Interclonal Variations in the Molecular Karyotype of Trypanosoma cruzi: Chromosome Rearrangements in a Single Cell-Derived Clone of the G Strain

Abstract

Trypanosoma cruzi comprises a pool of populations which are genetically diverse in terms of DNA content, growth and infectivity. Inter- and intra-strain karyotype heterogeneities have been reported, suggesting that chromosomal rearrangements occurred during the evolution of this parasite. Clone D11 is a single-cell-derived clone of the T. cruzi G strain selected by the minimal dilution method and by infecting Vero cells with metacyclic trypomastigotes. Here we report that the karyotype of clone D11 differs from that of the G strain in both number and size of chromosomal bands. Large chromosomal rearrangement was observed in the chromosomes carrying the tubulin loci. However, most of the chromosome length polymorphisms were of small amplitude, and the absence of one band in clone D11 in relation to its reference position in the G strain could be correlated to the presence of a novel band migrating above or below this position. Despite the presence of chromosomal polymorphism, large syntenic groups were conserved between the isolates. The appearance of new chromosomal bands in clone D11 could be explained by chromosome fusion followed by a chromosome break or interchromosomal exchange of large DNA segments. Our results also suggest that telomeric regions are involved in this process. The variant represented by clone D11 could have been induced by the stress of the cloning procedure or could, as has been suggested for Leishmania infantum, have emerged from a multiclonal, mosaic parasite population submitted to frequent DNA amplification/deletion events, leading to a 'mosaic' structure with different individuals having differently sized versions of the same chromosomes. If this is the case, the variant represented by clone D11 would be better adapted to survive the stress induced by cloning, which includes intracellular development in the mammalian cell. Karyotype polymorphism could be part of the T. cruzi arsenal for responding to environmental pressure.

Transcriptional and phenotypical heterogeneity of Trypanosoma cruzi cell populations

“…Thus, differences in expression and patterns between the different life-cycle stages might be explained by other differences such as levels of trans -acting factors (i.e. RNA-binding proteins and eukaryotic initiation translation factors), different codon usage and tRNA pools available for those sequences, as well as by the genomic plasticity shown by the replicative forms of the parasite (epimastigote and amastigote) [ 32 , 33 , 53 , 54 ].…”

“…Although, some reports have shown the presence of clonal and inter-strain karyotypic differences and copy number variations on multigene families including MASPs [ 28 , 32 , 33 ], this clonal heterogeneity remains incompletely characterized.…”

Neglected Tropical Diseases in the Post-Genomic Era

“…This aneuploidy was definitively demonstrated using a single cell resolution technique performed on multiple isolates of at least four species of Leishmania [84,85]. Several independent observations using cloned isolates also indicated that mosaic aneuploidy may be a shared feature with T. cruzi [86,87]. Moreover, small-scale studies [88,89] as well as comparative genomic hybridization of different T. cruzi strains have illustrated frequent variation in gene dosage as well as in chromosome copy numbers [90].…”

To bet or not to bet: deciphering cell to cell variation in protozoan infections

“…Comparative genomic hybridization (CGH) and PFGE affirmed the presence of these variations between strains, and also within isogenic clones, ranging from 100 bp to whole chromosomes [41][42][43]. Since the discovery of Chagas disease in 1909, the heterogeneity of T. cruzi strains has been implicated in the differential tissue tropism and the consequent different clinical forms of the disease [44,45].…”