Project description:Lineage-specific transcription factors (TFs) play key roles in maintaining the unique properties of cells, but the molecular mechanism that regulates the homeostasis of human corneal epithelial cells (CECs) is still poorly understood. We aimed to modulate KLF4 and PAX6 in human CECs using gene knockout system to clarify the regulatory network of KLF4, and then elucidate how KLF4 regulates the transcriptional genes of human CECs compared with PAX6. We performed a functional analysis of KLF4 via gene knockout using a lentivirus vector that carries both Cas9 and guide RNAs. We designed guide RNAs targeted for KLF4 and PAX6, and created KLF4-, PAX6-, and both KLF4- and PAX6-depleted CECs (KLF4-KO, PAX6-KO, and DKO, respectively). An empty vector was used as a control. The morphology of KLF4-KO CECs displayed an epithelial-mesenchymal transition (EMT)-like change, including upregulation of mesenchymal genes and downregulation of epithelial genes, as well as downregulation of keratin (KRT) 3 and KRT12. Global analyses using NGS revealed that the downregulated genes in KLF4-KO CECs were enriched in more widely keratin-related genes than PAX6-KO CECs. DKO cells showed disruption of the epithelial barrier due to downregulation of epithelial genes and showed more increase of KRT1 and KRT10 than PAX6-KO and KLF4-KO CECs, respectively. In conclusion, KLF4 modulates keratin-related genes as well as EMT-related genes and, together with PAX6, co-regulates the human CEC identity.
Project description:Ability of CTCF binding on various gene promoters is essential to regulate their expression. It's been demonstrated that cornea-specific Pax6 expression is regulated conversely by CTCF (Li et al.). circular chromosome conformation capture (4C) and ChIP-chip profiling have been performed using HTCE cells. This approach is to elicit the epigenetic mechanism involving CTCF-mediated chromatin remodeling that regulates Pax6 and some target gene interactions.
Project description:Since the initial discovery that OCT4, SOX2, KLF4 and c-MYC overexpression sufficed for the induction of pluripotency in somatic cells, methodologies replacing the original factors have enhanced our understanding of the reprogramming process. However, unlike in mouse, OCT4 has not been replaced successfully during reprogramming of human cells. Here we report on a strategy to do so. Through a combination of transcriptome and bioinformatic analysis we have identified factors previously characterized as being lineage specifiers that are able to replace OCT4 and SOX2 in the reprogramming of human fibroblasts. Our results show that is possible to replace OCT4 and SOX2 simultaneously with alternative lineage specifiers in the reprogramming of human cells. At a broader level, they also support a model in which counteracting lineage specification networks underlie the induction of pluripotency, We analyzed 3 arrays from human fibroblats; 1 array from 4F iPSC; 1 array from 4F iPSC; 1 array for GATA3SOX2, KLF4 and cMYC iPS; 1 array for GATA3vP16,SOX2VP16, KLF4 and cMYC iPS;1 array for GATA3vP16SOX2VP16, KLF4 and cMYC iPS; 1 array for GATA3vP16SOX2VP16, KLF4 and cMYC iPS; 1 array for hES4;1 array for hES10; 1 arrays for iPS generated with OCT4, ZIC2, ZNF521, ASCL1, HESX1,FOXD5,KLF4 and cMYC; 1 arrays for iPS generated with OCT4, ZIC2, ZNF521, ASCL1, HESX1,FOXD5,KLF4 and cMYC; 1 array for iPS generated with OCT4, SOX1, KLF4 and cMYC;1 array for iPS generated with OCT4, SOX1, KLF4 and cMYC;1 array for iPS generated with OCT4, ZNF521, KLF4 and cMYC: 1 array for iPS generated with OCT4, SOX3, KLF4 and cMYC
Project description:We generated Oct4 libraries by randomizing selected amino acids and by recombining domains of paralogous POU family genes. These libraries were subjected to iterative rounds of pooled screens to select variants that enhance pluripotency induction. We identified an artificially evolved POU factor (ePOU) that substantially outperforms wild-type Oct4 in terms of mouse embryonic fibrobast (MEF) reprogramming. To probe whether the ePOU and Oct4 differentially engage the chromatin of reprogramming cells, we performed chromatin immunoprecipitation sequencing (ChIPseq) for both factors and Sox2. Two cocktails Oct4 (O), Sox2 (S), Klf4 (K), c-Myc (M) and ePOU/S/K/M were transduced into OG2 MEF cells which is MEF cells with Oct4 promotor.
Project description:Cell fate transitions are accompanied by global transcriptional, epigenetic and topological changes driven by transcription factors (TFs), as is strikingly exemplified by reprogramming somatic cells to pluripotent stem cells (PSCs) via expression of OCT4, KLF4, SOX2 and cMYC. How TFs orchestrate the complex molecular changes around their target gene loci in a temporal manner remains incompletely understood. Here, using KLF4 as a paradigm, we provide the first TF-centric view of chromatin reorganization and its association to 3D enhancer rewiring and transcriptional changes of linked genes during reprogramming of mouse embryonic fibroblasts (MEFs) to PSCs. Inducible depletion of KLF factors in PSCs caused a genome-wide decrease in the connectivity of enhancers, while disruption of individual KLF4 binding sites from PSC-specific enhancers was sufficient to impair enhancer-promoter contacts and reduce expression of associated genes. Our study provides an integrative view of the complex activities of a lineage-specifying TF during a controlled cell fate transition and offers novel insights into the order and nature of molecular events that follow TF binding.
Project description:We generated Oct4 libraries by randomizing selected amino acids and by recombining domains of paralogous POU family genes. These libraries were subjected to iterative rounds of pooled screens to select variants that enhance pluripotency induction. We identified an artificially evolved POU factor (ePOU) that substantially outperforms wild-type Oct4 in terms of mouse embryonic fibrobast (MEF) reprogramming. To probe whether the ePOU and Oct4 differentially engage the chromatin of reprogramming cells, we performed Assay for Transposase-Accessible Chromatin with highthroughput sequencing (ATACseq) for both factors and different combination. Two cocktails Sox2 (S), Klf4 (K), c-Myc (M) plus Oct4 (O) or ePOU(e) were transduced into OG2 MEF cells which is MEF cells with Oct4 promotor.
Project description:Novel target genes for the two transcription factor isoforms Pax6 and Pax6(5a) were identified by generating mouse embryonic fibroblast cell lines stably expressing either Pax6 or Pax6(5a), and comparing their gene expression pattern with the original mouse embryonic fibroblast cell line.
Project description:Simultaneous expression of Oct4, Klf4, Sox2, and cMyc induces pluripotency in somatic cells (iPSCs). Replacing Oct4 with the neuro-specific factor Brn4 leads to the transdifferentiation of fibroblasts into induced neural stem cells (iNSCs). However, Brn4 was recently found to induce a transient acquisition of pluripotency before establishing the neural fate. We employed genetic lineage tracing and found that induction of iNSCs with individual vectors leads to direct lineage conversion. In contrast, polycistronic expression produces a Brn4-Klf4 fusion protein that enables the induction of pluripotency. Our study demonstrates that a combination of pluripotency and tissue-specific factors allows for direct somatic cell transdifferentiation, bypassing the acquisition of a pluripotent state. This result has major implications for lineage conversion technologies, which hold potential for providing a safer alternative to iPSCs for clinical application both in vitro and in vivo.
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