加州大學(xué)圣地亞哥分校醫(yī)學(xué)院及斯克里普斯研究所的干細(xì)胞科學(xué)家領(lǐng)導(dǎo)的跨國(guó)研究團(tuán)隊(duì),，記錄了在人類(lèi)胚胎干細(xì)胞(hESC)和誘導(dǎo)功能干細(xì)胞(iPSC)系中特殊的基因畸變,，題為《在細(xì)胞重組和培養(yǎng)過(guò)程中人類(lèi)胚胎干細(xì)胞和誘導(dǎo)多能干細(xì)胞的細(xì)胞增殖和全能性的拷貝數(shù)量上的動(dòng)態(tài)變化》已在1月7日的Cell Stem Cell上發(fā)表。該公布的發(fā)現(xiàn)強(qiáng)調(diào)了需要對(duì)多能干細(xì)胞進(jìn)行頻繁的基因檢測(cè)以保證其穩(wěn)定性和臨床安全性,。
該研究的第一作者,，加州大學(xué)圣地亞哥分校再生醫(yī)學(xué)系的路易斯.勞倫特博士認(rèn)為，我們發(fā)現(xiàn)人類(lèi)多能干細(xì)胞(hESC和iPSC)比其他類(lèi)型細(xì)胞有更高的基因畸變的頻率,。最令人吃驚的是,，與其他非多能干細(xì)胞樣本相比較，我們觀察到hESCs的基因擴(kuò)增和iPSC的缺失方面出現(xiàn)的頻率更高,。
人類(lèi)多能干細(xì)胞在人體內(nèi)具有發(fā)展成其他類(lèi)型細(xì)胞的能力,，可成為替換細(xì)胞治療的潛在來(lái)源。斯克里普斯研究員再生醫(yī)學(xué)中心主任,，珍妮.羅倫教授談到,，由于基因畸變常常與癌癥相關(guān)聯(lián)，免受癌癥相關(guān)的基因突變對(duì)于臨床使用的細(xì)胞系來(lái)說(shuō)至關(guān)重要,。
研究團(tuán)隊(duì)確認(rèn)了在多能干細(xì)胞系中可能發(fā)生突變的基因區(qū)域,。對(duì)于hESC而言，可觀察到的畸變大多是靠近多潛能相關(guān)基因區(qū)域的基因擴(kuò)增,；對(duì)于iPSC而言,，擴(kuò)增主要涉及細(xì)胞增殖基因及與腫瘤抑制基因相關(guān)的缺失。傳統(tǒng)的顯微技術(shù),，如染色體組型分析可能無(wú)法檢測(cè)到這些變化,。研究組使用一種高分辨率的分子技術(shù)，稱(chēng)為"單核苷酸多態(tài)性(SNP)",，能觀察到人類(lèi)基因組里一百多萬(wàn)個(gè)位點(diǎn)里的基因變化,。
勞倫說(shuō),，我們驚喜地發(fā)現(xiàn)在較短時(shí)間培養(yǎng)中的基因變化，例如在體細(xì)胞重編程為多能干細(xì)胞的過(guò)程以及在培養(yǎng)中細(xì)胞的分化過(guò)程,。我們不知道這會(huì)有怎樣的影響,，如果有的話，這些基因畸變都會(huì)對(duì)基礎(chǔ)研究或者臨床應(yīng)用的結(jié)果產(chǎn)生影響,，對(duì)此應(yīng)當(dāng)深究,。
勞倫總結(jié)到,，該研究結(jié)果解釋了有必要對(duì)多能干細(xì)胞培養(yǎng)進(jìn)行經(jīng)常性的基因監(jiān)控,，SNP分析仍不失人類(lèi)胚胎干細(xì)胞和多能干細(xì)胞日常監(jiān)控的一部分，但是這一結(jié)果提醒我們應(yīng)當(dāng)予以重視,。（生物谷Bioon.com）
原文鏈接：http://www.medicalnewstoday.com/articles/213047.php
譯文鏈接：http://www.chinastemcell.org/page/zixun_xwdtlist.aspx?infoid=970
生物谷推薦英文摘要：
Cell Stem Cell doi：10.1016/j.stem.2010.12.003
Dynamic Changes in the Copy Number of Pluripotency and Cell Proliferation Genes in Human ESCs and iPSCs during Reprogramming and Time in Culture
Louise C. Laurent, Igor Ulitsky, Ileana Slavin, Ha Tran, Andrew Schork, Robert Morey, Candace Lynch, Julie V. Harness, Sunray Lee, Maria J. Barrero, Sherman Ku, Marina Martynova, Ruslan Semechkin, Vasiliy Galat, Joel Gottesfeld, Juan Carlos Izpisua Belmonte, Chuck Murry, Hans S. Keirstead, Hyun-Sook Park, Uli Schmidt, Andrew L. Laslett, Franz-Josef Muller, Caroline M. Nievergelt, Ron Shamir, Jeanne F. Loring
The tremendous self-renewal and differentiation capabilities of human pluripotent stem cells (hPSCs) make them potential sources of differentiated cells for cell therapy. Cell therapies are subject to rigorous safety trials, and high priority is placed on demonstrating that the cells are nontumorigenic (Fox, 2008). Because genetic aberrations have been strongly associated with cancers, it is important that preparations destined for clinical use are free from cancer-associated genomic alterations. Human embryonic stem cell (hESC) lines have been shown to become aneuploid in culture (Baker et al., 2007,Draper et al., 2004,Imreh et al., 2006,Maitra et al., 2005,Mitalipova et al., 2005), and the most frequent changes, trisomies of chromosomes 12 and 17, are also characteristic of malignant germ cell tumors (Atkin and Baker, 1982,Rodriguez et al., 1993,Skotheim et al., 2002). Aneuploidies can be detected by karyotyping, but less easily detectable subchromosomal genetic changes may also have adverse effects. Small abnormalities have been detected in hESCs by using comparative genomic hybridization (CGH) and single-nucleotide polymorphism (SNP) genotyping (Lefort et al., 2008,N?rv? et al., 2010,Spits et al., 2008). These studies lacked sufficient resolution and power to identify cell type-associated duplications and deletions. A recent study has reported the use of gene expression data to detect genomic aberrations in a large number of hESCs and hiPSCs (Mayshar et al., 2010). However, the methods used could reliably detect only relatively large (≥10 megabase) aberrations, and the lack of nonpluripotent samples for comparison precluded the authors from determining which regions of genomic aberration were specific to pluripotent stem cells.
In this study, we performed high-resolution SNP genotyping on a large number of hESC lines, induced human pluripotent stem cell lines (hiPSCs), somatic stem cells, primary cells, and tissues. We found that hESC lines had a higher frequency of genomic aberrations compared to the other cell types. Furthermore, we identified regions in the genome that had a greater tendency to be aberrant in the hESCs when compared to the other cell types examined. Recurrent regions of duplication were seen on chromosome 12, encompassing the pluripotency-associated transcription factor NANOG and a nearby NANOG pseudogene, and on chromosome 20, upstream of the DNA methyltransferase DNMT3B. Although the frequency of genomic aberrations seen in the hiPSC lines was similar to those of cultured somatic cells and tissues, we observed one of the recurrent areas of duplication characteristic of hESCs in one of the hiPSC lines.
Furthermore, comparison of 12 hiPSC lines generated from the same primary fibroblast cell line identified genomic aberrations that were present in the hiPSC lines and absent from the original fibroblast line. Analysis of early- and late-passage samples from these hiPSC lines allowed us to distinguish between events that arose during the process of reprogramming and those that accumulated during long-term passage. In general, deletions tended to occur with reprogramming and involve tumor-suppressor genes, whereas duplications accumulated with passaging and tended to encompass tumor-promoting genes. These results suggest that human pluripotent stem cell populations are prone to genomic aberrations that could compromise their stability and utility for clinical applications and that reprogramming and expansion in culture may lead to selection for particular genomic changes.
