Genomic instability at the locus of sterol C24-methyltransferase promotes amphotericin B resistance in Leishmania parasites

Pountain, A. W. , Weidt, S. K., Regnault, C., Bates, P. A., Donachie, A. M., Dickens, N. J. and Barrett, M. P. (2019) Genomic instability at the locus of sterol C24-methyltransferase promotes amphotericin B resistance in Leishmania parasites. PLoS Neglected Tropical Diseases, 13(2), e0007052. (doi:10.1371/journal.pntd.0007052) (PMID:30716073)

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Abstract

Amphotericin B is an increasingly important tool in efforts to reduce the global disease burden posed by Leishmania parasites. With few other chemotherapeutic options available for the treatment of leishmaniasis, the potential for emergent resistance to this drug is a considerable threat. Here we characterised four novel amphotericin B-resistant Leishmania mexicana lines. All lines exhibited altered sterol biosynthesis, and hypersensitivity to pentamidine. Whole genome sequencing demonstrated resistance-associated mutation of the sterol biosynthesis gene sterol C5-desaturase in one line. However, in three out of four lines, RNA-seq revealed loss of expression of sterol C24-methyltransferase (SMT) responsible for drug resistance and altered sterol biosynthesis. Additional loss of the miltefosine transporter was associated with one of those lines. SMT is encoded by two tandem gene copies, which we found to have very different expression levels. In all cases, reduced overall expression was associated with loss of the 3’ untranslated region of the dominant gene copy, resulting from structural variations at this locus. Local regions of sequence homology, between the gene copies themselves, and also due to the presence of SIDER1 retrotransposon elements that promote multi-gene amplification, correlate to these structural variations. Moreover, in at least one case loss of SMT expression was not associated with loss of virulence in primary macrophages or in vivo. Whilst such repeat sequence-mediated instability is known in Leishmania genomes, its presence associated with resistance to a major antileishmanial drug, with no evidence of associated fitness costs, is a significant concern.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Donachie, Ms Anne Marie and Weidt, Dr Stefan and Barrett, Professor Michael and Regnault, Mr Clement and Pountain, Andrew and Dickens, Dr Nicholas
Creator Roles:
Pountain, A. W.Conceptualization, Formal analysis, Investigation, Writing – original draft, Writing – review and editing
Weidt, S. K.Formal analysis, Investigation
Regnault, C.Investigation
Donachie, A. M.Investigation
Dickens, N. J.Conceptualization, Supervision
Barrett, M. P.Conceptualization, Supervision, Writing – original draft, Writing – review and editing
Authors: Pountain, A. W., Weidt, S. K., Regnault, C., Bates, P. A., Donachie, A. M., Dickens, N. J., and Barrett, M. P.
College/School:College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
College of Medical Veterinary and Life Sciences > Institute of Cancer Sciences
Journal Name:PLoS Neglected Tropical Diseases
Publisher:Public Library of Science
ISSN:1935-2727
ISSN (Online):1935-2735
Copyright Holders:This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose
First Published:First published in PLoS Neglected Tropical Diseases 13(2): e0007052
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
645223Molecular Functions in Disease PhD Studentship (2013-2017)Michael BarrettWellcome Trust (WELLCOTR)102462/z/13/zIII - PARASITOLOGY
371799The Wellcome Centre for Molecular Parasitology ( Core Support )Andrew WatersWellcome Trust (WELLCOTR)104111/Z/14/Z & AIII - PARASITOLOGY