Genetic complementation analysis of two independently isolated hycanthone-resistant strains of Schistosoma mansoni

Pica‐Mattoccia, Livia; Dias, Luiz Cândido de Souza; Cioli, Donato

doi:10.1590/s0074-02761992000800032

Cited by 8 publications

(8 citation statements)

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“…Higher female survival rate following OXA treatment has been observed previously [30]. This represents a global survival rate of 1.86%, relative to the total number of cercariae used in the infections [56/(4 × 754) × 100 = 1.86%].…”

Section: Resultsmentioning

confidence: 57%

Efficient linkage mapping using exome capture and extreme QTL in schistosome parasites

et al. 2014

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BackgroundIdentification of parasite genes that underlie traits such as drug resistance and host specificity is challenging using classical linkage mapping approaches. Extreme QTL (X-QTL) methods, originally developed by rodent malaria and yeast researchers, promise to increase the power and simplify logistics of linkage mapping in experimental crosses of schistosomes (or other helminth parasites), because many 1000s of progeny can be analysed, phenotyping is not required, and progeny pools rather than individuals are genotyped. We explored the utility of this method for mapping a drug resistance gene in the human parasitic fluke Schistosoma mansoni.ResultsWe staged a genetic cross between oxamniquine sensitive and resistant parasites, then between two F1 progeny, to generate multiple F2 progeny. One group of F2s infecting hamsters was treated with oxamniquine, while a second group was left untreated. We used exome capture to reduce the size of the genome (from 363 Mb to 15 Mb) and exomes from pooled F2 progeny (treated males, untreated males, treated females, untreated females) and the two parent parasites were sequenced to high read depth (mean = 95-366×) and allele frequencies at 14,489 variants compared. We observed dramatic enrichment of alleles from the resistant parent in a small region of chromosome 6 in drug-treated male and female pools (combined analysis: = 11.07, p = 8.74 × 10-29). This region contains Smp_089320 a gene encoding a sulfotransferase recently implicated in oxamniquine resistance using classical linkage mapping methods.ConclusionsThese results (a) demonstrate the utility of exome capture for generating reduced representation libraries in Schistosoma mansoni, and (b) provide proof-of-principle that X-QTL methods can be successfully applied to an important human helminth. The combination of these methods will simplify linkage analysis of biomedically or biologically important traits in this parasite.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-617) contains supplementary material, which is available to authorized users.

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Section: Resultsmentioning

confidence: 57%

Efficient linkage mapping using exome capture and extreme QTL in schistosome parasites

et al. 2014

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“…MAP was sampled from a patient living in a city of São Paulo state, Brazil (Supplementary Fig. S1) (Pica-Mattoccia et al, 1992b), the neighboring state of that from which our samples were collected. This suggests that the allele has been segregating in Brazilian parasite populations for more than 25 years.…”

Section: Discussionmentioning

confidence: 99%

Independent origins of loss-of-function mutations conferring oxamniquine resistance in a Brazilian schistosome population

Chevalier

Clec’h

Eng

et al. 2016

International Journal for Parasitology

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Molecular surveillance provides a powerful approach to monitoring the resistance status of parasite populations in the field and for understanding resistance evolution. Oxamniquine (OXA) was used to treat Brazilian schistosomiasis patients (mid-1970s to mid-2000s) and several cases of parasite infections resistant to treatment were recorded. The gene underlying resistance (SmSULT-OR) encodes a sulfotransferase required for intracellular drug activation. Resistance has a recessive basis and occurs when both SmSULT-OR alleles encode for defective proteins. Here we examine SmSULT-OR sequence variation in a natural schistosome population in Brazil ~40 years after the first use of this drug. We sequenced SmSULT-OR from 189 individual miracidia (1–11 per patient) recovered from 49 patients, and tested proteins expressed from putative resistance alleles for their ability to activate OXA. We found nine mutations (four non-synonymous single nucleotide polymorphisms (SNPs), three non-coding SNPs and two indels). Both mutations (p.E142del and p.C35R) identified previously were recovered in this field population. We also found two additional mutations (a splice site variant and 1 bp coding insertion) predicted to encode non-functional truncated proteins. Two additional substitutions (p.G206V, p.N215Y) tested had no impact on OXA activation. Three results are of particular interest: (i) we recovered the p.E142del mutation from the field: this same deletion is responsible for resistance in an OXA-selected laboratory parasite population; (ii) frequencies of resistance alleles are extremely low (0.27–0.8%), perhaps due to fitness costs associated with carriage of these alleles; (iii) that four independent resistant alleles were found is consistent with the idea that multiple mutations can generate loss-of-function alleles.

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“…A higher number of mono-miracidial infections, using several strains of S. mansoni (as the induction seems to be strain dependent), and a larger number of clones (adult or schistosomula) from each mono-miracidial infection should be tested, as we still do not have a clear idea of the frequency of the phenomenon. Induction step can be done in vivo (for any of the tree types) but screening of resistant progeny has to be performed in vitro , as described by Coles and Bruce (1987) and Pica-Mattoccia et al (1992b). This is mandatory to make sure that all parasites have the same exposure to the drug.…”

Section: Discussionmentioning

confidence: 99%

“…In these lines, resistance was heritable and stable even in the absence of drug pressure over 9–30 generations (Dias and Olivier, 1985; Cioli et al, 1989; Drescher et al, 1993). Classic genetic crosses between sensitive and resistant strains, as well as genetic complementation demonstrated that a single recessive autosomal locus codes for the hycanthone/oxamniquine resistance in two strains, MAP (named from the initials of the patient from which it was isolated) and Baltimore Rome Resistant (BRR) (Cioli and Pica-Mattoccia, 1984; Cioli et al, 1989, 1992; Pica-Mattoccia et al, 1992b, 1993). Similar results were also obtained in vitro by Coles and Bruce (1987).…”

Section: Introductionmentioning

confidence: 99%

Exposure to hycanthone alters chromatin structure around specific gene functions and specific repeats in Schistosoma mansoni

et al. 2014

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Schistosoma mansoni is a parasitic plathyhelminth responsible for intestinal schistosomiasis (or bilharzia), a disease affecting 67 million people worldwide and causing an important economic burden. The schistosomicides hycanthone, and its later proxy oxamniquine, were widely used for treatments in endemic areas during the twentieth century. Recently, the mechanism of action, as well as the genetic origin of a stably and Mendelian inherited resistance for both drugs was elucidated in two strains. However, several observations suggested early on that alternative mechanisms might exist, by which resistance could be induced for these two drugs in sensitive lines of schistosomes. This induced resistance appeared rapidly, within the first generation, but was metastable (not stably inherited). Epigenetic inheritance could explain such a phenomenon and we therefore re-analyzed the historical data with our current knowledge of epigenetics. In addition, we performed new experiments such as ChIP-seq on hycanthone treated worms. We found distinct chromatin structure changes between sensitive worms and induced resistant worms from the same strain. No specific pathway was discovered, but genes in which chromatin structure modifications were observed are mostly associated with transport and catabolism, which makes sense in the context of the elimination of the drug. Specific differences were observed in the repetitive compartment of the genome. We finally describe what types of experiments are needed to understand the complexity of heritability that can be based on genetic and/or epigenetic mechanisms for drug resistance in schistosomes.

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Genetic complementation analysis of two independently isolated hycanthone-resistant strains of Schistosoma mansoni

Cited by 8 publications

References 0 publications

Efficient linkage mapping using exome capture and extreme QTL in schistosome parasites

Efficient linkage mapping using exome capture and extreme QTL in schistosome parasites

Independent origins of loss-of-function mutations conferring oxamniquine resistance in a Brazilian schistosome population

Exposure to hycanthone alters chromatin structure around specific gene functions and specific repeats in Schistosoma mansoni

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