Selective Condensation Drives Partitioning and Sequential Secretion of Cyst Wall Proteins in Differentiating Giardia lamblia

Konrad, Christian; Spycher, Cornelia; Hehl, Adrian B.

doi:10.1371/journal.ppat.1000835

Cited by 54 publications

(108 citation statements)

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“…At the same time, cyst wall components are being produced and transported to the periphery of the cell, a process that appears to be independent from, albeit simultaneous with, the nuclear division (Stefanic et al, 2009). In addition, although trophozoites in the early stages of encystation display larger rounded ESVs, by the time the nuclear division takes place, the cyst wall components have been transported to the periphery of the cell and exist in a more diffuse network, as previously reported (Konrad et al, 2010).…”

Section: Nuclei Are Inherited In Non-identical Pairssupporting

confidence: 63%

Nuclear Inheritance and Genetic Exchange without Meiosis in the Binucleate ParasiteGiardia intestinalis

Carpenter

Assaf

Gourguechon

et al. 2012

Journal of Cell Science

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SummaryThe protozoan parasite Giardia intestinalis (also known as Giardia lamblia) is a major waterborne pathogen. During its life cycle, Giardia alternates between the actively growing trophozoite, which has two diploid nuclei with low levels of allelic heterozygosity, and the infectious cyst, which has four nuclei and a tough outer wall. Although the formation of the cyst wall has been studied extensively, we still lack basic knowledge about many fundamental aspects of the cyst, including the sources of the four nuclei and their distribution during the transformation from cyst into trophozoite. In this study, we tracked the identities of the nuclei in the trophozoite and cyst using integrated nuclear markers and immunofluorescence staining. We demonstrate that the cyst is formed from a single trophozoite by a mitotic division without cytokinesis and not by the fusion of two trophozoites. During excystation, the cell completes cytokinesis to form two daughter trophozoites. The non-identical nuclear pairs derived from the parent trophozoite remain associated in the cyst and are distributed to daughter cells during excystation as pairs. Thus, nuclear sorting (such that each daughter cell receives a pair of identical nuclei) does not appear to be a mechanism by which Giardia reduces heterozygosity between its nuclei. Rather, we show that the cyst nuclei exchange chromosomal genetic material, perhaps as a way to reduce heterozygosity in the absence of meiosis and sex, which have not been described in Giardia. These results shed light on fundamental aspects of the Giardia life cycle and have implications for our understanding of the population genetics and cell biology of this binucleate parasite.

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Section: Nuclei Are Inherited In Non-identical Pairssupporting

confidence: 63%

Nuclear Inheritance and Genetic Exchange without Meiosis in the Binucleate ParasiteGiardia intestinalis

Carpenter

Assaf

Gourguechon

et al. 2012

Journal of Cell Science

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“…The cyst/ oocyst wall plays a key role by forming a highly resistant barrier to a large set of physicochemical stressors and by, at the same time, exhibiting surface properties involved in parasite-particle interactions (7,23,30,101). Though the biochemical composition and molecular architecture of their respective outer walls differ greatly (14,47,57,64,76,89,91) (Fig. 1), these three parasites could undergo similar surface interactions with their surrounding world due to their biophysical features (Table 1).…”

mentioning

confidence: 99%

“…described macromolecules composing the cyst/oocyst wall surface has been recently extended (57,64,76,91).…”

mentioning

confidence: 99%

Interaction Forces Drive the Environmental Transmission of Pathogenic Protozoa

Dumètre

Aubert

Puech

et al. 2012

Appl Environ Microbiol

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The protozoan parasites Giardia duodenalis, Cryptosporidium spp., and Toxoplasma gondii are pathogens that are resistant to a number of environmental factors and pose significant risks to public health worldwide. Their environmental transmission is closely governed by the physicochemical properties of their cysts (Giardia) and oocysts (Cryptosporidium and Toxoplasma), allowing their transport, retention, and survival for months in water, soil, vegetables, and mollusks, which are the main reservoirs for human infection. Importantly, the cyst/oocyst wall plays a key role in that regard by exhibiting a complex polymeric coverage that determines the charge and hydrophobic characteristics of parasites' surfaces. Interaction forces between parasites and other environmental particles may be, in a first approximation, evaluated following the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloidal stability. However, due to the molecular topography and nano-to microstructure of the cyst/oocyst surface, non-DVLO hydrophobic forces together with additional steric attractive and/or repulsive forces may play a pivotal role in controlling the parasite behavior when the organism is subjected to various external conditions. Here, we review several parameters that enhance or hinder the adhesion of parasites to other particles and surfaces and address the role of fast-emerging techniques for mapping the cyst/oocyst surface, e.g., by measuring its topology and the generated interaction forces at the nano-to microscale. We discuss why characterizing these interactions could be a crucial step for managing the environmental matrices at risk of microbial pollution.

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“…Synthesis and export of the cyst wall proteins (CWPs) to specialized organelles, termed encystation-specific vesicles (ESVs), is completed between 8 and 10 h postinduction (p.i.). After proteolytic cleavage of the CWP2 C terminus, the CWPs are sorted into two fractions which are deposited sequentially and polymerize on the surface of the cyst (18). The first layer of the CW, which eventually completely encloses the parasite (19,24), is secreted in the last minutes of differentiation simultaneously with nuclear division and morphological transformation of the cell (cyst formation).…”

mentioning

confidence: 99%

The Transcriptional Response to Encystation Stimuli in Giardia lamblia Is Restricted to a Small Set of Genes

Morf

Spycher

Rehrauer³

et al. 2010

Eukaryot Cell

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The protozoan parasite Giardia lamblia undergoes stage differentiation in the small intestine of the host to an environmentally resistant and infectious cyst. Encystation involves the secretion of an extracellular matrix comprised of cyst wall proteins (CWPs) and a ␤(1-3)-GalNAc homopolymer. Upon the induction of encystation, genes coding for CWPs are switched on, and mRNAs coding for a Myb transcription factor and enzymes involved in cyst wall glycan synthesis are upregulated. Encystation in vitro is triggered by several protocols, which call for changes in bile concentrations or availability of lipids, and elevated pH. However, the conditions for induction are not standardized and we predicted significant protocol-specific side effects. This makes reliable identification of encystation factors difficult. Here, we exploited the possibility of inducing encystation with two different protocols, which we show to be equally effective, for a comparative mRNA profile analysis. The standard encystation protocol induced a bipartite transcriptional response with surprisingly minor involvement of stress genes. A comparative analysis revealed a core set of only 18 encystation genes and showed that a majority of genes was indeed upregulated as a side effect of inducing conditions. We also established a Myb binding sequence as a signature motif in encystation promoters, suggesting coordinated regulation of these factors.The differentiation of Giardia lamblia cells to cysts is a key step in the simple life cycle of this ubiquitous intestinal parasite. Induced trophozoites, the flagellated, motile, and attachment-competent stage, exit the cell cycle at the G 2 -M transition (1) and begin to synthesize the components of an extracellular matrix, the cyst wall (CW). Synthesis and export of the cyst wall proteins (CWPs) to specialized organelles, termed encystation-specific vesicles (ESVs), is completed between 8 and 10 h postinduction (p.i.). After proteolytic cleavage of the CWP2 C terminus, the CWPs are sorted into two fractions which are deposited sequentially and polymerize on the surface of the cyst (18). The first layer of the CW, which eventually completely encloses the parasite (19,24), is secreted in the last minutes of differentiation simultaneously with nuclear division and morphological transformation of the cell (cyst formation). In vitro, the entire encystation process typically takes 20 to 24 h in our hands and can be induced by modifying medium components and/or the concentrations of bile, fatty acids (cholesterol), or lactic acid (3,10,15,22). Because the condition(s) which induce encystation in vivo are not known, all factors and components mentioned above are implicated since their concentrations vary in the small intestine, as does the pH, which increases from ϳ6 in the duodenum to 7.5 to 8.0 in the distal ileum. Although all available data indicate that differentiation is induced by one or several environmental signals, the mechanism(s) for reception and transduction have not been characterized. Upregulation...

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Selective Condensation Drives Partitioning and Sequential Secretion of Cyst Wall Proteins in Differentiating Giardia lamblia

Cited by 54 publications

References 50 publications

Nuclear Inheritance and Genetic Exchange without Meiosis in the Binucleate ParasiteGiardia intestinalis

Nuclear Inheritance and Genetic Exchange without Meiosis in the Binucleate ParasiteGiardia intestinalis

Interaction Forces Drive the Environmental Transmission of Pathogenic Protozoa

The Transcriptional Response to Encystation Stimuli in Giardia lamblia Is Restricted to a Small Set of Genes

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