Molecular cloning of a Schistosoma mansoni protein expressed in the gynecophoral canal of male worms.

Female members of the species Schistosoma mansoni require continual interaction with males to achieve sexual maturity [1,2]. The nature of the developmental stimuli provided by the adult male parasite are unknown. Aronstein and Strand have reported that the surface expression of an 86-kDa gynecophoral canal protein, SmGCP, is gender-specific in adult S. mansoni [3]. The antigen shows wide distribution on the surface of adult female worms, but in males surface expression is limited to the gynecophoral canal, the site of direct interaction between the mating pair. Expression of the antigen is undetectable or severely diminished in unmated male worms, suggesting a role for this glycoprotein in schistosome mating and/or egg production. We report here the molecular cloning and sequencing of a cDNA clone, SmGCP, which contains a deduced amino acid sequence of 688 residues with a predicted molecular mass of 79 kDa. SmGCP is encoded by a single RNA transcript of 2.4 kb. Enzymatic removal of N-linked glycans from native SmGCP results in a 7-kDa shift in molecular mass as observed by SDS-PAGE. SmGCP contains multiple short, conserved repeat regions with sequence similarity to the developmentally-regulated neural cell adhesion molecule fasciclin I. Although localized to the schistosome surface, SmGCP lacks a convincing transmembrane region. The identification of a gynecophoral canal-specific antigen may have implications for the reproductive development of schistosomes and may provide a novel target for anti-parasite therapeutics.