Trypanosoma cruzi surface components: Why so many? Why so polymorphic?

The genome of the Trypanosoma cruzi parasite exhibits a significant expansion of genes that encode surface proteins in comparison to other trypanosomatids, specifically Trypanosoma brucei and Leishmania. Many of these proteins are encoded by large and diverse gene families, predominantly expressed on the surface of the trypomastigote stage, which infects a variety of mammalian host cells and circulates in the bloodstream, disseminating the infection throughout the organism. While some members of these families may be found at the telomeres, the majority are clustered in long arrays of genes within the chromosomes. These regions, referred to as disruptive compartments, undergo more rapid evolution than the core compartments, which are enriched in conserved and housekeeping protein coding-genes common to other trypanosomatids. In this chapter, we will discuss the features and process underlying the variability of the largest T. cruzi gene families and its implications for parasite survival.