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Regulation of Trypanosoma brucei total and polysomal mRNA during development within its mammalian host

ABSTRACT: The gene expression of Trypanosoma brucei has been examined extensively in the blood of mammalian hosts and in forms found in the midgut of its arthropod vector, the tsetse fly. However, trypanosomes also undergo development within the mammalian bloodstream as they progress from morphologically ‘slender forms’ to transmissible ‘stumpy forms’ through morphological intermediates. This transition is temporally progressive within the first wave of parasitaemia such that gene expression can be monitored in relatively pure slender and stumpy populations as well as during the progression between these extremes. The development also represents the progression of cells from translationally active forms adapted for proliferation in the host to translationally quiescent forms, adapted for transmission. We have used metabolic labelling to quantitate translational activity in slender forms, stumpy forms and in forms undergoing early differentiation to procyclic forms in vitro. Thereafter we have examined the cohort of total mRNAs that are enriched in throughout development in the mammalian bloodstream (slender, intermediate and stumpy forms), irrespective of strain, revealing those that exhibit consistent developmental regulation rather than sample specific changes. Transcripts that cosediment with polysomes in stumpy forms and slender forms have also been identified to enrich transcripts that escape translational repression prior to transmission. Combined, the expression and polysomal association of transcripts as trypanosomes undergo development in the mammalian bloodstream haves been defined, providing a resource for trypanosome researchers. This facilitates the identification of those that undergo developmental regulation in the bloodstream and therefore those likely to have a role in the survival and capacity for transmission of stumpy forms.

ORGANISM(S): Trypanosoma brucei brucei

PROVIDER: GSE46388 | GEO | 2013/12/16

SECONDARY ACCESSION(S): PRJNA198907

REPOSITORIES: GEO

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Project description:The protozoan parasites Trypanosoma brucei spp. are responsible for important human and livestock diseases in sub Saharan Africa. In the mammalian blood, two developmental forms of the parasite exist: proliferative ?slender? forms and transmissible ?stumpy? forms that are quiescent, awaiting uptake in a tsetse fly bloodmeal. The slender to stumpy differentiation is a density-dependent response that resembles quorum sensing in microbial systems and is crucial for the parasite life cycle, ensuring both infection chronicity and disease transmission. The response is triggered by an elusive ?stumpy induction factor? (SIF) whose intracellular signaling pathway is also completely uncharacterized. Laboratory-adapted (monomorphic) trypanosome strains cannot respond to SIF, but can generate forms with stumpy characteristics when exposed to cell permeable cAMP and AMP analogues. Exploiting this, we have used a genome-wide RNAi library screen to identify the signaling components driving stumpy formation. In separate screens, monomorphic parasites were exposed to cell permeable cAMP or AMP analogues to select cells that remained proliferative and so were unresponsive to these signals. Genome-wide ion torrent-based RNA interference Target sequencing (RIT-seq) identified a cohort of genes implicated in all steps of the signaling pathway, from purine metabolism, through signal transducers (kinases, phosphatases) to gene expression regulators. The identified genes at each step have been validated in cells naturally capable of stumpy formation, confirming their role in SIF-induced density sensing and cellular quiescence. RNA was isolated from AnTat1.1 cells grown in mice with or without doxycycline. RBP7 (Tb927.10.12100) RNAi lines were grown in mice with or without doxycycline. Since the RBP7 RNAi is leaky (six independent cell lines were analysed and all were significantly leaky), transcripts that showed elevated or reduced abundance in both RNAi induced and uninduced populations were identified in comparison to the AnTat1.1 control. A similar approach was adopted for the RBP7 over-expressing lines.

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Regulation of Trypanosoma brucei total and polysomal mRNA during development within its mammalian host

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