Analysis of quadrupliex DNA structures in Schistosoma mansoni and their potential as therapetic targets

Abstract

Schistosomiasis is a neglected tropical disease yet causes the second greatest parasitic disease burden after malaria, with over 200 million people affected globally. Schistosoma mansoni, the most prolific agent of schistosomiasis, has a varied lifecycle that can make targeting difficult, and indeed the current gold standard Praziquantel has limitations in efficacy. In other parasites, there has been research into the repositioning of anticancer compounds that target solid tumours by stabilising quadruplex DNA. Quadruplexes (G4) are non-canonical four-stranded DNA structures that arise in single-stranded regions of guanine richness and are linked with affecting gene regulations, transcription and expression. Computational analysis of the genome found putative quadruplex sequences (PQS) within the S. mansoni genome for the first time. The capacity of these structures to resolve in situ was established through circular dichroism spectroscopy and enrichment analysis detailed overrepresentation of PQS within the 3’ UTRs of protein-coding genes and within the wnt signalling pathway. The application of BG4, a G4 detecting antibody, to wholemount fixed worms found localisation of G4 throughout the worm with signal concentrated in the nucleus that was ameliorated in the presence of DNase I, indicating the presence of these structures within the parasite for the first time. G4 were targeted in larval, juvenile and adult parasites by QF and CX5461, two smallmolecule G4 stabilising compounds that disrupt poli driven transcription of rDNA. QF was found to be effective against all life cycle stages but had a narrow window of selectivity. CX5461, while promising against larval stages, did not affect adult worms. Investigation of QF mechanism of action through rRNA transcript levels indicated there may be interference of pol I transcription, but this requires further exploration. Assessment of QF on F. hepatica newly excysted juveniles suggested sensitivity of F. hepatica to the compound, which may indicate the presence of G4 is conserved within flukes.

Date of Award	2019
Original language	English
Awarding Institution	Aberystwyth University
Supervisor	Karl Hoffmann (Supervisor) & Martin Swain (Supervisor)