Incubation of total protein extracts of Schistosoma mansoni
with ^3H 17-b-estradiol and 20-hydroxyecdysone, revealed
steroid binding proteins in both, male and female worms. The
interaction of nuclear proteins with restriction fragments of
the gender and stage-specific gene F-10 was investigated using
the "Band-Shift" technique. Distinct male and female nuclear
proteins bound to the fragments of this gene. Among the
nuclear proteins, only those rich in cysteine residues bound
to DNA. In vitro incubation of live worms with the estrogen
antagonist Tamoxifen, altered the pattern of the DNA binding
proteins, producing in females, a band profile similar to that
obtained with male worm protein extracts. When Tamoxifen was
injected into schistosome infected mice, the eggs produced by
females presented an abnormal morphology, compatible with non-
viable eggs. These results suggest that the regulation of
transcription of the F-10 gene might involve steroid
receptors.
