Analysis of the gene expression profile of Schistosoma japonicum cercariae by a strategy based on expressed sequence tags

We present an analysis of the expression profile of Schistosoma japonicum cercariae by a strategy based on expressed sequence tags (ESTs). A cDNA library from S. japoniucm cercariae was constructed and was used to generate ESTs. In total, 201 clones randomly selected from the library were sequenced; 136 ESTs were successfully obtained and sent to the BLAST server for homology searching. Among the 136 ESTs, 85 (62.50%) did not match any protein or gene sequence published in the BLAST databases; these comprised 75 (55.15%) ESTs matched (or partly matched) S. japonicum and Schistosoma mansoni ESTs, 4 (2.94%) matched human ESTs and 6 (4.41%) that did not match any sequence. Fifty-one (37.50%) ESTs were identified by the BLAST server; these consisted of 8 (5.88%), 9 (6.62%) and 34 (25.00%) that showed high homology with genes or proteins reported from S. japonicum, S. mansoni and other organisms, respectively. These identified ESTs can be grouped into nine categories: transporters (1.96%), secretory proteins (1.96%), kinases (3.92%), proteases (5.88%), structural and cytoskeletal proteins (13.73%), metabolism-related proteins (9.80%), regulatory and signaling proteins (11.76%), transcription and translation machinery (25.50%), and others (25.50%). Several interesting new genes cloned from this cDNA library are discussed here. These findings will be valuable for the understanding of the biology of this parasite.