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Background  Amastins are surface glycoproteins (approximately 180 residues long) initially described in  Trypanosoma cruzi  as particularly abundant during the amastigote stage of this protozoan parasite. Subsequently, they have been found to be encoded by large gene families also present in the genomes of several species of  Leishmania  and in other Trypanosomatids. Although most amastin genes are organized in clusters associated with tuzin genes and are up-regulated in the intracellular stage of  T. cruzi  and  Leishmania  spp, distinct genomic organizations and mRNA expression patterns have also been reported.    Results  Based on the analysis of the complete genome sequences of two  T. cruzi  strains, we identified a total of 14 copies of amastin genes in  T. cruzi  and showed that they belong to two of the four previously described amastin subfamilies. Whereas δ-amastin genes are organized in two or more clusters with alternating copies of tuzin genes, the two copies of β-amastins are linked together in a distinct chromosome. Most  T. cruzi  amastins have similar surface localization as determined by confocal microscopy and western blot analyses. Transcript levels for δ-amastins were found to be up-regulated in amastigotes from several  T. cruzi  strains, except in the G strain, which is known to have low infection capacity. In contrast, in all strains analysed, β-amastin transcripts are more abundant in epimastigotes, the stage found in the insect vector.    Conclusions  Here we showed that not only the number and diversity of  T. cruzi  amastin genes is larger than what has been predicted, but also their mode of expression during the parasite life cycle is more complex. Although most  T. cruzi  amastins have a similar surface localization, only δ-amastin genes have their expression up-regulated in amastigotes. The results showing that a sub-group of this family is up-regulated in epimastigotes, suggest that, in addition of their role in intracellular amastigotes,  T. cruzi  amastins may also serve important functions during the insect stage of the parasite life cycle. Most importantly, evidence for their role as virulence factors was also unveiled from the data showing that δ-amastin expression is down regulated in a strain presenting low infection capacity.

Distinct genomic organization, mRNA expression and cellular localization of members of two amastin sub-families present in Trypanosoma cruzi