Dnmt3amutations limit normal and autoreactive Tfh differentiation

Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation, strongly associated with the activity of autoreactive CD4+ T cells. DNMT3A mutations are the most common somatic mutations found in the hematopoietic system of patients with rheumatoid arthritis. However, the role of DNMT3A in CD4+ T cells and CD4+ T follicular helper (Tfh) cells is poorly understood. Since somatic mutations are not identified in standard genome-wide association studies, somatic mutations’ impact on the etiology of diseases could be underestimated. Here, we thoroughly characterized and used the KRN+ splenocyte transfer model of autoimmune joint inflammation and inactivated Dnmt3a using CRISPR-Cas9 and standard Cre/loxP approaches. Experiments with competitive bone marrow (BM) chimeras identified a positive role for Dnmt3a in Tfh differentiation, which was validated by comparing mice with Dnmt3a mutations in CD4+ cells to animals with WT Dnmt3a . In conclusion, We identify that Dnmt3a mutations limit normal and autoreactive Tfh differentiation. Key findings – Dnmt3a mutations limit Tfh differentiation, which could contribute to reduced immune responses in individuals with somatic DNMT3A mutations. – Deep characterization of the KRN+ splenocyte transfer model defines a dynamic process leading to reproducible autoimmune joint inflammation. – The immuno-CRISPR (iCR) methodology can be used to test the role of candidate genes in disease models.