Genome-wide Association Studies of the Pathogenic Sphingosine-1-Phosphate Gene in Ulcerative Colitis.

Background: Ulcerative colitis (UC) is a chronic inflammatory bowel disease that can lead to malignancies over time. Sphingosine-1-phosphate (S1P) receptor signaling affects lymphocyte trafficking and vascular integrity, influencing intestinal inflammation. This study aimed to identify S1P-related key genes in UC.

Methods: Differentially expressed genes (DEGs) between the UC and control groups were analyzed in the GSE87473 (training) dataset. Genes overlapping between the DEGs and S1P-related genes were considered candidate genes. These genes were incorporated into machine learning algorithms and subjected to expression analysis to identify key genes. Gene functions were determined through a gene-gene interaction network, enrichment analysis, and immune cell infiltration analysis. In addition, transcription factor-mRNA and mRNA-miRNA-lncRNA networks were constructed. Finally, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was performed to evaluate the expression of key candidate genes in UC and control tissues.

Results: This study identified two key genes (SPHK2 and SPNS2) associated with UC. Notably, SPHK2 expression was lower and SPNS2 expression was higher in the UC group in both training and validation datasets and in clinical UC tissues (RT-qPCR). The area under the curve values of SPHK2 and SPNS2 exceeded 0.7 in both datasets, indicating that the genes had good diagnostic efficacy for UC. Consistently, the nomogram showed that the two genes had promising diagnostic value in UC. SPHK2 and SPNS2 were found to be localized to the plasma membrane. The correlations of the two genes with different immune cells showed significantly opposite trends. In particular, SPHK2 had the strongest positive correlation with M2 macrophages (r = 0.6) and the strongest negative correlation with neutrophils. Moreover, mRNA-miRNA-lncRNA and transcription factor- mRNA networks of the key genes were constructed.

Conclusion: This study suggests that SPHK2 and SPNS2 are key genes associated with UC, highlighting their potential as effective diagnostic biomarkers.