We thank Chris Benner for implementing the X. tropicalis genome (xenTro2, xenTro2r) into HOMER and the Gilchrist lab for discussions on post-sequencing analysis. I.P. assisted the GO term analysis. G.E.G and J.C.S. were supported by the Wellcome Trust and are now supported by the Medical Research Council (program number U117597140).

<ol>
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E., Guptaa, R., Chuonga, E., Baker, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromatin+immunoprecipitation+and+deep+sequencing+in+Xenopus+tropicalis+and+Xenopus+laevis.">Chromatin immunoprecipitation and deep sequencing in Xenopus tropicalis and Xenopus laevis.</a> Methods. 66 (3), 410-421 (2014).</li><li>Metz, B., 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+formaldehyde-induced+modifications+in+proteins:+reactions+with+model+peptides.">Identification of formaldehyde-induced modifications in proteins: reactions with model peptides.</a> J Biol Chem. 279 (8), 6235-6243 (2004).</li><li>Landt, S. 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The authors declare that they have no competing financial interests.

我们的协议概括了如何制备和分析来自非洲爪蟾胚胎的全基因组染色质分布。它涵盖了每一个步骤，从交联蛋白的内源性基因位点在体内处理数以百万计的读取较丰富的基因组位点在硅片中。由于可用的基因组草案越来越多，该协议应适用于其他模型和非模式生物。最重要的实验部分，它设置该协议除了以前的工作8,31,33,34，是后定影过程以提取交联核。它有利于有效的染色质溶解和剪切，易倍增。连同文库制备的改进的效率这个协议允许的高复杂的ChIP-SEQ文库的构建从半两百万个细胞中表达感兴趣的染色质相关的表位。对于芯片的qPCR实验中，几10000这些细胞通常是足够检查DNA富集也许在六个不同的基因位点。这些数字是保守的估计，但可以根据蛋白质表达水平，抗体质量而变化，交联效率，以及表位可访问性。作为指导，单个爪蟾胚胎中含有大约4,000个细胞，在中期囊胚期（8.5新科普和费伯29之后），40,000个细胞的晚期原肠胚阶段（12）和100,000个细胞在早期tailbud阶段（20）。 需要精确固定的时间进行有效免疫凭经验由芯片定量PCR（第10条）确定。在一般情况下，较长的固定时间，如果实验涉及十需要蟾胚胎早期发育阶段，弱（或间接）DNA绑定属性。然而，不推荐固定爪蟾胚胎长于40分钟，或处理比表示（第3节）的更多的胚胎，如染色质剪切变得效率较低。重要的是不固定后使用任何甘氨酸作为淬火甲醛可使核提取蛋黄丰富的胚胎非常困难这个共同的一步。目前，这样做的原因是不知道。可以想到的是甲醛-甘氨酸加合物进一步反应与N-末端氨基的基团或精氨酸残基35。 抗体是关键的任何沉淀实验和足够的控制需要被进行，以显示它的特异性针对感兴趣的表位（参见由LANDT 等人 36的准则）。如果没有沉淀同类抗体是可用的，引入相应的表位标记的融合蛋白的可能是一个合法的替代，因为这些蛋白质可以占据内源性结合位点37。在这种情况下，未注射的胚胎是最好的作为阴性对照，而不是与非特异性血清芯片使用。如果感兴趣的蛋白被表达以低水平产生ENRI的差恢复这种策略也可应用高等教育委员会DNA。 作为用于制造芯片起库，因为在使用中的DNA的量低，则建议选择减少的清洗步骤的次数，并结合反应保持的DNA的任何损失在最小的程序。适配器和引物需要与多重测序和NGS平台兼容（见表具体材料/设备）。如果使用Y型适配器（含长单链臂），关键是要用三到五轮的PCR的大小选择的DNA插入之前预扩增文库（ 例如 ，100至300碱基对）用凝胶电泳。单链末端引起DNA片段迁移不均匀。试运行用不同量的输入的DNA（ 例如 ，0.1，0.5，1，2，第5，10和20毫微克）的建议，以确定PCR循环的总数（小于或等于18个循环），以使一个尺寸需要100至200毫微克 - 请选择库。减少的PCR周期数使得热镀的测序ndant读取的可能性较小。固相可逆固定化珠是良好清理试剂有效地回收感兴趣的DNA和可靠地从结扎和PCR反应除去任何游离的适配器和二聚体。 在的数量，类型和长度方面的读取，约20至3000万单端读出的36 bp的是足以满足大多数芯片起实验来覆盖整个基因组的爪蟾具有足够的深度。最普遍的NGS机器经常能够满足这些标准。然而，它可能是有益的，以增加数目的读出，如果读出的一个广泛分布的预期，与组蛋白修饰观察到的，而不是尖锐的峰。对于许多芯片起实验，4至5不同的索引库可以汇集并使用高性能NGS机测序在一个流动细胞车道。有时也建议使读扩展长度和序列的DNA模板的两端（配对末端），以增加mappability瓦特母鸡分析重复的基因组区域内染色质。 此协议已被成功地应用到各种各样的染色质的功能，如转录因子，信令介质和翻译后蛋白修饰。但是，胚胎细胞获得的异质性程度日益加深，因为他们发展和染色质分布变得难以解释。希望的步骤已在拟南芥和果蝇到组织特异性轮廓染色质景观通过提取细胞类型特异性核38,39。我们的协议包括核提取步骤，这可能铺平道路组织特异性的ChIP-SEQ其他胚胎。

The first attempts to characterize protein-DNA interactions in vivo were reported about 30 years ago in an effort to understand RNA polymerase-mediated gene transcription in bacteria and in the fruit fly1,2. Since then, the use of immunoprecipitation to enrich distinct chromatin features (ChIP) has been widely adopted to capture binding events and chromatin states with high efficiency3. Subsequently, with the emergence of powerful microarray technologies, this method led to the characterization of genome-wide chromatin landscapes4. More recently, chromatin profiling has become even more comprehensive and high-resolution, because millions of co-immunoprecipitated DNA templates can now be sequenced in parallel and mapped to the genome (ChIP-Seq)5. As increasing numbers of genome assemblies are available, ChIP-Seq is an attractive approach to learn more about the genome regulation that underlies biological processes. 
Here we provide a protocol to perform ChIP-Seq on yolk-rich embryos such as those of the frog Xenopus. Drafts of the genomes of both widely used Xenopus species&#8212;X. tropicalis and X. laevis&#8212;have now been released by the International Xenopus Genome Consortium6. The embryos of Xenopus species share many desirable features that facilitate and allow the interpretation of genome-wide chromatin studies, including the production of large numbers of high-quality embryos, the large size of the embryos themselves, and their external development. In addition, the embryos are amenable to classic and novel manipulations like cell lineage tracing, whole-mount in situ hybridisation, RNA overexpression, and TALEN/CRISPR-mediated knockout technology.
The following protocol builds on the work of Lee et al., Blythe et al. and Gentsch et al.7-9. Briefly, Xenopus embryos are formaldehyde-fixed at the developmental stage of interest to covalently bind (cross-link) proteins to their associated genomic DNA. After nuclear extraction, cross-linked chromatin is fragmented to focus subsequent sequencing on specific genomic binding or modification sites, and to minimize the contributions of flanking DNA sequences. Subsequently, the chromatin fragments are immunoprecipitated with a ChIP-grade antibody to enrich those containing the protein of interest. The co-immunoprecipitated DNA is stripped from the protein and purified before creating an indexed (paired-end) library for next-generation sequencing (NGS). At the end, simple command lines are offered for the post-sequencing analysis of ChIP-Seq data.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>1/16 inch tapered microtip</td>
			<td>Qsonica</td>
			<td>4417</td>
			<td>This microtip is compatible with Sonicator 3000 from Misonix and Q500/700 from Qsonica.</td>
		</tr>
		<tr>
			<td>8 ml glass sample vial with cap</td>
			<td>Wheaton</td>
			<td>224884</td>
			<td>8 ml clear glass sample vials for aqueous samples with 15-425 size phenolic rubber-lined screw caps.</td>
		</tr>
		<tr>
			<td>Adaptor</td>
			<td>IDT or Sigma</td>
			<td>NA</td>
			<td>TruSeq universal adaptor, 
AATGATACGGCGACCACCGAG 
ATCTACACTCTTTCCCTACAC 
GACGCTCTTCCGATC*T. TruSeq indexed adaptor, 
P-GATCGGAAGAGCACACGTC 
TGAACTCCAGTCAC &#8208;NNNNNN&#8208; 
ATCTCGTATGCCGTCT TCTGCTT*G. *, phosphorothioate bondphosphate group at 5&#39; end. NNNNNN, index (see TruSeq ChIP Sample Preparation Guide for DNA sequence). Order adaptors HPLC purified. Adaptors can be prepared by combining equimolar amounts (each 100 &#181;M) of the universal and the indexed adaptor and cooling them down slowly from 95 &#176;C to room temperature. Use 1.5 pmol per ng of input DNA. Store at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>b2g4pipe (software)</td>
			<td>Blast2GO</td>
			<td>non-commercial</td>
			<td>http://www.blast2go.com/data/blast2go/b2g4pipe_v2.5.zip</td>
		</tr>
		<tr>
			<td>BLAST+ (software)</td>
			<td>Camacho et al.</td>
			<td>non-commercial</td>
			<td>http://blast.ncbi.nlm.nih.gov/Blast.cgi?PAGE_TYPE=BlastDocs&#38;DOC_TYPE=Download</td>
		</tr>
		<tr>
			<td>Bowtie (software)</td>
			<td>Langmead et al.</td>
			<td>non-commercial</td>
			<td>http://bowtie-bio.sourceforge.net/index.shtml</td>
		</tr>
		<tr>
			<td>cisFinder (software)</td>
			<td>Sharov et al.</td>
			<td>non-commercial</td>
			<td>http://lgsun.grc.nia.nih.gov/CisFinder/</td>
		</tr>
		<tr>
			<td>Chip for capillary electrophoresis</td>
			<td>Agilent Technologies</td>
			<td>5067-1504</td>
			<td>Load this chip with 1 &#181;l DNA for library quality control. Store at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>Chip-based capillary electrophoresis system</td>
			<td>Agilent Technologies</td>
			<td>G2940CA</td>
			<td>The Agilent 2100 BioAnalyzer is used to check the quality of ChIP-Seq libraries. Keep reagents at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>ChIP-Seq library preparation kit (KAPA Hyper Prep Kit)</td>
			<td>Kapa Biosystems</td>
			<td>KK8504</td>
			<td>Kit contains KAPA end repair and A-tailing enzyme mix, end Repair and A-tailing buffer, DNA ligase, ligation buffer, KAPA HiFi HotStart ReadyMix (2X), and KAPA library amplification primer mix (10X) (see also PCR primers). Adaptors are not included. Store at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>ChIP-Seq library preparation kit (alternative, ThruPLEX-FD Prep Kit)</td>
			<td>Rubicon Genomics</td>
			<td>R40048</td>
			<td>Kit uses their own stem-loop adaptors and primers. This kit eliminates intermediate purification steps and is as sensitive as the KAPA Hyper Prep Kit. Store at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>Cluster3 (software)</td>
			<td>de Hoon et al.</td>
			<td>non-commercial</td>
			<td>http://bonsai.hgc.jp/~mdehoon/software/cluster</td>
		</tr>
		<tr>
			<td>FastQC (software)</td>
			<td>Simon Andrews</td>
			<td>non-commercial</td>
			<td>http://www.bioinformatics.babraham.ac.uk/projects/fastqc</td>
		</tr>
		<tr>
			<td>Fluorometer</td>
			<td>life technologies</td>
			<td>Q32866</td>
			<td>Qubit 2.0 Fluorometer</td>
		</tr>
		<tr>
			<td>Fluorometer reagents</td>
			<td>life technologies</td>
			<td>Q32851</td>
			<td>The kit provides concentrated assay reagent, dilution buffer, and pre-diluted DNA standards for the Qubit fluorometer. Store DNA standards at 4 &#176;C, buffer and dye at room temperature.</td>
		</tr>
		<tr>
			<td>Formaldehyde</td>
			<td>Sigma</td>
			<td>F8775-4X25ML</td>
			<td>Formaldehyde solution, for molecular biology, 36.5-38% in H2O, stabilised with 10-15% methanol. Store at room temperature. CAUTION: Formaldehyde is corrosive and highly toxic.</td>
		</tr>
		<tr>
			<td>Gel (E-Gel EX agarose , 2%)</td>
			<td>life technologies</td>
			<td>G4010</td>
			<td>Pre-cast gel with 11 wells, openable format. Leave one lane between ladder and library empty to avoid cross-contamination. Store gels at room temperature.</td>
		</tr>
		<tr>
			<td>Gel electrophoresis system</td>
			<td>life technologies</td>
			<td>G6465</td>
			<td>E-Gel iBase and E-Gel Safe Imager combo kit for size-selecting ChIP-Seq libraries.</td>
		</tr>
		<tr>
			<td>Gel extraction kit</td>
			<td>Qiagen</td>
			<td>28706</td>
			<td>Store all reagents at room temperature. Use 500 &#181;l of QG buffer per 100 mg of 2% agarose gel slice to extract DNA. Use MinElute columns (from MinElute PCR purification kit) to elute DNA twice.</td>
		</tr>
		<tr>
			<td>HOMER (software)</td>
			<td>Chris Benner</td>
			<td>non-commercial</td>
			<td>http://homer.salk.edu/homer/index.html</td>
		</tr>
		<tr>
			<td>Hybridization oven</td>
			<td>Techne</td>
			<td>FHB1D</td>
			<td>Hybridizer HB-1D</td>
		</tr>
		<tr>
			<td>IGV (software)</td>
			<td>Robinson et al.</td>
			<td>non-commercial</td>
			<td>http://www.broadinstitute.org/igv/home</td>
		</tr>
		<tr>
			<td>Illumina CASAVA-1.8 quality filter (software)</td>
			<td>Assaf Gordon</td>
			<td>non-commercial</td>
			<td>http://cancan.cshl.edu/labmembers/gordon/fastq_illumina_filter</td>
		</tr>
		<tr>
			<td>Java TreeView (software)</td>
			<td>Alok Saldanha</td>
			<td>non-commercial</td>
			<td>http://jtreeview.sourceforge.net</td>
		</tr>
		<tr>
			<td>Laboratory jack</td>
			<td>Edu-Lab</td>
			<td>CH0642</td>
			<td>This jack is used to elevate sample in sound enclosure for sonication.</td>
		</tr>
		<tr>
			<td>Ladder, 100 bp</td>
			<td>New England BioLabs</td>
			<td>N3231</td>
			<td>Keep 1x solution at room temperature. Store stock at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>Ladder, 1 kb</td>
			<td>New England BioLabs</td>
			<td>N3232</td>
			<td>Keep 1x solution at room temperature. Store stock at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>Low-retention 1.5-ml microcentrifuge tubes</td>
			<td>life technologies</td>
			<td>AM12450</td>
			<td>nonstick, RNase-free microfuge tubes, 1.5 ml</td>
		</tr>
		<tr>
			<td>MACS2 (software)</td>
			<td>Tao Liu</td>
			<td>non-commercial</td>
			<td>https://github.com/taoliu/MACS</td>
		</tr>
		<tr>
			<td>Magnetic beads</td>
			<td>life technologies</td>
			<td>11201D</td>
			<td>These Dynabeads are superparamagnetic beads with affinity purified polyclonal sheep anti-mouse IgG covalently bound to the bead surface. Store at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>Magnetic beads</td>
			<td>life technologies</td>
			<td>11203D</td>
			<td>These Dynabeads are superparamagnetic beads with affinity purified polyclonal sheep anti-rabbit IgG covalently bound to the bead surface. Store at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>Magnetic beads</td>
			<td>life technologies</td>
			<td>10001D</td>
			<td>These Dynabeads are superparamagnetic beads with recombinant protein A covalently bound to the bead surface. Store at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>Magnetic beads</td>
			<td>life technologies</td>
			<td>10003D</td>
			<td>These Dynabeads are superparamagnetic beads with recombinant protein G covalently bound to the bead surface. Store at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>Magnetic rack</td>
			<td>life technologies</td>
			<td>12321D</td>
			<td>DynaMag-2 magnet</td>
		</tr>
		<tr>
			<td>MEME</td>
			<td>Bailey et al.</td>
			<td>non-commercial</td>
			<td>http://meme.nbcr.net/meme/</td>
		</tr>
		<tr>
			<td>Na3VO4</td>
			<td>New England BioLabs</td>
			<td>P0758</td>
			<td>Sodium orthovanadate (100 mM) is a commonly used general inhibitor for protein phosphotyrosyl phosphatases. Store at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>NaF</td>
			<td>New England BioLabs</td>
			<td>P0759</td>
			<td>Sodium fluoride (500 mM) is commonly used as general inhibitor of phosphoseryl and phosphothreonyl phosphatases. Store at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>NGS machine</td>
			<td>Illumina</td>
			<td>SY-301-1301</td>
			<td>Genome Analyzer IIx</td>
		</tr>
		<tr>
			<td>NGS machine (high performance)</td>
			<td>Illumina</td>
			<td>SY-401-2501</td>
			<td>HiSeq</td>
		</tr>
		<tr>
			<td>Normal serum (antibody control)</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-2028</td>
			<td>Use as control for goat polyclonal IgG antibodies in ChIP-qPCR experiments. Store at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>Normal serum (antibody control)</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-2025</td>
			<td>Use as control for mouse polyclonal IgG antibodies in ChIP-qPCR experiments. Store at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>Normal serum (antibody control)</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-2027</td>
			<td>Use as control for rabbit polyclonal IgG antibodies in ChIP-qPCR experiments. Store at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>Nucleic acid staining solution</td>
			<td>iNtRON</td>
			<td>21141</td>
			<td>Use RedSafe nucleic acid staining solution at 1:50,000. Store at room temperature.</td>
		</tr>
		<tr>
			<td>Orange G</td>
			<td>Sigma</td>
			<td>O3756-25G</td>
			<td>1-Phenylazo-2-naphthol-6,8-disulfonic acid disodium salt. Store at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>PCR primers</td>
			<td>e.g., IDT or Sigma</td>
			<td>NA</td>
			<td>Primers to enrich adaptor-ligated DNA fragments by PCR: AATGATACGGCGACCACCGA*G and CAAGCAGAAGACGGCATACGA*G, phosphorothioate bond. Primers designed by Ethan Ford. Combine primers at 5 &#181;M each. Use 5 &#181;l in a 50 &#181;l PCR reaction. Store at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>MinElute PCR purification kit&#160;</td>
			<td>Qiagen</td>
			<td>28006</td>
			<td>for purification of ChIP-qPCR and shearing test samples. Store MinElute spin columns at 4 &#176;C, all other buffers and collection tubes at room temperature.</td>
		</tr>
		<tr>
			<td>Phenol:chloroform:isoamyl alcohol (25:24:1, pH 7.9)</td>
			<td>life technologies</td>
			<td>AM9730</td>
			<td>Phenol:Chloroform:IAA (25:24:1) is premixed and supplied at pH 6.6. Use provided Tris alkaline buffer to raise pH to 7.9. Store at 4 &#176;C. CAUTION: phenol:chloroform:isoamyl alcohol is corrosive, highly toxic and combustible.</td>
		</tr>
		<tr>
			<td>Primer3 (software)</td>
			<td>Steve Rozen &#38; Helen Skaletsky</td>
			<td>non-commercial</td>
			<td>http://biotools.umassmed.edu/bioapps/primer3_www.cgi</td>
		</tr>
		<tr>
			<td>Protease inhibitor tablets</td>
			<td>Roche</td>
			<td>11836170001</td>
			<td>cOmplete, Mini, EDTA-free. Use 1 tablet per 10 ml. Store at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>Protease inhibitor tablets</td>
			<td>Roche</td>
			<td>11873580001</td>
			<td>cOmplete, EDTA-free. Use 1 tablet per 50 ml. Store at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>Proteinase K</td>
			<td>life technologies</td>
			<td>AM2548</td>
			<td>proteinase K solution (20 &#181;g/&#181;l). Store at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>RNase A</td>
			<td>life technologies</td>
			<td>12091-039</td>
			<td>RNase A (20 &#181;g/&#181;l). Store at room temperature.</td>
		</tr>
		<tr>
			<td>Rotator</td>
			<td>Stuart</td>
			<td>SB3</td>
			<td>Rotator SB3</td>
		</tr>
		<tr>
			<td>SAMtools (software)</td>
			<td>Li et al.</td>
			<td>non-commercial</td>
			<td>http://samtools.sourceforge.neta</td>
		</tr>
		<tr>
			<td>Solid phase reversible immobilisation beads</td>
			<td>Beckman Coulter</td>
			<td>A63882</td>
			<td>The Agencourt AMPure XP beads are used to minimise adaptor dimer contamination in ChIP-Seq libraries. Store at 4 &#176;C.</td>
		</tr>
		<tr>
			<td>Sonicator 3000</td>
			<td>Misonix/Qsonica</td>
			<td>NA</td>
			<td>Newer models are now available. Q125, Q500 or Q700 are all suitable for shearing crosslinked chromatin.</td>
		</tr>
		<tr>
			<td>Sound enclosure</td>
			<td>Misonix/Qsonica</td>
			<td>NA</td>
			<td>optional: follow the manufacturer&#39;s recommendation to obtain the correct sound enclosure.</td>
		</tr>
		<tr>
			<td>Thermomixer</td>
			<td>eppendorf</td>
			<td>22670000</td>
			<td>Thermomixer for 24 x 1.5 mL tubes. Precise temperature control from 4 &#176;C above room temperature to 99 &#176;C.</td>
		</tr>
	</tbody>
</table>

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.

相同的结果的那些这里提出预计如果是公执行的协议和所使用的抗体是芯片级质量（见讨论）。该协议允许核的甲醛固定爪蟾胚胎提取和染色质的通过超声处理的效率的剪切（ 图1A-C）。剪切染色示出的DNA片段，主要范围为100至1000碱基对和300至500碱基对（ 图1C）峰值的不对称分布。一个最小的50皮克免疫沉淀的DNA是必需的成功做出与同样大小的DNA插入（ 图2A）的索引配对末端芯片序列库。该库应该基本上不含适配器二聚体，其可以在电泳可以看出在大约120碱基对。 在测序边合成，处理前读被映射到基因组中（ 图2B，C）。在一个成功的实验<eM&gt; X。热带胚胎，通常为50％至70％的单端的40 bp的读取可以唯一地映射到V7.1的基因组装配与最多两个错配。而输入读取对准相当均匀分布在基因组芯片的排列读取结果链特有的富集侧翼感兴趣的染色功能。这是因为所有的片段是从5&#39;端（ 图2C）25测序。扩展排列在阅读方向的平均片段大小产生单质特性准确的配置文件，如转录因子结合事件。当IGV或任何其它相容的基因组浏览器可视化这些DNA占有率显示为峰。峰呼叫者像磁珠被用来确定这些峰（ 图3A）的位置。这样的结合位点数万一直在X.确定热带基因组的T-box转录因子如VegT 26。芯片的qPCR experiments应确认通过的ChIP-SEQ（ 图3B）发现的局部富集。 芯片起实验允许探索的染色质的功能的全基因组的特性。例如，在计算过的基因组的元素的读取分配如转录起始和终止位点可能突出围绕的基因的任何空间结合偏好（ 图3C）。同样地，读出分布在峰值位置的热图被用于在全基因组规模（ 图3D）来比较不同的染色质的功能。某些转录因子结合的基因组DNA的基本峰DNA序列特异性。 从头主题的分析可以获取此类信息，包括潜在的共同因素（ 图3E）共同丰富图案。绝大多数的靶基因的表现在一个较低的DNA占用，而不是更高的水平（ 图3F）。此无尺度的功能似乎是潮流当中相当普遍anscription因素和表明靶基因的仅一小部分直接与生物相关27,28调节。的富集的GO术语或其它的属性，如靶基因的差异表达可以进一步揭示见解在爪蟾胚胎（ 图3G）的染色质功能的生物功能的分析。 <img alt="图1" src="/files/ftp_upload/52535/52535fig1highres.jpg" /> 数字爪蟾胚胎1.染色质免疫沉淀的过程。 （A）的胚胎是甲醛固定在感兴趣的共价结合（交联）与基因组DNA相关联的任何蛋白质的发育阶段。在核提取（B）中 ，交联的染色质片段化来缩小的基因组DNA结合或染色质修饰位点通过最小化侧翼的DN序列（C）。随后，将染色质片段免疫沉淀与芯片级抗体充实那些含有目的（D）中的表位。共免疫沉淀DNA被剥离的蛋白质和创建芯片片段库NGS（ 图2）之前纯化（E）。 <a href="https://www.jove.com/files/ftp_upload/52535/52535fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图2" src="/files/ftp_upload/52535/52535fig2highres.jpg" /> 图2.芯片起文库制备，测序边合成，映射和峰呼叫。 （A）中的电泳显示具有250〜450碱基对的DNA模板的好芯片起库。这些模板带来的由通用（58基点）两侧感兴趣的DNA插入和索引（63基点）的适配器。（B） </强&gt;百万簇，每个含有相同的模板簇，是测序碱通过碱在所有四种核苷酸具有可逆的，鲜明的荧光团和相同的终止性质的存在。荧光图像的实时处理，以调用相应的碱，这最终组装成的读取。（℃）仅读取地图唯一到爪蟾基因组被保留。因为所有的片段是从5&#39;末端测序，芯片的映射读取结果中链特异峰侧翼感兴趣的染色质功能。因此，峰值检测呼叫者源自免疫沉淀和延长读取到平均片段长度精确定位功能的染色质丰富。 <a href="https://www.jove.com/files/ftp_upload/52535/52535fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img aLT =“图3”SRC =“/文件/ ftp_upload / 52535 / 52535fig3highres.jpg”/&gt; 图3.后测序分析和数据的可视化的由合子的T-box转录因子VegT（zVegT），所有读这里显示计数归一千万唯一映射和非冗余的读取。（A）的摘录的装置的一个例子的zVegT的全基因组信息X中的结合热带原肠胚（阶段11至12.5新科普和麦嘉华29后）。每个峰，一个堆积的扩展读出，表示一个结合位点。这些峰被称为由MACS2具有小于1％的错误发现率（FDR）。每个MESP基因显示出非常近端和上游zVegT结合，但只有mespa和mespb由该阶段（RNA测序数据30）来表示。（B）的 zVegT由芯片的qPCR在几个位点所确定的DNA的占用水平（包括非-被结合区0.5 kb的β 肌动蛋白的上游）的配RM通过芯片序列中发现的具体富集。比较结果mespa峰值称为（红色条）中（A）。该DNA占用等级被可视作为输入的两个百分比，与VegT抗体（IgG同种型的兔多克隆）和与抗体对照（正常兔IgG）的芯片中的芯片上。误差棒反映两个生物学重复的标准偏差。（C）的基因表达谱分析显示优先zVegT结合（标记分级超过25碱基对）相对于周围的任何其他基因组区域和基因机构内的启动子。（D）的热图显示了K均值集群（K = 5）DNA入住率（分级标签超过25个基点）的zVegT和的Smad2 / Smad3蛋白（芯片序列数据31），相对于全部zVegT结合的地区，在原肠期。热图是记录2基础，集中在每个碱基5标签。（E） 从头主题分析，发现了典型的T-box转录因子结合基序zVegT- 38％如果底层基序得分标准化为5％的发现率在背景序列结合的区域。该密度图表示最高富集在zVegT结合位点中心的T型盒基序，而典型的Smad2 / Smad3蛋白结合基序是难以富集。（F）的直方图显示zVegT DNA的占用程度，这是计算每个靶基因从5 kb的上游之间的所有峰（+/- 200基点）[ - ]。相应的转录起始位点和1 kb的下游[+]（G）300强的基因与内-5 kb的DNA最高的入住率和1 kb的是富集的早期胚胎发育的生物过程。这些GO条款与zVegT的假定的功能线。罗斯福是基于双尾Fisher精确检验和多重检验校正。 <a href="https://www.jove.com/files/ftp_upload/52535/52535fig3large.jpg" target="_blank">请点击此处查看该图的放大版本。</a>

Watch this Scientific Journal Video about Genome-wide Snapshot of Chromatin Regulators and States in Xenopus Embryos by ChIP-Seq at JoVE.com

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

如何染色质监管机构和染色质状态的问题会影响体内的基因组是关键，我们的细胞命运决定是如何在早期发育中的胚胎制成的认识。芯片起，最流行 ​​的做法在全球范围内，在这里介绍的爪蟾胚胎研究染色质的功能。

染色质监管机构和各国的全基因组快照<em&gt;爪</em&gt;通过胚胎的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 ...

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

12.1K 次观看.  MRC National Institute for Medical Research. 如何染色质监管机构和染色质状态的问题会影响体内的基因组是关键，我们的细胞命运决定是如何在早期发育中的胚胎制成的认识。芯片起，最流行 ​​的做法在全球范围内，在这里介绍的爪蟾胚胎研究染色质的功能。 