We thank Matt Raymond for editorial assistance. This work was supported by funds from the National Institute of Health (U01HL099773, R01HL116221, and P51 RR000167) and The Charlotte Geyer Foundation.

1. Virus Preparations and Transcription Factor Combinations
<ol>
	<li>Prepare solutions with pSIN-EF1&#945; lentiviral expression plasmid containing protein-coding DNA for ETV2, GATA1, GATA2, TAL1 and LMO2 (Table 1).</li>
	<li>Measure the concentration and purity of plasmid preparations used for lentiviral production by recording UV absorption with a spectrophotometer at 230 nm, 260 nm, and 280 nm. Note: DNA preparations demonstrating A260/280 and A260/230 values greater than 1.8 are generally ...

<ol>
	<li>Zape, J. P., Zovein, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hemogenic+endothelium:+origins,+regulation,+and+implications+for+vascular+biology.">Hemogenic endothelium: origins, regulation, and implications for vascular biology.</a> Semin Cell Dev Biol. 22, 1036-1047 (2011).</li><li>Swiers, G., Rode, C., Azzoni, E., de Bruijn, M. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+short+history+of+hemogenic+endothelium.">A short history of hemogenic endothelium.</a> Blood Cells, Mol &amp; Dis. 51, 206-212 (2013).</li><li>Kennedy, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=T+lymphocyte+potential+marks+the+emergence+of+definitive+hematopoietic+progenitors+in+human+pluripotent+stem+cell+differentiation+cultures.">T lymphocyte potential marks the emergence of definitive hematopoietic progenitors in human pluripotent stem cell differentiation cultures.</a> Cell Rep. 2, 1722-1735 (2012).</li><li>Wang, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+and+hematopoietic+cell+fate+of+human+embryonic+stem+cells+originates+from+primitive+endothelium+with+hemangioblastic+properties.">Endothelial and hematopoietic cell fate of human embryonic stem cells originates from primitive endothelium with hemangioblastic properties.</a> Immunity. 21, 31-41 (2004).</li><li>Rafii, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+ESC-derived+hemogenic+endothelial+cells+undergo+distinct+waves+of+endothelial+to+hematopoietic+transition.">Human ESC-derived hemogenic endothelial cells undergo distinct waves of endothelial to hematopoietic transition.</a> Blood. 121 (5), 770-780 (2012).</li><li>Choi, K. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+the+hemogenic+endothelial+progenitor+and+its+direct+precursor+in+human+pluripotent+stem+cell+differentiation+cultures.">Identification of the hemogenic endothelial progenitor and its direct precursor in human pluripotent stem cell differentiation cultures.</a> Cell Rep. 2, 553-567 (2012).</li><li>Vodyanik, M. A., Thomson, J. A., Slukvin, I. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leukosialin+(CD43)+defines+hematopoietic+progenitors+in+human+embryonic+stem+cell+differentiation+cultures.">Leukosialin (CD43) defines hematopoietic progenitors in human embryonic stem cell differentiation cultures.</a> Blood. 108, 2095-2105 (2006).</li><li>Wang, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TGFbeta+inhibition+enhances+the+generation+of+hematopoietic+progenitors+from+human+ES+cell-derived+hemogenic+endothelial+cells+using+a+stepwise+strategy.">TGFbeta inhibition enhances the generation of hematopoietic progenitors from human ES cell-derived hemogenic endothelial cells using a stepwise strategy.</a> Cell Res. 22, 194-207 (2012).</li><li>Uenishi, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tenascin+C+promotes+hematoendothelial+development+and+T+lymphoid+commitment+from+human+pluripotent+stem+cells+in+chemically+defined+conditions.">Tenascin C promotes hematoendothelial development and T lymphoid commitment from human pluripotent stem cells in chemically defined conditions.</a> Stem Cell Rep. 3, 1073-1084 (2014).</li><li>Elcheva, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+induction+of+haematoendothelial+programs+in+human+pluripotent+stem+cells+by+transcriptional+regulators.">Direct induction of haematoendothelial programs in human pluripotent stem cells by transcriptional regulators.</a> Nat Commun. 5, 4372 (2014).</li><li>Tiscornia, G., Singer, O., Verma, I. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+and+purification+of+lentiviral+vectors.">Production and purification of lentiviral vectors.</a> Nat Protoc. 1, 241-245 (2006).</li><li>Vodyanik, M. A., Slukvin, I. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hematoendothelial+differentiation+of+human+embryonic+stem+cells.">Hematoendothelial differentiation of human embryonic stem cells.</a> Curr Protoc Cell Biol. Chapter 23, Unit 23.6 (2007).</li><li>Cao, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+gene-transfer+efficiency+in+human+embryonic+stem+cells.">Comparison of gene-transfer efficiency in human embryonic stem cells.</a> Mol Imgn and Biol. 12, 15-24 (2010).</li></ol>

I.S. is a founding shareholder and consultant for Cynata.

The above-described method for hematopoietic differentiation of hPSCs by overexpression of TFs, represents a rapid and efficient approach for the generation of HE and myeloid and erytho-magakaryocytic progenitors from hESCs and iPSCs, thereby allowing the production of up to 30 millions blood cells from one million pluripotent stem cells10. This method exhibited consistent differentiation in multiple hESC and iPSCs lines10. During differentiation by ETV2 and GATA2, GATA1 factors as well as GATA2 and...

The unique ability of human pluripotent stem cells (hPSCs) to self-renew and to differentiate into cells of the three germ layers, including blood, make them a valuable tool for the mechanistic studies of hematopoietic development, modeling of blood diseases, drug screening, toxicity studies, and the development of cellular therapies. Because blood formation in the embryo proceeds from hemogenic endothelium (HE) through an endothelial hematopoietic transition1,2, the generation of HE in cultures would be essential to study the molecular mechanisms regulating the endothelial to hematopoietic transition and hematopoietic specification. Current methods for studies of HE are based on the induction of hematoendothelial differentiation in aggregates (EBs) with the addition of hematopoietic cytokines3-5, and coculture of hPSCs with hematopoiesis-supportive stromal cells6,7 or in two-dimensional cultures with extracellular matrices and cytokines8,9. These classical differentiation methods are based on the introduction of external signals acting at the cell surface and initiating cascades of molecular pathways that eventually lead to the activation of transcriptional program guiding hematoendothelial development. Thus, the efficiency of hPSCs differentiations in these systems relies on an effective induction of those signals, signal transduction to the nucleus, and the resulting activation of specific transcriptional regulators. In addition, the study of HE in conventional differentiation cultures requires the additional step of isolating HE cells using cell sorting. Here, we describe a simple protocol for the direct induction of HE and blood by overexpression of hematopoietic transcription factors. This method allows for the efficient induction of HE in a dish and direct observation of the endothelial to hematopoietic transition without the need for isolation of HE using a cumbersome cell sorting procedure.
Formation of HE and blood from human pluripotent stem cells can be efficiently induced by overexpressing just a few transcription factors (TFs). The optimal combination of TFs capable of inducing robust pan-myeloid hematopoiesis from hPSCs includes ETV2 and GATA1 or GATA2. In contrast, combination of GATA2 and TAL1 induces erythromegakaryocytopoiesis10. Programming hPSCs through overexpression of these factors differentiates hPSCs directly to the VE-cad+CD43-CD73- HE cells that gradually acquire the hematopoietic phenotype defined by the expression of the early hematopoietic marker CD437. This lentiviral-based method for the direct programming of human pluripotent stem cells method is applicable for the generation of HE and blood cells for mechanistic studies, studies of endothelial to hematopoietic transition, and transcriptional regulation of hematopoietic development and specification. Although the current protocol describes blood production using constitutive expression of the transgenes, similar results could be obtained using modified mRNA10.

Table 1. Induction of hPSCs differentiation with trancription factors and analysis of hemogenic endothelium and blood cells.
<table>
	<tbody>
		<tr>
			<td>pSIN4-EF1a-ETV2-IRES-Puro&#160;</td>
			<td>Addgene</td>
			<td>Plasmid #61061</td>
			<td>Lentiviral Vector</td>
		</tr>
		<tr>
			<td>pSIN4-EF1a-GATA2-IRES-Puro&#160;</td>
			<td>Addgene</td>
			<td>Plasmid #61063</td>
			<td>Lentiviral Vector</td>
		</tr>
		<tr>
			<td>pSIN4-EF1a-GATA1-IRES-Puro&#160;</td>
			<td>Addgene</td>
			<td>Plasmid #61062</td>
			<td>Lentiviral Vector</td>
		</tr>
		<tr>
			<td>pSIN4-EF1a-TAL1-IRES-Puro&#160;</td>
			<td>Addgene</td>
			<td>Plasmid #61062</td>
			<td>Lentiviral Vector</td>
		</tr>
		<tr>
			<td>pSIN4-EF1a-LMO2-IRES-Puro&#160;</td>
			<td>Addgene</td>
			<td>Plasmid #61064</td>
			<td>Lentiviral Vector</td>
		</tr>
		<tr>
			<td>Hexadimethrine bromide (Polybrene)&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>107689-10G</td>
			<td>Cationic polymer used to increase the efficiency of infection</td>
		</tr>
		<tr>
			<td>Y-27632 (Dihydrochloride) ROCK inhibitor</td>
			<td>STEMCELL Technologies</td>
			<td>72302</td>
			<td>RHO/ROCK pathway inhibitor Inhibits ROCK</td>
		</tr>
		<tr>
			<td rowspan="2">StemPro Accutase Cell Dissociation Reagent</td>
			<td rowspan="2"><a href="http://www.lifetechnologies.com/us/en/home/life-science/stem-cell-research/stem-cell-culture/stem-cell-research-misc/stempro-accutase.html">Life Technologies</a></td>
			<td rowspan="2">A11105-01</td>
			<td rowspan="2">Cell Dissociation Reagent</td>
		</tr>
		<tr>
		</tr>
		<tr>
			<td>Incomplete (growth factor- free) culture medium&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; mTeSR1 Custom formulation&#160;</td>
			<td>WiCell Research Institute (Madison, WI)</td>
			<td>MCF</td>
			<td><a name="RANGE!D12">Serum-free mTeSR1 medium without bFGF and TGFb&#160;</a></td>
		</tr>
		<tr>
			<td>human SCF</td>
			<td>Peprotech</td>
			<td>300-07</td>
			<td>Premium grade</td>
		</tr>
		<tr>
			<td>human TPO</td>
			<td>Peprotech</td>
			<td>300-18</td>
			<td>Research grade</td>
		</tr>
		<tr>
			<td>human FGF-basic</td>
			<td>Peprotech</td>
			<td>100-18B</td>
			<td>Premium grade</td>
		</tr>
		<tr>
			<td>CD144 (VE-cad) FITC</td>
			<td>BD Biosciences</td>
			<td>560411</td>
			<td>Endothelial marker (FACS)</td>
		</tr>
		<tr>
			<td>CD226 PE</td>
			<td>BD Biosciences</td>
			<td>338305</td>
			<td>Hematopoietic (FACS)</td>
		</tr>
		<tr>
			<td>CD43 PE</td>
			<td>BD Biosciences</td>
			<td>560199</td>
			<td>Hematopoietic (FACS)</td>
		</tr>
		<tr>
			<td>CD73 APC</td>
			<td>R&#38;D Systems</td>
			<td>FAB5795A</td>
			<td>Endothelial marker (FACS)</td>
		</tr>
		<tr>
			<td>CD45 APC</td>
			<td>BD Biosciences</td>
			<td>555485</td>
			<td>Hematopoietic (FACS)</td>
		</tr>
		<tr>
			<td>7AAD</td>
			<td>Life Technologies</td>
			<td>A1310</td>
			<td>Live/Dead assay (FACS)</td>
		</tr>
		<tr>
			<td>Paraformaldehyde&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>P6148-500G</td>
			<td>Cell fixation&#160;</td>
		</tr>
		<tr>
			<td>Triton X-100&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>T9284-500ML&#160;</td>
			<td>Permeabilization&#160;</td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>Fisher Scientific</td>
			<td>SH3007003</td>
			<td>Fetal bovine serum</td>
		</tr>
		<tr>
			<td>Mouse anti-human CD43</td>
			<td>BD Biosciences</td>
			<td>551457</td>
			<td>Pure, primary antibody for Immunofluorescence (IF) staining</td>
		</tr>
		<tr>
			<td>Rabbit anti-human VE-cadherin</td>
			<td>BenderMedSystem</td>
			<td>BMS158</td>
			<td>Primary (IF)</td>
		</tr>
		<tr>
			<td>Anti-rabbit Alexa Fluor 488-conjugated</td>
			<td>JacksonResearch</td>
			<td>715-486-152</td>
			<td>Secondary (IF)</td>
		</tr>
		<tr>
			<td>Anti-mouse Alexa Fluor 594-conjugated</td>
			<td>JacksonResearch</td>
			<td>715-516-150&#160;</td>
			<td>Secondary (IF)</td>
		</tr>
		<tr>
			<td>DAPI nucleic acid stain</td>
			<td><a href="http://www.lifetechnologies.com/us/en/home/life-science/stem-cell-research/stem-cell-culture/stem-cell-research-misc/stempro-accutase.html">Life Technologies</a></td>
			<td>D1306&#160;</td>
			<td>Live/Dead assay (IF)</td>
		</tr>
		<tr>
			<td>Clonogenic medium MethoCult H4435 Enriched</td>
			<td>STEMCELL Technologies</td>
			<td>4435</td>
			<td>CFC-assay</td>
		</tr>
		<tr>
			<td>Wright Stain solution</td>
			<td>Sigma -Aldrich</td>
			<td>32857</td>
			<td>Staining cytospins</td>
		</tr>
	</tbody>
</table>

Table 2. hPSCs culture.
<table>
	<tbody>
		<tr>
			<td>Human Pluripotent Stem Cells (hPSCs)&#160;</td>
			<td>WiCell Research Institute (Madison, WI)</td>
			<td>hESCs (WA01, WA09) human Embryonic Stem cells; iPSCs (DF-19-9-7T, DF-4-3-7T) transgene-free induced Pluripotent Stem Cells</td>
			<td>hPSCs are able to self-renew and to differentiate into cells of three germ layers</td>
		</tr>
		<tr>
			<td>Complete serum-free medium for culture of hPSCs&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; mTeSR1 media&#160;&#160;</td>
			<td>WiCell Research Institute (Madison, WI)</td>
			<td>M500&#160;</td>
			<td>Serum-free&#160; medium with growth factors for feeder free culture of ESC/iPSCs</td>
		</tr>
		<tr>
			<td>Matrigel</td>
			<td>BD Biosciences/ Corning&#160;</td>
			<td>356234</td>
			<td>Matrix for maintenance of human ESC/iPSCs</td>
		</tr>
		<tr>
			<td>DMEM/F-12, powder&#160;</td>
			<td><a href="http://www.lifetechnologies.com/us/en/home/life-science/stem-cell-research/stem-cell-culture/stem-cell-research-misc/stempro-accutase.html">Life Technologies</a></td>
			<td>12500-062</td>
			<td>Basal Medium&#160;</td>
		</tr>
		<tr>
			<td>HyClone Dulbecco&#39;s PBS powder</td>
			<td>Fisher Scientific</td>
			<td>dSH30013.04</td>
			<td>PBS</td>
		</tr>
		<tr>
			<td rowspan="2">Dispase II, powder</td>
			<td rowspan="2"><a href="http://www.lifetechnologies.com/us/en/home/life-science/stem-cell-research/stem-cell-culture/stem-cell-research-misc/stempro-accutase.html">Life Technologies</a></td>
			<td rowspan="2">17105-041</td>
			<td rowspan="2">Neutral protease, Cell dissociation</td>
		</tr>
		<tr>
		</tr>
	</tbody>
</table>
Table 3. Primers for detection of virus genomic integration.
<table>
	<tbody>
		<tr>
			<td>Primer&#39;s Name</td>
			<td>Forward (Fwd)&#160; 5&#8217; --&#62;3&#8217;</td>
			<td>Reverse (Rev) 5&#8217;--&#62;3&#8217;</td>
			<td>Discription&#160;</td>
		</tr>
		<tr>
			<td>pSIN EF1a Fwd</td>
			<td>TTC CAT TTC AGG TGT CGT GA</td>
			<td>--</td>
			<td>EF1a promoter sequence</td>
		</tr>
		<tr>
			<td>GATA1 Rev</td>
			<td>--</td>
			<td>TCC CTG TAG TAG GCC AGT GC</td>
			<td>&#160;Coding Region&#160;</td>
		</tr>
		<tr>
			<td>GATA2 Rev</td>
			<td>--</td>
			<td>GGT TGG CAT AGT AGG GGT TG</td>
			<td>&#160;Coding Region&#160;</td>
		</tr>
		<tr>
			<td>TAL1 Rev</td>
			<td>--</td>
			<td>AGG CGG AGG ATC TCA TTC TT</td>
			<td>&#160;Coding Region&#160;</td>
		</tr>
		<tr>
			<td>LMO2 Rev</td>
			<td>--</td>
			<td>GGC CCA GTT TGT AGT AGA GGC</td>
			<td>&#160;Coding Region&#160;</td>
		</tr>
		<tr>
			<td>ETV2 Rev</td>
			<td>--</td>
			<td>GAA CTT CTG GGT GCA GTA AC&#160;</td>
			<td>&#160;Coding Region&#160;</td>
		</tr>
	</tbody>
</table>

direct induction of hemogenic endothelium and blood by overexpression of transcription factors in human pluripotent stem cells

During development, hematopoietic cells arise from a specialized subset of endothelial cells, hemogenic endothelium (HE). Modeling HE development in vitro is essential for mechanistic studies of the endothelial-hematopoietic transition and hematopoietic specification. Here, we describe a method for the efficient induction of HE from human pluripotent stem cells (hPSCs) by way of overexpression of different sets of transcription factors. The combination of ETV2 and GATA1 or GATA2 TFs is used to induce HE with pan-myeloid potential, while a combination of GATA2 and TAL1 transcription factors allows for the production of HE with erythroid and megakaryocytic potential. The addition of LMO2 to GATA2 and TAL1 combination substantially accelerates differentiation and increases erythroid and megakaryocytic cells production. This method provides an efficient and rapid means of HE induction from hPSCs and allows for the observation of the endothelial-hematopoietic transition in a culture dish. The protocol includes hPSCs transduction procedures and post-transduction analysis of HE and blood progenitors.

The schematic diagram of HE and blood induction from hPSCs by overexpression of transcription factors is shown in Figure 1. ETV2 with GATA1 or GATA2 combination induces pan-myeloid hematopoiesis, while a GATA2, TAL1 +/- LMO2 combination induces predominantly erythro-megakaryocytic hematopoiesis. Both TF combinations directly induced HE cells that subsequently transformed into blood progenitors with a distinct spectrum of hematopoietic differentiation. Differentiation of hPSCs from the pluripotent state t...

Watch this Scientific Journal Video about Direct Induction of Hemogenic Endothelium and Blood by Overexpression of Transcription Factors in Human Pluripotent Stem Cells at JoVE.com

Direct Induction of Hemogenic Endothelium and Blood by Overexpression of Transcription Factors in Human Pluripotent Stem Cells

This protocol describes the efficient induction of hemogenic endothelium and multipotential hematopoietic progenitors from human pluripotent stem cells via the forced expression of transcription factors.

During development, hematopoietic cells arise from a specialized subset of endothelial cells, hemogenic endothelium (HE). Modeling HE development in vitro ...

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7.5K Views.  University of Wisconsin-Madison. This protocol describes the efficient induction of hemogenic endothelium and multipotential hematopoietic progenitors from human pluripotent stem cells via the forced expression of transcription factors. 