Identification and first characterization of pairing-dependently transcribed genes in Schistosoma mansoni males
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Schistosoma mansoni males have a key role in the unique reproduction biology of these parasitic flatworms. Without a constant pairing contact to the male the female is unable to complete or maintain its sexual maturation, which is the prerequisite for egg production. The eggs themselves are the causative agent of a disease with world-wide importance: schistosomiasis. Little is known about the process by which males affect female development. Different types of molecules have been suggested as stimulus but none was identified so far. It was also hypothesized that males are influenced by pairing as well, obtaining a status of competence which enables them to induce female sexual maturation. Again, only scarce information is available on such processes in males. EST and genome projects for schistosomes have opened new possibilities to study these male mechanisms also on the transcriptome level. The here described study was performed to identify differences between pairing-experienced (EM) and pairing-unexperienced (UM) males.Preliminary experiments had indicated a stimulatory effect of pairing and tumor necrosis factor alpha (TNFalpha) on the mitotic activity (MA) in males. Furthermore, evidence was provided for the differential expression of a S. mansoni cGMP-dependent protein kinase (SmcGK1) between EM and UM. While the effect of pairing on the MA of males was not confirmed by results obtained in this thesis, a concentration and medium-dependent stimulation of MA in males as response to TNF& #945; was observed. SmcGK1 was not found to be differentially transcribed between EM and UM. However, localization studies detected SmcGK1 transcripts in the reproductive organs of male and female worms, and inhibitor studies indicated an influence of SmcGK1 on worm motility and egg production.To unravel differences between EM and UM on a larger scale, the transcriptomes of these two male stages were compared combining two different methods, microarrays and SuperSAGE. As expected, both methods confirmed and complement each other. Additional confirmation of the results was obtained by real-time PCR experiments. Usage of bioinformatic tools such as gene ontology analysis, Ingenuity Pathway Analysis and schistosome-specific metabolome analysis facilitated data interpretation. Different statistical analyses were used and their influence on the data was emphasized.Microarray analyses and SuperSAGE detected 9,344 and 7,494 sense transcripts, respectively. Merging both data-sets it was found that 6,326 transcripts were detected by both analyses, of which 29 were significantly differentially (q < 0.01; p < 1-10; log2ratios > 0.585 or < -0.585) transcribed between EM and UM. To date, this is the most comprehensive data-set on differential transcription in male S. mansoni. The data indicated differences in metabolic processes between EM and UM, confirming previous hypotheses. Beyond that evidence was obtained for the contribution of neuronal signaling, anti-sense regulation and schistosome-specific protein coding genes, in the male-female interaction. Genes protruding from the analyses were among others, a dopa-decarboxylase, the signaling molecules dock and pinch, and the TGFbeta-pathway inhibitor follistatin (SmFst). First characterization studies provided evidence for SmFst transcription in the reproductive organs of EM, UM and females. Furthermore, the interaction of SmFst with an inhibin/activin-like protein (SmInAct) and a bone morphogenic protein (SmBMP) of S. mansoni was shown by yeast-two-hybrid experiments. Localization studies demonstrated that all three transcripts localize in the testes of EM and UM. These findings indicate a yet unknown function of the TGFbeta-pathway in male schistosomes and a possible influence of pairing on the male gonad.Verknüpfung zu Publikationen oder weiteren Datensätzen
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