Project description:Replacing the transcription factor OCT4, one of the master pluripotency regulators, by small molecules has been a long standing challenge to establish small molecule based reprogramming for the generation of human chemically induced pluripotent stem cells (hciPSCs). Using a cell-based high throughput screen, we have previously identified a new series of OCT4-inducing compounds (O4Is). In this paper, we prepared metabolically stable analogues, including O4I4, which strongly activate pluripotency-associated signaling. In combination with a transcription factor cocktail of SOX2, KLF4, MYC, and LIN28 (collectively referred to as CSKML) we achieved to reprogram human fibroblasts into a stable and authentic pluripotent state independent of exogenous OCT4. Transcriptomic analysis of fibroblasts reprogrammed by this approach revealed that O4I4 activated bone morphogenetic protein (BMP)/SMAD/ID signaling at the early stage of reprogramming and subsequent expression of the chromatin modifier, high mobility group A1 (HMGA1), resulting in re-activation of endogenous OCT4 to initiate the reprogramming process. Consistently, chemical or genetic inhibition of BMP/SMAD/ID or HMGA1 was found to block cellular reprogramming. In C.elegans and Drosophila, O4I4 expanded life spans in a BMP-signaling pathway-dependent manner. Given limitations of OCT4-based reprogramming, our findings provide an alternative to OSKM-mediated iPSC generation, and importantly unravel previously-unrecognized molecular mechanisms of pluripotency in the context of regenerative medicine and rejuvenation therapy.
Project description:Somatic cells can be reprogrammed into induced pluripotent stem (iPS) cells by Oct4, Sox2, Klf4, plus c-Myc. Recently, Sox2 plus Oct4 were shown to reprogram fibroblasts and Oct4 alone to reprogram mouse and human neural stem cells (NSCs) into iPS cells. Here we report that Bmi1 leads to dedifferentiation of mouse fibroblasts into NSC-like cells and, in combination with Oct4, replaces Sox2, Klf4 and c-Myc during reprogramming fibroblasts to iPS cells. Furthermore, activation of sonic hedgehog signalling (by Shh, purmorphamine, or oxysterol) replaces the effects of Bmi1, and, in combination with Oct4, reprograms mouse embryonic and adult fibroblasts into iPS cells. One-and two-factor iPS cells are similar to mouse embryonic and adult fibroblasts into iPS cells in global gene expression profile, epigenetic status, in vitro and in bibo differentiation into all three ferm layers, as well as teratoma formation and germline transmission in vivo. These data support that fibroblasts can be reprogrammed into iPS cells by Oct4 alone. Total RNAs were isolated from indicated cells and labeled with Cy3. Hybridization was performed once for each sample.
Project description:SOX2 and OCT4, in conjunction with KLF4 and cMYC, are sufficient to reprogram human fibroblasts to induced pluripotent stem cells (iPSCs), but it is unclear if they function as transcriptional activators or as repressors. We now show that, like OCT4, SOX2 functions as a transcriptional activator. We substituted SOX2-VP16 (a strong activator) for wild-type (WT) SOX2, and we saw an increase in the efficiency and rate of reprogramming, whereas the SOX2-HP1 fusion (a strong repressor) eliminated reprogramming. We report that, at an early stage of reprogramming, virtually all DNA-bound OCT4, SOX2, and SOX2-VP16 were embedded in putative enhancers, about half of which were created de novo. Those associated with SOX2-VP16 were, on average, stronger than those bearing WT SOX2. Many newly created putative enhancers were transient, and many transcription factor locations on DNA changed as reprogramming progressed. These results are consistent with the idea that, during reprogramming, there is an intermediate state that is distinct from both parental cells and iPSCs
Project description:SOX2 and OCT4, in conjunction with KLF4 and cMYC, are sufficient to reprogram human fibroblasts to induced pluripotent stem cells (iPSCs), but it is unclear if they function as transcriptional activators or as repressors. We now show that, like OCT4, SOX2 functions as a transcriptional activator. We substituted SOX2-VP16 (a strong activator) for wild-type (WT) SOX2, and we saw an increase in the efficiency and rate of reprogramming, whereas the SOX2-HP1 fusion (a strong repressor) eliminated reprogramming. We report that, at an early stage of reprogramming, virtually all DNA-bound OCT4, SOX2, and SOX2-VP16 were embedded in putative enhancers, about half of which were created de novo. Those associated with SOX2-VP16 were, on average, stronger than those bearing WT SOX2. Many newly created putative enhancers were transient, and many transcription factor locations on DNA changed as reprogramming progressed. These results are consistent with the idea that, during reprogramming, there is an intermediate state that is distinct from both parental cells and iPSCs.
Project description:Somatic cells can be reprogrammed into induced pluripotent stem (iPS) cells by Oct4, Sox2, Klf4, plus c-Myc. Recently, Sox2 plus Oct4 were shown to reprogram fibroblasts and Oct4 alone to reprogram mouse and human neural stem cells (NSCs) into iPS cells. Here we report that Bmi1 leads to dedifferentiation of mouse fibroblasts into NSC-like cells and, in combination with Oct4, replaces Sox2, Klf4 and c-Myc during reprogramming fibroblasts to iPS cells. Furthermore, activation of sonic hedgehog signalling (by Shh, purmorphamine, or oxysterol) replaces the effects of Bmi1, and, in combination with Oct4, reprograms mouse embryonic and adult fibroblasts into iPS cells. One-and two-factor iPS cells are similar to mouse embryonic and adult fibroblasts into iPS cells in global gene expression profile, epigenetic status, in vitro and in bibo differentiation into all three ferm layers, as well as teratoma formation and germline transmission in vivo. These data support that fibroblasts can be reprogrammed into iPS cells by Oct4 alone.
Project description:SOX2 and OCT4, in conjunction with KLF4 and cMYC, are sufficient to reprogram human fibroblasts to induced pluripotent stem cells (iPSCs), but it is unclear if they function as transcriptional activators or as repressors. We now show that, like OCT4, SOX2 functions as a transcriptional activator. We substituted SOX2-VP16 (a strong activator) for wild-type (WT) SOX2, and we saw an increase in the efficiency and rate of reprogramming, whereas the SOX2-HP1 fusion (a strong repressor) eliminated reprogramming. We report that, at an early stage of reprogramming, virtually all DNA-bound OCT4, SOX2, and SOX2-VP16 were embedded in puta- tive enhancers, about half of which were created de novo. Those associated with SOX2-VP16 were, on average, stronger than those bearing WT SOX2. Many newly created putative enhancers were tran- sient, and many transcription factor locations on DNA changed as reprogramming progressed. These results are consistent with the idea that, during re- programming, there is an intermediate state that is distinct from both parental cells and iPSCs.
Project description:The evolutionary origins of the gene network underlying cellular pluripotency, a central theme in developmental biology, have yet to be elucidated. In mammals, Oct4 is a factor crucial in the reprogramming of differentiated cells into induced pluripotent stem cells. The Oct4 and Pou2 genes evolved from a POU class V gene ancestor, but it is unknown whether pluripotency induced by Oct4 gene activity is a feature specific to mammals or was already present in ancestral vertebrates. Here we report that different vertebrate Pou2 and Oct4 homologues can induce pluripotency in mouse and human fibroblasts and that the inability of zebrafish Pou2 to establish pluripotency is not representative of all Pou2 genes, as medaka Pou2 and axolotl Pou2 are able to reprogram somatic cells into pluripotent cells. Therefore, our results indicate that induction of pluripotency is not a feature specific to mammals, but existed in the Oct4/Pou2 common ancestral vertebrate. 16 samples were analyzed Notation: O: stands for OCT4 reprogramming factor from human; o: stands for Oct4 reprogramming factor from Axolotl S: stands for SOX2 reprogramming factor from human; s: stands for SOX2 reprogramming factor from Axolotl K: stands for KLF4 reprogramming factor from human
Project description:The success of Yamanaka factor reprogramming mouse embryonic fibroblasts (MEFs) into induced pluripotent stem cells (iPSCs) suggests that some factor(s) must remodel the nuclei from a condensed state to a relaxed state to facilitate factor binding to target genes. We asked how the Yamanaka factor-dependent chromatin opening occurs. We found Oct4, but neither Sox2 nor Klf4, is responsible for the loosening of the condensed state. Oct4 acts as a pioneer factor that facilitates the binding of Klf4 and the expression of epithelial genes in the early stage of reprogramming.
Project description:Resolution of early molecular events preceding endogenous OCT4 activation is critical to understanding the mechanism of reprogramming somatic cells to induced pluripotent stem cells (iPSCs), yet capturing transient regulators at the onset of reprogramming is difficult in heterogeneous populations of asynchronously reprogramming fibroblasts following four-factor transduction. To address this need, we used a heterokaryon system to identify an early and transiently expressed homeobox transcription factor, NKX3-1. Upon knockdown of NKX3-1, iPSC reprogramming is abrogated. Further, we identify that NKX3-1 functions downstream of the IL6-STAT3 regulatory network to activate endogenous OCT4. Importantly, we show that NKX3-1 can substitute for exogenous OCT4 to reprogram both mouse and human fibroblasts at comparable efficiencies generate fully pluripotent stem cells. Our findings establish an essential role for NKX3-1, previously known as a prostate-specific tumor suppressor, in iPSC reprogramming.
Project description:Resolution of early molecular events preceding endogenous OCT4 activation is critical to understanding the mechanism of reprogramming somatic cells to induced pluripotent stem cells (iPSCs), yet capturing transient regulators at the onset of reprogramming is difficult in heterogeneous populations of asynchronously reprogramming fibroblasts following four-factor transduction. To address this need, we used a heterokaryon system to identify an early and transiently expressed homeobox transcription factor, NKX3-1. Upon knockdown of NKX3-1, iPSC reprogramming is abrogated. Further, we identify that NKX3-1 functions downstream of the IL6-STAT3 regulatory network to activate endogenous OCT4. Importantly, we show that NKX3-1 can substitute for exogenous OCT4 to reprogram both mouse and human fibroblasts at comparable efficiencies generate fully pluripotent stem cells. Our findings establish an essential role for NKX3-1, previously known as a prostate-specific tumor suppressor, in iPSC reprogramming.