Amplification of the multidrug resistance gene in some chloroquine-resistant isolates of P. falciparum

Foote, Simon J.; Thompson, J. K.; Cowman, Alan F.; Kemp, David J.

doi:10.1016/0092-8674(89)90330-9

Cited by 562 publications

(313 citation statements)

References 32 publications

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“…For this analysis we compared the msp1 (Holder and Freeman, 1984;Tanabe et al, 1987;Miller et al, 1993) gene on chromosome 9 and the pfmdr1 (Foote et al, 1989;Wilson et al, 1989) gene on chromosome 5, and either analyzed 1000 bp of flanking sequence or until the next predicted gene. Both of these genes are likely to be under selective pressure, either immune or drug pressure, respectively, and are known to be highly polymorphic within their coding regions.…”

Section: Snps Are Nonrandomly Distributed Between Coding and Noncodinmentioning

confidence: 99%

Genomic heterogeneity in the density of noncoding single-nucleotide and microsatellite polymorphisms in Plasmodium falciparum

Volkman

Lozovsky

Barry

et al. 2007

Gene

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The density and distribution of single-nucleotide polymorphisms (SNPs) across the genome has important implications for linkage disequilibrium mapping and association studies, and the level of simple-sequence microsatellite polymorphisms has important implications for the use of oligonucleotide hybridization methods to genotype SNPs. To assess the density of these types of polymorphisms in P. falciparum, we sampled introns and noncoding DNA upstream and downstream of coding regions among a variety of geographically diverse parasites. Across 36,229 base pairs of noncoding sequence representing 41 genetic loci, a total of 307 polymorphisms including 248 polymorphic microsatellites and 39 SNPs were identified. We found a significant excess of microsatellite polymorphisms having a repeat unit length of one or two, compared to those with longer repeat lengths, as well as a nonrandom distribution of SNP polymorphisms. Almost half of the SNPs localized to only three of the 41 genetic loci sampled. Furthermore, we find significant differences in the frequency of polymorphisms across the two chromosomes (2 and 3) examined most extensively, with an excess of SNPs and a surplus of polymorphic microsatellites on chromosome 3 as compared to chromosome 2 (P = 0.0001). Furthermore, at some individual genetic loci we also find a nonrandom distribution of polymorphisms between coding and flanking noncoding sequences, where completely monomorphic regions may flank highly polymorphic genes. These data, combined with our previous findings of nonrandom distribution of SNPs across chromosome 2, suggest that the Plasmodium falciparum genome may be a mosaic with regard to genetic diversity, containing chromosomal regions that are highly polymorphic interspersed with regions that are much less polymorphic.

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Section: Snps Are Nonrandomly Distributed Between Coding and Noncodinmentioning

confidence: 99%

Genomic heterogeneity in the density of noncoding single-nucleotide and microsatellite polymorphisms in Plasmodium falciparum

Volkman

Lozovsky

Barry

et al. 2007

Gene

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“…The DNA fragments were transferred to a nylon membrane and hybridized with a radiolabeled pfmdr1 probe. 5 The copy number of pfmdr1 was compared with that of the circumsporozoite gene, which occurs in a single copy in the genome. 14 …”

Section: Methodsmentioning

confidence: 99%

“…The oligonucleotide primers were synthesized based on the published pfmdr1 sequences. 5 The pfmdr1 sequence was amplified from field samples. Removal of unincorporated PCR primers and nucleotides was performed using selective precipitation of double-stranded DNA by polyethylene glycol.…”

Section: Methodsmentioning

confidence: 99%

“…[5][6][7][8] It is encoded by the P. falciparum multidrug resistance 1 (pfmdr1) gene and is localized on the membrane of the digestive vacuole of this parasite. 8,9 High levels of Pgh 1 expression have been shown in drug-resistant cell lines to confer a chloroquine-sensitive phenotype and in yeast to complement the ste 6 functions, 10 suggesting a role as a drug transporter.…”

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Analysis of mefloquine resistance and amplification of pfmdr1 in multidrug-resistant Plasmodium falciparum isolates from Thailand.

Chaiyaroj

Buranakiti²,

Angkasekwinai³

et al. 1999

The American Journal of Tropical Medicine and Hygiene

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Abstract. Resistance to quinoline-containing compound has been associated with the Plasmodium falciparum multidrug resistance 1 (pfmdr1) gene. We analyzed wild P. falciparum isolates with high levels of chloroquine and mefloquine resistance for their macrorestriction maps of chromosome 5 and sequence of pfmdr1. Two types of chromosome 5 amplification were found. Eleven of 62 resistant isolates displayed Bgl I fragments larger than 100 kb. Twenty-nine isolates possessed multiple copies of the fragments. We failed to detect any amplification of this region on chromosome 5 in 22 mefloquine-resistant isolates, suggesting that other mechanisms can mediate the mefloquine-resistant phenotype. There was no direct association between pfmdr1 mutations and chloroquine sensitivity. Resistant lines could have Asn-86 and Tyr-184 or Phe-184, the predicted sequence of those chloroquine-sensitive isolates. No mutation at Asn-1042 and Asp-1246 was detected among these chloroquine-resistant isolates. Therefore, a few base substitutions in the pfmdr1 gene may not be sufficient to account for all chloroquine-resistant phenotypes.In Thailand, malaria continues to be a major public health problem due to the emergence of multidrug-resistant organisms. Increasing levels and prevalence of Plasmodium falciparum resistance to choloroquine 1 and mefloquine 2-4 have been reported. This has made the treatment and prophylaxis of malaria increasingly complicated. Although new drugs and several drug combinations are being introduced, it is important to elucidate the molecular mechanism of aminoquinoline drug resistance to develop the appropriate strategies for malaria therapy.A P-glycoprotein homolog (Pgh 1) has been implicated in chloroquine-and mefloquine-resistant phenotypes of P. falciparum. [5][6][7][8] It is encoded by the P. falciparum multidrug resistance 1 (pfmdr1) gene and is localized on the membrane of the digestive vacuole of this parasite. 8,9 High levels of Pgh 1 expression have been shown in drug-resistant cell lines to confer a chloroquine-sensitive phenotype and in yeast to complement the ste 6 functions, 10 suggesting a role as a drug transporter. Controversy exists regarding the pfmdr 1 gene and chloroquine resistance from the work of Wellems and others 11 in that there is no linkage between pfmdr 1 and such resistance. In addition, in vitro selection of parasites for increased chloroquine resistance resulted in parasites with higher sensitivity to mefloquine. 12 Surprisingly, chromosome 5 of these parasite clones demonstrated deamplification and the expression of Pgh 1 was also decreased. 12 In subsequent drug selection studies, the higher levels of mefloquine resistance have been associated with amplification of pfmdr1. 8,13 Data from several field isolates with mefloquine resistance suggested that the amplification of pfmdr1 and an increase in mRNA expression is associated with natural resistance. Furthermore, cross-resistance to other related drugs such as halofantrine and quinine was also observed. [13][14][15] In this s...

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“…Los estudios moleculares muestran que P falciparum contiene dos glicoproteinas homólogas a las de células humanas, Pgh-1 (28) y Pgh-2 (29), codificadas por dos genes separados: pfmdrl y pfmdr2 (30,31). Dado que la amplificación del gen pfmdrl se observó en algunos parásitos resistentes a la cloroquina y que se encontraron mutaciones en éste que parecían estar relacionadas con el fenotipo resistente (30), se realizaron estudios usando sistemas de expresión heteróloga (32) para dilucidar el mecanismo de resistencia. Los resultados obtenidos indicaron que la sola presencia de alteraciones en Pgh-1 no era suficiente para conferir resistencia.…”

Section: Teorías Acerca De La Resistenciaunclassified

Cloroquina: hipótesis acerca de los mecanismos de Cloroquina: hipótesis acerca de los mecanismos de resistencia en Plasmodium falciparum

Bustamante¹,

Giralda²

1999

biomedica

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ResumenLos estudios farrnacológicos sugieren que la resistencia a cloroquina está asociada con una reducción de la concentración intracelular de la droga por debajo de niveles biológicamente efectivos. En general, se han considerado tres mecanismos diferentes: (i) un incremento en el pH lisosomal que reduciría la acumulación ácido-trópica de cloroquina; (ii) la generación de un mecanismo rápido de flujo hacia el exterior; y (iii) la reducción de la entrada de cloroquina a la célula. Sin embargo, la caracterización del mecanismo molecular mediante estudios bioquímicos, moleculares y genéticos ha proporcionado resultados ambiguos. Se han identificado dos candidatos que pueden tener un papel en la resistencia. El primero es el genpfmdr1,en el que se han encontrado mutaciones que parecen estar asociadas con resistencia a cloroquina; sin embargo, los resultados de diferentes experimentos indican que la sola presencia de alteraciones en este gen no confiere resistencia. El otro candidato es el gen cg2, que posee regiones de secuencias repetidas en tándem con polimorfismos específicos, que en Asia y Africa se han correlacionado con resistencia a cloroquina. Adicionalmente, un estudio reciente ha propuesto un modelo consistente con un factor de resistencia que actúa en la vacuola digestiva, en donde se encuentra CG2, lo que ha fortalecido la hipótesis de que esta proteína juega un papel importante en el desarrollo de resistencia. No obstante lo anterior, se requieren más investigaciones que involucren el conocimiento que se tiene y permitan dilucidar el mecanismo o los mecanismos involucrados en la aparición de resistencia a cloroquina.

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Amplification of the multidrug resistance gene in some chloroquine-resistant isolates of P. falciparum

Cited by 562 publications

References 32 publications

Genomic heterogeneity in the density of noncoding single-nucleotide and microsatellite polymorphisms in Plasmodium falciparum

Genomic heterogeneity in the density of noncoding single-nucleotide and microsatellite polymorphisms in Plasmodium falciparum

Analysis of mefloquine resistance and amplification of pfmdr1 in multidrug-resistant Plasmodium falciparum isolates from Thailand.

Cloroquina: hipótesis acerca de los mecanismos de Cloroquina: hipótesis acerca de los mecanismos de resistencia en Plasmodium falciparum

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