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Stem Cells:诱导多能干细胞分化的神经干细胞自发恢复多能性

来源:生物谷 2014-06-09 13:35

 2014年6月6日讯/生物谷BIOON/-通过转入外源的重编程因子,分化的体细胞能够被重编程为多能干细胞。当诱导多能干细胞形成后,外源基因就会沉默。在多能性状态,逆转录病毒携带的整合进入宿主基因组的基因通过表观转录调控保持失活状态。

在近期的研究中,Do JT的研究团队试图通过一种体外系统确定外源基因是否保持沉默,或者在失去多能性或分化的过程中重新活化。他们首先把ips细胞在体外诱导分化成神经干细胞(NSC)。这些神经干细胞与脑来源的神经干细胞在形态学上相同,同时对于神经干抗体Nestin和Sox2染色显示阳性。这些ips来源的神经干细胞(ips-NSC)也有分化成3种神经亚型的能力。有趣的是,ips-NSC在长时间培养的过程中自发形成聚集并对于Oct4-GFP标记显示阳性,之后还会形成ES细胞样的克隆。这种自发逆转的GFP阳性细胞(ips-NSC-GFP+)表达高水平的多能性标记(Oct4和Nanog),能够进入嵌合体的生殖细胞系,
这些表明ips-NSC-GFP+相对于原始的ips细胞具有相同的多能性。沉默基因的再次活化与ips细胞分化过程中DNA甲基转移酶(Dnmts)下调紧密相关。Do JT表示这种现象在多西环素可诱导的ips细胞中没有出现,在这种细胞中
外源基因只有通过多西环素处理诱导表达。
 
这项研究表明通过外源基因的重新活化细胞能够重新获得多能性,这与分化的ips细胞中Dnmt的动态水平相关。(生物谷Bioon.com)
 
 
Neural stem cells differentiated from iPS cells spontaneously regain pluripotency.
 
Differentiated somatic cells can be reprogrammed into pluripotent stem cells by transduction of exogenous reprogramming factors. After induced pluripotent stem (iPS) cells are established, exogenous genes are silenced. In the pluripotent state, retroviral genes integrated in the host genome are kept inactive through epigenetic transcriptional regulation. In the present study, we tried to determine whether exogenous genes remain silenced or are reactivated upon loss of pluripotency or on differentiation by using an in vitro system. We induced differentiation of iPS cells into neural stem cells (NSCs) in vitro; the NSCs appeared morphologically indistinguishable from brain-derived NSCs and stained positive for the NSC markers Nestin and Sox2. These iPS cell-derived NSCs (iPS-NSCs) were also capable of differentiating into all three neural subtypes. Interestingly, iPS-NSCs spontaneously formed aggregates on long-term culture and showed reactivation of the Oct4-GFP marker, which was followed by the formation of ES cell-like colonies. The spontaneously reverted GFP-positive (iPS-NSC-GFP+ ) cells expressed high levels of pluripotency markers (Oct4 and Nanog) and formed germline chimeras, indicating that iPS-NSC-GFP+ cells had the same pluripotency as the original iPS cells. The reactivation of silenced exogenous genes was tightly correlated with the downregulation of DNA methyltransferases (Dnmts) during differentiation of iPS cells. This phenomenon was not observed in doxycycline-inducible iPS cells, where the reactivation of exogenous genes could be induced only by doxycycline treatment. These results indicate that pluripotency can be regained through reactivation of exogenous genes, which is associated with dynamic change of Dnmt levels during differentiation of iPS cells.
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