Fig 2: Screen of upregulated overlapping DEGs for key genes. (A,B) Top 15 upregulated overlapping DEGs analyzed with the stress (A) and betweenness (B) algorithms of cytoHubba plugin in Cytoscape, shown in yellow, orange, and red in the middle of the circle. Different colors represent different connectivity with other genes in the PPI network. (C) Violin plot of the gene expression analysis of the 15 key genes after eliminating the batch effect of the original analysis. The 15 genes were more highly expressed in IgAN patients than in healthy control subjects (P < 0.01). (D) Screen of the top five key genes based on AUC value in the ROC curve analysis. The ROC plot shows AUC (95% CI), sensitivity, and specificity values for POSTN, GATA3, C1QA, ACAT2, and FGL2. (E) Verification of the five hub genes (POSTN, GATA3, C1QA, ACAT2, and FGL2) in GSE37460 by ROC curve analysis, with AUC (95% CI), sensitivity, and specificity values.

Fig 3: High levels of POSTN enhance the proliferation and suppress apoptosis in MMCs. (A,B) Immunoblot analysis and quantification of POSTN in MMCs treated with indicated concentrations of TGF-β1 for 48 h. (C–I) Immunoblot analysis and quantification of POSTN, BAX, and PCNA in MMCs treated with 20 ng/ml TGF-β1. (H,I) Immunoblot analysis and quantification of BAX and PCNA in MMCs treated with indicated concentrations of recombinant POSTN protein for 24 h. (J) Proliferation of MMCs as detected with the CCK-8 assay. (K) Detection of apoptotic cells with the TUNEL assay. Scale bar: 50 μm. (L,M) siRNA-mediated POSTN knockdown in MMCs. Immunoblot analysis and quantification of POSTN and BAX levels in TGF-β1–treated MMCs after POSTN knockdown. (N) POSTN mRNA level in TGF-β1–treated MMCs after POSTN knockdown. (O,P) Immunoblot analysis and quantification of PCNA in TGF-β1–treated MMCs after POSTN knockdown. (Q,R) Detection of proliferation and apoptosis with the CCK-8 and TUNEL assays, respectively, in TGF-β1–treated MMCs after POSTN knockdown. Scale bar: 50 μm. Data are presented as mean ± SEM (n = 3). *P < 0.05, **P < 0.01.

Fig 4: POSTN is highly expressed in the kidney of IgAN patients and is closely related to renal dysfunction. (A–C) IHC and quantification of POSTN and PCNA in human renal tissue. (D) TUNEL staining of renal tissue samples from IgAN patients and healthy controls. Scale bar: 50 μm. (E,F) Pearson correlation analysis of the correlation between POSTN and creatinine/eGFR. Data are presented as mean ± SEM (IgAN patients, n = 35 and healthy controls, n = 15). **P < 0.01.

Fig 5: Relationship between key modules and clinical features and GO analysis of genes in the key module. (A,B) Scatterplots of GS vs. MM in the royalblue module with creatinine and eGFR of IgAN patients. The correlation between GS and creatinine and eGFR was 0.53 (P = 1.2e−08) and 0.21 (P = 0.035), respectively. POSTN had the highest MM and GS for creatinine (MM = 0.82 and GS = 0.66) and eGFR (MM = 0.82 and GS = −0.67) of all genes in the royalblue module. (C) Heatmap and bar graph of gene expression distribution of 101 genes in the royalblue module. (D) GO analysis of genes in the royalblue module, with threshold count ≥2 and P < 0.05. (E) Only one KEGG pathway (protein digestion and absorption) was enriched for the royalblue module; three additional pathways (ECM–receptor interaction, focal adhesion, and amoebiasis) are shown.