A human mutation in STAT3 promotes type 1 diabetes through a defect in CD8+ T cell tolerance

Naturally occurring cases of monogenic type 1 diabetes (T1D) help establish direct mechanisms driving this complex autoimmune disease. A recently identified de novo germline gain-of-function (GOF) mutation in the transcriptional regulator STAT3 was found to cause neonatal T1D. We engineered a novel knock-in mouse incorporating this highly diabetogenic human STAT3 mutation (K392R) and found that these mice recapitulated the human autoimmune diabetes phenotype. Paired single-cell TCR and RNA sequencing revealed that STAT3-GOF drives proliferation and clonal expansion of effector CD8(+) cells that resist terminal exhaustion. Single-cell ATAC-seq showed that these effector T cells are epigenetically distinct and have differential chromatin architecture induced by STAT3-GOF. Analysis of islet TCR clonotypes revealed a CD8(+) cell reacting against known antigen IGRP, and STAT3-GOF in an IGRP-reactive TCR transgenic model demonstrated that STAT3-GOF intrinsic to CD8(+) cells is sufficient to accelerate diabetes onset. Altogether, these findings reveal a diabetogenic CD8(+) T cell response that is restrained in the presence of normal STAT3 activity and drives diabetes pathogenesis.

Automated summary

This study identified a novel germline gain-of-function mutation that causes T1D in CD8+ T cells, with experiments demonstrating the impact of STAT3-GOF on autoimmune diabetes and revealing the pathogenesis of the disease, providing new insights for further research on diabetes.