Ionizing radiation effect on Trypanosoma cruzi chromosomal organization

Abstract

Trypanosoma cruzi, the etiologic agent of Chagas' disease, is a protozoan parasite transmitted to the vertebrate hosts by insect vectors. The disease has a broad spectrum of clinical presentations which may reflect the genetic variability of the parasite. T. cruzi taxon shows remarkable genetic heterogeneity. It is composed by a set of populations which differ with regard to infectivity, pathogenicity, growth rate, number of chromosomes and amount of DNA. The genome structure of T. cruzi is the most divergent among eukaryotes indicating that the phylogenetic lineages of this parasite have diverged from the main eukaryotic lineage very early in the evolution.DNA Repair mechanisms may be responsible for the genome plasticity found in diverse organisms and may play a role in generating genetic diversity found in T. cruzi populations. Lesions more complex and possibly more harmful to the cells are double-stranded breaks in DNA (DSBs), which can be induced by chemical (drugs) or physical (ionizing radiation) agents. The DSBs are repaired by homologous recombination mechanisms (HR - "homologous recombination"), nonhomologous recombination. It has been reported that T. cruzi is an organism highly resistant to ionizing radiation. Following a dose of 500 Gy of gamma radiation, the fragmented genomic DNA is gradually reconstructed and the pattern of chromosomal bands is restored. The goal of our project is to investigate the effects of ionizing radiation on the chromosomal organization of T. cruzi by analyzing possible recombination events which may alter the molecular karyotype and contribute to the genetic diversity of the parasite. To achieve the goal we intend to analyze the karyotype of parasites submitted to ionizing irradiation by pulsed-field gel electrophoresis (PFGE) and hybridization with chromosome-specific markers. Thus we intend to obtain new information about the generation of large genetic diversity observed in different strains and strains.