Molecular characterization of Smtdc-1 and Smddc-1 discloses roles as male-competence factors for the sexual maturation of Schistosoma mansoni females

An improved medium for in vitro studies of female reproduction and oviposition in Schistosoma japonicum

BACKGROUND

Schistosomiasis is a disease primarily caused by eggs laid by pathogens called schistosomes. Among the schistosome species infecting humans, Schistosoma japonicum possesses the largest fecundity; each adult female produces an average of 3500 eggs per day. The lack of proper culture conditions supporting continuous oviposition in vitro has precluded detailed investigation of mechanisms regulating sexual maturation and egg production in Schistosoma japonicum.

METHODS

We optimized in vitro culture conditions by replacing reagents that are part of the classical ABC169 medium. Fast Blue BB staining and 4',6-diamidino-2-phenylindole (DAPI) labeling were applied to observe the sexual development status of the females. In vitro RNA interference (RNAi) technology was used to validate the capability of the modified medium. The detection of male β-alanyl-tryptamine (BATT) was conducted using liquid chromatography-mass spectrometry (LC-MS).

RESULTS

Both m-AB169 (1640) and AB169 (1640) media are capable of facilitating the sexual development of paired virgin female S. japonicum, as well as sustaining the mature reproductive organs and egg production of adult S. japonicum for at least 22 days in vitro. M-AB169 (1640) provided a more stable condition for supporting the sexual maturity of female S. japonicum, as evidenced by the consistent initiation of egg production compared with AB169 (1640). Through a comparative analysis of S. japonicum and S. mansoni in diverse media, we demonstrated that these closely related species display distinct demands for their sexual development and egg production, suggesting a potential influence of nutritional factors on the observed variations in host ranges among different schistosome species. Importantly, we successfully identified the presence of the pheromone β-alanyl-tryptamine (BATT) in S. japonicum, previously identified in S. mansoni, highlighting its conserved role in schistosome reproductive development. Through the employment of double-stranded RNA (dsRNA) treatment to silence two genes that are involved in either the male (gli1, glioma-associated oncogene homolog 1) or female (vf1, vitellogenic factor 1) side in male-induced female reproductive development of S. mansoni, we confirmed that the combination of m-AB169 (1640) and RNAi technology has the capacity to facilitate in vitro studies of S. japonicum's reproductive and oviposition processes.

CONCLUSIONS

We developed a novel medium, m-AB169 (1640), that not only maintains the mature reproductive organs and continuous oviposition of adult female Schistosoma japonicum for up to 22 days but also supports the reproductive development and subsequent egg-laying of virgin females after pairing with male worms. This study provides a valuable in vitro platform for functional studies of the mechanisms underlying the fascinating biology of the female sexual development and egg production of S. japonicum, which may accelerate the development of new strategies targeting schistosome egg production.

Rhodopsin orphan GPCR20 interacts with neuropeptides and directs growth, sexual differentiation, and egg production in female Schistosoma mansoni

IMPORTANCE

Schistosomes cause schistosomiasis, one of the neglected tropical diseases as defined by the WHO. For decades, the treatment of schistosomiasis relies on a single drug, praziquantel. Due to its wide use, there is justified fear of resistance against this drug, and a vaccine is not available. Besides its biological relevance in signal transduction processes, the class of G protein-coupled receptors (GPCRs) is also well suited for drug design. Against this background, we characterized one GPCR of Schistosoma mansoni, SmGPCR20, at the molecular and functional level. We identified two potential neuropeptides (NPPs) as ligands, SmNPP26 and SmNPP40, and unraveled their roles, in combination with SmGPCR20, in neuronal processes controlling egg production, oogenesis, and growth of S. mansoni females. Since eggs are closely associated with the pathogenesis of schistosomiasis, our results contribute to the understanding of processes leading to egg production in schistosomes, which is under the control of pairing in this exceptional parasite.