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Coordinated Changes in Gene Expression Throughout Encystation of Giardia intestinalis
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Microbiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology. Natl Vet Inst, Dept Microbiol, S-75007 Uppsala, Sweden.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology. Univ Kiel, Inst Clin Mol Biol, Kiel, Germany.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
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2016 (English)In: PLoS Neglected Tropical Diseases, ISSN 1935-2727, E-ISSN 1935-2735, Vol. 11, no 3, e0004571Article in journal (Refereed) Published
Abstract [en]

Differentiation into infectious cysts through the process of encystation is crucial for transmission and survival of the intestinal protozoan parasite Giardia intestinalis. Hitherto the majority of studies have focused on the early events, leaving late encystation poorly defined. In order to further study encystation, focusing on the later events, we developed a new encystation protocol that generates a higher yield of mature cysts compared to standard methods. Transcriptome changes during the entire differentiation from trophozoites to cysts were thereafter studied using RNA sequencing (RNA-seq). A high level of periodicity was observed for up-and down-regulated genes, both at the level of the entire transcriptome and putative regulators. This suggests the trajectory of differentiation to be coordinated through developmentally linked gene regulatory activities. Our study identifies a core of 13 genes that are consistently up-regulated during initial encystation. Of these, two constitute previously uncharacterized proteins that we were able to localize to a new type of encystation-specific vesicles. Interestingly, the largest transcriptional changes were seen in the late phase of encystation with the majority of the highly up-regulated genes encoding hypothetical proteins. Several of these were epitope-tagged and localized to further characterize these previously unknown genetic components of encystation and possibly excystation. Finally, we also detected a switch of variant specific surface proteins (VSPs) in the late phase of encystation. This occurred at the same time as nuclear division and DNA replication, suggesting a potential link between the processes.

Place, publisher, year, edition, pages
2016. Vol. 11, no 3, e0004571
National Category
Cell Biology Microbiology
URN: urn:nbn:se:uu:diva-264538DOI: 10.1371/journal.pntd.0004571ISI: 000373272500076OAI: oai:DiVA.org:uu-264538DiVA: diva2:860875
Swedish Research Council, 2012-3364
Available from: 2015-10-14 Created: 2015-10-14 Last updated: 2016-06-20Bibliographically approved
In thesis
1. Comparative Cell Biology in Diplomonads
Open this publication in new window or tab >>Comparative Cell Biology in Diplomonads
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The diplomonads are a diverse group of eukaryotic flagellates found in microaerophilic and anaerobic environments. The most studied diplomonad is the intestinal parasite Giardia intestinalis, which infects a variety of mammals and cause diarrheal disease. Less is known about Spironucleus salmonicida, a parasite of salmonid fish, known to cause systemic infections with high mortality.

We created a transfection system for S. salmonicida to study cellular functions and virulence in detail (Paper I). The system was applied to explore the mitochondrion-related organelle (MRO) in S. salmonicida. We showed that S. salmonicida possesses a hydrogenosome (Paper II) with a higher metabolic capacity than the corresponding MRO of Giardia, the mitosome. Evolutionary analysis of key hydrogenosomal proteins showed ancient origin, indicating their presence in the ancestral diplomonad and subsequent loss in Giardia. Annexins are of evolutionary interest since these proteins are found across all kingdoms. Annexin-like proteins are intriguingly expanded into multigene families in Giardia and Spironucleus. The annexins of S. salmonicida were characterized (Paper III) with distinct localizations to various cellular structures, including a putative adhesion structure anterior in the cell.

The disease-causing Giardia trophozoites differentiate into infectious cysts, a process essential for transmission and virulence of the parasite. Cysts are often spread via contaminated water and exposed to environmental stressors, such as UV irradiation. We studied the survival and transcriptional response to this stress factor (Paper IV) and results showed the importance of active DNA replication machinery for parasite survival after DNA damage. In addition, we studied transcriptional changes along the trajectory of encystation (Paper V), which revealed a coordinated cascade of gene regulation. This was observed for the entire transcriptome as well as putative regulators. Large transcriptional changes appeared late in the process with the majority of differentially regulated genes encoding hypothetical proteins. We studied the localizations of several of these to gain information of their possible function.

To conclude, the diplomonads are complex eukaryotic microbes with cellular processes adjusted to match their life styles. The work in this thesis has provided insight of their adaptations, differences and similarities, but also new interesting leads for future studies of diplomonad biology and virulence. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 84 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1303
Giardia intestinalis, Spironucleus salmonicida, intestinal parasite, hydrogenosome, encystation, gene regulation, transfection, diplomonad, antigenic variation, annexin
National Category
urn:nbn:se:uu:diva-264541 (URN)978-91-554-9374-5 (ISBN)
Public defence
2015-12-04, A1:111a, BMC, Husargatan 3, Uppsala, 09:15 (English)
Available from: 2015-11-12 Created: 2015-10-14 Last updated: 2015-11-13

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Einarsson, ElinTroell, KarinGrabherr, MannfredRibacke, UlfSvärd, Staffan G.
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