複製人的契機？

Producing primate embryonic stem cells by somatic cell nuclear transfer

複製的相關進展  複製技術 體細胞的細胞核經由體細胞核轉殖到卵母細胞而產生 的囊胚 可發育出活的個體 可培養成胚胎幹細胞 暗示了卵母細胞的細胞質可能含有一些因子可以將轉 殖後的體細胞核重新導引到具有多能性的狀態 2006 年日本京都大學山中伸（ Shinya Yamanaka) 教授將四種基因 Oct4 、 Sox2 、 c-Myc 、 Klf4 轉殖到 老鼠已經分化的纖維母細胞 已分化的纖維組織母細胞重新設定變回幹細胞

In vitro reprogramming of fibroblasts into a pluripotent ES-cell-like state  Nuclear transplantation can reprogramme a somatic genome back into an embryonic epigenetic state, and the reprogrammed nucleus can create a cloned animal or produce pluripotent embryonic stem cells. One potential use of the nuclear cloning approach is the derivation of 'customized' embryonic stem (ES) cells for patient- specific cell treatment, but technical and ethical considerations impede the therapeutic application of this technology. Reprogramming of fibroblasts to a pluripotent state can be induced in vitro through ectopic expression of the four transcription factors Oct4 (also called Oct3/4 or Pou5f1), Sox2, c-Myc and Klf4. Here we show that DNA methylation, gene expression and chromatin state of such induced reprogrammed stem cells are similar to those of ES cells. Notably, the cells—derived from mouse fibroblasts—can form viable chimaeras, can contribute to the germ line and can generate live late-term embryos when injected into tetraploid blastocysts. Our results show that the biological potency and epigenetic state of in- vitro-reprogrammed induced pluripotent stem cells are indistinguishable from those of ES cells.

Successful reprogramming of differentiated human somatic cells into a pluripotent state would allow creation of patient- and disease-specific stem cells. We previously reported generation of induced pluripotent stem (iPS) cells, capable of germline transmission, from mouse somatic cells by transduction of four defined transcription factors. Here, we demonstrate the generation of iPS cells from adult human dermal fibroblasts with the same four factors: Oct3/4, Sox2, Klf4, and c-Myc. Human iPS cells were similar to human embryonic stem (ES) cells in morphology, proliferation, surface antigens, gene expression, epigenetic status of pluripotent cell-specific genes, and telomerase activity. Furthermore, these cells could differentiate into cell types of the three germ layers in vitro and in teratomas. These findings demonstrate that iPS cells can be generated from adult human fibroblasts.

Somatic CELL nuclear transfer allows trans-acting factors present in the mammalian oocyte to reprogram somatic CELL nuclei to an undifferentiated state. Here we show that four factors (OCT4, SOX2, NANOG, and LIN28) are sufficient to reprogram human somatic CELLs to pluripotent STEM CELLs that exhibit the essential characteristics of embryonic STEM CELLs. These human induced pluripotent STEM CELLs have normal karyotypes, express telomerase activity, express CELL surface markers and genes that characterize human ES CELLs, and maintain the developmental potential to differentiate into advanced derivatives of all three primary germ layers. Such human induced pluripotent CELL lines should be useful in the production of new disease models and in drug development as well as application in transplantation medicine once technical limitations (for example, mutation through viral integration) are eliminated.