Name: an alternative culture method to maintain genomic hypomethylation of mouse embryonic stem cells using mek inhibitor pd0325901 and vitamin c
Uploaded: 2018-06-01T13:00:00
Description: Watch this Scientific Journal Video about An Alternative Culture Method to Maintain Genomic Hypomethylation of Mouse Embryonic Stem Cells Using MEK Inhibitor PD0325901 and Vitamin C at JoVE.com

This work was supported by the National Natural Science Foundation of China (21435008 and 21327006 to H.W.), and the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB14030200 to H.W.).

1. Preparations
<ol>
	<li>Prepare a solution of 1.0 mM PD0325901 (MEK inhibitor) and 3.0 mM CHIR99021 (GSK3 inhibitor).
	<ol>
		<li>Weigh 2 mg of PD0325901 and add 4.15 mL of DMSO in an amber glass vial.</li>
		<li>Weigh 2 mg of CHIR99021 and add 1.43 mL of DMSO in an amber glass vial.</li>
		<li>Following reconstitution, store aliquots (50 &#181;L/tube in 200 &#181;L PCR tubes) at -20 &#176;C and protected from light. Remove a tube containing the frozen stock from a freezer and thaw at room temperatur...

<ol>
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In the work, we demonstrated a novel method of combining Vc and PD0325901 to sustain mouse ES cells at an undifferentiated and hypomethylated state, which was achieved by a synergistic action of promoting DNA demethylation by Vc and suppressing de novo DNA methylation by PD0325901. Moreover, mouse ES cells showed great morphology under the Vc/PD0325901 culture system.
To better sustain the state of mouse ES cells in the Vc/PD0325901 culture system, there are some critical steps. First...

ES cells are originated from the ICM of a blastocyst1. The cells are in a pluripotency state and can form all somatic lineages and germline cells2. Establishment of ES cells provides the opportunity to investigate the development processes in vitro and can generate cells of medical relevance for regenerative medicine based on their pluripotency3.
Two groups seminally established the mouse ES cell lines in 1981 and when cells derived from the early mouse embryo were cultured in fetal bovine serum (FBS)-containing medium with mouse embryonic fibroblasts (MEFs) as the feeder layer1,4. MEFs were inactivated mitotically and were pre-grown in dishes prior to culturing ES cells. MEFs provide support for mouse ES cell attachment and produce growth factors to promote propagation and repress the differentiation5, while FBS offers essential trophic factors and hormones for cell proliferation. Subsequent studies indicated that LIF produced by feeder cells was the key cytokine for self-renewal and maintenance of pluripotency in mouse ES cells, and the addition of LIF into the medium could substitute for feeder cells6. Currently, the sustainment of mouse ES cells in FBS/LIF medium on feeders is still the standard method adopted by many researchers. However, some problems arise with this classical culture approach. Firstly, feeder cells secrete excess and uncontrolled factors and may cause pathogenic contamination7. To avoid this interference, coating the surface of dishes with gelatin and the addition of LIF in serum-containing medium are alternative methods for maintaining mouse ES cells without feeder-layer cells. Additionally, mouse ES cells grown under serum/LIF conditions exhibit morphological heterogeneity in cell populations and even in the expression level of pluripotency-related factors8. Recent studies suggest that under serum/LIF conditions, the pluripotency-related core transcription factors (including SOX2, Nanog, and OCT4) can sustain the pluripotency through LIF and WNT signaling; however, notably, they also activate a fibroblast growth factor (FGF) signal to trigger differentiation8. Due to the ambivalent dual action of the core transcription factors, mouse ES cells cultured in serum present heterogeneity, consisting of two interchangeable populations, one similar to ICM and another resembling the primed epiblast state8. Moreover, mouse ES cells in serum often exhibit global hypermethylation9, whereas ICM and PGCs are in a global hypomethylated state, which is closely linked with their pluripotency9,10.
There is a considerable demand to develop new methods for culturing mouse ES cells. Several improved protocols have been established since 200311 but there continues to be some limitations and shortcomings7. Since 2008, the combined utilization of two small-molecule kinase inhibitors, PD0325901 (the inhibitor of the mitogen-activated protein kinase (MAPK)/extracellular-signal-regulated kinase (ERK) (MEK)) and CHIR99021 (the inhibitor of glycogen synthase kinase 3 (GSK3)), in N2B27 medium with LIF and without serum has opened new perspectives for culturing mouse ES cells12. This new defined medium is characterized by the use of two inhibitors (2i). Mouse ES cells cultured in 2i/LIF medium are more homogeneous in cell populations and the expression of pluripotency factors. In addition, 2i/LIF-cultured mouse ES cells exhibit DNA hypomethylation globally, which is closer to ICM-like cells9,13. Even so, 2i culture has its disadvantages. PD0325901 and CHIR99021 are insoluble in water and generally are dissolved in dimethyl sulfoxide (DMSO)-based stock solution to add them in culture medium. Studies have showed that long-term and low-dose exposure of cells to DMSO can lead to cytotoxicity14.
Here, we utilized two small-molecule compounds and developed a new culture method of mouse ES cells. The novel culture method combines Vc and MEK inhibitor PD0325901 to promote DNA hypomethylation rapidly and effectively to a comparable level of PGC, named as the Vc/PD0325901 culturing protocol. Mouse ES cells in Vc/PD0325901-added serum-containing medium exhibit homogeneity in morphology and are sustained in a ground state. Compared to 2i culture, mouse ES cells cultured under Vc/PD0325901 conditions exhibit faster kinetics of DNA demethylation and can reach the hypomethylation level comparable to that of PGC. In addition, the use of a single inhibitor (PD0325901) decreases the input amount of DMSO into medium in comparison to that used in 2i (PD0325901/CHIR99021) and reduces the damage to cells.

<table border="0" cellpadding="0" cellspacing="0" width="790">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">fetal bovine serum Australia source</td>
			<td style="width:205px;">Corning</td>
			<td style="width:119px;">35-076-CV</td>
			<td style="width:251px;">Component of mouse ES cell medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DMEM/high glucose</td>
			<td style="width:205px;">Hyclone</td>
			<td style="width:119px;">SH30022</td>
			<td>Component of mouse ES cell medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LIF</td>
			<td>Millipore</td>
			<td style="width:119px;">ESG1107</td>
			<td>Component of mouse ES cell medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">non-essential amino acids (NEAA)</td>
			<td style="width:205px;">Gibco</td>
			<td style="width:119px;">11140050</td>
			<td>Component of mouse ES cell medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">sodium pyruvate</td>
			<td style="width:205px;">Gibco</td>
			<td style="width:119px;">11360070</td>
			<td>Component of mouse ES cell medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">L-glutamine</td>
			<td style="width:205px;">Gibco</td>
			<td style="width:119px;">25030081</td>
			<td>Component of mouse ES cell medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">penicillin streptomycin solution</td>
			<td style="width:205px;">Gibco</td>
			<td style="width:119px;">15140122</td>
			<td>Component of mouse ES cell medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">PBS</td>
			<td style="width:205px;">Sigma</td>
			<td style="width:119px;">P5493</td>
			<td>Cells rinse</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">trypsin</td>
			<td style="width:205px;">Hyclone</td>
			<td style="width:119px;">SH30042</td>
			<td>Cell dissociation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">gelatin</td>
			<td style="width:205px;">Sigma</td>
			<td style="width:119px;">48722</td>
			<td>Dishes coating</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PD0325901</td>
			<td>Stemolecule</td>
			<td>04-0006-10</td>
			<td>small-molecule chemical for cell culture</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CHIR99021</td>
			<td>Stemolecule</td>
			<td>04-0004</td>
			<td>small-molecule chemical for cell culture</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">vitamin C</td>
			<td style="width:205px;">Sinopharm Chemical Reagent Co.,Ltd&#160;</td>
			<td style="width:119px;">XW00508171</td>
			<td>small-molecule chemical for cell culture</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ultra Bioscience water purification systemr</td>
			<td style="width:205px;">Purelab</td>
			<td style="width:119px;">Ultra</td>
			<td>Ultra water</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">DMSO</td>
			<td style="width:205px;">Sigma</td>
			<td style="width:119px;">D8418</td>
			<td>Cell freezing medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">centrifuger</td>
			<td style="width:205px;">Eppendorf</td>
			<td style="width:119px;">5427R</td>
			<td>DNA and protein extraction</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">protease inhibitor cocktail</td>
			<td style="width:205px;">Sigma</td>
			<td style="width:119px;">P8340</td>
			<td>Component of RIPA buffer</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">PMSF Protease Inhibitor</td>
			<td style="width:205px;">ThermoFisher Scientific</td>
			<td style="width:119px;">36978</td>
			<td>Component of RIPA buffer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DTT</td>
			<td style="width:205px;">Sigma</td>
			<td style="width:119px;">43815</td>
			<td>Component of RIPA buffer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">EGTA</td>
			<td style="width:205px;">Sigma</td>
			<td style="width:119px;">E3889</td>
			<td>Component of RIPA buffer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Genomic DNA Purification Kit&#160;</td>
			<td style="width:205px;">Promega</td>
			<td style="width:119px;">A1125</td>
			<td>Genomic DNA extraction</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:21px;">NanoDrop 2000</td>
			<td style="width:205px;">ThermoFisher Scientific</td>
			<td style="width:119px;">NanoDrop 2000</td>
			<td>Determination of DNA concentration</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">calf intestinal phosphatase</td>
			<td>New England Biolabs</td>
			<td style="width:119px;">M0290</td>
			<td>DNA digestion</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DNase I</td>
			<td>New England Biolabs</td>
			<td style="width:119px;">M0303</td>
			<td>DNA digestion</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">snake venom phosphodiesterase I</td>
			<td style="width:205px;">Sigma</td>
			<td style="width:119px;">P4506</td>
			<td>DNA digestion</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nanosep 3K Omega</td>
			<td>Pall</td>
			<td style="width:119px;">OD003C35</td>
			<td>filtration of digested DNA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1290 UHPLC system</td>
			<td style="width:205px;">Agilent&#160;</td>
			<td style="width:119px;">1290</td>
			<td>UHPLC separation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">G6410B triple quadrupole mass spectrometer</td>
			<td style="width:205px;">Agilent&#160;</td>
			<td style="width:119px;">G6410B</td>
			<td>MS/MS analysis</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Zorbax Eclipse Plus C18 column</td>
			<td style="width:205px;">Agilent&#160;</td>
			<td style="width:119px;">Zorbax Eclipse Plus</td>
			<td>colume for UHPLC separation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">5-methylcytosine</td>
			<td>Solarbio Life Sciences</td>
			<td style="width:119px;">SM8900&#160;</td>
			<td>standard 5mC</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">5-hydroxymethylcytosine (standard)</td>
			<td>Toronto Research Chemicals</td>
			<td style="width:119px;">M295900</td>
			<td>standard 5hmC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Prdm14 antibody</td>
			<td>bioworld</td>
			<td>BS7634</td>
			<td>Western blot analysis-primary antibody</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dnmt3a antibody</td>
			<td>bioworld</td>
			<td>BS6587</td>
			<td>Western blot analysis-primary antibody</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dnmt3b antibody</td>
			<td>abcam</td>
			<td>ab13604</td>
			<td>Western blot analysis-primary antibody</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dnmt3l antibody</td>
			<td>abcam</td>
			<td>ab3493</td>
			<td>Western blot analysis-primary antibody</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dnmt1 antibody</td>
			<td>abcam</td>
			<td>ab13537</td>
			<td>Western blot analysis-primary antibody</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">&#946;-tubulin antibody</td>
			<td>bioworld</td>
			<td>BS1482MH</td>
			<td>Western blot analysis-primary antibody</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">goat anti-rabbit IgG</td>
			<td>abcam</td>
			<td style="width:119px;">ab6721</td>
			<td>Western blot analysis-secondary antibody</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">goat anti-mouse IgG</td>
			<td>abcam</td>
			<td style="width:119px;">ab6789</td>
			<td>Western blot analysis-secondary antibody</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Trizol</td>
			<td style="width:205px;">Invitrogen</td>
			<td>15596-026</td>
			<td>RNA extraction</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">reverse transcription system</td>
			<td style="width:205px;">Promega</td>
			<td style="width:119px;">A3500</td>
			<td>RNA reverse transcription</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">GoTaq qPCR Master Mix</td>
			<td style="width:205px;">Promega</td>
			<td style="width:119px;">A6001</td>
			<td>RT-PCR</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">StemTAG alkaline phosphatase staining and activity assay kit</td>
			<td style="width:205px;">Cells Biolabs, Inc.</td>
			<td>CBA-302</td>
			<td>&#160;alkaline phosphatase staining analysis</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:216px;">mouse ES cells: WT, 129 SvEv</td>
			<td style="width:205px;">Provided by Professor Guoliang Xu (Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China)</td>
			<td style="width:119px;"></td>
			<td>cell strain of mouse ES cells</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">microscope</td>
			<td style="width:205px;">Zeiss</td>
			<td style="width:119px;">LSM510</td>
			<td>cells observation</td>
		</tr>
		<tr height="81">
			<td height="81" style="height:81px;width:216px;">GraphPad Prism 5.0</td>
			<td style="width:205px;">GraphPad Prism Software Inc.</td>
			<td style="width:119px;">5.0</td>
			<td>statistical analysis</td>
		</tr>
	</tbody>
</table>

an alternative culture method to maintain genomic hypomethylation of mouse embryonic stem cells using mek inhibitor pd0325901 and vitamin c

Embryonic stem (ES) cells have the potential to differentiate into any of the three germ layers (endoderm, mesoderm, or ectoderm), and can generate many lineages for regenerative medicine. ES cell culture in vitro has long been the subject of widespread concerns. Classically, mouse ES cells are maintained in serum and leukemia inhibitory factor (LIF)-containing medium. However, under serum/LIF conditions, cells show heterogeneity in morphology and the expression profile of pluripotency-related genes, and are mostly in a metastable state. Moreover, cultured ES cells exhibit global hypermethylation, but na&#239;ve ES cells of the inner cell mass (ICM) and primordial germ cells (PGCs) are in a state of global hypomethylation. The hypomethylated state of ICM and PGCs is closely associated with their pluripotency. To improve mouse ES cell culture methods, we have recently developed a new method based on the selectively combined utilization of two small-molecule compounds to maintain the DNA hypomethylated and pluripotent state. Here, we present that the co-treatment of vitamin C (Vc) and PD0325901 can erase about 90% of 5-methylcytosine (5mC) at 5 days in mouse ES cells. The generated 5mC content is comparable to that in PGCs. The mechanistic investigation shows that PD0325901 up-regulates Prdm14 expression to suppress Dnmt3b (de novo DNA methyltransferase) and Dnmt3l (the cofactor of Dnmt3b), by reducing de novo 5mC synthesis. Vc facilitates the conversion of 5mC to 5-hydroxymethylcytosine (5hmC) catalyzed mainly by Tet1 and Tet2, indicating the involvement of both passive and active DNA demethylations. Moreover, under Vc/PD0325901 conditions, mouse ES cells show homogeneous morphology and pluripotent state. Collectively, we propose a novel and chemical-synergy culture method for achieving DNA hypomethylation and maintenance of pluripotency in mouse ES cells. The small-molecule chemical-dependent method overcomes the major shortcomings of serum culture, and holds promise to generate homogeneous ES cells for further clinical applications and researches.

Vc/PD0325901 synergistically induced global erasure of mouse ES cells. Mouse ES cells in serum exhibit DNA hypermethylation, while pluripotent ICM cells and PGCs show global erasure of DNA methylation and the hypomethylated state is closely associated with their pluripotency9,10.
Previously, we and others found that Vc may enhance Tet-mediated 5mC demethylation<sup class...

Watch this Scientific Journal Video about An Alternative Culture Method to Maintain Genomic Hypomethylation of Mouse Embryonic Stem Cells Using MEK Inhibitor PD0325901 and Vitamin C at JoVE.com

An Alternative Culture Method to Maintain Genomic Hypomethylation of Mouse Embryonic Stem Cells Using MEK Inhibitor PD0325901 and Vitamin C

We described in detail two chemical-based protocols for culturing mouse embryonic stem cells. This new method utilizes synergistic mechanisms of promoting Tet-mediated oxidation (by vitamin C) and repressing de novo synthesis of 5-methylcytosine (by PD0325901) to maintain DNA hypomethylation and pluripotency of mouse embryonic stem cells.

Embryonic stem (ES) cells have the potential to differentiate into any of the three germ layers (endoderm, mesoderm, or ectoderm), and can generate many ...

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