No abstract

Embryonic stem cells (ESCs) are pluripotent cells and have the capability for differentiation into any of the three embryonic germ layers. The Wnt/β-Catenin pathway has been shown to play an essential role in ESC differentiation regulation. Activation of β-Catenin by post-translational modification has been extensively studied. However, mechanism(s) of post-transcriptional regulation of β-Catenin are not well defined. In this study, we report an RNA recognition motif-containing protein (RNA binding motif protein 46, RBM46) which regulates the degradation of β-Catenin mRNA. Our results show that Rbm46 is distributed primarily in the cytoplasm of mouse ESCs (mESCs) and is elevated during the process of ESC differentiation. In addition, overexpression of Rbm46 results in differentiation of mESCs into trophectoderm, while knock-down of Rbm46 leads to mESC differentiation into endoderm. β-Catenin, a key effector in the Wnt pathway which has been reported to play a significant role in the regulation of ESC differentiation, is post-transcriptionally regulated by Rbm46. Our study reveals Rbm46 plays a novel role in the regulation of ESC differentiation.

Blastocyst formation represents the first lineage specification by segregation of the trophectoderm from the inner cell mass in early embryonic development. Transcriptional regulation of Cdx2, which is selectively expressed in and essential for the specification of trophectoderm, has been extensively studied. However, post-transcriptional regulation of Cdx2 remains largely unknown. In this study, we report that RNA-binding protein motif 46 (Rbm46), an RNA-binding motif protein with unknown function, directly binds to and stabilizes Cdx2 mRNA in early mouse embryos. In addition, knockdown of Rbm46 using RNA interference downregulated the majority of trophectoderm markers in mouse embryonic stem cells and blocked the allocation of blastomere cells to the trophectoderm in mouse embryos. Our study revealed a novel mechanism by which Rbm46 regulates trophectoderm specification through stabilizing Cdx2 mRNA in early mouse embryos.