Genetic Variability and Phylogenetic Relationships within Trypanosoma cruzi I Isolated in Colombia Based on Miniexon Gene Sequences

Abstract

Phylogenetic studies of Trypanosoma cruzi have identified the existence of two groups: T. cruzi I and T. cruzi II. There are aspects that still remain unknown about the genetic variability within the T. cruzi I group. Given its epidemiological importance, it is necessary to have a better understanding of T. cruzi transmission cycles. Our purpose was to corroborate the existence of haplotypes within the T. cruzi I group and to describe the genetic variability and phylogenetic relationships, based on single nucleotide polymorphisms (SNPs) found in the miniexon gene intergenic region, for the isolates from different hosts and epidemiological transmission cycles in Colombian regions. 31 T. cruzi isolates were molecularly characterized. Phylogenetic relationships within T. cruzi I isolates showed four haplotype groups (Ia-Id), associated with their transmission cycle. In previous studies, we reported that haplotype Ia is mainly associated with the domestic cycle and domiciliated Rhodnius prolixus. Haplotype Ib is associated with the domestic cycle and peridomestic cycle, haplotype Ic is closely related with the peridomestic cycle, and haplotype Id is strongly associated with the sylvatic cycle. The phylogenetic methodologies applied in this study are tools that bolster the associations among isolates and thus shed light on Chagas disease epidemiology.

Figure 1

A microsatellite region with an average of 56 nt in which the variability between the 4 proposed haplotypes can be clearly observed. Alignment of the miniexon gene from T. cruzi strains. *Differences are not observed in the alignment. The boxed area corresponds to the nucleotide polymorphisms (SNPs) found between the four proposed haplotypes.

Figure 2

Unrooted phylogenetic tree depicting the evolutionary relationships among T. cruzi I isolates. The tree was constructed by the maximum likelihood method. Numbers in larger fonts represent the bootstrap values for the main cluster of the haplotypes. The topology obtained for this method represents the consensus from 236 trees (100 replicates each producing, on average, 4 most parsimonious trees), bootstrap 50% majority rule consensus.

Figure 3

Unrooted phylogenetic tree depicting the evolutionary relationships between T. cruzi I isolates. Phylogram showing support nodes from Bayesian-estimated likelihood with 10 million Monte-Carlo Markovian chain generation node support from the >50%-majority rule consensus GTR+I+G model. Invariant sites and gamma distribution values are at the right side of the slash (MP bootstrap values/Bayesian probabilities × 100/ML bootstrap values).