FEMALE-SPECIFIC SEQUENCES ISOLATED FROM SCHISTOSOMA-MANSONI BY REPRESENTATIONAL DIFFERENCE ANALYSIS

Representational difference analysis (RDA), a recently described, poly merase-chain-reaction-based modification of the subtractive hybridizat ion process was employed to isolate female-specific sequences of Schis tosoma mansoni. Using HindIII-derived amplicons, an excess of male sch istosome DNA was employed to remove sequences common to both male and female adult S. mansoni genomes from female genomic DNA. Following thr ee rounds of RDA, the enriched sequences included two female-specific repetitive elements. One of these exhibited 76% homology to the SM alp ha family of retroposons and represents a W chromosome-specific varian t of that family. The other sequence represents a novel, female-specif ic repetitive sequence. These sequences have been designated SM alpha fem-1 and W2, respectively, and both are apparently arrayed as tandem repeats on the W chromosome of S. mansoni. The isolation and character ization of the two female-specific sequences by RDA indicates that thi s procedure should also find utility in the definition of traits and s equences that differ among other groups of schistosomes.