Project description:Epigenetic memory in induced pluripotent stem cells (iPSCs), with regards to their somatic cell type of origin, might lead to variations in their differentiation capacities. In this context, iPSCs from human CD34+ hematopoietic stem cells (HSCs) might be more suitable for hematopoietic differentiation than commonly used fibroblast-derived iPSCs. To investigate the influence of an epigenetic memory on the ex vivo expansion of iPSCs into erythroid cells, we compared iPSCs from human neural stem cells (NSCs) and human cord blood-derived CD34+ HSCs and evaluated their potential for differentiation into hematopoietic progenitor and mature red blood cells (RBCs). Although genome-wide DNA methylation profiling at all promoter regions demonstrates an epigenetic memory of iPSCs with regards to their somatic cell type of origin, we found a similar hematopoietic induction potential and erythroid differentiation pattern. All human iPSC lines showed terminal maturation into normoblasts and enucleated RBCs, producing predominantly fetal hemoglobin. Differences were only observed in the growth rate of erythroid cells, which was slightly higher in the CD34+ HSC-derived iPSCs. More detailed methylation analysis of the hematopoietic and erythrocyte promoters identified similar CpG methylation levels in the CD34+ iPSCs and NSC iPSCs, which confirms their comparable erythroid differentiation potential. To investigate the influence of an epigenetic memory on the ex vivo expansion of iPSCs into erythroid cells, we compared iPSCs from human neural stem cells (NSCs) and human cord blood-derived CD34+ HSCs and evaluated their potential for differentiation into hematopoietic progenitor and mature red blood cells (RBCs). RNA samples for microarray analysis were prepared using RNeasy columns (Qiagen, Germany) with on-column DNA digestion. 300ng of total RNA per sample was used as the input in the linear amplification protocol (Ambion), which involved the synthesis of T7-linked double-stranded cDNAs and 12hrs of in vitro transcription incorporating the biotin-labeled nucleotides. Purified and labeled cRNA was then hybridized for 18hrs onto HumanHT-12 v4 expression BeadChips (Illumina, USA) following the manufacturer's instructions. After the recommended washing, the chips were stained with streptavidin-Cy3 (GE Healthcare) and scanned using the iScan reader (Illumina) and the accompanying software. The samples were exclusively hybridized as biological replicates. 8 samples were analyzed: CD34 1, Human CD34+ Cord blood CD34+ Hematopoyetic Stem Cell(HSC) population 1, 1 replicate CD34 2, Human CD34+ Cord blood CD34+ Hematopoyetic Stem Cell(HSC) population 2, 1 replicate CD34 OSiPS 1, Human Human two factors (POU5F1, SOX2) induced Pluripotent Cell (iPSC) reprogrammed from CD34+ Cord blood CD34+ Hematopoyetic Stem Cell(HSC) induced Pluripotent Cell (iPSC) population 1, 1 replicate CD34 OSKMiPS 1, Human Human four factors (POU5F1, SOX2, KLF4, CMYC) induced Pluripotent Cell (iPSC) reprogrammed from CD34+ Cord blood CD34+ Hematopoyetic Stem Cell(HSC) induced Pluripotent Cell (iPSC) population 1, 1 replicate CD34 OSiPS 2, Human Human two factors (POU5F1, SOX2) induced Pluripotent Cell (iPSC) reprogrammed from CD34+ Cord blood CD34+ Hematopoyetic Stem Cell(HSC) induced Pluripotent Cell (iPSC) population 2, 1 replicate CD34 OSKMiPS 2, Human Human four factors (POU5F1, SOX2, KLF4, CMYC) induced Pluripotent Cell (iPSC) reprogrammed from CD34+ Cord blood CD34+ Hematopoyetic Stem Cell(HSC) induced Pluripotent Cell (iPSC) population 2, 1 replicate H1, Human H1 embryonic stem cell (ESC), 1 replicate H9, Human H9 embryonic stem cell (ESC), 1 replicate

Project description:Human embryonic stem cells (hESCs) offer an important model for investigating the human hematopoietic celldevelopment. Here, we used long serial analysis of gene expression and quantitative real-time PCR to characterize two subsets of primitive hematopoietic cells derived in vitro from hESCs. This revealed differences in their expression of genes associated with lymphoid and myeloid development, cellular biosynthetic processes, and cell cycle regulation. Further comparisons with analogous data for primitive hematopoietic cells isolated from first trimester human fetal liver and newborn cord blood showed a strong similarity between the transcriptomes of the most primitive hESC- and in vivo-derived populations, with the main differences involving genes that regulate HSC development, self-renewal and homing, chromatin remodeling, AP1 transcription complex genes, and non-coding RNAs. These data suggest that primitive hematopoietic cells are generated from hESCs in vitro by processes similar to those operative during human embryogenesis in vivo, although some differences were also detected. Human embryonic stem cells (hESCs) are capable of indefinite self-renewal but can also be induced to undergo a stepwise process of differentiation into a spectrum of recognizable mature blood cell types. However, a clear understanding of the molecular mechanism by which the first hematopoietic stem cells (HSCs) acquire their unique defining properties of self-renewal and repopulating potential is lacking. As a first step towards obtaining the information needed to close this gap, we have undertaken a comparative gene expression analysis of different highly purified primitive human hematopoietic subpopulations (erythroid-megakaryocytic progenitor enriched CD43+CD235a+CD41a+/- cells, mutiplepotent progenitor enriched lin-CD34+CD43+CD45-, and lin-CD34+CD43+CD45+ cells) generated either in vitro from hESCs or in vivo from fetal (human fetal liver lin-CD34+CD38- cells) or neonatal hematopoietic primitive cells (human cord blood lin-CD34+CD38- and lin-CD34+CD38+ cells). This involved preparing a long serial analysis of gene expression (LongSAGE) library from an extracts of each prospectively isolated subpopulation and then sequencing each library to a depth of 200,000 tags.

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