Name: carip-seq and chip-seq: methods to identify chromatin-associated rnas and protein-dna interactions in embryonic stem cells
Uploaded: 2018-05-25T14:00:00
Description: Watch this Scientific Journal Video about CARIP-Seq and ChIP-Seq: Methods to Identify Chromatin-Associated RNAs and Protein-DNA Interactions in Embryonic Stem Cells at JoVE.com

This work was supported by Wayne State University, Karmanos Cancer Institute, a grant from the National Heart, Lung and Blood Institute (1K22HL126842-01A1) awarded to B.L.K. This work utilized the Wayne State University High Performance Computing Grid for computational resources (&#60;https://www.grid.wayne.edu/&#62;). We thank Jiji Kurup for assistance with CARIP-Seq data analysis.
AUTHORS&#8217; CONTRIBUTIONS:
B.L.K. conceived of the CARIP-Seq method, designed and carried out the ChIP-Seq and CARIP-Seq experiments, analyzed the sequencing data, and drafted the manuscript. All authors have read and approved the final version of this manuscript.

1. Culture of Mouse ES Cells in Feeder-Free Conditions.
NOTE: Mouse ES cells are conventionally cultured in media on a cell culture dish coated with gelatin and a mono-layer of mouse embryonic fibroblasts (MEF), which have been mitotically inactivated (iMEFs). However, MEFs should be removed prior to downstream epigenetic or expression analyses to prevent the contamination of MEF-associated chromatin and RNA.
<ol>
	<li>Preparation of a feeder layer: Gelatin coat a 6-well cell culture plate b...

<ol>
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ChIP-Seq is a useful method to evaluate the location of global protein-DNA interactions (e.g., transcription factors/histone modifying enzymes/histone modifications and DNA) in ES cells, while the newly developed CARIP-Seq protocol is useful in interrogating genome-wide association of RNAs with chromatin constituents. ChIP-Seq is a fundamental tool that is used to evaluate epigenetic landscapes of ES cells and other cell types. The quality of ChIP-Seq and CARIP-Seq libraries is largely dependent on ChIP-grade an...

Embryonic stem (ES) cell fate decisions are regulated by communication between extracellular signals and a host of transcriptional-regulators, including histone modifiers, and post-translation modification of histone tails. These interactions facilitate chromatin accessibility and packaging of chromatin into one of two states: euchromatin, which is open and transcriptionally active, and heterochromatin, which is compact and generally transcriptionally inactive. Transcription factors with DNA sequence-specific binding affinities and epigenetic modifiers associate with euchromatic regions to participate in controlling gene expression. Next-generation sequencing methods, including ChIP-Seq1, have been instrumental in mapping genome-wide transcriptional networks that are fundamental for ES cell self-renewal and pluripotency2,3,4,5,6. Moreover, while RNA immunopreciation followed by next-generation sequencing (RIP-Seq)7 evaluations of RNA-protein interactions suggest that DNA binding proteins interact with RNAs to regulate transcriptional events7,8,9,10,11,12, few studies have investigated the genome-wide localization of RNAs associated with chromatin12, or global interactions between RNA and histone modifications. Long non-coding RNAs (lncRNAs) are one class of RNAs which have been found to regulate the activity of chromatin-associated proteins13,14,15. For example, Xist is a lncRNA that regulates, in female mammalian cells, inactivation of one X chromosome, through the recruitment of epigenetic repressors16,17. However, the full spectrum of RNAs associated with chromatin is largely unknown. Here, we describe a novel protocol, chromatin-associated RNA immunoprecipitation (CARIP) followed by next-generation sequencing (CARIP-Seq), to identify chromatin-associated RNAs on a genome-wide basis in ES cells, including library preparation for next-generation sequencing, and ChIP-Seq to map global occupancy of histone modifications, transcription factors, and epigenetic modifiers. Unlike other RIP-Seq methods7, CARIP-Seq includes crosslinking and sonication steps, which allow for the direct identification of RNAs associated with chromatin. Together, ChIP-Seq is a powerful tool to identify genome-wide protein-DNA interactions, while CARIP-Seq is a powerful method to survey RNAs associated with chromatin components.

<table>
	<tbody>
		<tr>
			<td>Mouse leukemia inhibitory factor (ESGRO LIF)</td>
			<td>EMD Millipore</td>
			<td></td>
			<td>106 or 107 units</td>
		</tr>
		<tr>
			<td>GSK3&#946; inhibitor CHIR99021 (GSK3i)</td>
			<td>Stemgent</td>
			<td></td>
			<td>Solvent: DMSO 10mM</td>
		</tr>
		<tr>
			<td>MEK inhibitor PD0325901 (MEKi)</td>
			<td>Stemgent</td>
			<td></td>
			<td>Solvent: DMSO 10mM</td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle Medium (DMEM), high glucose</td>
			<td>Invitrogen</td>
			<td>11965092</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS (phosphate buffered saline)</td>
			<td>Invitrogen</td>
			<td>10010031</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin-EDTA (0.25%), phenol red</td>
			<td>Gibco</td>
			<td>25200056</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin (10,000 U/mL)</td>
			<td>Gibco</td>
			<td>15140122</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Mercaptoethanol (50 mM)</td>
			<td>Gibco</td>
			<td>31350010</td>
			<td></td>
		</tr>
		<tr>
			<td>MEM Non-Essential Amino Acids Solution (100X)</td>
			<td>Gibco</td>
			<td>11140076</td>
			<td></td>
		</tr>
		<tr>
			<td>EmbryoMax ES Cell Qualified Fetal Bovine Serum, 500 ml</td>
			<td>EMD Millipore</td>
			<td>ES-009-B</td>
			<td></td>
		</tr>
		<tr>
			<td>EmbryoMax 0.1% Gelatin Solution</td>
			<td>EMD Millipore</td>
			<td>ES-006-B</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Sigma</td>
			<td>G7126-500G</td>
			<td>1.25 M stock conentration in water</td>
		</tr>
		<tr>
			<td>Formaldehyde solution</td>
			<td>Sigma</td>
			<td>F8775-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>TE (Tris EDTA) pH 8.0 1X</td>
			<td>Quality Biological</td>
			<td>351-011-131</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenylmethanesulfonyl fluoride (PMSF) solution</td>
			<td>Sigma</td>
			<td>93482-250ML-F</td>
			<td></td>
		</tr>
		<tr>
			<td>cOmplete Protease Inhibitor Cocktail</td>
			<td>Roche</td>
			<td>11697498001</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium dodecyl sulfate solution (20%)</td>
			<td>Quality Biological</td>
			<td>A611-0837-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Q125 sonifier</td>
			<td>Qsonica</td>
			<td>4422</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100 solution</td>
			<td>Sigma</td>
			<td>93443-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium deoxycholate</td>
			<td>Sigma</td>
			<td>30970</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma</td>
			<td>S7653</td>
			<td></td>
		</tr>
		<tr>
			<td>Dynabeads Protein G for Immunoprecipitation</td>
			<td>Invitrogen</td>
			<td>10004D</td>
			<td></td>
		</tr>
		<tr>
			<td>Dynabeads Protein A for Immunoprecipitation</td>
			<td>Invitrogen</td>
			<td>10002D</td>
			<td></td>
		</tr>
		<tr>
			<td>Dynabeads Protein A/Protein G and Magnet Starter Pack</td>
			<td>Invitrogen</td>
			<td>10015D</td>
			<td></td>
		</tr>
		<tr>
			<td>Lithium chloride</td>
			<td>Sigma</td>
			<td>L4408</td>
			<td></td>
		</tr>
		<tr>
			<td>IGEPAL CA-630</td>
			<td>Sigma</td>
			<td>I8896</td>
			<td></td>
		</tr>
		<tr>
			<td>RNeasy Mini Kit</td>
			<td>Qiagen</td>
			<td>74104</td>
			<td></td>
		</tr>
		<tr>
			<td>Dynabeads mRNA Purification Kit (for mRNA purification from total RNA preps)</td>
			<td>Invitrogen</td>
			<td>61006</td>
			<td></td>
		</tr>
		<tr>
			<td>SuperScript Double-Stranded cDNA Synthesis Kit</td>
			<td>Invitrogen</td>
			<td>11917010</td>
			<td></td>
		</tr>
		<tr>
			<td>QIAquick PCR Purification Kit</td>
			<td>Qiagen</td>
			<td>28104</td>
			<td></td>
		</tr>
		<tr>
			<td>End-It DNA End-Repair Kit</td>
			<td>Lucigen</td>
			<td>ER81050</td>
			<td></td>
		</tr>
		<tr>
			<td>Klenow Fragment (3&#39;&#8594;5&#39; exo-)</td>
			<td>NEB</td>
			<td>M0212L</td>
			<td></td>
		</tr>
		<tr>
			<td>dATP (10 mM)</td>
			<td>Invitrogen</td>
			<td>18252015</td>
			<td></td>
		</tr>
		<tr>
			<td>T4 DNA ligase</td>
			<td>NEB</td>
			<td>M0202L</td>
			<td></td>
		</tr>
		<tr>
			<td>TrackIt 1 Kb Plus DNA Ladder</td>
			<td>Invitrogen</td>
			<td>10488085</td>
			<td></td>
		</tr>
		<tr>
			<td>E-gel EX agarose gels, 2%</td>
			<td>Invitrogen</td>
			<td>G402002</td>
			<td></td>
		</tr>
		<tr>
			<td>Phusion high-fidelity 2X master mix with HF buffer</td>
			<td>Thermo Fisher</td>
			<td>F531LPM</td>
			<td></td>
		</tr>
		<tr>
			<td>ChIPAb+ Trimethyl-Histone H3 (Lys4) - ChIP Validated Antibody</td>
			<td>EMD Millipore</td>
			<td>17-614</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Histone H3 (di methyl K4) antibody [Y47] - ChIP Grade (ab32356)</td>
			<td>Abcam</td>
			<td>ab32356</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning Costar Flat Bottom Cell Culture Plates (6-well)</td>
			<td>Fisher</td>
			<td>720083</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon Standard Tissue Culture Dishes (10cm)</td>
			<td>Fisher</td>
			<td>08772E</td>
			<td></td>
		</tr>
		<tr>
			<td>Bioruptor pico</td>
			<td>Diagenode</td>
			<td>B01010001</td>
			<td></td>
		</tr>
		<tr>
			<td>Qubit Flurometer 2.0</td>
			<td>Thermo Fisher</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Qubit dsDNA HS Assay Kit</td>
			<td>Thermo Fisher</td>
			<td>Q32851</td>
			<td></td>
		</tr>
		<tr>
			<td>MinElute Reaction Cleanup Kit</td>
			<td>Qiagen</td>
			<td>28204</td>
			<td></td>
		</tr>
		<tr>
			<td>MinElute Gel Extraction Kit</td>
			<td>Qiagen</td>
			<td>28604</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Histone H4 (tri methyl K20) antibody - ChIP Grade (ab9053)</td>
			<td>Abcam</td>
			<td>ab9053</td>
			<td></td>
		</tr>
		<tr>
			<td>Labquake rotator</td>
			<td>Thermo Fisher</td>
			<td>400110Q</td>
			<td></td>
		</tr>
		<tr>
			<td>Illumina HiSeq platform</td>
			<td>Illumina</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>TURBO DNase</td>
			<td>Invitrogen</td>
			<td>AM2238</td>
			<td></td>
		</tr>
	</tbody>
</table>

carip-seq and chip-seq: methods to identify chromatin-associated rnas and protein-dna interactions in embryonic stem cells

Embryonic stem (ES) cell self-renewal&#160;and differentiation is governed by extrinsic signals and intrinsic networks of transcription factors, epigenetic regulators, and post-translation modifications of histones that combinatorially influence the gene expression state of nearby genes. RNA has also been shown to interact with various proteins to regulate chromatin dynamics&#160;and gene expression. Chromatin-associated RNA immunoprecipitation (CARIP) followed by next-generation sequencing (CARIP-Seq) is a novel method to survey RNAs associated with chromatin proteins, while chromatin immunoprecipitation followed by next-generation sequencing (ChIP-Seq) is a powerful genomics technique to map the location of post-translational modification of histones, transcription factors, and epigenetic modifiers on a global-scale in ES cells. Here, we describe methods to perform CARIP-Seq and ChIP-Seq, including library construction for next-generation sequencing, to generate global chromatin-associated RNA and epigenomic maps in ES cells.

We successfully interrogated the genome-wide binding of H3K4me3, H3K4me2, and KDM5B in ES cells using this ChIP-Seq protocol6. ES cells were cultured in feeder-free conditions (Figure 1), and cross-linked as described above. Sonication was subsequently performed as described in step 3.2 of the ChIP-Seq protocol, and evaluated by running DNA on a 2% agarose gel (Figure 2). Next, ChIP was performed as descri...

Watch this Scientific Journal Video about CARIP-Seq and ChIP-Seq: Methods to Identify Chromatin-Associated RNAs and Protein-DNA Interactions in Embryonic Stem Cells at JoVE.com

CARIP-Seq and ChIP-Seq: Methods to Identify Chromatin-Associated RNAs and Protein-DNA Interactions in Embryonic Stem Cells

Here, we describe methods to perform ChIP-Seq and CARIP-Seq, including library preparation for next-generation sequencing, to generate global epigenomic and chromatin-associated RNA maps in ES cells.

Embryonic stem (ES) cell self-renewal&#160;and differentiation is governed by extrinsic signals and intrinsic networks of transcription factors, ...

The overall goal of CARIP-Seq is to survey genome-wide chromatin-associated RNAs. The goal of ChIP-Seq is to evaluate protein-DNA interactions on a global scale in embryonic stem cells. These methods can help answer key questions in the epigenetics and stem cell fields, identify the genome location transcription factors or epigenetic regulator binding or histone modification occupancy or chromatin-associated RNAs in embryonic stem cells.The main advantage of these techniques is that they allow for the genome-wide unbiased interrogation of RNAs associated with chromatin constituents and global identification of protein DNA interactions. Though these methods can provide insight into embryonic stem cell biology, they can also be applied to other mammalian cell types to study cancer biology or other human diseases. To harvest the embryonic stem cells, wash the cells first with phosphate buffered saline.Then, detach the cells with 0.25%trypsin, pre-warmed to 37 degrees Celsius. After trypsinizing, resuspend the cells in pre-warmed MEF medium, supplemented with 10%fetal bovine serum. Then, add 37%formaldehyde to the cells in a conical tube to a final concentration of 1%and incubate at 37 degrees Celsius for eight minutes to cross-link the cells.To stop the fixation reaction, add 1.25 molar glycine pre-chilled at four degrees Celsius to a final concentration of 0.125 molar. Then, place the tube on a rotator and invert it at eight revolutions per minute for five minutes at room temperature. After five minutes, centrifuge the sample at 300g for five minutes at room temperature.After the centrifugation is over, discard the supernatant. Then, wash the pellet with pre-chilled phosphate buffered saline and again centrifuge the sample. Then, remove the phosphate buffered saline and freeze the cells in liquid nitrogen for a minute.Once the embryonic stem cells are thawed on ice, resuspend the pellet in 2.5 milliliters of sonication buffer. To study transcription factors or epigenetic factors, resuspend the cell pellet in sonication buffer without sodium dodecyl sulfate. For histone modifications, resuspend the cell pellet in buffer containing sodium dodecyl sulfate.Next, for chromatin immunoprecipitation, sonicate the chromatin for 14 to 18 cycles at 40%amplitude with 30 seconds on and 30 seconds rest mode. To solubilize the chromatin for the protein factor ChIP, supplement the sonication buffer with 28 microliters of 10%sodium dodecyl sulfate. For protein factors in histone modifications, add 28 microliters of sodium deoxycholate and 0.28 milliliters of 10%Triton X-100 and mix well.Then, centrifuge the sample at 10, 000g for 10 minutes at four degrees Celsius to pre-clear the chromatin. In a 1.5 milliliter low binding tube, add 40 microliters of A or G magnetic beads. Then, wash the beads with 600 microliters of phosphate buffered saline and transfer the tube with the beads on a rack containing a magnet and incubate for a minute at room temperature.Then, remove the phosphate buffered saline and again resuspend the beads in 100 microliters of phosphate buffered saline. To the tube, add two to four micrograms of antibody and incubate it by placing on a rotator for 40 minutes at eight revolutions per minute to promote antibody binding to the beads. Then, add 200 microliters of phosphate buffered saline to wash the beads.After washing, incubate the sonicated chromatin extract on a rotator at four degrees Celsius overnight to immunoprecipitate the chromatin-bound proteins. The next day, wash the beads and incubate with RIPA buffer, RIPA buffer with salt, lithium chloride buffer, Tris-EDTA buffer with Triton X-100, and Tris-EDTA buffer, each for 10 minutes on a rotator. To decrosslink for ChIP, resuspend the beads in 100 microliters of Tris-EDTA buffer.Then add three microliters of 10%sodium dodecyl sulfate and five microliters of 20 milligrams per milliliter of Proteinase K, and incubate the beads at 65 degrees Celsius overnight. After incubation, the next day, invert the tubes several times, leave them on the magnetic rack, and transfer the supernatant to a fresh tube. Then, wash the magnetic beads by adding 100 microliters of Tris-EDTA buffer, containing 0.5 molar sodium chloride and combine the two supernatants.To decrosslink for CARIP, resuspend the beads in 100 microliters of Tris-EDTA buffer. Then, add three microliters of 10%sodium dodecyl sulfate and five microliters of 20 milligrams per milliliter of Proteinase K and incubate the beads at 65 degrees Celsius for four to 12 hours. Again, invert the tube several times and place on the magnetic rack to transfer the supernatant to a fresh tube.Then, wash the magnetic beads by adding 100 microliters of Tris-EDTA buffer, containing 0.5 molar sodium chloride and then combine the two supernatants. Finally, isolate the RNA sample by using phenol chloroform isoamyl alcohol in 25 to 24 to one volume by volume ratio. Next, use DNase to remove DNA from the chromatin associated immunoprecipitated RNA sample.Then, add 10X DNase buffer to the CARIP sample and adjust the final volume to 1X concentration. Then, incubate the sample at 37 degrees Celsius for 30 minutes. Next, synthesize the first strand of complimentary DNA by setting up a PCR reaction by adding 10.5 microliters of RNA and one microliter of three micrograms per milliliter of random hexamer primers.To denature the secondary structure, first, incubate the tube at 65 degrees Celsius for five minutes, and then on ice for two minutes. Then, add the master mix to the PCR tube and incubate at 25 degrees Celsius for two minutes. Then, add one microliter of 200 units per microliter of superscript two and run the thermocycler program.To synthesize the second strand of complimentary DNA, set up the reaction on ice by adding the reagents, buffer, and enzymes. Then, vortex to mix the reagents gently and incubate at 16 degrees Celsius for two hours. After the DNA has been synthesized, purify the complimentary DNA using a PCR purification kit.Then, defragment the double-stranded DNA, use a water bath sonifier and a 1.5 milliliter tube to share the DNA to a size of 250 to 500 base pairs for three times 10 minutes or four times 10 minutes. Then, prepare the library and perform next generation sequencing. Here, phase contrast images of embryonic stem cells were captured to visualize the stem cell colonies.In this protocol, the cells were cultured in the presence or absence of mitotically inactivated mouse embryonic fibroblasts with LIF and/or GSK3i in the culture media to prevent the differentiation of the cells. Then, to visualize the efficiency of sonication of the cross-linked embryonic stem cell chromatin, sonicated double-stranded DNA was loaded on a 2%agarose gel. The gel image shows sheared chromatin in the range of 200 to 500 base pairs.Next, ChIP-Seq libraries were generated and sequenced using a next generation sequencing platform to evaluate genome-wide occupancy of a histone modifying enzyme and histone modifications in embryonic stem cells. From the custom UCSC browser view, enriched H3K4 trimethylation, H3K4 dimethylation, and KDM5B are visible at the core pluripotency regulator gene, POU5F1 and at the HOXC cluster. CARIP-Seq analysis was also performed to evaluate chromatin-associated RNAs in embryonic stem cells.The custom UCSC browser view shows H4K20 trimethylation associated RNA and H4K20 trimethylation occupancy in embryonic stem cells. From the CARIP-Seq results, it can be interpreted that although the RNA is associated with H4K20 trimethylation, it might not interact with the particular locus. Once mastered, this technique can be done in four days if it is performed properly.After watching this video, you should have a good understanding of how to survey chromatin-associated RNAs using CARIP-Seq and identify protein DNA interactions on a global scale in embryonic stem cells.

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Research

JoVE Journal

Developmental Biology

Genome-wide Snapshot of Chromatin Regulators and States in Xenopus Embryos by ChIP-Seq

The recruitment of chromatin regulators and the assignment of chromatin states to specific genomic loci are pivotal to cell fate decisions and tissue and organ formation during development. Determining the locations and levels of such chromatin features in vivo will provide valuable information about the spatio-temporal regulation of genomic elements, and will support aspirations to mimic embryonic tissue development in vitro. The most commonly used method for genome-wide and high-resolution profiling is chromatin immunoprecipitation followed by next-generation sequencing (ChIP-Seq). This protocol outlines how yolk-rich embryos such as those of the frog Xenopus can be processed for ChIP-Seq experiments, and it offers simple command lines for post-sequencing analysis. Because of the high efficiency with which the protocol extracts nuclei from formaldehyde-fixed tissue, the method allows easy upscaling to obtain enough ChIP material for genome-wide profiling. Our protocol has been used successfully to map various DNA-binding proteins such as transcription factors, signaling mediators, components of the transcription machinery, chromatin modifiers and post-translational histone modifications, and for this to be done at various stages of embryogenesis. Lastly, this protocol should be widely applicable to other model and non-model organisms as more and more genome assemblies become available.

Genome-wide Snapshot of Chromatin Regulators and States in Xenopus Embryos by ChIP-Seq

The question of how chromatin regulators and chromatin states affect the genome in vivo is key to our understanding of how early cell fate decisions are made in the developing embryo. ChIP-Seq&#8212;the most popular approach to investigate chromatin features at a global level&#8212;is outlined here for Xenopus embryos.

The recruitment of chromatin regulators and the assignment of chromatin states to specific genomic loci are pivotal to cell fate decisions and tissue and ...

Neural Differentiation of Mouse Embryonic Stem Cells in Serum-free Monolayer Culture

The ability to differentiate mouse embryonic stem cells (ESC) to neural progenitors allows the study of the mechanisms controlling neural specification as well as the generation of mature neural cell types for further study. In this protocol we describe a method for the differentiation of ESC to neural progenitors using serum-free, monolayer culture. The method is scalable, efficient and results in production of ~70% neural progenitor cells within 4 - 6 days. It can be applied to ESC from various strains grown under a variety of conditions. Neural progenitors can be allowed to differentiate further into functional neurons and glia or analyzed by microscopy, flow cytometry or molecular techniques. The differentiation process is amenable to time-lapse microscopy and can be combined with the use of reporter lines to monitor the neural specification process. We provide detailed instructions on media preparation and cell density optimization to allow the process to be applied to most ESC lines and a variety of cell culture vessels.

This protocol describes in detail the method for generating neural progenitors from embryonic stem cells using a serum-free monolayer method. These progenitors can be used to derive mature neural cell types or to study the process of neural specification and is amenable to multiwell format scaling for compound screening.

The ability to differentiate mouse embryonic stem cells (ESC) to neural progenitors allows the study of the mechanisms controlling neural specification as ...

Generating CRISPR/Cas9 Mediated Monoallelic Deletions to Study Enhancer Function in Mouse Embryonic Stem Cells

Enhancers control cell identity by regulating tissue-specific gene expression in a position and orientation independent manner. These enhancers are often located distally from the regulated gene in intergenic regions or even within the body of another gene. The position independent nature of enhancer activity makes it difficult to match enhancers with the genes they regulate. Deletion of an enhancer region provides direct evidence for enhancer activity and is the gold standard to reveal an enhancer's role in endogenous gene transcription. Conventional homologous recombination based deletion methods have been surpassed by recent advances in genome editing technology which enable rapid and precisely located changes to the genomes of numerous model organisms. CRISPR/Cas9 mediated genome editing can be used to manipulate the genome in many cell types and organisms rapidly and cost effectively, due to the ease with which Cas9 can be targeted to the genome by a guide RNA from a bespoke expression plasmid. Homozygous deletion of essential gene regulatory elements might lead to lethality or alter cellular phenotype whereas monoallelic deletion of transcriptional enhancers allows for the study of cis-regulation of gene expression without this confounding issue. Presented here is a protocol for CRISPR/Cas9 mediated deletion in F1 mouse embryonic stem (ES) cells (Mus musculus129 x Mus castaneus). Monoallelic deletion, screening and expression analysis is facilitated by single nucleotide polymorphisms (SNP) between the two alleles which occur on average every 125 bp in these cells.

Experimental validation of enhancer activity is best approached by loss-of-function analysis. Presented here is an efficient protocol that uses CRISPR/Cas9 mediated deletion to study allele-specific regulation of gene transcription in F1 ES cells which contain a hybrid genome (Mus musculus129 x Mus castaneus).

Enhancers control cell identity by regulating tissue-specific gene expression in a position and orientation independent manner. These enhancers are often ...

Epigenetic Regulation of Cardiac Differentiation of Embryonic Stem Cells and Tissues

Specific gene transcription is a key biological process that underlies cell fate decision during embryonic development. The biological process is mediated by transcription factors which bind genomic regulatory regions including enhancers and promoters of cardiac constitutive genes. DNA is wrapped around histones that are subjected to chemical modifications. Modifications of histones further lead to repressed, activated or poised gene transcription, thus bringing another level of fine tuning regulation of gene transcription. Embryonic Stem cells (ES cells) recapitulate within embryoid bodies (i.e., cell aggregates) or in 2D culture the early steps of cardiac development. They provide in principle enough material for chromatin immunoprecipitation (ChIP), a technology broadly used to identify gene regulatory regions. Furthermore, human ES cells represent a human cell model of cardiogenesis. At later stages of development, mouse embryonic tissues allow for investigating specific epigenetic landscapes required for determination of cell identity. Herein, we describe protocols of ChIP, sequential ChIP followed by PCR or ChIP-sequencing using ES cells, embryoid bodies and cardiac specific embryonic regions. These protocols allow to investigating the epigenetic regulation of cardiac gene transcription.

A fine tuning regulation of gene transcription underlies embryonic cell fate decision. Herein, we describe chromatin immunoprecipitation assays used to investigate epigenetic regulation of both cardiac differentiation of stem cells and cardiac development of mouse embryos.

Specific gene transcription is a key biological process that underlies cell fate decision during embryonic development. The biological process is mediated ...

Isolation of Murine Embryonic Hemogenic Endothelial Cells

The specification of hemogenic endothelial cells from embryonic vascular endothelium occurs during brief developmental periods within distinct tissues, and is necessary for the emergence of definitive HSPC from the murine extra embryonic yolk sac, placenta, umbilical vessels, and the embryonic aorta-gonad-mesonephros (AGM) region. The transient nature and small size of this cell population renders its reproducible isolation for careful quantification and experimental applications technically difficult. We have established a fluorescence-activated cell sorting (FACS)-based protocol for simultaneous isolation of hemogenic endothelial cells and HSPC during their peak generation times in the yolk sac and AGM. We demonstrate methods for dissection of yolk sac and AGM tissues from mouse embryos, and we present optimized tissue digestion and antibody conjugation conditions for maximal cell survival prior to identification and retrieval via FACS. Representative FACS analysis plots are shown that identify the hemogenic endothelial cell and HSPC phenotypes, and describe a methylcellulose-based assay for evaluating their blood forming potential on a clonal level.

Hematopoietic stem and progenitor cells (HSPC) derive from specialized (hemogenic) endothelial cells during development, yet little is known about the process by which some endothelial cells specify to become blood forming. We demonstrate a flow-cytometry based method allowing simultaneous isolation of hemogenic endothelial cells and HSPC from murine embryonic tissues.

The specification of hemogenic endothelial cells from embryonic vascular endothelium occurs during brief developmental periods within distinct tissues, ...

A Simple Method to Identify Kinases That Regulate Embryonic Stem Cell Pluripotency by High-throughput Inhibitor Screening

Embryonic stem cells (ESCs) can self-renew or differentiate into all cell types, a phenomenon known as pluripotency. Distinct pluripotent states have been described, termed &#34;na&#239;ve&#34; and &#34;primed&#34; pluripotency. The mechanisms that control na&#239;ve-primed transition are poorly understood. In particular, we remain poorly informed about protein kinases that specify na&#239;ve and primed pluripotent states, despite increasing availability of high-quality tool compounds to probe kinase function. Here, we describe a scalable platform to perform targeted small molecule screens for kinase regulators of the na&#239;ve-primed pluripotent transition in mouse ESCs. This approach utilizes simple cell culture conditions and standard reagents, materials and equipment to uncover and validate kinase inhibitors with hitherto unappreciated effects on pluripotency. We discuss potential applications for this technology, including screening of other small molecule collections such as increasingly sophisticated kinase inhibitors and emerging libraries of epigenetic tool compounds.

Here, we present a quantitative and scalable protocol to perform targeted small molecule screens for kinase regulators of the na&#239;ve-primed pluripotent transition.

Embryonic stem cells (ESCs) can self-renew or differentiate into all cell types, a phenomenon known as pluripotency. Distinct pluripotent states have been ...

Horizontal Whole Mount: A Novel Processing and Imaging Protocol for Thick, Three-dimensional Tissue Cross-sections of Skin

Processing a tissue of interest to generate a microscopic image that supports a scientific argument can be challenging. The acquisition of high-quality microscopic images is not entirely dependent upon the quality of the microscope, but also upon the methods of tissue processing, which often involve multiple critical actions or steps. Furthermore, mesenchymal cell types in the skin and other tissues represent a new challenge for tissue preparation and imaging. Here, we present a complete process, from tissue harvest to microscopy. Our technique, called &#34;horizontal whole mount,&#34; is one that novices can quickly become proficient in and that allows for antigen preservation and detection in 60-300 &#181;m-thick sections cut with a cryostat. Sections of this thickness provide enhanced visualization of tissue microarchitecture in a three-dimensional environment. In addition, the protocol preserves mesenchymal cells in a manner that enhances image quality when compared to standard cryostat or paraffin sections, thereby increasing the efficacy and reliability of immunostaining. We believe that this protocol will benefit all laboratories that visualize skin, and possibly other tissues and organs.

This work presents a novel processing and imaging protocol for thick, three-dimensional tissue cross-section analysis that enables the full exploitation of confocal imaging modalities. This protocol preserves antigenicity and represents a robust system to analyze skin histology and potentially other tissue types.

Processing a tissue of interest to generate a microscopic image that supports a scientific argument can be challenging. The acquisition of high-quality ...

Rapid, Directed Differentiation of Retinal Pigment Epithelial Cells from Human Embryonic or Induced Pluripotent Stem Cells

We describe a robust method to direct the differentiation of pluripotent stem cells into retinal pigment epithelial cells (RPE). The purpose of providing a detailed and thorough protocol is to clearly demonstrate each step and to make this readily available to researchers in the field. This protocol results in a homogenous layer of RPE with minimal or no manual dissection needed. The method presented here has been shown to be effective for induced pluripotent stem cells (iPSC) and human embryonic stem cells. Additionally, we describe methods for cryopreservation of intermediate cell banks that allow long-term storage. RPE generated using this protocol might be useful for iPSC disease-in-a-dish modeling or clinical application.

This protocol describes how to produce retinal pigment epithelial cells (RPE) from pluripotent stem cells. The method uses a combination of growth factors and small molecules to direct the differentiation of stem cells into immature RPE in fourteen days and mature, functional RPE after three months.

We describe a robust method to direct the differentiation of pluripotent stem cells into retinal pigment epithelial cells (RPE). The purpose of providing ...

Single-cell Photoconversion in Living Intact Zebrafish

Animal and plant tissue is composed of distinct populations of cells. These cells interact over time to build and maintain the tissue and can cause disease when disrupted. Scientists have developed clever techniques to investigate characteristics and natural dynamics of these cells within intact tissue by expressing fluorescent proteins in subsets of cells. However, at times, experiments require more selected visualization of cells within the tissue, sometimes at the single-cell or population-of-cells manner. To achieve this and visualize single cells within a population of cells, scientists have utilized single-cell photoconversion of fluorescent proteins. To demonstrate this technique, we show here how to direct UV light to an Eos-expressing cell of interest in an intact, living zebrafish. We then image those photoconverted Eos+ cells 24 h later to determine how they changed in the tissue. We describe two techniques: single cell photoconversion and photoconversions of populations of cell. These techniques can be used to visualize cell-cell interactions, cell-fate and differentiation, and cell migrations, making it a technique that is applicable in numerous biological questions.

Here, we present a protocol to show how cell photoconversion is achieved through UV exposure to specific areas expressing the fluorescent protein, Eos, in living animals.

Animal and plant tissue is composed of distinct populations of cells. These cells interact over time to build and maintain the tissue and can cause ...

Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton

The Caenorhabditis elegans (C. elegans) germline is used to study several biologically important processes including stem cell development, apoptosis, and chromosome dynamics. While the germline is an excellent model, the analysis is often two dimensional due to the time and labor required for three-dimensional analysis. Major readouts in such studies are the number/position of nuclei and protein distribution within the germline. Here, we present a method to perform automated analysis of the germline using confocal microscopy and computational approaches to determine the number and position of nuclei in each region of the germline. Our method also analyzes germline protein distribution that enables the three-dimensional examination of protein expression in different genetic backgrounds. Further, our study shows variations in cytoskeletal architecture in distinct regions of the germline that may accommodate specific spatial developmental requirements. Finally, our method enables automated counting of the sperm in the spermatheca of each germline. Taken together, our method enables rapid and reproducible phenotypic analysis of the C. elegans germline.

Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton

We present an automated method for three-dimensional reconstruction of the Caenorhabditis elegans germline. Our method determines the number and position of each nucleus within the germline and analyses germline protein distribution and cytoskeletal structure.

The Caenorhabditis elegans (C. elegans) germline is used to study several biologically important processes including stem cell development, apoptosis, and ...