Análise da diversidade, clusterização e estudo de mecanismos evolutivos geradores de diversidade nas grandes famílias gênicas de Trypanosoma cruzi

Abstract

With the publication of the results of the genome project Trypanosoma cruzi, approaches aimed at contributing to a better understanding of the diversity of genes encoding the large family of parasite surface proteins can be applied to genomic scale. One of multigene families of T. cruzi best studied is the trans-sialidase / sialidase-like (TCS). Although four groups of this family have already been identified in previous work and qpenas one host active trans-sialidase, all family members are recorded in the database with trans-sialidase. this paper, using clustering methodologies sequences, the 508 full members of Tcs family were divided into eight distinct groups, TcS I to VIII. The eight groups were characterized based on the presence of typical reasons of family, chromosomal location, gene expression and antigenicity. Interestingly, members of different groups have a distinct pattern of chromosomal location. Members Tcs II, which host proteins involved in cell adhesion and invasion, are preferably located in the subtelomeric regions, while the members of the new, larger family group (TcS V) have internal chromosomal location. Results of expression using RT-PCR in real time, show that the CTs genes in general are more expressed in the forms found in the vertebrate host and expression variation exists between members even within the groups. New B cell epitopes have been identified in TcS family members previously described groups as well as of new group members. Some of the reactive peptides are found in many family members. The cross-reactivity between various epitopes TcS and family sequence variability can contribute to the parasite strategy escape the immune system to attack by simultaneous exposure of B cell epitopes related generating spurious and non-neutralizing immune responses. In a second part of this work, we performed comparative analyzes of diversity of gene families encoding T. cruzi surface protein.These families have highly heterogeneous diversity, ranging from low levels (DGF- 1 and SAP), intermediate (RHS and mucin - like) and high (TcMUC, TcS, GP63, MASP) diversity. MDS type graphics (Multidimensional scaling) were generated to represent the diversity of each family and the K-means method to define the intr-family groups. MASP TcMUC and have a similar pattern of diversity in coding regions and 3 'flaqueadora. The coding sequences of both families show a continuous pattern diversity while the 3 'region flanking each family is highly conserved. We speculate that recombination events between members of each family may contribute to this pattern diversity in a mechanism similar to that previously described for the MSP2 gene Anaplasma. In fact, we have identified fragments shared between members of the MASP family who belong to different K-means groups. We also identified fragments shared between different gene families of T. cruzi. most of these fragments are located in the 3 'end of the genes, again suggesting that these regions may be involved in these mechanisms possible recombination