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Disease-specific modules and potential hub genes for intervention strategies: A co-expression network-based approach for Plasmodium falciparum clinical isolates

ABSTRACT: Systems biology approaches that are based on gene expression and bioinformatics analysis have been successful in predicting the functions of many genes in Plasmodium falciparum, a protozoan parasite responsible for most of the deaths due to malaria. However, methods that can provide information about the biological processes that are active in this parasite during complicated malaria conditions have not been employed yet. Here, we report the use of a weighted gene co-expression-based network analysis approach to construct a P. falciparum in vivo systems network. Gene expression profiles of 21 P. falciparum clinical isolates were utilized to construct the same. A total of 20 highly interacting modules were identified post network creation, of which at least 10% members of 12 modules were found to be differentially regulated in complicated isolates compared to uncomplicated isolates. Enrichment analysis identified biological processes like oxidation-reduction, electron transport chain, protein synthesis, ubiquitin-dependent catabolic processes, RNA binding and purine nucleotide metabolic processes to be associated with these modules. Additionally, for each module, highly connected hub genes were identified. Detailed functional analysis of many hub genes with known annotated function underline their importance in parasite development and survival, suggesting that other hub genes with unknown function might be playing crucial roles in parasite biology and are potential candidate for intervention strategies.

ORGANISM(S): Plasmodium falciparum

PROVIDER: GSE64931 | GEO | 2016/01/30

SECONDARY ACCESSION(S): PRJNA272530

REPOSITORIES: GEO

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Project description:In temperate and sub-tropical regions of Latin America, complicated malaria manifested as hepatic dysfunction or renal dysfunction is seen in all age groups. There has been a concerted focus on understanding the patho-physiological and molecular basis of complicated malaria in children, much less is known about it in adults. This can be attributed to many factors: one of which is the expression of clonally variant families of adhesion proteins: PfEMP1 on the iRBC surface. We report here, the analysis of data from a custom, cross strain microarray (Agilent Platform) using material from patient samples, showing hepatic dysfunction or renal failure. These are the most common manifestations seen in adults along with cerebral malaria. The data has been analyzed with reference to variable surface antigens, encoded by the var, rifin and stevor gene families. The differential regulation profiles of key genes (comparison of PFC and PFU) have been observed. The exportome has been analyzed using similar parameters. GO term based functional enrichment of differentially regulated genes identified, up-regulated genes stastically enriched (p<0.5) to critical biological processes. Systems network based functional enrichment of overall differentially regulated genes yielded a similar result. We are reporting here, up-regulation of var group A and B genes whose proteins are predicted to interact with CD36 receptor in the host as also the up-regulation of group A rifins and many of the stevors. This is contrary to most other reports from pediatric patients, with cerebral malaria where the up-regulation of var A group genes have been seen. A protein-protein interaction based network has been created and analysis performed. This co-expression and text mining based network has shown overall connectivity between the variable surface antigens and the exportome. The up-regulation of var group B and C genes encoding PfEMP1 with different domain architecture would be important for deciding strategies for disease prevention. Plasmodium falciparum isolates were collected from patients (n=12) with differing clinical conditions. The patients exhibited symptoms categorized as uncomplicated (n=5) or complicated malaria (n=7). Criteria for determination of complicated disease were based on World Health Organization year 2000 guidelines. Microarray array based transcriptional profiling was carried out to find out differentailly expressed genes in complicated malaria isolates (non-cerebral malaria) compared to un-complicated malaria isolates.

Project description:Plasmodium vivax is the most geographically widespread human malaria parasite causing approximately 130-435 million infections annually. It is an economic burden in many parts of the world and poses a public health challenge along with the other Plasmodium sp. The biology of this parasite is very little understood. Emerging evidences of severe complications due to infections by this parasite provides an impetus to focus research on the same. Investigating this parasite directly from the infected patients is the most feasible way to study its biology and any pathogenic mechanisms which may exist. Gene expression studies of this parasite directly obtained from the patients has provided evidence of gene regulation resulting in varying amount of transcript levels in the different blood stages. However, the mechanisms regulating gene expression in malaria parasites are not well understood. Discovery of natural antisense transcripts (NATs) in P. falciparum has suggested that these might play an important role in regulating gene expression. We report here the genome-wide occurrence of NATs in P. vivax parasites from patients with differing clinical symptoms. A total of 1348 NATs against annotated gene loci have been detected using a custom designed strand specific microarray. Majority of NATs identified from this study shows positive correlation with the expression pattern of the sense transcript. Our data also shows condition specific expression patterns of varying S and AS transcript levels. Genes with AS transcripts enrich to various biological processes. This is the first report detailing the presence of NATs from clinical isolates of P. vivax. The data suggests differential regulation of gene expression in diverse clinical conditions and would lead to future detailed investigations of genome regulation. Plasmodium vivax isolates were collected from patients (n = 8) with differing clinical conditions.The patients exhibited symptoms categorized as un-complicated (n =1) or complicated malaria (n = 7). Criteria for determination of complicated disease were based on World Health Organization year 2010 guidelines. Microarray array based transcriptional profiling was carried out to detect prevalence of natural antisense transcripts.

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Project description:Mechanisms regulating gene expression in malaria parasites are not well understood. Little is known about how this parasite regulates its gene expression during transition from one developmental stage to another and in response to various environmental conditions. Parasites in a diseased host face environments which differ from the static, well adapted in vitro conditions in culture. Parasites thus need to adapt quickly and effectively to these conditions by establishing transcriptional states which is best suited for better survival. With the discovery of natural antisense transcripts (NATs) in this parasite and considering the various proposed mechanisms by which NATs might regulate gene expression, it has been speculated that these might be playing a critical role in gene regulation. We report here the diversity of NATs that exist in this parasite, using isolates taken directly from patients with differing clinical symptoms caused by malaria infection. A total of 797 NATs targeted against annotated loci have been detected using a custom designed strand specific microarray. Out of these, 545 are unique to this study. The majority of NATs were positively correlated with the expression pattern of the sense transcript. Many were found to be differentially regulated in response to disease conditions. Antisense transcripts mapped to a wide variety of biochemical/ metabolic pathways, especially pathways pertaining to the central carbon metabolism and stress related pathways. Our data strongly suggests that a large group of NATs detected here are unannotated transcription units antisense to annotated gene models. The results reveal a previously unknown set of NATs that prevails in this parasite, their differential regulation in disease conditions and mapping to functionally well annotated genes. The results detailed here call for studies to deduce the possible mechanism of action, which would help in understanding the in vivo pathological adaptations of these parasites. Plasmodium falciparum isolates were collected from patients (n = 11) with differing clinical conditions.The patients exhibited symptoms categorized as un-complicated (n =2) or complicated malaria (n = 9). Criteria for determination of complicated disease were based on World Health Organization year 2000 guidelines. Microarray array based transcriptional profiling was carried out to detect prevalence of natural antisense transcript.

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Disease-specific modules and potential hub genes for intervention strategies: A co-expression network-based approach for Plasmodium falciparum clinical isolates

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