Evidence for viable and stable triploid Trypanosoma congolense parasites

Abstract

BackgroundRecent whole genome sequencing (WGS) analysis identified a viable triploid strain of Trypanosoma congolense. This triploid strain BANANCL2 was a clone of the field isolate BANAN/83/CRTRA/64 that was collected from cattle in Burkina Faso in 1983.ResultsWe demonstrated the viability and stability of triploidy throughout the complete life-cycle of the parasite by infecting tsetse flies with the triploid clone BANANCL2. Proboscis-positive tsetse flies efficiently transmitted the parasites to mice resulting in systemic infections. WGS of the parasites was performed at all life-cycle stages, and a method based on a block alternative allele frequency spectrum was developed to efficiently detect the ploidy profiles of samples with low read depth. This approach confirmed the triploid profile of parasites throughout their life-cycle in the tsetse fly and the mammalian host, demonstrating that triploidy is present at all stages and is stable over time.ConclusionThe presence of viable field-isolated triploid parasites indicates another possible layer of genetic diversity in natural T. congolense populations. The comparison between triploid and diploid parasites provides a unique model system to study the impact of chromosome copy number variations in African trypanosomes. In addition, the consequences of triploidy can be further investigated using this stable triploid model.Electronic supplementary materialThe online version of this article (10.1186/s13071-017-2406-z) contains supplementary material, which is available to authorized users.

Meiotic sex in Chagas disease parasite Trypanosoma cruzi

“…A third possibility, high levels of aneuploidy via frequent asymmetric chromosome allotment in mitotically dividing nuclei 35 , also finds direct support in this dataset. Unlike occasional accounts of stable aneuploidy in the Trypanosoma genus 23,36,37 , we detected short-term somy reductions in one of three re-sequenced aneuploid clones and also found evidence for sub-clonal ploidy variation, often termed mosaic aneuploidy in Leishmania research 35 . Congruent aneuploidies observed in closely-related Cluster 2 genotypes may thus reflect strain-specific or pre-adapted amplification programs as in Leishmania spp.…”

Variant antigen diversity in Trypanosoma vivax is not driven by recombination

“…These produced assemblies with n50 between 238 and 2852 bp (median = 353; mean = 985). The ratio of read depth of an alternative allele over the total read depth was calculated to detect mixed infections 58,59 . All samples were from single infections only.…”

Genome plasticity driven by aneuploidy and loss of heterozygosity in Trypanosoma cruzi

“…Genomic studies on T. cruzi have shown aneuploidy changes after passages during cultivation, the same results have been observed in Leishmania . Here, we controlled the number of culture passages after the cloning process, however, our results show the presence of aneuploidy patterns for different chromosomes among TcI clones, indicating a possible influence of culture pressure over genome stability that impacts the number of chromosomes copies, as they are in many pathogenic fungi () [15, 27, 28, 30, 31, 52–54]. Chromosomal mosaicism has been previously discussed including parasexuality, failed or incomplete meiotic processes and meiosis and posterior reduction in the chromosome copies.…”

“…Changes in chromosomal somy appear to be well tolerated in trypanosomatids such as Leishmania, T. congolense and T. cruzi, conversely, T. brucei sub-species have not shown aneuploidy, possibly related to different mechanisms of DNA replication and recombination [29,31,32,52]. Ploidy plasticity is believed to be important in responding to environmental stress during the life cycle and precursors of resistance mechanisms against treatment for some Leishmania species [23,24].…”