DNA methylation and demethylation have been proposed to play an important role in somatic cell reprogramming. Here, we demonstrate that the DNA hydroxylase Tet1 facilitates pluripotent stem cell induction by promoting Oct4 demethylation and reactivation. Moreover, Tet1 (T) can replace Oct4 and initiate somatic cell reprogramming in conjunction with Sox2 (S), Klf4 (K), and c-Myc (M). We established an efficient TSKM secondary reprogramming system and used it to characterize the dynamic profiles of 5-methylcytosine (5mC), 5-hydroxymethylcytosine (5hmC), and gene expression during reprogramming. Our analysis revealed that both 5mC and 5hmC modifications increased at an intermediate stage of the process, correlating with a transition in the transcriptional profile. We also found that 5hmC enrichment is involved in the demethylation and reactivation of genes and regulatory regions that are important for pluripotency. Our data indicate that changes in DNA methylation and hydroxymethylation play important roles in genome-wide epigenetic remodeling during reprogramming.
The generation of induced pluripotent stem cells (iPSCs) from differentiated somatic cells by over-expression of several transcription factors has the potential to cure many genetic and degenerative diseases currently recalcitrant to traditional clinical approaches. One such genetic disease is β-thalassemia major (Cooley's anemia). This disease is caused by either a point mutation or the deletion of several nucleotides in the β-globin gene, and it threatens the lives of millions of people in China. In the present study, we successfully generated iPSCs from fibroblasts collected from a 2-year-old patient who was diagnosed with a homozygous 41/42 deletion in his β-globin gene. More importantly, we successfully corrected this genetic mutation in the β-thalassemia iPSCs by homologous recombination. Furthermore, transplantation of the genetically corrected iPSCs-derived hematopoietic progenitors into sub-lethally irradiated immune deficient SCID mice showed improved hemoglobin production compared with the uncorrected iPSCs. Moreover, the generation of human β-globin could be detected in the mice transplanted with corrected iPSCs-derived hematopietic progenitors. Our study provides strong evidence that iPSCs generated from a patient with a genetic disease can be corrected by homologous recombination and that the corrected iPSCs have potential clinical uses.
These results suggest that GH mainly enhances proliferative activities, whereas GLN promotes the differentiation potential of ISCs.
Protein arginine methylation is emerging as a pivotal posttranslational modification involved in regulating various cellular processes; however, its role in erythropoiesis is still elusive. Erythropoiesis generates circulating red blood cells which are vital for body activity. Deficiency in erythroid differentiation causes anemia which compromises the quality of life. Despite extensive studies, the molecular events regulating erythropoiesis are not fully understood. This study showed that the increase in protein arginine methyltransferase 1 (PRMT1) levels, via transfection or protein transduction, significantly promoted erythroid differentiation in the bipotent human K562 cell line as well as in human primary hematopoietic progenitor CD34+ cells. PRMT1 expression enhanced the production of hemoglobin and the erythroid surface marker glycophorin A, and also up-regulated several key transcription factors, GATA1, NF-E2 and EKLF, which are critical for lineage-specific differentiation. The shRNA-mediated knockdown of PRMT1 suppressed erythroid differentiation. The methyltransferase activity-deficient PRMT1G80R mutant failed to stimulate differentiation, indicating the requirement of arginine methylation of target proteins. Our results further showed that a specific isoform of p38 MAPK, p38α, promoted erythroid differentiation, whereas p38β did not play a role. The stimulation of erythroid differentiation by PRMT1 was diminished in p38α- but not p38β-knockdown cells. PRMT1 appeared to act upstream of p38α, since expression of p38α still promoted erythroid differentiation in PRMT1-knockdown cells, and expression of PRMT1 enhanced the activation of p38 MAPK. Importantly, we showed for the first time that PRMT1 was associated with p38α in cells by co-immunoprecipitation and that PRMT1 directly methylated p38α in in vitro methylation assays. Taken together, our findings unveil a link between PRMT1 and p38α in regulating the erythroid differentiation program and provide evidence suggesting a novel regulatory mechanism for p38α through arginine methylation.
Lysophosphatidic acid (LPA), an extracellular lipid mediator, exerts multiple bioactivities through activating G protein-coupled receptors. LPA receptor 3 (LPA 3 ) is a member of the endothelial differentiation gene family, which regulates differentiation and development of the circulation system. However, the relationship among the LPA receptors (LPARs) and erythropoiesis is still not clear. In this study, we found that erythroblasts expressed both LPA 1 and LPA 3 , and erythropoietic defects were observed in zLPA 3 antisense morpholino oligonucleotide-injected zebrafish embryos. In human model, our results showed that LPA enhanced the erythropoiesis in the cord blood-derived human hematopoietic stem cells (hHSCs) with erythropoietin (EPO) addition in the plasma-free culture. When hHSCs were treated with Ki16425, an antagonist of LPA 1 and LPA 3 , erythropoietic process of hHSCs was also blocked, as detected by mRNA and protein expressions of CD71 and GlyA. In the knockdown study, we further demonstrated that specific knockdown of LPA 3 , not LPA 1 , blocked the erythropoiesis. The translocation of b-catenin into the nucleus, a downstream response of LPAR activation, was blocked by Ki16425 treatment. In addition, upregulation of erythropoiesis by LPA was also blocked by quercetin, an inhibitor of the b-catenin/ T-cell factor pathway. Furthermore, the enhancement of LPA on erythropoiesis was diminished by blocking c-Junactivated kinase/signal transducer and activator of transcription and phosphatidylinositol 3-kinase/AKT activation, the downstream signaling pathways of EPO receptor, suggested that LPA might play a synergistic role with EPO to regulate erythropoietic process. In conclusion, we first reported that LPA participates in EPO-dependent erythropoiesis through activating LPA 3 .
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