Risk Allele rs117026326-Mediated Alternative Splicing of GTF2I Promotes B Cell Proliferation in Primary Sjögren's Syndrome.

Objectives

Primary Sjögren's syndrome (pSS) is associated with a risk allele T of rs117026326 located at a potential splicing enhancer within the intronic region of general transcription factor II-I (GTF2I). This study aimed to explore the rs117026326-regulated alternative splicing of GTF2I and its role in B cell overactivation in pSS.

Methods

GTF2I isoform expressions and rs117026326 genotypes of pSS peripheral blood mononuclear cells (PBMCs) were examined using quantitative PCR and Sanger sequencing, respectively. GTF2IΔ was overexpressed in B cells, T cells, and macrophages using plasmid transfection. Proliferation of B cells and T cells was determined using Cell Counting Kit-8 (CCK8) assay. CD4+ T cell differentiation was inspected using flow cytometry. Proinflammatory cytokine production of macrophages was investigated using quantitative PCR. c-FOS expression in GTF2IΔ-transfected B cells was tested by quantitative PCR, and proliferation of GTF2IΔ-transfected B cells treated with c-FOS siRNA or c-FOS inhibitor was interrogated using CCK8 assay.

Results

pSS patients with risk allele of rs117026326 expressed higher levels of GTF2IΔ and GTF2Iζ isoforms. GTF2IΔ expression was correlated with serum immunoglobulin G (IgG). GTF2IΔ promoted B cell proliferation and upregulated c-FOS expression. Knocking down or inhibition of c-FOS reversed B cell proliferation driven by GTF2IΔ.

Conclusion

pSS risk allele of rs117026326 modulates alternative splicing of GTF2I and upregulates GTF2IΔ isoform, which promotes B cell proliferation through enhancing binding and transcription of c-FOS.