actin–myosin invasion complex with the gene encoding YFP allowed easy identification and analysis of reliable knockouts. Surprisingly, genes encoding two components of the invasion complex, myosin A (MyoA) and micronemal protein 2 (MIC2), which previously had been described as essential, were dispensable in the gene swap experiments. The isolation of viable MyoA and MIC2 knockout clones suggests the existence of a novel, as-yet-uncharacterized invasion mechanism in T. gondii.