Importin-β家族的成员识别核定位信号(NLS)和核输出信号(NES)。这些蛋白质在细胞的各种核质转运过程中起重要作用。这里,我们检查了21个鉴定的Importin-β基因在小鼠胚胎干细胞(mESCs)中的表达模式,小鼠胚胎成纤维细胞(MEF)和mESC分化成神经外胚层(NE)或中内胚层(ME)。我们观察到这些细胞类型中Importin-βmRNA表达水平的惊人差异。我们还发现,选定的Importin-β基因的敲除导致Nanog的抑制,并改变了Oct4/Sox2表达比率的平衡,这对NE/ME谱系选择很重要。此外,我们证明了XPO4,RanBP17,RanBP16或IPO7的敲低差异影响分化mESC的谱系选择。更具体地说,XPO4敲低选择性刺激mESC向定形内胚层分化,同时抑制NE分化。RanBP17敲低也促进了内胚层分化,对NE分化没有影响。RanBP16敲低导致分化为ME,而IPO7敲低抑制NE分化,对其他谱系没有明显影响。总的来说,我们的结果表明,Importin-βs在mESCs的细胞命运决定过程中发挥重要作用,例如在分化过程中维持多能性或选择谱系。
Members of the Importin-β family recognize nuclear localization signals (NLS) and nuclear export signals (NES). These proteins play important roles in various nucleocytoplasmic transport processes in cells. Here, we examined the expression patterns of 21 identified Importin-β genes in mouse embryonic stem cells (mESCs), mouse embryonic fibroblast (MEF) and mESCs differentiated into neural ectoderm (NE) or mesoendoderm (ME). We observed striking differences in the Importin-β mRNA expression levels within these cell types. We also found that knockdown of selected Importin-β genes led to suppression of Nanog, and altered the balance of Oct4/Sox2 expression ratio, which is important for NE/ME lineage choice. Furthermore, we demonstrated that knockdown of XPO4, RanBP17, RanBP16, or IPO7 differentially affected the lineage selection of differentiating mESCs. More specifically, knockdown of XPO4 selectively stimulated the mESC differentiation towards definitive endoderm, while concomitantly inhibiting NE differentiation. RanBP17 knockdown also promoted endodermal differentiation with no effect on NE differentiation. RanBP16 knockdown caused differentiation into ME, while IPO7 knockdown inhibited NE differentiation, without obvious effects on the other lineages. Collectively, our results suggest that Importin-βs play important roles in cell fate determination processes of mESCs, such as in the maintenance of pluripotency or selection of lineage during differentiation.