Gene structure and splicing in schistosomes

Schistosomes are blood dwelling platyhelminths with a complex life cycle and persist in the definitive host during decades, indicating that they are very successful parasites. The challenge of infecting two hosts from different evolutionary branches, namely an invertebrate snail and a vertebrate, suggests that Schistosomes must display a very sophisticated genetic program to circumvent all the barriers imposed by the hosts' immune systems. Recent large-scale genome and transcriptome data from Schistosomes are facilitating the analysis of gene structure and splicing. Studying the structure of genes coding for secreted proteins is of particular interest since these proteins mediate processes in the host-parasite interface. Recent description of Micro-Exon Genes (MEGs), polymorphic mucin genes (SmPoMucs) and venom allergen-like (SmVALs) proteins with unusual gene structure apparently oriented towards generation of protein variability through alternate splicing, and the presence of multiple copies of these genes, indicate that the parasite developed a sophisticated system to interact with its hosts. This opens up opportunities for further studies with the use of proteomic techniques to better characterize the protein variability created by these systems and their role in parasite survival. Complete description of the functions of these variable proteins will greatly contribute to our understanding of host-parasite interactions.