Acquisition of ARRGs
To identify ARRGs, WGCNA was performed with the GSE75011 dataset. Sample clustering analysis showed no outliers in the dataset (Fig. 1A). The β was 4 (Fig. 1B), and each gene module contained a minimum of 100 genes. Three modules were eventually identified, each with a unique color (Fig. 1C-D). The blue module correlated markedly with AR (cor = -0.35, P = 0.03) (Fig. 1D). Finally, 66 ARRGs were gained and utilized for further analysis (Fig. 1E).
Acquisition And Functional Enrichment Of Lmr Degs
The 25 samples were standardized for the GSE75011 dataset and are presented as box plots in Fig. 2A-B. The volcano plot and heatmap show 1621 DEGs between the AR and control groups, including 810 upregulated and 811 downregulated genes (Fig. 2C-D). A total of 73 LMR DEGs (Additional file 2) were obtained by Venn analysis with LMRGs (810 genes) and DEGs (1621 genes), with a significant difference detected based on a heatmap (Fig. 2E-F). Enrichment analysis of the 73 LMR DEGs by Metascape showed a total of 334 functional pathways (Fig. 2G-H) to be related to the LMR DEGs, such as metabolism of lipids, lipid biosynthetic process, and sterol regulatory element-binding protein (SREBP) signaling. DO enrichment results showed that the LMR DEGs are significantly associated with 10 diseases, namely, xanthomatosis, increased serum pyruvate, decreased high-density lipoprotein, hypoalphalipoproteinemia, myoglobinuria, insulin-resistant diabetes, neonatal death, thin skin, myalgia and cardiomegaly (Fig. 2I).
Acquisition Of Hub Genes
The PPI network was created for LMR DEGs. As illustrated in Fig. 3A-B, SREBF1 interacts with multiple proteins, such as LPIN1, GPAM, and MED1. To identify the most important genes, the 22 genes common to the 4 algorithms were used as hub genes (Fig. 3C), and a PPI network of hub genes was created (Fig. 3D). The results showed that GPAM interacts with 7 genes, namely, PPARG, NFYA, SREBF1, ACSL3, LPIN1, HMGCS1 and AACS.
Acquisition Of Diagnostic Genes
Four candidate genes associated with diagnosis of AR were obtained by 66 ARRGs with 22 hub genes taking intersections: LPCAT1, SREBF1, SMARCD3, and SGPP1 (Fig. 4A). The four candidate genes were involved in 133 GO items, including 114 GO BP, 9 GO CC and 10 GO MF, such as retina development in camera-type eye, npBAF complex, and transcription coregulator binding (Fig. 4B).
The diagnostic value of four candidate genes was assessed via ROC curve in GSE75011 and GSE46171. The AUC values for the three genes (LPCAT1, SMARCD3, and SGPP1) were greater than 0.7 in both datasets, suggesting that the three genes have diagnostic value for AR (Fig. 4C-D). The AUCs for age, sex and time point were 0.4492, 0.4839, and 0.7166, respectively, in GSE46171, revealing that sex might be a diagnostic factor for AR (Fig. 4E).
Finally, the nomograms were created containing the three diagnostic genes in GSE75011 and GSE46171 (Fig. 5A-B), and the AUC values in both datasets were above 0.6 (Fig. 5C-D). The results demonstrated that the nomogram has good prediction ability for AR .
Immuno-infiltration Analysis In Ar And Control Groups
Analysis of the percentage of immune cells by ssGESA in all samples showed the highest for T cells (Fig. 6A). Differences in infiltrating immune cells between the AR and control groups were illustrated by a violin plot (Fig. 6B). The results suggested that infiltration of regulatory T cells (TRegs) and T follicular helper cells (TFHs) was markedly lower in the AR group. There was significant relevance between SMARCD3 and TFHs. However, neither LPCAT1 nor SGPP1 correlated with differential immune cells (TRegs and TFHs); therefore, SMARCD3 was selected for further analysis (Fig. 6C-E).
Correlation Analysis Of Clinical Features, Enrichment Analysis And Infiltration Analysis Of Smarcd3
Pearson correlation analysis demonstrated that SMARCD3 was significantly associated with clinical characteristics (age and sex) (Fig. 7A-C). Then, GSEA for SMARCD3 was performed, revealing 256 GO enrichment (Additional file 3) and 33 KEGG (Additional file 4) pathways (Fig. 7D-E). Overall, SMARCD3 was involved in immune-related pathways, for instance, the B-cell receptor signaling pathway and T-cell receptor signaling pathway. Four immune cells displayed marked variations between the high and low expression groups, namely, macrophages, T helper cells, Tcm, and TFH cells, reflecting the strong relevance between SMARCD3 and the immune microenvironment (Fig. 7F).
Mrna Levels Of Diagnostic Genes
The significant differences in expression of SGPP1, LPCAT1 and SMARCD3 between control and AR in GSE75011 and GSE46171 were clearly observed via visualized data (Fig. 8A-B). Moreover, the changes of the three genes expression were consistent in blood and nasal mucosal tissues, suggesting that these three genes are of high diagnostic value.
To verify diagnostic gene expression, we collected blood samples to assess mRNA expression levels of three prognostic genes via RT-qPCR. The expression trends of LPCAT1 and SMARCD3 were consistent with public databases, and the expression was lower in AR group (Fig. 9A-B). However, SGPP1 exhibited the opposite trend compared to the results of public database, possibly due to different experimental designs or analysis methods (Fig. 9C).