SummaryLong intergenic noncoding RNAs (lincRNAs) regulate biological processes in health and disease. Recent findings highlight the importance of lincRNAs in regulating T cell development and function. Here, we identified a lincRNA, LINC01871, which is highly induced upon CD4+ T cell activation and is predominantly located in the cytoplasm. The anti-inflammatory cytokine TGF-β was found to suppress its expression. Silencing LINC01871 led to a modest decrease in IL-2 secretion. Notably, LINC01871 expression was highly specific to NK cells and T cells in several cross-tissue single cell RNA-seq atlases. These data suggest that LINC01871 is specifically expressed in T and NK cells and may contribute to T cell-mediated immunity in humans. Graphical abstract Highlights•LINC01871 is a cytoplasmic lincRNA induced upon CD4+ T cell activation•TGF-β negatively regulates LINC01871 expression•Expression of LINC01871 is restricted to effector and memory T and NK cells Immunology; Molecular biology; Cell biology

Enhancers and transcription factors (TFs) are crucial in regulating cellular processes. Current multiomic technologies to study these elements in gene regulatory mechanisms lack multiplexing capability and scalability. Here we present single-cell ultra-high-throughput multiplexed sequencing (SUM-seq) for co-assaying chromatin accessibility and gene expression in single nuclei. SUM-seq enables profiling hundreds of samples at the million cell scale and outperforms current high-throughput single-cell methods. We demonstrate the capability of SUM-seq to (1) resolve temporal gene regulation of macrophage M1 and M2 polarization to bridge TF regulatory networks and immune disease genetic variants, (2) define the regulatory landscape of primary T helper cell subsets and (3) dissect the effect of perturbing lineage TFs via arrayed CRISPR screens in spontaneously differentiating human induced pluripotent stem cells. SUM-seq offers a cost-effective, scalable solution for ultra-high-throughput single-cell multiomic sequencing, accelerating the unraveling of complex gene regulatory networks in cell differentiation, responses to perturbations and disease studies. This work presents SUM-seq, an ultra-high-throughput method for co-profiling chromatin accessibility and gene expression in single nuclei across multiplexed samples, advancing the study of gene regulation in diverse biological systems.

Polymyositis (PM) is a systemic autoimmune disease characterized by muscular inflammatory infiltrates and degeneration. T-cell immunoreceptor with Ig and ITIM domains (TIGIT) contributes to immune tolerance by inhibiting T cell-mediated autoimmunity. Here, we show that a reduced expression of TIGIT in CD4+ T cells from patients with PM promotes these cells’ differentiation into Th1 and Th17 cells, which could be rescued by TIGIT overexpression. Knockout of TIGIT enhances muscle inflammation in a mouse model of experimental autoimmune myositis. Mechanistically, we find that TIGIT deficiency enhances CD28-mediated PI3K/AKT/mTOR co-stimulatory pathway, which promotes glucose oxidation, citrate production, and increased cytosolic acetyl-CoA levels, ultimately inducing epigenetic reprogramming via histone acetylation. Importantly, pharmacological inhibition of histone acetylation suppresses the differentiation of Th1 and Th17 cells, alleviating muscle inflammation. Thus, our findings reveal a mechanism by which TIGIT directly affects the differentiation of Th1 and Th17 T cells through metabolic‒epigenetic reprogramming, with important implications for treating systemic autoimmune diseases. Aberrant activation of autoreactive T cells is a hallmark of autoimmune diseases. Here, by analysing CD4 T cells from patients with polymyositis and mice with experimental autoimmune myositis, the authors show that TIGIT limits the differentiation of inflammatory Th1 and Th17 cells via a metabolic-epigenetic mechanism, which involves the inhibition of CD28-mediated PI3K/AKT/mTOR costimulatory signaling.