A key role for telomerase reverse transcriptase unit in modulating human embryonic stem cell proliferation, cell cycle dynamics, and in vitro differentiation
A key role for telomerase reverse transcriptase unit in modulating human embryonic stem cell proliferation, cell cycle dynamics, and in vitro differentiation
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DOI：
10.1634/stemcells.2007-0677
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发表时间：
2008-04-01
期刊：
影响因子：
5.2
通讯作者：
Lako, Majlinda
中科院分区：
文献类型：
--
作者：
Yang, Chunbo;Przyborski, Stefan;Lako, Majlinda
胚胎干细胞（ESC）是一种独特的细胞群，具有自我更新和分化为所有三个胚层的能力。人胚胎干细胞表达端粒酶逆转录酶（TERT）基因和端粒酶RNA（TR），并显示端粒酶活性，但在分化过程中，TERT、TR和端粒酶均下调。为了研究端粒酶在人ESC自我更新和分化中的作用，我们调节了TERT的表达。端粒酶活性的上调和端粒酶活性的增加增强了人ESC的增殖和集落形成能力，以及以减少G1期为代价增加细胞周期的S期。TERT表达的上调与细胞周期蛋白D1和CDC6表达的增加以及RB的过度磷酸化有关。对照ESC的分化后代表现出端粒DNA缩短，作为端粒酶活性丧失的结果。相反，分化的细胞从TERT过表达ESC保持高端粒酶活性和积累的过氧化物浓度较低的野生型细胞，这意味着更大的抗氧化应激。尽管TERT过表达的人ESC能够在体内形成由三个胚层组成的畸胎瘤，但它们在体外向所有原始和胚胎谱系的分化受到抑制。相反，下调TERT导致ESC增殖减少，G1期增加，S期减少。最重要的是，TERT的下调导致多能性丧失以及人ESC向胚外和胚胎谱系分化。我们的研究结果首次表明了TERT在维持人ESC多能性、细胞周期调控和体外分化能力方面的重要作用。
Embryonic stem cells (ESC) are a unique cell population with the ability to self-renew and differentiate into all three germ layers. Human ESC express the telomerase reverse transcriptase (TERT) gene and the telomerase RNA (TR) and show telomerase activity, but TERT, TR, and telomerase are all downregulated during the differentiation process. To examine the role of telomerase in human ESC self-renewal and differentiation, we modulated the expression of TERT. Upregulation of TERT and increased telomerase activity enhanced the proliferation and colony-forming ability of human ESC, as well as increasing the S phase of the cell cycle at the expense of a reduced G1 phase. Upregulation of TERT expression was associated with increases in CYCLIN D1 and CDC6 expression, as well as hyperphosphorylation of RB. The differentiated progeny of control ESC showed shortening of telomeric DNA as a result of loss of telomerase activity. In contrast, the differentiated cells from TERT-overexpressing ESC maintained high telomerase activity and accumulated lower concentrations of peroxides than wild-type cells, implying greater resistance to oxidative stress. Although the TERT-overexpressing human ESC are able to form teratoma composed of three germ layers in vivo, their in vitro differentiation to all primitive and embryonic lineages was suppressed. In contrast, downregulation of TERT resulted in reduced ESC proliferation, increased G1, and reduced S phase. Most importantly, downregulation of TERT caused loss of pluripotency and human ESC differentiation to extraembryonic and embryonic lineages. Our results indicate for the first time an important role for TERT in the maintenance of human ESC pluripotency, cell cycle regulation, and in vitro differentiation capacity.