Project description:Human artificial chromosomes (HACs) have unique characteristics as gene-delivery vector, e.g., episomal transmission and transfer of multiple, large transgenes. Here, we demonstrate the advantages of HAC vectors for reprogramming mouse embryonic fibroblasts (MEFs) to induced pluripotent stem (iPS) cells. Two HAC vectors (iHAC1 and iHAC2) were constructed. Both carried four reprogramming factors, and iHAC2 also encoded a p53-knockdown construct (see Kazuki et al 2011). The iHAC1 partially reprogrammed MEFs, and the iHAC2 efficiently reprogrammed MEFs. Global gene expression showed that the iHACs, unlike other vectors, generated relatively uniform iPS cells. We established iHAC-free iPS cells by isolating cells that spontaneously lost the iHAC2. Analyses of pluripotent markers, teratomas, and chimeras confirmed that these iHAC-free iPS cells were pluripotent. Moreover, iHAC-free iPS cells with a re-introduced HAC encoding Herpes Simplex Virus Thymidine Kinase were eliminated by Ganciclovir treatment; therefore, the HAC safeguard system functioned in iPS cells. Thus, the HAC vector could generate uniform, integration-free iPS cells with a safeguard system.
Project description:Human artificial chromosomes (HACs) have unique characteristics as gene-delivery vector, e.g., episomal transmission and transfer of multiple, large transgenes. Here, we demonstrate the advantages of HAC vectors for reprogramming mouse embryonic fibroblasts (MEFs) to induced pluripotent stem (iPS) cells. Two HAC vectors (iHAC1 and iHAC2) were constructed. Both carried four reprogramming factors, and iHAC2 also encoded a p53-knockdown construct (see Kazuki et al 2011). The iHAC1 partially reprogrammed MEFs, and the iHAC2 efficiently reprogrammed MEFs. Global gene expression showed that the iHACs, unlike other vectors, generated relatively uniform iPS cells. We established iHAC-free iPS cells by isolating cells that spontaneously lost the iHAC2. Analyses of pluripotent markers, teratomas, and chimeras confirmed that these iHAC-free iPS cells were pluripotent. Moreover, iHAC-free iPS cells with a re-introduced HAC encoding Herpes Simplex Virus Thymidine Kinase were eliminated by Ganciclovir treatment; therefore, the HAC safeguard system functioned in iPS cells. Thus, the HAC vector could generate uniform, integration-free iPS cells with a safeguard system. Total RNA from mouse embryonic fibroblasts, two control ES cells (TT2 and B6ES), retrovirus vector-derived iPS cells (20D17), and twelve HAC-derived iPS clones were hybridized to the Agilent Whole Mouse Genome microarrays.
Project description:We tested various architectures of artificial transcription factors (ATFs) in HEK293 cells to test the contribution of the interaction domain, nuclear localization domain, size of DNA-binding domain, and activation domain. Then we made a genome-scale ATF library and tested it in reprogramming mouse embryonic fibroblasts to induced pluripotent stem (iPS) cells. Three combinations of ATFs (C2, C3, and C4) could induce pluripotency when expressed with Sox2, Klf4, and c-Myc. We harvested polyadenylated RNAs from 11 cell types derived with different sets of factors. The transcriptional profiles of ATF-induced iPS cells are similar to that of iPS cells induced with Oct4, Sox2, Klf4, and c-Myc and mouse embryonic stem cells, exhibiting up-regulation of pluripotency markers and down-regulation of fibroblast markers. Comparisons of cells undergoing reprogramming at an intermediate stage before becoming fully reprogrammed suggest that ATFs activate a different set of genes than the set activated by Oct4. This study provides a proof-of-principle that a gene-activating ATF library can be used to identify cell fate-defining transcriptional networks in an unbiased manner.
Project description:RNA sequencing of salinity tolerant Arabidopsis thaliana mutants expressing zinc finger artificial transcription factors (ZF-ATFs), with and without salt treatment (0 mM and 75 mM NaCl).
Project description:Ectopic expression of four transcription factors including Oct4, Sox2, Klf4 and c-Myc in differentiated fibroblast cells could reset the cell fate of fibroblast cells to pluripotent state. Subsequently, fully pluripotency of these so-called induced pluripotent stem cells (iPSCs) has been demonstrated as viable mice could be generated autonomously from iPS cells through tetraploid blastocyst complementation. Moreover, the generation of human and patient-specific iPS cells have raised the possibility of utilizing iPS cells clinically. However, the utilization of c-Myc in iPS cells induction greatly increased the incidence of tumorigenecity in the iPS-chimeric mice and also might hinder the clinical application of human iPS cells in the future. Fortunately, c-Myc has been recently found dispensable for iPS induction even though the iPS induction efficiency is greatly reduced in the absence of c-Myc. However, it remains unknown if these three factors-induced iPS cells are fully pluripotent. In the present study, we have successfully demonstrated that 3-factor iPS cells could also be fully pluripotent as viable mice could be generated from 3-factor iPS cells autonomously via tetraploid complementation and moreover, our data indicated that the pluripotency regulatory mechanism in 3-factor iPS cells might be distinct from 4-factor iPS cells.