Adenosine-to-Inosine Safeguards Early Human T-cell Lymphopoiesis by Suppressing MDA5-Mediated dsRNA Sensing

While epigenetic and transcriptional factors governing this process are well reported in both humans and mice, the epitranscriptomic regulation is largely unexplored. In this study, we investigated ADAR1-mediated adenosine-to-inosine (A-to-I) RNA editing during early human T-cell maturation using both human thymic tissues and an artificial thymic organoid (ATO) system.

ADAR1 was highly expressed in early T-cell progenitors, and its expression declines as T-cell progenitors progress to the CD4⁺CD8⁺ double-positive (DP) and single-positive (SP) stages. ShRNA-mediated ADAR1 depletion coupled with single-cell RNA sequencing (scRNA-seq) reveals that ADAR1 loss blocks the developmental transition from the Thy2 to Thy3 stage within the CD34⁺ progenitor compartment and leads to the emergence of distinct cell clusters encompassing mixed lineage cells with distinct gene expression patterns marked by global activation of interferon response pathways.