Transcriptional program of Kpna2/Importin-α2 regulates cellular differentiation-coupled circadian clock development in mammalian cells

Significance The emergence of the cell-autonomous circadian oscillator is coupled with cellular differentiation. Cellular differentiation, as well as reprogramming, results in global alterations of the transcriptional program via epigenetic modification such as DNA methylation. We here demonstrate that c-Myc constitutive expression and Dnmt1 ablation disrupt the differentiation-coupled emergence of the clock from mouse ES cells (ESCs). Using these model ESCs, 484 genes were identified by global gene expression analysis as factors correlated with circadian clock development. Among them, we find that misregulation of Kpna2 ( Importin-α2 ) during the differentiation culture of ESCs significantly impairs clock development, and KPNA2 facilitates cytoplasmic localization of PER1/2. These results suggest that the programmed gene expression network regulates the differentiation-coupled circadian clock development in mammalian cells. The circadian clock in mammalian cells is cell-autonomously generated during the cellular differentiation process, but the underlying mechanisms are not understood. Here we show that perturbation of the transcriptional program by constitutive expression of transcription factor c-Myc and DNA methyltransferase 1 ( Dnmt1 ) ablation disrupts the differentiation-coupled emergence of the clock from mouse ESCs. Using these model ESCs, 484 genes are identified by global gene expression analysis as factors correlated with differentiation-coupled circadian clock development. Among them, we find the misregulation of Kpna2 ( Importin-α2 ) during the differentiation of the c-Myc -overexpressed and Dnmt1 ⁻/⁻ ESCs, in which sustained cytoplasmic accumulation of PER proteins is observed. Moreover, constitutive expression of Kpna2 during the differentiation culture of ESCs significantly impairs clock development, and KPNA2 facilitates cytoplasmic localization of PER1/2. These results suggest that the programmed gene expression network regulates the differentiation-coupled circadian clock development in mammalian cells, at least in part via posttranscriptional regulation of clock proteins.