Deciphering cell-specific genetic insights: Unraveling the immunogenetic landscape of systemic lupus erythematosus.

Functional genes within genomic loci associated with systemic lupus erythematosus (SLE), as identified by genome-wide association studies, exhibit cell-specific characteristics. This study delves into the impact of genetic variants within SLE loci on gene expression in different types of immune cells, unraveling the complex interplay between genetics and immunopathogenesis. Through the integration of genetic association and single-cell transcriptomic sequencing data, we identified potential cell-specific susceptibility genes for SLE across diverse immune cell subsets. The single-cell eQTL analysis revealed 30,409 associations involving 3583 SLE-associated SNPs. These SNPs exhibited associations with expression levels of 147 genes across 14 distinct cell types. The single-cell summary data-based Mendelian randomization (SMR) analysis identified 119 significant associations between the expression levels of 44 genes and SLE. Notably, myeloid cells exhibited associations solely within the MHC region, while T, B, and natural killer cells showed associations with both MHC and non-MHC genes in relation to SLE. Analysis of single-cell transcriptomic data from 33 children SLE cases and 11 match controls (227,303 cells), as well as 7 adult SLE cases and 5 match controls (78,414 cells) highlights differential expression of key genes. Notably, genetic variants within HLA-DRB1, HLA-DRB5, HLA-DQA1, HLA-DQB1, IRF7, IRF5, BLK and HLA-DPA1 play a pivotal role in mediating immune dysregulation in specific immune cell types. Our study contributes to a comprehensive understanding of the intricate relationships between genetics, gene expression and SLE susceptibility. The findings shed light on the cell-specific impacts of genetic variants within SLE-associated genomic loci.