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Description

"Induced pluripotent stem (iPS) cells were first generated from somatic cells by the ectopic expression of the four Yamanaka transcription factors, Oct4, Klf4, Sox2, and c-Myc (OKSM) (Takahashi, 2006). Four factor reprogrammed mouse iPSCs closely resemble mouse embryonic stem cells (ESC) in their morphology, proliferation, and global gene expression profiles. In addition, fully reprogrammed mouse iPSCs have been shown to give rise to chimeric mice that are competent for germline transmission. However, both the chimeras and progenies derived from mouse iPSC have an increased incidence of tumor formation, mainly due to the expression of the oncogene c-Myc (Okita, 2007). The elimination of c-Myc may provide less incidence of tumors in iPSCs. Reprogramming is possible using three factors (OKS) without c-Myc, however the efficiency is extremely low and the kinetics of reprogramming is significantly delayed compared to reprogramming with four factors (Huangfu, 2008). Recent studies have shown that small molecule treatments, by modulating specifc signaling pathways and epigenetic status, can not only enhance reprogramming efficiency but can also replace one or more of the transcription factors., The Mouse STEMCCA Cre-Excisable Constitutive Polycistronic (OKS) Lentivirus Reprogramming Kit contains high titer Cre-excisable polycistronic (OKS) lentivirus that expresses a modified ""stem cell cassette"" or STEMCCA comprised of the three transcription factors Oct4, Klf4, and Sox2 (OKS) separated by the self-cleaving 2A peptide and IRES sequences. Also included in the kit are three small molecule reprogramming supplements and Polybrene transfection reagent. Due to the removal of c-Myc, the Cre-Excisable Constitutive Polycistronic (OKS) Lentivirus must be used in combination with the small molecule medium supplements to generate mouse iPS colonies. Together these components have been validated for the generation of mouse iPS colonies from mouse embryonic fibroblasts (MEFs). Mouse iPS cells obtained with this kit displayed characteristic ES cell-like morphology, stained positive for alkaline phosphatase, expressed the correct mouse ES cell marker phenotype (SSEA-1 and Sox-2) and can be rapidly expanded in normal mouse ES cell culture conditions. Following Cre-mediated excision, transgene-free mouse iPS cells can be further expanded and banked."