Transcriptional Program of Kpna2 (Importin-alpha2) Regulates Cellular 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 transcriptional program by constitutive expression of c-Myc and Dnmt1 ablation disrupts the differentiation-coupled emergence of the clock from mouse embryonic stem cells (ESCs). Using these model ESCs, 484 genes are identified by global gene expression analysis as correlating factors with differentiation-coupled circadian clock development. Among them, we find the misregulation of Kpna2 (Importin-alpha2) during the differentiation of the c-Myc over-expressed and Dnmt1-/- ESCs, in which sustaining 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 post-transcriptional regulation of clock proteins. Overall design: Examination of whole transcriptome in ES cells and in vitro differentiated cells.

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Umemura Y, Koike N, Matsumoto T, Yoo SH, Chen Z, Yasuhara N, Takahashi JS, Yagita K