EXPRESSED SEQUENCE TAGS (ESTS) OF BIOMPHALARIA-GLABRATA, AN INTERMEDIATE SNAIL HOST OF SCHISTOSOMA-MANSONI - USE IN THE IDENTIFICATION OF RFLP MARKERS

To identify some of the genes expressed in the snail Biomphalaria glab rata, a major intermediate host for the trematode parasite Schistosoma mansoni, we sequenced random cDNA clones from either a whole body or a cerebral ganglia cDNA library to generate 111 expressed sequence tag s (ESTs). Searches of existing public databases showed that the majori ty of the snail sequences (54%) showed no significant homology to gene s listed in either DNA or protein databases. Thirty one EST sequences showed significant matches with other genes in the databases. These in cluded genes involved in gene expression, such as ribosomal proteins a nd translation factors, and those involved in cell communication, such as acetylcholine receptor and ATP-dependent transporter. Some ESTs us ed as probes demonstrated the occurrence of restriction fragment lengt h polymorphisms (RFLPs) between parasite-resistant and parasite-suscep tible snail stocks. Southern hybridization of parasite DNA with the sn ail EST encoding the acetylcholine receptor as probe showed the presen ce of a related sequence in the parasite genome, with the heterologous probe, indicating that this may be a useful method to identify closel y related genes between the host and parasite.