Search bioRxiv⌕ Search

Biology subjects

Kafsack, B. F. C.

Publications and source records attributed to Kafsack, B. F. C..

7 recordsLinked to original sources

Safe, effective, and inexpensive clearance of mycoplasma contamination from cultures of apicomplexan parasites with Sparfloxacin.

Most commercial products cannot be used for clearance of mycoplasma contamination from cultures of apicomplexan parasites due to the parasites dependence on the apicoplast, an essential organelle with DNA replication and translation machinery of cyanobacterial origin. The lone exception, Mycoplasma Removal Agent (MRA), is relatively expensive and some mycoplasma strains have shown resistance to clearance with MRA. Here, we report that the fluoroquinolone antibiotic Sparfloxacin is a safe, effective, and inexpensive alternative for treatment of mycoplasma contamination in cultures of apicomplexan parasites. Sparfloxacin cleared both MRA- sensitive and MRA-resistant mycoplasma species from P. falciparum cultures at 1 and 4 g/mL, respectively. We show that cultures of three different apicomplexan parasites can be maintained at concentrations of Sparfloxacin required to clear mycoplasma without resulting in substantial deleterious effects on parasite growth. We also describe an alternative low-cost, in-house PCR assay for detecting mycoplasma. These findings will be useful to laboratories maintaining apicomplexan parasites in vitro, especially in low-resource environments, where the high cost of commercial products creates an economic barrier for detecting and eliminating mycoplasma from culture.

microbiology↗

Global Profiling of Histone Modifications in Plasmodium falciparum using CUT&RUN.

We recently adapted a CUT&RUN protocol for genome-wide profiling of chromatin modifications in the human malaria parasite Plasmodium. Using the step-by-step protocol described below, we were able to generate high quality profiles of multiple histone modifications using only a small fraction of the cells required for ChIPseq. Using antibodies against two commonly profiled histone modifications, H3K4me3 and H3K9me3, we show here that CUT&RUN profiling is highly reproducible and closely recapitulates previously published ChIPseq-based abundance profiles of histone marks. Finally, we show that CUT&RUN requires substantially lower sequencing coverage for accurate profiling compared to ChIPseq.

microbiology↗

PfD123 modulates K13-mediated survival and recovery after artemisinin exposure.

Recent advances in curbing the deadly toll of malaria have been threatened by the emergence of parasites resistant to the front-line antimalarial artemisinin. Resistance is mediated by point-mutations in the parasite protein Kelch13, but the mechanism of resistance is multi-factorial and only partially understood. Resistance-conferring Kelch13 mutations have been shown to lead to low-level activation of the parasites integrated stress response (ISR) which has a protective effect against artemisinin through an unclear mechanism. Furthermore, only a subpopulation of resistant parasites ever survives drug exposure, implying an underlying heterogeneity. By applying scRNAseq to the resistance-relevant early ring stage, we found expansion of a subpopulation in Kelch13 mutant parasites that is chiefly characterized by transcription of the putative positive translational regulator D123, while we conversely observed reduced D123 protein levels at the same stage. Analogous inverse changes in D123 expression are produced by experimental activation of the ISR, and genetically manipulating D123 expression modulates sensitivity to artemisinin, establishing it as a stress-responsive gene that contributes to artemisinin resistance in Kelch13-mutant malaria parasites.

microbiology↗

Metabolic competition between lipid metabolism and histone methylation regulates sexual differentiation in human malaria parasites.

For Plasmodium falciparum, the most widespread and virulent malaria parasite that infects humans, persistence depends on continuous asexual replication in red blood cells, while transmission to their mosquito vector requires asexual blood-stage parasites to differentiate into non-replicating gametocytes. This decision is controlled by stochastic de-repression of a heterochromatin-silenced locus encoding PfAP2-G, the master transcription factor of sexual differentiation. The frequency of pfap2-g de-repression was shown to be responsive to extracellular phospholipid precursors but the mechanism linking these metabolites to epigenetic regulation of pfap2-g was unknown. Here we show that this response is mediated by metabolic competition for the methyl donor S-adenosylmethionine between histone methyltransferases and phosphoethanolamine methyltransferase, a critical enzyme in the parasites pathway for de novo phosphatidylcholine synthesis. When phosphatidylcholine precursors are scarce, increased consumption of SAM for de novo phosphatidylcholine synthesis impairs maintenance of the histone methylation responsible for silencing pfap2-g, increasing the frequency of derepression and sexual differentiation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/476397v3_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@5e2c69org.highwire.dtl.DTLVardef@b5a7d6org.highwire.dtl.DTLVardef@1e118aorg.highwire.dtl.DTLVardef@1191a6_HPS_FORMAT_FIGEXP M_FIG C_FIG

systems biology↗

Activity of epigenetic inhibitors against Babesia divergens.

Babesiosis in a tick-borne parasitic disease of humans and livestock, that has dramatically increased in frequency and geographical range over the past few decades. Infection of cattle often causes large economic losses, and human infection can be fatal in immunocompromised patients. Unlike for malaria, another disease caused by hemoprotozoan parasites, limited treatment options exist for Babesia infections. As epigenetic regulation is a promising target for new anti-parasitic drugs, we screened 324 epigenetic inhibitors against Babesia divergens blood stages and identified 75 (23%) and 17 (5%) compounds that displayed [≥]90% inhibition at 10 {micro}M and 1 {micro}M, respectively, including over a dozen compounds with activity in the low nanomolar range. We observed differential activity of some inhibitor classes against Babesia divergens and Plasmodium falciparum parasites and identified pairs of compounds with a high difference in activity, despite a high similarity in chemical structure, highlighting new insights into the development of epigenetic inhibitors as anti-parasitic drugs.

microbiology↗

Homeodomain protein 1 is an essential regulator of gene expression during sexual differentiation of malaria parasites

Transmission of Plasmodium falciparum and other malaria parasites requires their differentiation from asexual blood stages into gametocytes, the non-replicative sexual stage necessary for transmission to the mosquito vector. This transition involves changes in gene expression and chromatin reorganization that result in the activation and silencing of stage-specific genes. However, the genomes of malaria parasites have been noted for their dearth of transcriptional and chromatin regulators and the molecular mediators of these changes remain largely unknown. We recently identified HomeoDomain Protein 1 (HDP1) as a DNA-binding protein that enhances the expression of key genes that are critical for early sexual differentiation. The discovery of a homeodomain-like DNA-binding protein marks a new class of transcriptional regulator in malaria parasites outside of the better-characterized ApiAP2 family. In this study, we show that HDP1 facilitates the necessary upregulation of inner membrane complex components during early gametocytogenesis that gives P. falciparum gametocytes they characteristic shape and is required for gametocyte maturation and parasite transmission.

microbiology↗

Activity of epigenetic inhibitors against Plasmodium falciparum asexual and sexual blood stages.

Regulation of gene expression by epigenetic processes is critical for malaria parasite survival in multiple life stages. To evaluate the suitability of targeting these pathways we screened 350 epigenetic inhibitors against asexual blood stages and gametocytes of P. falciparum. We observed [≥]90% inhibition at 10 {micro}M for 28% of compounds, of which a third retained [≥]90% inhibition at 1 {micro}M. These results suggest epigenetic regulation as a promising target for the development of new multi-stage anti-malarials.

microbiology↗