IRAK4 constrains cellular plasticity during chemically-induced cell fate reprogramming into multiple lineages
Chemical reprogramming holds transformative potential for regenerative medicine. However, the regulatory mechanisms governing cell fate transitions are not well understood. Here, we identify Interleukin-1 Receptor-Associated Kinase 4 (IRAK4) as a barrier to multi-lineage reprogramming. Pharmacological inhibition of IRAK4 enhances the reprogramming of mouse embryonic fibroblasts (MEFs) through a chemically activated multi-lineage priming (CaMP) state and extraembryonic endoderm (XEN)-like intermediates, increasing colony formation, and the expression of core XEN regulators (Sox17, Gata4, Sall4, and Foxa2). Genetic knockdown of Irak4 similarly accelerates reprogramming, whereas its overexpression blocks cell fate transitions. IRAK4 inhibition enhances chromatin accessibility and reshapes cell cycle dynamics, characterized by G0/G1 shortening and G2/M lengthening, potentially contributing to multi-lineage state establishment. Furthermore, IRAK4 suppression enhances the direct conversion of MEFs to neuron-like and hepatocyte-like cells, which exhibit enhanced functional maturity, including increased glycogen storage and improved detoxification capacity. Our findings establish IRAK4 as a regulator that constrains cellular plasticity potentially by coordinating chromatin accessibility and cell cycle dynamics. IRAK4 is a barrier to chemical reprogramming and lineage conversion. Pharmacological or genetic inhibition of IRAK4 enhances multi-lineage priming, accelerates reprogramming, and improves the functional maturity of directly converted neuron-like and hepatocyte-like cells. IRAK4 inhibition promotes the chemical reprogramming of mouse embryonic fibroblasts through a CaMP state and XEN-like intermediates, increasing colony formation and the expression of core XEN regulators (Sox17, Gata4, Sall4, Foxa2). IRAK4 suppression enhances chromatin accessibility and reshapes cell cycle dynamics, which may facilitate the establishment of multi-lineage states. Inhibition of IRAK4 boosts direct conversion to neuron-like and hepatocyte-like cells. IRAK4 inhibition promotes the chemical reprogramming of mouse embryonic fibroblasts through a CaMP state and XEN-like intermediates, increasing colony formation and the expression of core XEN regulators (Sox17, Gata4, Sall4, Foxa2). IRAK4 suppression enhances chromatin accessibility and reshapes cell cycle dynamics, which may facilitate the establishment of multi-lineage states. Inhibition of IRAK4 boosts direct conversion to neuron-like and hepatocyte-like cells. IRAK4 is a barrier to chemical reprogramming and lineage conversion. Pharmacological or genetic inhibition of IRAK4 enhances multi-lineage priming, accelerates reprogramming, and improves the functional maturity of directly converted neuron-like and hepatocyte-like cells.