Modulação diferencial da expressão gênica em camundongos infectados com duas cepas de Trypanosoma cruzi: uma análise transcriptômica

Abstract

The protozoan Trypanosoma cruzi, from the Kinetoplastida class, is the causative agentof the Chagas disease in humans. For decades, physicians and scientists have beenstudying the mal de Chagas and searching for disease treatments, while also dealing withthe creation of efficient therapeutic strategies that deal with the variable tissue distributionof parasites in different patients during the chronic stage, which can affect the heart andother organs of the digestive system, such as the esophagus and colon. Researchperformed at the Laboratório de Genética e Bioquímica (LGB) of UFMG, indicated thatgenetic characteristics of the host and of the T. cruzi parasites were important to definethe tissue tropism observed. However, until the present moment, there was still a lack ofunderstanding of the molecular basis of this differential tissue tropism. Thus, the goal ofthe present work is to expand the knowledge of this mechanism of differential distributionby distinct T. cruzi strains, Col1.7G2 (T. cruzi I) and JG (T. cruzi II) strains, in the heartsand intestines (rectums) of BALB/c mice in the acute phase of the disease. Highthroughput RNA sequencing (RNA-Seq) was used to evaluate the expression differencescaused by the infection with two strains of T. cruzi. To perform this study, mice wereinoculated with sterile PBS (Control), Col1.7G2, JG or a mixture of both. The animals weresacrificed on the 15th day post-infection and the hearts and a segment of the rectum wereremoved and preserved inside liquid nitrogen. Next, the RNA was extracted and submittedto sequencing by the Illumina-Hiseq 2000 platform. The generated reads were evaluatedby their quality and later the transcript abundance was measured by a pseudoalignmenttechnique with the software Kallisto using the mouse transcriptome (Gencode releaseM21). Finally, the statistical package Sleuth was used to determine the differentiallyexpressed genes among the experimental groups and the non-infected controls. The geneontology categories, biological processes, were evaluated by the package TopGO,implemented in R. The obtained data showed that the T. cruzi strains induce distinctexpression profiles. In the principal component analysis, heart of control and infected miceformed separated groups. The mice infected with a mixture were grouped in between JGand Col1.7G2. Interestingly, Col1.7G2-infected mice exhibit a high number of upregulatedgenes related to the immune response of the host (including innate and adaptivepathways), inflammatory response and pathogens (virus, bacteria and protozoans). Onanother hand, JG-infected mice showed not only fewer genes related to the inflammatorypathways, but also a strong downregulation of ribosomal protein genes (large and smallsubunits) and of proteins that have a role inside the mitochondria such as the citric acidcycle and the electron transport chain. Moreover, mice infected with a mixture of Col1.G2and JG strains showed both gene expression profiles. Conversely, the rectum of theseanimals did not show substantial gene expression changes in this period of infection.Taken together, the data obtained allow us to better understand the complex hostpathogeninteraction in the context of the experimental Chagas disease and the effectsthat two T. cruzi strains may have on the host gene expression.