Mutually Exclusive Transcription of Subtelomeric Gene Families in Plasmodium falciparum is Restricted to var Genes
Ontology highlight
ABSTRACT:
ORGANISM(S): Plasmodium falciparum
SUBMITTER: Yen Hoon Luah
PROVIDER: E-GEOD-31829 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
Similar Datasets
Project description:The P. falciparum genome is equipped with several subtelomeric gene families that are implicated in parasite virulence and immune evasion. The members of these gene families are uniformly positioned within heterochromatic domains of the genome and are thus subject to variegated expression. The best-studied example is that of the var gene family encoding the major parasite virulence factor P. falciparum erythrocyte membrane protein 1 (PfEMP1). Transcriptional regulation of other subtelomeric gene families and their role in parasite biology is much less understood. Here, we investigated the mode of transcriptional control of var, rif, stevor, phist and pfmc-2tm families by comparative genome-wide transcriptional profiling of transgenic parasite lines. Our results establish a clear functional distinction between var and non-var transcriptional control mechanisms. Unlike var promoters, we find that promoters of non-var families are not silenced by default. Moreover, we show that mutually exclusive transcription is unique to the var gene family.
2011-09-02 | GSE31829 | GEO
Project description:The var multigene family encodes clonally variant surface antigens that are key to immune evasion and pathogenesis in the human malaria parasite, Plasmodium falciparum. Epigenetics and nuclear organization regulate the var gene family in a system of mutually exclusive expression; however, few factors have been shown to play a direct role in these processes. Thus, we adapted a CRISPR-based immunoprecipitation-mass spectrometry approach for identification of novel factors associated with var genes in their natural chromatin context. A tagged, catalytically inactive Cas9 (“dCas9”) was targeted to the promoters or introns of a subset of var genes and subjected to immunoprecipitation followed by label-free LC-MS/MS. A non-targeted dCas9 served as a control.
2020-07-15 | PXD013131 | Pride
Project description:Background: The cytoadherence of Plasmodium falciparum is thought to be mediated by variant surface antigens (VSA), encoded by var, rif, stevor and pfmc-2tm genes. The last three families have rarely been studied in the context of cytoadherence. As most VSA genes are unique, the variability among sequences has impeded the functional study of VSA across different P. falciparum strains. However, many P. falciparum genomes have recently been sequenced, allowing the development of specific microarray probes to each VSA gene. Methods: All VSA sequences from the HB3, Dd2 and IT/FCR3 genomes were extracted using HMMer. Oligonucleotide probes were designed with OligoRankPick and added to the 3D7-based microarray chip. As a proof of concept, IT/R29 parasites were selected for and against rosette formation and the transcriptomes of isogenic rosetting and non-rosetting parasites were compared by microarray. Results: From each parasite strain 50-56 var genes, 125-132 rif genes, 26-33 stevor genes and 3-8 pfmc-2tm genes were identified. The ability of the VSA-supplemented microarray chip to detect cytoadherence-related genes was assessed using P. falciparum clone IT/R29, in which rosetting is known to be mediated by PfEMP1 encoded by ITvar9. Whole transcriptome analysis showed that the most highly upregulated gene in rosetting parasites was ITvar9 (19 to 429-fold upregulated over six time points). Only one rif gene (IT4rifA_042) was upregulated by more than 4-fold (5-fold at 12 hours post-invasion), and no stevor or pfmc-2tm genes were upregulated by more than 2-fold. 49 non-VSA genes were upregulated in rosetting parasites by more than 3-fold in at least two time-points, although none as markedly as ITvar9. Conclusions: We demonstrate that the VSA of newly sequenced P. falciparum strains can be added to the 3D7-based microarray chip, allowing the analysis of the entire transcriptome of multiple strains. For the rosetting clone IT/R29, the striking transcriptional upregulation of ITvar9 was confirmed, and the data did not support the involvement of other VSA families in rosette formation. Plasmodium falciparum parasites, strain IT/R29, were selected for (R29R+) or against (R29R-) rosetting. Both cultures (R29R+ and R29R-) were tightly synchronised before a timecourse experiment was performed. 6 samples, named time points 1 to 6, were taken every 8 hours. 12μg of RNA from the R29 non-rosetting parasites at each of the 6 time points was combined together to form the reference pool. The pool and 12μg of each individual time point sample from both rosetting and non-rosetting parasites were then used for cDNA synthesis. For microarray hybridizations,each cDNA sample was coupled to Cy5 (red dye) while Cy3 (green dye) was added to the pool. Cy5-labelled time point samples were mixed with the same amount of Cy3-labelled pool sample. The solution was loaded on a microarray slide and hybridized for 14–16 h.
2011-07-01 | E-GEOD-28990 | biostudies-arrayexpress
Project description:The pir genes comprise the largest multi-gene family in Plasmodium, with members found in P. vivax, P. knowlesi and the rodent malaria species. Despite comprising up to 5% of the parasite genome, little is known about the functions of the proteins encoded by pir genes. P. chabaudi causes chronic infection in mice, which may be due antigenic variation. In this model, pir genes are called cirs and may be involved in this mechanism allowing evasion of host immune responses. We have annotated the cir repertoire and performed detailed bioinformatic characterization of the encoded CIR proteins. Two major sub-families were identified: A and B, which display different amino acid motifs, and are thus predicted to have undergone functional divergence. The expression of all cirs was analyzed via RNA sequencing and microarray. Up to 40% of cir genes were expressed in the parasite population during infection, including members of both sub-families. Dominant cir transcripts could also be identified. Finally, specific cir genes were expressed at different time points during the blood stages of infection. Together our data characterizing the cir genes and their expression throughout the intra-erythrocytic cycle of development indicate that CIR proteins are likely to be important for parasite survival in the host. P. chabaudi AS is a highly synchronous parasite for which development in the blood follows its hostM-bM-^@M-^Ys circadian rhythm. Twelve time-points were then collected; one every two hours, to cover the entire 24 h cycle of blood stage development. At the peak of parasitaemia, one mouse was sacrificed at each time point and thin blood films were made and stained with Giemsa for optical microscopy. The pan-rodent microarray was designed using the OligoRankPick program as previously described: Liew, K et al.2010, Defining species specific genome differences in malaria parasites. BMC genomics 11,128. The RNA preparation, Cy-dye coupling to cDNA, hybridization and slide scanning were performed as described by Bozdech and colleagues Bozdech, Z et al 2003, The transcriptome of the intraerythrocytic developmental cycle of Plasmodium falciparum. PLoS Biol 1, E5.
2012-05-31 | E-GEOD-33333 | biostudies-arrayexpress
Project description:The process of erythrocyte invasion by merozoites of Plasmodium falciparum involves multiple steps, including the formation of a moving junction characterized by the redundancy of many of the receptor-ligand interactions involved. Several of the parasite proteins that interact with erythrocyte receptors or participate in other steps of the process of invasion are encoded by small subtelomerically-located multigene families of four to seven members. We report here that members of the multigene families pfRh, eba, rhopH1/clag and acbp exist in either an active or a silenced state. In the case of two members of the rhopH1/clag family, clag3.1 and clag3.2, expression was mutually exclusive. Silencing occurred in the absence of detectable DNA alterations, suggesting that it is transmitted epigenetically. This was unambiguously demonstrated for eba-140, which was silenced by the formation of facultative heterochromatin. Our data demonstrate that variant expression, epigenetic silencing and mutually exclusive expression in Plasmodium are not unique to genes encoding proteins exported to the surface of the erythrocyte like var genes but also occur for genes involved in host cell invasion..
2007-11-26 | E-SGRP-9 | biostudies-arrayexpress
Project description:Plasmodium multigene families are thought to play important roles in the pathogenesis of malaria. Plasmodium interspersed repeat (pir) genes comprise the largest multigene family in many Plasmodium species. However, their expression pattern and localisation remain to be elucidated. Protein subcellular localisation is fundamental to be able to elucidate the functional importance and cell-cell interactions of the PIR proteins. Here, we use the rodent malaria parasite, Plasmodium chabaudi chabaudi, as a model to investigate the localisation pattern of this gene family. We found that most PIR proteins are co-expressed in clusters during acute and chronic infection; members of the S7 clade are predominantly expressed during the acute-phase, whereas members of the L1 clade dominate the chronic-phase of infection. Using peptide antisera specific for S7 or L1 PIRS, we show that S7 and L1 PIRs have different localisations within the infected red blood cells. S7 PIRs are exported into the infected red blood cells cytoplasm where they are co-localised with parasite-induced host cell modifications termed Maurer's clefts, whereas L1 PIRs are localised on or close to the parasitophorous vacuolar membrane. This localisation pattern changes following mosquito transmission and during progression from acute- to chronic-phase of infection. However, neither S7 nor L1 PIR proteins detected by the peptide antisera are localised on the surface of infected red blood cells, suggesting that they are unlikely to be targets of surface variant-specific antibodies or be involved directly in adhesion of infected red blood cells to host cells, as described for Plasmodium falciparum VAR proteins. Their presence on Maurer’s clefts, as seen for Plasmodium falciparum RIFIN and STEVOR proteins, might further suggest trafficking of the PIRs on the surface of the infected erythrocytes. The differences in subcellular localisation of the two major clades of Plasmodium chabaudi PIRs across the blood cycle, and the apparent lack of expression on the red cell surface strongly suggest that the function(s) of this gene family may differ from those of other multigene families of Plasmodium, such as the var genes of Plasmodium falciparum.
2022-06-14 | PXD031586 | Pride
Project description:Variant antigens that are encoded by large multigene families play an important role in the adaptation and immune evasion of a wide range of pathogens. However, the study of their biological function is significantly hampered by the difficulty in controlling their expression in its cellular setting. The genomes of Plasmodium spp. encode a number of different multigene families that are thought to play a critical role for their survival. However, with the exception of the P. falciparum var genes very little is known about the biological roles of any of the other multigene families. Here we report a highly efficient genetic system to study variant antigens in Plasmodium spp. using the Selection Linked Integration method; we are able to activate the expression of a single member of a multigene of our choice using its endogenous promoter.
2020-07-03 | GSE152162 | GEO
Project description:The increasing spread of drug-resistant malaria strains underscores the need for new antimalarial agents with novel modes of action (MOAs). Here, we describe a compound representative of a new class of antimalarials. This molecule, ACT-213615, potently inhibits in vitro erythrocytic growth of all tested Plasmodium falciparum strains, irrespective of their drug resistance properties, with IC(50) values in the low single-digit nanomolar range. Like the clinically used artemisinins, the compound equally and very rapidly affects all three asexual erythrocytic parasite stages. In contrast, microarray studies suggest that the MOA of ACT-213615 is different from that of the artemisinins and other known antimalarials. ACT-213615 is orally bioavailable in mice, exhibits activity in the murine P. berghei model and efficacy comparable to that of the reference drug chloroquine in the recently established P. falciparum SCID mouse model.ACT-213615 represents a new class of potent antimalarials that merits further investigation for its clinical potential. Histone deacetylase (HDACs) inhibitors are being intensively pursued as potential new antimalarial drugs, and are also emerging as valuable tools for investigating transcriptional control in malaria parasites. In this study, the genome-wide transcriptional effects of three structurally related hydroxamate HDAC inhibitors were profiled in Plasmodium falciparum, the most lethal of the malaria parasite species that infects humans. Trophozoite-stage P. falciparum cells were treated with ACT-213615 for increasing amount of time at IC50 concentration and cells were harvested in parralled with DMSO treated controls for microarray-based transcriptional profiling.
2012-07-19 | E-GEOD-39485 | biostudies-arrayexpress
Project description:Quantitative studies of the P. falciparum transcriptome have shown that the tightly controlled progression of the parasite through the intraerythrocytic developmental cycle (IDC) is accompanied by a continuous gene expression cascade where most expressed genes exhibit a single transcriptional peak. Since proteins represent the decisive business end of gene expression, understanding the correlation between mRNA and protein levels is crucial for inferring biological activity from transcriptional gene expression data. While pertinent studies on other organisms show that as little as 20-40% of protein abundance variation may be attributable to corresponding mRNA levels, the situation in Plasmodium is further complicated by the dynamic nature of the cyclic gene expression cascade where the mRNA levels of most genes change constantly during the IDC. In this study, we simultaneously determined mRNA and protein abundance profiles for P. falciparum parasites during the IDC at 2-hour resolution based on spotted oligonucleotide microarrays and 2D-protein gels in combination with DIGE fluorescent dyes. Intriguingly, most proteins are represented by more than one isoform, presumably due to post-translational modifications. Analysis of 366 protein abundance profiles and the corresponding mRNA levels shows that in 67.2% of cases the protein abundance peaks at least 8 hours after the mRNA level peak. While it may be tempting to interpret this as evidence for widespread post-transcriptional gene regulation additional analyses including computer modeling demonstrate that in >60% of these cases the observed protein profiles including the peak lag times could arise as a consequence of the corresponding mRNA levels when simple translation and degradation dynamics are assumed. We further characterize and illustrate these dynamics and show that even human host proteins within the parasite may be subject to similar dynamics as their parasite counterparts. 24 timepoint samples were harvested from a tightly synchronous 6.5 liter biofermenter culture of P. falciparum (Dd2) at 2-hour intervals during one entire intraerythrocytic developmental cycle and compared against a 3D7 RNA reference pool.
2011-06-07 | E-GEOD-24416 | biostudies-arrayexpress
Project description:Background: Malaria is a one of the most important infectious diseases and is caused by parasitic protozoa of the genus Plasmodium. Previously, the quantitative characterization of the P. falciparum transcriptome demonstrated that the strictly controlled progression of these parasites through their intra-erythrocytic developmental cycle is accompanied by a continuous cascade of gene expression. Although such analyses have proven immensely useful, the precise correlations between transcript and protein abundance remain under-scrutinized. Results: Here, we present a quantitative time-course analysis of relative protein abundance for schizont-stage parasites (34-46 hours post-invasion) based on 2D-gel electrophoresis of protein samples labeled with DIGE fluorescent dyes. For this purpose we analyzed parasite samples taken at four-hour intervals from a tightly synchronized culture and established more than 500 individual protein abundance profiles with high temporal resolution and quantitative reproducibility. Approximately half of all profiles exhibit a significant change in abundance and 12% display an expression peak during the observed 12-hour time interval. Intriguingly, identification of 54 protein spots by mass spectrometry revealed that 58% of the corresponding proteins including actin-I, enolase, eIF4A, eIF5A, and several heat shock proteins are represented by more than one isoform, presumably due to post-translational modifications, with the various isoforms of a given protein frequently showing different expression patterns. Furthermore, comparisons with transcriptome data generated from the same parasite samples reveal significant post-transcriptional gene expression regulation. Conclusions: Together, our data indicate that both post-transcriptional and post-translational events are widespread and of presumably great biological significance during the intra-erythrocytic development of P. falciparum. Additional comment: In essence, the microarray data generated in this study is a repeat of the transcriptome analysis described in Bozdech et al., PLoS Biol 2003, 1(1):E5. Differences include (1) an improved set of oligonucleotides [see Hu et al., BMC Bioinformatics 2007, 8:350] used in the study associated with this GEO entry, and (2) the sampling at only four timepoints during the intra-erythrocytic development cycle (schizont stage) to match and complement the samples processed in the concomitant proteomics analysis. Four timepoint samples were harvested from a tightly synchronized 6 liter biofermenter culture of P. falciparum during schizont stage (at 34, 38, 42, and 46 hours post-invasion) and compared against a 3D7 RNA reference pool.
2010-05-05 | E-GEOD-13251 | biostudies-arrayexpress