Generation and characterization of the human iPSC line PBMC1-iPS4F1 from adult peripheral blood mononuclear cells

AbstractHere we describe the generation and characterization of the human induced pluripotent stem cell (iPSC) line PBMC1-iPS4F1 from peripheral blood mononuclear cells from a healthy female with Spanish background. We used heat sensitive, non-integrative Sendai viruses containing the reprogramming factors Oct3/4, Sox2, Klf4 and c-Myc, whose expression was silenced in the established iPSC line. Characterization of the PBMC1-iPS4F1 cell line included analysis of typical pluripotency-associated factors at mRNA and protein level, alkaline phosphatase enzymatic activity, and in vivo and in vitro differentiation studies

Engineered LINE-1 retrotransposition in nondividing human neurons

Half the human genome is made of transposable elements (TEs), whose ongoing activity continues to impact our genome. LINE-1 (or L1) is an autonomous non-LTR retrotransposon in the human genome, comprising 17% of its genomic mass and containing an average of 80-100 active L1s per average genome that provide a source of inter-individual variation. New LINE-1 insertions are thought to accumulate mostly during human embryogenesis. Surprisingly, the activity of L1s can further impact the somatic human brain genome. However, it is currently unknown whether L1 can retrotranspose in other somatic healthy tissues or if L1 mobilization is restricted to neuronal precursor cells (NPCs) in the human brain. Here, we took advantage of an engineered L1 retrotransposition assay to analyze L1 mobilization rates in human mesenchymal (MSCs) and hematopoietic (HSCs) somatic stem cells. Notably, we have observed that L1 expression and engineered retrotransposition is much lower in both MSCs and HSCs when compared to NPCs. Remarkably, we have further demonstrated for the first time that engineered L1s can retrotranspose efficiently in mature nondividing neuronal cells. Thus, these findings suggest that the degree of somatic mosaicism and the impact of L1 retrotransposition in the human brain is likely much higher than previously thought.We thank current members of the J.L.G.-P. laboratory for helpful discussions. We also thank Drs. Geoffrey Faulkner (Mater Research, Australia) and John V. Moran (University of Michigan) for sharing unpublished data and for critical input during the project; Ms. Raquel Marrero (Microscopy Unit, Genyo) for technical support; Simon Mendez-Ferrer (CNIC, Spain) for providing total RNA isolated from human mesenspheres; Dr. Oliver Weichenrieder (Max-Planck, Tubingen, Germany) for providing a polyclonal L1-ORF1p antibody; and Dr. Aurelien Doucet (IRCAN, Nice, France) for providing a plasmid containing an UBC-driven EGFP retrotransposition indicator cassette. J.L.G. was funded by the US Department of Defense, Breast Cancer Research Program (award #BC051386), the National Institutes of Health (NIH) National Institute of Neurological Disorders and Stroke (1R03NS087290-01), and the ALS Therapy Alliance (2013-F-067). A.M. has been partially funded by a Marie Curie IRG project (FP7-PEOPLE-2007-4-3-IRG: SOMATIC LINE-1). J.L.G.-P's laboratory is supported by CICE-FEDER-P09-CTS-4980, CICE-FEDER-P12-CTS-2256, Plan Nacional de I+D+I 2008–2011 and 2013–2016 (FIS-FEDER-PI11/01489 and FIS-FEDER-PI14/02152), PCIN-2014-115-ERA-NET NEURON II, the European Research Council (ERC-Consolidator ERC-STG-2012-233764), by an International Early Career Scientist grant from the Howard Hughes Medical Institute (IECS-55007420), and by The Wellcome Trust–University of Edinburgh Institutional Strategic Support Fund (ISFF2).S

Enhanced hemato-endothelial specification during human embryonic differentiation through developmental cooperation between AF4-MLL and MLL-AF4 fusions.

The t(4;11)(q21;q23) translocation is associated with high-risk infant pro-B-cell acute lymphoblastic leukemia and arises prenatally during embryonic/fetal hematopoiesis. The developmental/pathogenic contribution of the t(4;11)-resulting MLL-AF4 (MA4) and AF4-MLL (A4M) fusions remains unclear; MA4 is always expressed in patients with t(4;11)+ B-cell acute lymphoblastic leukemia, but the reciprocal fusion A4M is expressed in only half of the patients. Because prenatal leukemogenesis manifests as impaired early hematopoietic differentiation, we took advantage of well-established human embryonic stem cell-based hematopoietic differentiation models to study whether the A4M fusion cooperates with MA4 during early human hematopoietic development. Co-expression of A4M and MA4 strongly promoted the emergence of hemato-endothelial precursors, both endothelial- and hemogenic-primed. Double fusion-expressing hemato-endothelial precursors specified into significantly higher numbers of both hematopoietic and endothelial-committed cells, irrespective of the differentiation protocol used and without hijacking survival/proliferation. Functional analysis of differentially expressed genes and differentially enriched H3K79me3 genomic regions by RNA-sequencing and H3K79me3 chromatin immunoprecipitation-sequencing, respectively, confirmed a hematopoietic/endothelial cell differentiation signature in double fusion-expressing hemato-endothelial precursors. Importantly, chromatin immunoprecipitation-sequencing analysis revealed a significant enrichment of H3K79 methylated regions specifically associated with HOX-A cluster genes in double fusion-expressing differentiating hematopoietic cells. Overall, these results establish a functional and molecular cooperation between MA4 and A4M fusions during human hematopoietic development.Wellcome Trust, CRUK, Bloodwise, ERC, Generalitat de Catalunya, Spanish Ministry of Economy and Competitiveness, Spanish Association Against cancer, Health Institute Carlos III, NIHR GOSH BRC, Great Ormond Steet Hospital Children's Charity, Deutsche José Carreras Leukämie Stiftung, Obra Social La Caixa-Fundaciò Josep Carreras, Spanish Association of Cancer Researc

Generation and characterization of the human iPSC line PBMC1-iPS4F1 from adult peripheral blood mononuclear cells

Here we describe the generation and characterization of the human induced pluripotent stem cell (iPSC) line PBMC1-iPS4F1 from peripheral blood mononuclear cells from a healthy female with Spanish background. We used heat sensitive, non-integrative Sendai viruses containing the reprogramming factors Oct3/4, Sox2, Klf4 and c-Myc, whose expression was silenced in the established iPSC line. Characterization of the PBMC1-iPS4F1 cell line included analysis of typical pluripotency-associated factors at mRNA and protein level, alkaline phosphatase enzymatic activity, and in vivo and in vitro differentiation studies

Hoxa9 and EGFP reporter expression in human Embryonic Stem Cells (hESC) as useful tools for studying human development

HoxA9 is an evolutionarily conserved homeobox gene implicated in embryo development. To study the roles of Hoxa9 during human development we generated a transgenic H9 (hESC) line that overexpresses HoxA9 and the Enhanced Green Fluorescent Protein (EGFP), and a control H9 with a stable expression of the EGFP. The resulting H9-HoxA9-EGFP and H9-EGFP cell lines allow an efficient visualization of hESCs by fluorescent microscopy, quantification by flow cytometry and cell differentiation tracking. Both transgenic cell lines maintained the pluripotent phenotype, the ability to differentiate into all three germ layers and a normal karyotype

RUNX1c Regulates Hematopoietic Differentiation of Human Pluripotent Stem Cells Possibly in Cooperation with Proinflammatory Signaling.

Runt-related transcription factor 1 (Runx1) is a master hematopoietic transcription factor essential for hematopoietic stem cell (HSC) emergence. Runx1-deficient mice die during early embryogenesis due to the inability to establish definitive hematopoiesis. Here, we have used human pluripotent stem cells (hPSCs) as model to study the role of RUNX1 in human embryonic hematopoiesis. Although the three RUNX1 isoforms a, b, and c were induced in CD45+ hematopoietic cells, RUNX1c was the only isoform induced in hematoendothelial progenitors (HEPs)/hemogenic endothelium. Constitutive expression of RUNX1c in human embryonic stem cells enhanced the appearance of HEPs, including hemogenic (CD43+) HEPs and promoted subsequent differentiation into blood cells. Conversely, specific deletion of RUNX1c dramatically reduced the generation of hematopoietic cells from HEPs, indicating that RUNX1c is a master regulator of human hematopoietic development. Gene expression profiling of HEPs revealed a RUNX1c-induced proinflammatory molecular signature, supporting previous studies demonstrating proinflammatory signaling as a regulator of HSC emergence. Collectively, RUNX1c orchestrates hematopoietic specification of hPSCs, possibly in cooperation with proinflammatory signaling. Stem Cells 2017;35:2253-2266