De Muylder, G. | bioRxiv Science

bioRxiv2021

Genomic and phenotypic characterization of experimentally selected resistant Leishmania donovani reveals a role for dynamin-1 like protein in the mechanism of resistance to a novel anti-leishmanial compound

The implementation of prospective drug resistance (DR) studies in the R&D pipelines is a common practice for many infectious diseases, but not for Neglected Tropical Diseases. Here, we explored and demonstrated the importance of this approach, using as paradigms Leishmania donovani, the etiological agent of Visceral Leishmaniasis (VL), and TCMDC-143345, a promising compound of the GSK Leishbox to treat VL. We experimentally selected resistance to TCMDC-143345 in vitro and characterized resistant parasites at genomic and phenotypic levels. We found that it took more time to develop resistance to TCMDC-143345 than to other drugs in clinical use and that there was no cross resistance to these drugs, suggesting a new and unique mechanism. By whole genome sequencing, we found two mutations in the gene encoding the L. donovani dynamin-1-like protein (LdoDLP1) that were fixed at highest drug pressure. Through phylogenetic analysis, we identified LdoDLP1 as a family member of the dynamin-related proteins, a group of proteins that impacts the shapes of biological membranes by mediating fusion and fission events, with a putative role in mitochondrial fission. We found that L. donovani lines genetically engineered to harbor the two identified LdoDLP1 mutations were resistant to TCMDC-143345 and displayed altered mitochondrial properties. By homology modeling, we showed how the two LdoDLP1 mutations may influence protein structure and function. Taken together, our data reveal a clear involvement of LdoDLP1 in the adaptation/resistance of L. donovani to TCMDC-143345. ImportanceHumans and their pathogens are continuously locked in a molecular arms race during which the eventual emergence of pathogen drug resistance (DR) seems inevitable. For neglected tropical diseases (NTDs), DR is generally studied retrospectively, once it has already been established in clinical settings. We previously recommended to keep one step ahead in the host-pathogen arms race and implement prospective DR studies in the R&D pipeline, a common practice for many infectious diseases, but not for NTDs. Here, using Leishmania donovani, the etiological agent of Visceral Leishmaniasis (VL), and TCMDC-143345, a promising compound of the GSK Leishbox to treat VL, as paradigms, we experimentally selected resistance to the compound and proceeded to genomic and phenotypic characterization of DR parasites. The results gathered in the present study suggest a new DR mechanism involving the L. donovani dynamin-1 like protein (LdoDLP1) and demonstrate the practical relevance of prospective DR studies.

microbiology↗

bioRxiv2019

C-5 DNA methyltransferase 6 does not generate detectable DNA methylation in Leishmania

Cytosine C5 methylation is an important epigenetic control mechanism in a wide array of Eukaryotic organisms and generally carried out by proteins of C-5 DNA methyltransferase family (DNMTs). In several protozoans the status of this mechanism remains elusive, such as in Leishmania, the causative agent of the disease leishmaniasis in humans and a wide array of vertebrate animals. In this work, we show that the Leishmania donovani genome contains a C-5 DNA methyltransferase (DNMT) from the DNMT6 subfamily, of which the function is still unclear, and verified its expression at RNA level. We created viable overexpressor and knock-out lines of this enzyme and characterised their genome-wide methylation patterns using whole-genome bisulfite sequencing, together with promastigote and amastigote control lines. Interestingly, despite DNMT6 presence, we found that methylation levels were equal to or lower than 0.0003% at CpG sites, 0.0005% at CHG sites and 0.0126% at CHH sites at genome scale. As none of the methylated sites were retained after manual verification, we conclude that there is no evidence for DNA methylation in this species. We demonstrate that this difference in DNA methylation between the parasite (no detectable DNA methylation) and the vertebrate host (DNA methylation), allows enrichment of parasite versus host DNA using Methyl-CpG-binding domain columns, readily available in commercial kits. As such, we depleted methylated DNA from mixes of Leishmania promastigote and amastigote DNA with human DNA, resulting in average Leishmania:human enrichments from 62x up to 263x. These results open a promising avenue for unmethylated DNA enrichment as a pre-enrichment step before sequencing Leishmania clinical samples.

molecular biology↗