The karyotype of Trypanosoma cruzi Dm 28c: comparison with other T. cruzi strains and trypanosomatids.

Chromosome-sized DNA molecules from Trypanosoma cruzi clone Dm 28c were analyzed and compared with other T. cruzi strains and monogenetic trypanosomatids by orthogonal field alteration gel electrophoresis. The results showed that T. cruzi Dm 28c displays at least 18 chromosomes ranging from 550 to more than 1500 kb and that in general the trypanosomatids have smaller chromosomes distributed in the size range from 300 to 1500 kb. With the exception of T. cruzi strain G49, there is no evidence of minichromosomes, suggesting they are not widely distributed among different isolates of the parasite. The hybridization of T. cruzi chromosomal Southern blots with probes for T. cruzi-specific genes showed that their location can change from one strain to another, supporting the idea of the plasticity of the parasite genome. Furthermore, the chromosome pattern is strictly conserved during the transformation of T. cruzi Dm 28c epimastigotes to metacyclic trypomastigotes, suggesting that extensive chromosomal rearrangements do not occur during at least part of the life cycle of the parasite.