292 GENERATION OF MOUSE INDUCED PLURIPOTENT STEM CELLS FROM VARIOUS GENETIC BACKGROUND BY SLEEPING BEAUTY TRANSPOSON-MEDIATED GENE TRANSFER

Abstract

Induced pluripotent stem (iPS) cell technology allows the reprogramming of somatic cells to a pluripotent state; however, it requires viral gene transduction and permanent existence of the exogenous genes in the genome, which is a potential risk for abnormalities in the derived iPS cells. Recently, there was report that iPS cells have been made with piggyBack transposon. Here, we first reported that nonviral transfection of a Sleeping Beauty transposon, which comprises c-Myc, Klf-4, Oct3/4 (Pou5f1), and Sox-2, can reprogram mouse fibroblasts from 3 different genetic backgrounds: ICR (outbred), C57BL/6 (inbred), and F1 hybrid (C57BL/6 × DBA/2J), with parallel robust expression of all exogenous (c-Myc, Klf-4, Oct3/4, and Sox-2) and endogenous (e.g. Nanog) pluripotency genes. The iPS cells were cultured under standard conditions with promotion of differentiate by withdrawal of leukemia inhibitory factor. We chose 6 cloned of each line that exhibited characteristics typical for undifferentiated embryonic stem (ES) cell: ES-cell-like morphology, alkaline phosphatase positivity, and gene expression pattern [quantitative real-time PCR and immunofluorescence of ES cell markers (e.g. Oct-4, SSEA1, Nanog]. Furthermore, cells were able to form embryoid bodies and beat rhythmically and expressed cardiac markers assayed by immunofluorescence (e.g. cardiac Troponin T, desmin). In vivo testing of iPS cell lines for their developmental potential (diploid and tetraploid embryo complementation assay) is currently underway. The iPS cell lines generated from the ICR strain appeared the earliest in time (ICR-d11, F1 day-2 and Bl6-d12), with higher efficiency than colonies from the other 2 backgrounds. The differentiation potential of the iPS lines derived from the 3 genetic backgrounds was similar. Interestingly, the ICR-iPS lines had higher differentiation potential than did the ICR-ES cell lines: the rate of embryoid bodies forming rhythmically beating cardiomyocytes was 4% in ICR-ES and 79% in ICR-iPS cells, respectively. Our results suggest that the iPS technology provide a new tool to generate pluripotent stem cells from genetic backgrounds where good-quality ES cell generation is difficult. These studies provide new insights into virus-free iPS technology and contribute to defining future cell-based therapies, drug screening methods, and production of transgenic animals with genetically modified iPS cells.