Transcripts of alternatively spliced immune related genes in Schistosoma mansoni . (A) MEG 1 has 18 isoforms. These isoforms display very lifestage specific transcription. The exact role of MEG1 is unknown. (B) MEG 3 has four members with three, 10, three, and two isoforms four family members with 3, 1 and 4 isoforms each. MEG 3 is also known as GRAIL. (C) The 10–3 surface antigen also known as MEG 4 has different transcription start sites that give rise to two isoforms that are expressed at different stages in the parasites lifecycle. (D) SmVAL6 contains 38 exons, the four largest code for conserved protein motifs, while the smaller exons are alternately spliced to give rise to at least 5 isoforms. SmVAL6 probably arose due to a recombination event between a MEG gene and a SmVAL gene.