RESUMEN
Schistosomes undergo various morphological and metabolic changes during their development, reflected in a finely tuned regulation of protein and/or gene expression. The mechanisms involved in the control of gene expression during the development of the parasite are not understood. Two actin genes had been previously cloned and observed to be differentially expressed during the maturation of the parasite. The SmAct gene contains four putative cis-regulatory elements (TATA-, CCAAT-, E- and CArG-boxes). Our objective was to investigate in greater detail the expression pattern of two actin genes and verify if the binding of nuclear proteins to the promoter elements of SmAct correlated with the expression profile observed. We detected little variation in the expression of actin genes during the first seven days of schistosomula culture in vitro. However, we observed significantly higher levels of expression in males compared to female adults. CArG and CCAAT elements bound to a greater extent and formed distinct complexes with male in comparison to female nuclear extracts. In contrast, female extracts bound weakly to the E-box probe while no binding was observed with male extracts. Taken together these results describe cis-acting elements that appear to be involved in sexually regulated gene expression in Schistosoma mansoni