Recurrent polymorphisms in small chromosomes of Leishmania tarentolae after nutrient stress or subcloning

Rovai, Leonor E.; Tripp, Cindy; Stuart, Kenneth; Simpson, Larry

doi:10.1016/0166-6851(92)90249-j

Cited by 47 publications

(30 citation statements)

References 30 publications

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“…By contrast, chromosome gain or loss (aneuploidy) in multicellular eukaryotes is either lethal or results in severe abnormalities, for example trisomy of chromosome 21 in humans with Down syndrome [6]. Despite the predominantly negative effects of aneuploidy, supernumerary chromosomes have been reported in tumor cells, yeast, and recently the protozoan Leishmania [7][8][9][10][11].…”

Section: The Flexible Genomes Of Leishmaniamentioning

confidence: 99%

“…Remarkably, the chromosomes reverted to disomy in the absence of drug pressure, which indicates that aneuploidy was not stable and could assist drug resistance. Other experimental stresses such as subcloning could contribute to chromosomal polymorphism [9], however, a recent report indicates that, in most cases, the chromosome ploidy pattern in clones is similar to that of the parental strain [26].…”

Section: The Flexible Genomes Of Leishmaniamentioning

confidence: 99%

“…The sand fly gut and mammalian macrophages are the primary Leishmania microenvironments. These differ in pH, temperature, and nutrients, and therefore require substantial alterations in gene expression during parasite life cycle differentiation [9,58]. The cells undergo drastic changes in motility, shape, and metabolism when they alternate between hosts.…”

Section: Why Does Leishmania Tolerate Aneuploidy?mentioning

confidence: 99%

See 2 more Smart Citations

Adaptive mechanisms in pathogens: universal aneuploidy in Leishmania

Mannaert

Downing

Imamura

et al. 2012

Trends in Parasitology

129

102

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Section: The Flexible Genomes Of Leishmaniamentioning

confidence: 99%

Section: The Flexible Genomes Of Leishmaniamentioning

confidence: 99%

Section: Why Does Leishmania Tolerate Aneuploidy?mentioning

confidence: 99%

See 1 more Smart Citation

Adaptive mechanisms in pathogens: universal aneuploidy in Leishmania

Mannaert

Downing

Imamura

et al. 2012

Trends in Parasitology

129

102

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“…The parasite undergoes several developmental transitions, alternating between an extracellular transmissible form, which is carried in the gut of phlebotomine sand flies, and an intracellular form, which resides within the phagolysosome of vertebrate macrophages. The genome of the parasite has been shown to be quite plastic, undergoing a number of mutational and recombinational events including deletions, gene amplifications, chromosomal rearrangements, and alterations in ploidy (2,4,7,20,47,54,59,66). Many of these have been implicated in biological phenomena such as drug resistance and virulence, making their study relevant to the understanding and control of this important disease.…”

mentioning

confidence: 99%

Selection against the Dihydrofolate Reductase-Thymidylate Synthase (DHFR-TS) Locus as a Probe of Genetic Alterations in Leishmania major

Gueiros‐Filho

Beverley

1996

Molecular and Cellular Biology

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The genome of the trypanosomatid protozoan genus Leishmania has been shown to undergo a number of changes relevant to drug resistance and virulence, such as gene amplification, chromosomal rearrangement, and variation in ploidy. Experimental approaches to the study of genomic changes have in some cases been limited by the fact that Leishmania cells are asexual diploids, as are some other trypanosomatids, pathogenic fungi, and cultured mammalian cells. Here we report upon a system which permits the measurement of several types of genomic change occurring at the dihydrofolate reductase-thymidylate synthase (DHFR-TS) locus. First, we show that DHFR-TS can function as a positive/negative marker. We used selection against DHFR-TS on a heterozygous line (؉/HYG) to generate colonies exhibiting both loss of heterozygosity and structural mutations in DHFR-TS, permitting the first measurement of mutation frequencies in this parasite. Loss of heterozygosity occurred at a frequency ranging from 10 ؊4 to 10 ؊6 and was elevated 24-fold by treatment with ␥-irradiation, while the frequency of other events was less than 10 ؊6 and was increased more than 1,000-fold by nitrosoguanidine treatment. The frequency of loss of heterozygosity relative to other processes such as mutation and gene replacement has important implications for genetic variability in natural Leishmania populations and the generation of both targeted and random mutations. We also developed a protocol for null targeting of diploid cells, in which transfection of a DHFR-TS deletion construct into Leishmania cells followed by negative selection yielded parasites lacking DHFR-TS or foreign sequences. The null-targeting method can be applied to any diploid cell, at any locus for which a negative selection exists. Such marker-free auxotrophic Leishmania cells show potential as an attenuated vaccine, and the methods developed here provide a new approach for manipulating and characterizing the plasticity of the Leishmania genome.

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“…To purify mitochondrial DNA, CsCl-Hoechst 33258 equilibrium density centrifugation (24) Pulsed-field gel electrophoresis. Agarose blocks with embedded cells were prepared as described elsewhere (23). CHEF (contour-clamped homogeneous electric field) 1.3% agarose gels were run at 150 V with switch times of 60 s for 21 h, 90 s for 8 h, and 120 s for 21 h.…”

mentioning

confidence: 99%

RNA editing and mitochondrial genomic organization in the cryptobiid kinetoplastid protozoan Trypanoplasma borreli.

Maslov¹,

Simpson²

1994

Mol. Cell. Biol.

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The bodonids and cryptobiids represent an early diverged sister group to the trypanosomatids among the kinetoplastid protozoa. The trypanosome type of uridine insertion-deletion RNA editing was found to occur in the cryptobiid fish parasite Trypanoplasma borreli. A pan-edited ribosomal protein, S12, and a novel 3'-and 5'-edited cytochrome b, in addition to an unedited cytochrome oxidase III gene and an apparently unedited 12S rRNA gene, were found in a 6-kb fragment of the 80-to 90-kb mitochondrial genome. The gene order differs from that in trypanosomatids, as does the organization of putative guide RNA genes; guide RNA-like molecules are transcribed from tandemly repeated 1-kb sequences organized in 200-and 170-kb molecules instead of minicircles. The presence of pan-editing in this lineage is consistent with an ancient evolutionary origin of this process.The evolutionary origin of the uridine (U) insertion-deletion type of RNA editing which occurs in the mitochondrion of the trypanosomatid kinetoplastid protozoa is an intriguing problem. Within the kinetoplastid protozoa there are two suborders, the Trypanosomatina and the Bodonina, as determined by morphological characters and life cycles. The trypanosomatids consist of approximately 8 to 10 obligately parasitic genera in a single family, and the bodonids consist of two major families containing both free-living and parasitic organisms (the Bodonidae and the Cryptobiidae) (30). RNA editing in several trypanosomatids, including the digenetic genera Trypanosoma and Leishmania and the monogenetic genera Crithidia, Blastocrithidia, and Herpetomonas, has been investigated (7,26,28). It has been shown previously that extensive editing or pan-editing, which is mediated by multiple overlapping guide RNAs (gRNAs), represents a primitive character state within the trypanosomatid lineage and that 5' editing and even loss of editing represent derived traits which possibly arose on account of replacement of pan-edited original versions of the genes, with partially or fully edited versions derived from mRNAs (11)(12)(13)(14). Little is known about mitochondrial DNA in the bodonids and cryptobiids, which is also termed kinetoplast DNA since it is present as a large DNAcontaining structure situated within the single mitochondrion (Fig. 1). In the free-living bodonid Bodo caudatus, there is no network of catenated minicircles and maxicircles such as that which exists in the trypanosomatids; instead, a variety of large circular molecules with heterogeneous sizes is found (8). In this paper, we show the occurrence of the uridine insertiondeletion type of RNA editing in the cryptobiid Trypanoplasma borreli, with some novel features, and we show that small gRNA-like transcripts are encoded in tandemly repeated 1-kb

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Recurrent polymorphisms in small chromosomes of Leishmania tarentolae after nutrient stress or subcloning

Cited by 47 publications

References 30 publications

Adaptive mechanisms in pathogens: universal aneuploidy in Leishmania

Adaptive mechanisms in pathogens: universal aneuploidy in Leishmania

Selection against the Dihydrofolate Reductase-Thymidylate Synthase (DHFR-TS) Locus as a Probe of Genetic Alterations in Leishmania major

RNA editing and mitochondrial genomic organization in the cryptobiid kinetoplastid protozoan Trypanoplasma borreli.

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