Biology subjects

Nixon, C. P.

Publications and source records attributed to Nixon, C. P..

2 recordsLinked to original sources

bioRxiv2023

Single cell transcriptional changes across the blood stages of artemisinin resistant K13C580Y mutant Plasmodium falciparum upon dihydroartemisinin exposure

Artemisinin-based therapies have been central to malaria control, but partial resistance in Plasmodium falciparum, driven by mutations in the Kelch13 (K13) protein, threatens these gains. To investigate the molecular basis of this resistance, we applied single-cell RNA sequencing to coisogenic parasite lines, K13 wild-type (K13C580) and the artemisinin-resistant mutant (K13580Y), following a 6 hour pulse of dihydroartemisinin (DHA). This approach enabled high-resolution profiling across intraerythrocytic stages. Both lines exhibited stage-specific transcriptional responses, with pronounced changes in ring and trophozoite stages. Using Manifold Enhancement of Latent Dimensions (MELD), a computational framework for quantifying transcriptional perturbation, DHA-treatment induces stage-specific differences in protein export and metabolic pathways in K13C580 and K13580Y parasites, relating to an altered metabolic stress response state. GARP, a potential therapeutic target, was highly differentially expressed in untreated ring stages of K13580Y and K13C580. Functional assays confirmed that anti-GARP antibodies retained efficacy against K13580Y, supporting its potential as a therapeutic target. These findings provide a comprehensive view of the cellular responses related to artemisinin resistance, identify molecular features of pathogenesis, and highlight surface proteins like GARP as promising intervention targets. This work underscores the power of single-cell approaches to dissect drug responses and guide strategies to overcome resistant parasites.

microbiology↗

bioRxiv2022

Non-allelic homologous recombination driven translocation explains histidine-rich protein 3 deletion mechanism in Plasmodium falciparum

Most malaria rapid diagnostic tests (RDTs) detect Plasmodium falciparum histidine-rich protein 2 (PfHRP2) and PfHRP3, but deletions of pfhrp2 and phfrp3 genes make parasites undetectable by RDTs. We analyzed 19,313 public whole-genome-sequenced P. falciparum field samples to understand these deletions better. Pfhrp2 deletion only occurred by chromosomal breakage with subsequent telomere healing. Pfhrp3 deletions involved loss from pfhrp3 to the telomere and showed 3 patterns: no other associated rearrangement with evidence of telomere healing at breakpoint (Asia; Pattern 13-TARE1); associated with duplication of a chromosome 5 segment containing multidrug-resistant-1 gene (Asia; Pattern 13-5++); and most commonly, associated with duplication of a chromosome 11 segment (Americas/Africa; Pattern 13-11++). We confirmed a 13-11 hybrid chromosome with long-read sequencing, consistent with a translocation product arising from recombination between large interchromosomal ribosome-containing segmental duplications. Within most 13-11++ parasites, the duplicated chromosome 11 segments were identical. Across parasites, multiple distinct haplotype groupings were consistent with emergence due to clonal expansion of progeny from intrastrain meiotic recombination. Together, these observations suggest negative selection normally removes 13-11++ pfhrp3 deletions, and specific conditions are needed for their emergence and spread including low transmission, findings that can help refine surveillance strategies.

genomics↗