Identifying and validating the presence of Guanine-Quadruplexes (G4) within the blood fluke parasiteSchistosoma mansoni
Authors: Craven Holly M , Bonsignore Riccardo , Lenis Vasilis , Santi Nicolo , Berrar Daniel , Swain Martin , Whiteland Helen , Casini Angela , Hoffmann Karl F 
Published: September 2020

Background

Schistosomiasis is a neglected tropical disease that currently affects over 250 million individuals worldwide. In the absence of an immunoprophylactic vaccine and the recognition that mono-chemotherapeutic control of schistosomiasis by praziquantel has limitations, new strategies for managing disease burden are urgently needed. A better understanding of schistosome biology could identify previously undocumented areas suitable for the development of novel interventions.

Methodology/Principal findings

Here, for the first time, we detail the presence of G-quadruplexes (G4) and putative quadruplex forming sequences (PQS) within theSchistosoma mansonigenome. We find that G4 are present in both intragenic and intergenic regions of the seven autosomes as well as the sex- defining allosome pair. Amongst intragenic regions, G4 are particularly enriched in 3’ UTR regions. Gene Ontology (GO) term analysis evidenced significant G4 enrichment in thewntsignalling pathway (p<0.05) and PQS oligonucleotides synthetically derived fromwnt-related genes resolve into parallel and hybrid G4 motifs as elucidated by circular dichroism (CD) spectroscopy. Finally, utilising a single chain anti-G4 antibody called BG4, we confirm thein situpresence of G4 within both adult female and male worm nuclei.

Conclusion/Significance

These results collectively suggest that G4-targeted compounds could be tested as novel anthelmintic agents and highlights the possibility that G4-stabilizing molecules could be progressed as candidates for the treatment of schistosomiasis.

Author Summary

Schistosoma mansonicauses schistosomiasis, a parasitic disease that affects millions of people living in resource-deprived areas of developing countries. No vaccine exists and the current drug treatment has limitations, notably inefficacy against the larval stages of the parasite. New drugs are, therefore, needed to sustainably control schistosomiasis. A further understanding of parasite biology will uncover new targets and lead to the development of novel therapies. Here, we identify the presence of G-Quadruplexes (G4s) inS. mansoni. G4s are four-stranded DNA structures that can affect gene function and, to date, have not been previously found in any parasitic helminth. Computational analysis predicted potential G4 folding sequences within theS. mansonigenome, several of which were confirmed to fold by circular dichroism spectroscopy. Analysis of G4-containing protein coding genes found an enrichment within thewntsignalling pathway, a developmental pathway crucial for axial development in the parasite. Additionally, G4s could be detected within adult worms using a fluorescent antibody that selectively recognises quadruplex structures in nucleic acids. This research describes the presence of a previously unknown structure within the parasite, which could present a new target for developing novel treatments.