Stage and sex specific differences in actin gene expression in Schistosoma mansoni

We have characterized actin gene expression in Schistosoma mansoni at the RNA and protein levels. Northern blot analyses showed two size classes of actin mRNA in eggs, cercariae and adult worms of both sexes, approximately 1 900 and 1 400 bases in length. A higher abundance of actin mRNA of both size classes was demonstrated in male worms than in eggs, cercariae, and females. Using a phalloidin-rhodamine conjugate, male worms were observed to contain more actin protein than females. Southern blot-hybridization indicated that the sexual differences in actin mRNA and protein levels were not related to some S. mansoni actin genes being sex linked. In addition, two other trematodes, Schistosoma japonicum and Fasciola hepatica and a cestode, Taenia pisiformis contained two classes of actin mRNA similar in size as those in S. mansoni. In contrast, a turbellarian, Dugesia tigrina contained only a single short actin message size class approximately 1 400 bases in length.