Epigenetic Modulation of Host Immunity related genes in Pulmonary Tuberculosis: A Comprehensive Analysis of DNA Methylation Profiles in Peripheral Blood Mononuclear Cells
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Background
In the last few years, there has been increasing evidence in the literature for promoter hypermethylation of various host genes following infection with various pathogens. Therefore, in the present study, the role of epigenetic reprogramming of host cells through DNA methylation was evaluated which indicates that the disease progression takes place through changes in host immune response related genes.
Objective
To elucidate the differential genome-wide DNA methylation profile of peripheral blood mononuclear cells in pulmonary tuberculosis (PTB) patients.
Materials and methods
To decipher the methylation profile of PBMCs in PTB patients whole genome bisulphite sequencing was performed using 4 DNA samples from each study group i.e. PTB, healthy controls and diseased controls. Briefly, the samples were subjected to bisulphite conversion followed by library preparation and whole genome bisulphite sequencing. The data then were analysed for differential methylation analysis followed by gene set enrichment analysis to select DMRs for validation by sanger sequencing. Further the GEOR2 online server was used to investigate the mRNA expression of selected genes associated with hypermethylated DMRs in promoter region.
Results
Differential methylation region analysis was performed for the following comparisons. TB v/s Diseased (Hypermethylated=1756; Hypomethylated=1886), TB v/s Healthy( Hypermethylated=2203; Hypomethylated=2466), Diseased v/s Healthy ( Hypermethylated=1656; Hypomethylated=3936). Further gene set enrichment analysis showed that the hypermetylated regions belonged to genes that are involved in immune responses mainly T cell functioning and T cell mediated immune processes. There were 8 DMR belonging to TAF8,FZD5, HLA-DRB, MIR483, PVRIG, SH2B2, ZAP70, TNFRSF13C simultaneously (n=10 from each study group). mRNA expression analysis with GEOR2 (Datasets used n= 12) revealed significant downregulation of TNFRSF13C, ZAP70, PVRIG Among the selected genes associated with hypermethylated DMRs in promoter region.
(e) Conclusion
The altered differential methylation profile of PBMCs from TB patients shows that on onset the active disease there occurs aberrant methylation of expression regulating regions that in turn results in decreased T cell functions and hence suboptimal immune responses in TB
