IRAK4 constrains cellular plasticity during chemically-induced cell fate reprogramming into multiple lineages

Here, we identify Interleukin-1 Receptor-Associated Kinase 4 (IRAK4), a key innate immune kinase, as a previously unrecognized barrier to multi-lineage reprogramming. We discovered that pharmacological inhibition of IRAK4 potently enhances reprogramming of mouse embryonic fibroblasts (MEFs) through the chemically activated multi-lineage priming (CaMP) state and extraembryonic endoderm (XEN)-like intermediates, significantly increasing colony formation and expression of core XEN regulators (Sox17/Gata4/Sall4/Foxa2).

Genetic knockdown of Irak4 similarly accelerated reprogramming, while its overexpression blocked cell fate transitions. Mechanistically, IRAK4 inhibition enhances chromatin accessibility and reshapes cell cycle dynamics (G0/G1 shortening and G2/M lengthening), enabling multi-lineage establishment. Moreover, demonstrating the broad role of IRAK4 in restricting cellular plasticity, its suppression also significantly enhanced MEF-to-hepatocyte-like cells (iHeps) direct conversion with ~7-8 folds increasing of Alb⁺Cyp3a11⁺ iHeps, which exhibited enhanced functional maturity including increased glycogen storage and improved detoxification.