材料の性質が残る場合も＝ｉＰＳ細胞、マウスで確認－米チーム
増殖能力が高く、身体のあらゆる細胞に変わる万能細胞「人工多能性幹（ｉＰＳ）細胞」は、血液細胞から作った場合は血液に変えやすいなど、材料の体細胞の性質が残る場合があることがマウスの実験で確認された。米ハーバード大などの研究チームが２０日、英科学誌ネイチャー電子版に発表した。
特定の細胞に変えて再生医療や新薬開発試験に使う場合、この傾向は便利だが、さまざまな種類の細胞に変えて幅広く利用する場合は、材料の体細胞の性質をほぼ完全になくす工夫が必要という。
ｉＰＳ細胞は、血液や皮膚、神経、内臓など多様な体細胞が材料となる。山中伸弥京都大教授らが開発した３、４種類の遺伝子をウイルスなどを使って導入すると、細胞が特定の役割を果たすように遺伝子群を制御していた「メチル化」という作用が解除され、受精卵に近い状態に初期化されると考えられてきた。
（時事ドットコム）
http://www.jiji.com/jc/c?g=soc_30&k=2010072000066
想定の範囲内ですね。
ただ、これを欠点とみるか利点とみるかは、利用法によって異なるでしょう。
こちらです。
Nature doi:10.1038/nature09342
Received 08 February 2010 Accepted 12 July 2010 Published online 19 July 2010
Epigenetic memory in induced pluripotent stem cells
K. Kim, A. Doi, B. Wen, K. Ng, R. Zhao, P. Cahan, J. Kim, M. J. Aryee, H. Ji, L. I. R. Ehrlich, A. Yabuuchi, A. Takeuchi, K. C. Cunniff, H. Hongguang, S. Mckinney-Freeman, O. Naveiras, T. J. Yoon, R. A. Irizarry, N. Jung, J. Seita, J. Hanna, P. Murakami, R. Jaenisch, R. Weissleder, S. H. Orkin, I. L. Weissman, A. P. Feinberg & G. Q. Daley
http://www.nature.com/nature/journal/vnfv/ncurrent/abs/nature09342.html
Somatic cell nuclear transfer and transcription-factor-based reprogramming revert adult cells to an embryonic state, and yield pluripotent stem cells that can generate all tissues. Through different mechanisms and kinetics, these two reprogramming methods reset genomic methylation, an epigenetic modification of DNA that influences gene expression, leading us to hypothesize that the resulting pluripotent stem cells might have different properties. Here we observe that low-passage induced pluripotent stem cells (iPSCs) derived by factor-based reprogramming of adult murine tissues harbour residual DNA methylation signatures characteristic of their somatic tissue of origin, which favours their differentiation along lineages related to the donor cell, while restricting alternative cell fates. Such an ‘epigenetic memory’ of the donor tissue could be reset by differentiation and serial reprogramming, or by treatment of iPSCs with chromatin-modifying drugs. In contrast, the differentiation and methylation of nuclear-transfer-derived pluripotent stem cells were more similar to classical embryonic stem cells than were iPSCs. Our data indicate that nuclear transfer is more effective at establishing the ground state of pluripotency than factor-based reprogramming, which can leave an epigenetic memory of the tissue of origin that may influence efforts at directed differentiation for applications in disease modelling or treatment.