Copy Number Variation of HLA-DQA1 and APOBEC3A/3B Contribute to the Susceptibility of Systemic Sclerosis in the Chinese Han Population

Multi-Level Analyses of Genome-Wide Association Study to Reveal Significant Risk Genes and Pathways in Neuromyelitis Optica Spectrum Disorder

Background

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disease of the central nervous system and it is understandable that environmental and genetic factors underlie the etiology of NMOSD. However, the susceptibility genes and associated pathways of NMOSD patients who are AQP4-Ab positive and negative have not been elucidated.

Methods

Secondary analysis from a NMOSD Genome-wide association study (GWAS) dataset originally published in 2018 (215 NMOSD cases and 1244 controls) was conducted to identify potential susceptibility genes and associated pathways in AQP4-positive and negative NMOSD patients, respectively (132 AQP4-positive and 83 AQP4-negative).

Results

In AQP4-positive NMOSD cases, five shared risk genes were obtained at chromosome 6 in AQP4-positive NMOSD cases by using more stringent p-Values in both methods (p < 0.05/16,532), comprising CFB, EHMT2, HLA-DQA1, MSH5, and SLC44A4. Fifty potential susceptibility gene sets were determined and 12 significant KEGG pathways were identified. Sixty-seven biological process pathways, 32 cellular-component pathways, and 29 molecular-function pathways with a p-Value of <0.05 were obtained from the GO annotations of the 128 pathways identified. In the AQP4 negative NMOSD group, no significant genes were obtained by using more stringent p-Values in both methods (p < 0.05/16,485). The 22 potential susceptibility gene sets were determined. There were no shared potential susceptibility genes between the AQP4-positive and negative groups, furthermore, four significant KEGG pathways were also identified. Of the GO annotations of the 165 pathways identified, 99 biological process pathways, 37 cellular-component pathways, and 29 molecular-function pathways with a p-Value of <0.05 were obtained.

Conclusion

The potential molecular mechanism underlying NMOSD may be related to proteins encoded by these novel genes in complements, antigen presentation, and immune regulation. The new results may represent an improved comprehension of the genetic and molecular mechanisms underlying NMOSD.

Autoimmune diseases in China

Autoimmune diseases, such as rheumatoid arthritis, systematic lupus erythematosus and Sjögren's syndrome, are a group of diseases characterized by the activation of immune cells and excessive production of autoantibodies. Although the pathogenesis of these diseases is still not completely understood, studies have shown that multiple factors including genetics, environment and immune responses play important roles in the development and progression of the diseases. In China, there are great achievements in the mechanisms of autoimmune diseases during the last decades. These studies provide new insight to understand the diseases and also shed light on the development of novel therapy.

Genome-Wide DNA Methylation Analysis in Systemic Sclerosis Reveals Hypomethylation of IFN-Associated Genes in CD4+ and CD8+ T Cells

Epigenetic modifications, including DNA methylation, play an important role in the pathogenesis of autoimmune diseases. In this study, we characterized the DNA methylome in primary T cells of patients with systemic sclerosis. Genome-wide DNA methylation assays of CD4⁺ and CD8⁺ T cells from 24 systemic sclerosis patients and 24 matched controls were conducted and differentially methylated regions were validated. In the discovery stage, we found that hypomethylation of genes involved in the type I IFN signaling pathway was significantly enriched in both CD4⁺ (P = 7.59 × 10^-6) and CD8⁺ (P = 2.10 × 10^-8) differentially methylated regions. In the validation stage, we confirmed these changes for five type I IFN-associated genes. In addition, protein levels of both type I IFN-α (P < 0.0001) and β (P = 0.002) were significantly elevated in the sera of systemic sclerosis patients. Moreover, significant associations between type I IFN-α/β protein levels with the DNA methylation status as well as the expression profiles of these IFN-associated genes were confirmed. In conclusion, the type I IFN pathway is dysfunctional at the epigenetic level in systemic sclerosis patients, indicating that hypomethylation and upregulation of type I IFN-associated genes might be critical in systemic sclerosis pathogenesis.