Zfp143 regulates Nanog through modulation of Oct4 binding

Identification of regulators governing the maintenance of embryonic stem (ES) cells is crucial to the understanding of ES cell biology. We identified a zinc finger protein, Zfp143, as a novel regulator for self-renewal. Depletion of Zfp143 by RNA interference causes loss of self-renewal of ES cells. Chromatin immunoprecipitation and electrophoretic mobility shift assays show the direct binding of Zfp143 to the Nanog proximal promoter. Knockdown of Zfp143 or mutation of the Zfp143 binding motif significantly downregulates Nanog proximal promoter activity. Importantly, enforced expression of Nanog is able to rescue the Zfp143 knockdown phenotype, indicating that Nanog is one of the key downstream effectors of Zfp143. More interestingly, we further show that Zfp143 regulates Nanog expression through modulation of Oct4 binding. Coimmunoprecipitation experiments revealed that Zfp143 and Oct4 physically interact with each other. This interaction is important because Oct4 binding to the Nanog promoter is promoted by Zfp143. Our study reveals a novel regulator functionally important for the self-renewal of ES cells and provides new insights into the expanded regulatory circuitry that maintains ES cell pluripotency. Disclosure of potential conflicts of interest is found at the end of this article.     

人脐带间充质干细胞表达胚胎干细胞相关转录因子

背景：Nanog、Oct4和Sox2通过调节胚胎干细胞的基因转录,对其多潜能性和自我更新的能力具有关键性的调控作用,脐带间充质干细胞中这些胚胎干细胞相关转录因子的表达情况如何还不太清楚。 目的：研究脐带间充质干细胞中Nanog、Oct4和Sox2等这些胚胎干细胞相关转录因子的表达情况。 方法：胶原酶和胰酶消化法培养脐带间充质干细胞;mTeSRTM1体系进行无滋养层培养人胚胎干细胞,定量PCR比较上述两种细胞中Nanog、Oct4和Sox2 mRNA表达量的差异;免疫荧光检测上述两种细胞中Nanog、Oct4和Sox2的表达情况。 结果与结论：间充质干细胞表达胚胎干细胞标记Nanog、Oct4和Sox2,但Oct4主要表达在胞浆,且以Oct4B为主。脐带间充质干细胞Nanog、Oct4A和Sox2的表达量明显低于胚胎干细胞,其mRNA表达量分别为胚胎干细胞的20%,0.3%,10%左右。通过了解两种细胞Nanog、Oct4和Sox2的表达差异,可为优化脐带间充质干细胞重编程提供依据,也为进一步研究胚胎干细胞相关转录因子在成体干细胞表达起何种作用提供参考。     

转录因子Oct4、Nanog及相关调控网络与多能干细胞特性的维持

多能干细胞具有自我更新能力和高度增殖、多向分化的潜能。其特征的维持受到多种调控因子通过多条调控途径所形成网络的精密调节。Oct4、Nanog是调控网络中的核心因子,通过与靶基因调控区的结合选择性地抑制分化基因的表达或者激活多能性基因的表达而达到调控目的,此调控过程有时间和空间上的特异性。Oct4等也是细胞重编程不可或缺的转录因子。通过多种方法的研究各个击破网络结点上的关键因子,调控网络的调控机制自然会日渐明朗。     

Differentiation-independent fluctuation of pluripotency-related transcription factors and other epigenetic markers in embryonic stem cell colonies

Embryonic stem cells (ESCs) maintain their pluripotency through high expression of pluripotency-related genes. Here, we show that differing levels of Oct4, Nanog, and c-myc proteins among the individual cells of mouse ESC (mESC) colonies and fluctuations in these levels do not disturb mESC pluripotency. Cells with strong expression of Oct4 had low levels of Nanog and c-myc proteins and vice versa. In addition, cells with high levels of Nanog tended to occupy interior regions of mESC colonies. In contrast, peripherally positioned cells within colonies had dense H3K27-trimethylation, especially at the nuclear periphery. We also observed distinct levels of endogenous and exogenous Oct4 in particular cell cycle phases. The highest levels of Oct4 occurred in G2 phase, which correlated with the pKi-67 nuclear pattern. Moreover, the Oct4 protein resided on mitotic chromosomes. We suggest that there must be an endogenous mechanism that prevents the induction of spontaneous differentiation, despite fluctuations in protein levels within an mESC colony. Based on the results presented here, it is likely that cells within a colony support each other in the maintenance of pluripotency.     

人参皂苷Rg1干预骨髓间充质干细胞转化为多潜能干细胞关键基因mRNA的表达

背景：将成体细胞重编程为诱导多潜能干细胞方案主要通过反转录病毒将Oct-4, Sox2, c-Myc, Klf4等基因转入成体细胞而实现。 目的：观察人参皂苷Rg1作用于骨髓间充质干细胞后,对成体细胞向诱导多潜能干细胞转化的关键性基因Oct4、Sox2、c-Myc、Klf4、Nanog mRNA表达的影响。 方法：培养骨髓间充质干细胞,对照组培养基为α-MEM,体积分数5%FBS,1%双抗;用药组培养基为α-MEM,体积分数15%FBS,1 000 U/mL Rat ESGRO®,1%双抗,并加入6.25 μmol/L和12.5 μmol/L人参皂苷Rg1。检测骨髓间充质干细胞Oct4,Sox2,c-Myc,Klf4,Nanog等mRNA的表达。 结果与结论：人参皂苷Rg1 6.25 μmol/L培养30 d,Nanog、c-Myc、Oct、Klf4、Sox2 mRNA表达均有升高,且Nanog、c-Myc与对照组差异有显著性意义。人参皂苷Rg1能促进骨髓间充质干细胞表达c-Myc,Nanog,但Nanog阳性的诱导多潜能干细胞在基因表达谱上很难与胚胎干细胞区分出来,提示人参皂苷Rg1对骨髓间充质干细胞向诱导多潜能干细胞转化可能具有促进作用。     

ATP Dependent Chromatin Remodeling Enzymes in Embryonic Stem Cells

Embryonic stem (ES) cells are pluripotent cells that can self renew or be induced to differentiate into multiple cell lineages, and thus have the potential to be utilized in regenerative medicine. Key pluripotency specific factors (Oct 4/Sox2/Nanog/Klf4) maintain the pluripotent state by activating expression of pluripotency specific genes and by inhibiting the expression of developmental regulators. Pluripotent ES cells are distinguished from differentiated cells by a specialized chromatin state that is required to epigenetically regulate the ES cell phenotype. Recent studies show that in addition to pluripotency specific factors, chromatin remodeling enzymes play an important role in regulating ES cell chromatin and the capacity to self-renew and to differentiate. Here we review recent studies that delineate the role of ATP dependent chromatin remodeling enzymes in regulating ES cell chromatin structure.