The calmodulin intergenic spacer as molecular target for characterization of Leishmania species

Human leishmaniasis is a neglected disease caused by parasites of the genus Leishmania. Clinical aspects of this disease can vary significantly, reflecting the wide range of parasites in the genus Leishmania. Knowing accurately the Leishmania species infecting humans is important for clinical case management and evaluation of epidemiological risk. Calmodulin is an essential gene in trypanosomatids that modulates the calcium metabolism in various cellular activities. Despite its strong conservation in trypanosomatids, it has been recently observed that its untranslated regions (UTR) diverge among species.

In this study we analyzed the sequences and the absolute dinucleotide frequency of the intergenic spacer of the calmodulin gene (containing both, 3' and 5'UTR) in nine reference Leishmania species and ten clinical isolates obtained from patients with cutaneous leishmaniasis.

We show that the short calmodulin intergenic spacers exhibit features that make them interesting for applications in molecular characterization and phylogenetic studies of Leishmania. Dendrograms based on sequence alignments and on the dinucleotide frequency indicate that this particular region of calmodulin gene might be useful for species typing between the Leishmania and Viannia subgenera.

Mutations and composition of the calmodulin intergenic spacer from Leishmania species might have taxonomic value as parameters to define if an isolate is identical to a certain species or belongs to one of the two current subgenera.