ZFP36L1 and ZFP36L2 cooperatively regulate thymic epithelial cell function to prevent early-onset thymic involution

The thymus generates immunocompetent T cells, but its function declines with age. Thymic activity relies on proper differentiation of thymic epithelial cells (TECs), which establish unique niches for T-cell development. However, the molecular mechanisms governing the differentiation of functional cortical (c) and medullary (m) TEC subsets from common progenitors remain poorly understood. Using dual conditional knockout (dcKO) and lineage-tracing mouse models, we demonstrated that RNA-binding proteins ZFP36L1 and ZFP36L2 cooperatively maintain a functional TEC microenvironment. TEC-specific deletion of Zfp36l1 and Zfp36l2 in dcKO mouse models led to early-onset thymic hypoplasia and a marked reduction in TEC and thymocyte numbers. Mechanistically, single-cell transcriptomics revealed significant alterations in the composition and transcriptional programs of cTECs, mTECs, and thymic mimetic cells, linking Zfp36l1 and Zfp36l2 deficiency to a widespread increase in metabolic gene dysregulation in adult dcKO TECs. The erosion of the TEC compartment and the accumulation of age-associated TECs suggested impaired differentiation of mature lineages from their progenitors. Concordantly, fate-mapping analysis revealed that dual deficiency in Zfp36l1 and Zfp36l2 disrupted the canonical developmental trajectory from β5t-expressing TEC progenitors into mature TECs. Our findings uncover a previously unappreciated layer of post-transcriptional regulation in TEC biology, identifying a cooperative role for ZFP36L1 and ZFP36L2 in orchestrating TEC differentiation to sustain thymic function and prevent premature involution.