Molecular karyotype and chromosomal evolution in Trypanosoma cruzi: polymorphism, syntenic analysis and aneuploidy among isolates of different strains of T. cruzi and between clones isolated from the same strain
Trypanosoma cruzi comprises a pool of populations which are genetically diverse in terms of DNA content, isoenzyme profiles, growth and infectivity. Inter- and intra-strain karyotype heterogeneities have been reported, suggesting that chromosomal rearrangements occurred during the evolution of this parasite. The genome of T. cruzi was sequenced from a hybrid strain (CL Brener). However, due to the high allelic variation and the repetitive nature of the genome, the complete linear sequence of T. cruzi chromosomes has not been determined. For this reason, the determination of the full complement of chromosomes and ploidy are important to define the genome organization of this parasite. T. cruzi is generally considered to be diploid, although the occurrence of aneuploid chromosome regions has been detected by genomic comparative hybridization (aCGH). It has been suggested that chromosomal polymorphism could be part of the T. cruzi arsenal for responding to environmental pressure.In this project, we propose to investigate the polymorphism and chromosome ploidy in clones of T. cruzi derived from the same parental strain by combining two approaches: 1) comparison of the molecular karyotype - identification of chromosomal rearrangements by hybridization of specific chromosome-markers with the chromosomal bands separated by pulsed field-gel electrophoresis (PFGE), and 2) comparative genomic hybridization on microarrays DNA (aCGH). Karyotype analysis and hybridization with specific markers allow the identification of chromosomal rearrangements (deletion, duplication and translocation). The aCGH technique is able to detect the loss, gain, and amplifying the copy number of genes in the chromosomes of a cell population. This study will be carried out in single-cell-derived clones of two parental T. cruzi strains: clone D11 from G strain and clones CL14 and CL Brener from CL strain. In a preliminary work, we have shown that the karyotype of these clones differ from that of respective parental strain in both number and size of chromosomal bands. Large chromosomal rearrangements were observed with specific chromosome-markers. We will look for chromosomal mosaicism as a constitutive feature in T. cruzi as it has been described in Leishmania.
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