BK Polyoma Virus Induces Aberrant Methylation of Host Genome to Promote Epithelial Mesenchymal Transition and Fibrosis
Bibliographic record
Abstract
Although most people are infected during early childhood, BK polyoma virus (BKV) reactivates and causes disease primarily in renal transplant patients. BKV is currently the leading cause of graft loss during the first two years after renal transplant. Activation of BKV is associated with inflammation, tissue destruction and progression to fibrosis through a process involving the transformation of epithelial cells in to mesenchymal phenotype. Understanding how BKV causes these changes will help us in better prediction and management of BKV nephropathy. As the primary site of BKV tropism is renal tubular epithelial cells, it needs to device ways to promote the transition and proliferation of these terminally differentiated cells. We hypothesized that BK may activate epigenetic mechanisms to promote these changes by inducing or inhibiting key genes involved in maintaining cellular integrity and stability. DNA CpG methylation is one such epigenetic mechanism which can control gene regulation by causing changes to the DNA which inhibit the accessibility of transcription factors to gene promoters. For our experiments, we have used primary human proximal renal tubular epithelial cells (HPTC) isolated from donor kidneys or procured from ATCC. Cells were infected with BKV for different time points. Real-time expression profiling was done to identify key genes modulated by BKV. Bisulfite conversion and Methylation specific PCR was used to identify specific CpG changes induced by BKV. Sequencing of the bisulfite converted DNA was done to identify the methylation status of entire CpGs islands in the promoters of these genes. Promoter region with specific CpGs was then cloned in pGL3 luciferase reporter vector to specify the role of particular CpGs in regulation and rule out the effect of trans-acting elements. For luciferase assays, CCD1105 KIDtr and HPTC cells were transfected using Lipofectamine- LTX and Plus reagent, infected with BK virus and assayed using Dual luciferase assay. Cell cycle analysis was done using propidium iodide staining and flow cytometry. Infection of renal epithelial cells by BKV caused induction of proinflammatory genes such as Cox-2 and interleukin 1 Beta along with Vimentin which is the marker for epithelial mesenchymal transition. More importantly, it inhibited retinoblastoma (RB1) and E-cadherin (CDH1) genes. We have for the first time identified that BK inhibits these genes by causing hypermethylation of specific CpG islands in their upstream regulatory promoters. These genes are important regulators of cell-cell adhesion (CDH1) and cell cycle (RB1), and their inhibition may lead to loss of adhesion and cell proliferation respectively. Luciferase Reporter assay using cloned RB1 promoter confirmed the involvement of these CpG islands and showed progressive decrease in RB1 promoter activity with increasing BK infection. Our studies also suggest that BKV infection may lead to increased aneuploidy in these cells further contributing to cellular instability and transformation. The changes induced by BKV may ultimately lead to inflammation, cellular proliferation and progression to renal fibrosis and graft loss. Specific CpG methylation patterns induced by BKV may also serve as biomarkers to predict the initiation of BKV nephropathy and help in devising relevant control strategies.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".