This research was supported by Netherlands Organisation for Scientific Research (NWO/ALW/MEERVOUD/836.12.010, H.Z.) (NWO/ALW/Open Competition/ALWOP 376, H.Z., J.G.A.S.); Radboud University fellowship (H.Z.); and Chinese Scholarship Council grant 201406330059 (J.Q.).

<ol>
	<li>Hardman, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Skin+equivalents+for+studying+the+secrets+of+skin:+from+development+to+disease.">Skin equivalents for studying the secrets of skin: from development to disease.</a> British Journal of Dermatology. 173 (2), 320-321 (2015).</li><li>Borowiec, A. S., Delcourt, P., Dewailly, E., Bidaux, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimal+differentiation+of+in+vitro+keratinocytes+requires+multifactorial+external+control.">Optimal differentiation of in vitro keratinocytes requires multifactorial external control.</a> PLoS One. 8 (10), 77507 (2013).</li><li>Van Ruissen, 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=Induction+of+normal+and+psoriatic+phenotypes+in+submerged+keratinocyte+cultures.">Induction of normal and psoriatic phenotypes in submerged keratinocyte cultures.</a> Journal of Cellular Physiology. 168 (2), 442-452 (1996).</li><li>Ojeh, N., Pastar, I., Tomic-Canic, M., Stojadinovic, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stem+Cells+in+Skin+Regeneration,+Wound+Healing,+and+Their+Clinical+Applications.">Stem Cells in Skin Regeneration, Wound Healing, and Their Clinical Applications.</a> International Journal of Molecular Sciences. 16 (10), 25476-25501 (2015).</li><li>Ali, N., 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=Skin+equivalents:+skin+from+reconstructions+as+models+to+study+skin+development+and+diseases.">Skin equivalents: skin from reconstructions as models to study skin development and diseases.</a> British Journal of Dermatology. 173 (2), 391-403 (2015).</li><li>Luis, N. 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=Regulation+of+human+epidermal+stem+cell+proliferation+and+senescence+requires+polycomb-+dependent+and+-independent+functions+of+Cbx4.">Regulation of human epidermal stem cell proliferation and senescence requires polycomb- dependent and -independent functions of Cbx4.</a> Cell Stem Cell. 9 (3), 233-246 (2011).</li><li>Mulder, K. W., 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=Diverse+epigenetic+strategies+interact+to+control+epidermal+differentiation.">Diverse epigenetic strategies interact to control epidermal differentiation.</a> Nature Cell Biology. 14 (7), 753-763 (2012).</li><li>Poumay, Y., Pittelkow, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+density+and+culture+factors+regulate+keratinocyte+commitment+to+differentiation+and+expression+of+suprabasal+K1/K10+keratins.">Cell density and culture factors regulate keratinocyte commitment to differentiation and expression of suprabasal K1/K10 keratins.</a> Journal of Investigative Dermatology. 104 (2), 271-276 (1995).</li><li>Kouwenhoven, E. N., 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=Transcription+factor+p63+bookmarks+and+regulates+dynamic+enhancers+during+epidermal+differentiation.">Transcription factor p63 bookmarks and regulates dynamic enhancers during epidermal differentiation.</a> EMBO Rep. 16 (7), 863-878 (2015).</li><li>Qu, J., 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=Mutant+p63+Affects+Epidermal+Cell+Identity+through+Rewiring+the+Enhancer+Landscape.">Mutant p63 Affects Epidermal Cell Identity through Rewiring the Enhancer Landscape.</a> Cell Reports. 25 (12), 3490-3503 (2018).</li><li>Brunner, H. G., Hamel, B. C., Van Bokhoven, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+p63+gene+in+EEC+and+other+syndromes.">The p63 gene in EEC and other syndromes.</a> Journal of Medical Genetics. 39 (6), 377-381 (2002).</li><li>Browne, 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=Differential+altered+stability+and+transcriptional+activity+of+DeltaNp63+mutants+in+distinct+ectodermal+dysplasias.">Differential altered stability and transcriptional activity of DeltaNp63 mutants in distinct ectodermal dysplasias.</a> Journal of Cell Science. 124, 2200-2207 (2011).</li><li>. KGM Gold Keratinocyte Growth Medium BulletKit Available from: <a target="_blank" href="https://bioscience.lonza.com/Lonza_bs/CH/en/Culture-Media-and-Reagents/p/000000000000192060/KGM-Gold-Keratinocyte-Growth-Medium-BulletKit">https://bioscience.lonza.com/Lonza_bs/CH/en/Culture-Media-and-Reagents/p/000000000000192060/KGM-Gold-Keratinocyte-Growth-Medium-BulletKit</a> (2019)</li><li>Doyle, K. a. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Protocols and applications guide. , (1996).</li><li>. Hyperprep Kit Available from: <a target="_blank" href="https://sequencing.roche.com/en-us/products-solutions/by-category/Library-preparation/rna-library-preparation/kapa-rna-hyperprep-kit-with-riboerasehmr.html">https://sequencing.roche.com/en-us/products-solutions/by-category/Library-preparation/rna-library-preparation/kapa-rna-hyperprep-kit-with-riboerasehmr.html</a> (2019)</li><li>. TrimGalore Available from: <a target="_blank" href="https://github.com/FelixKrueger/TrimGalore">https://github.com/FelixKrueger/TrimGalore</a> (2019)</li><li>Dobin, A., 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=STAR:+ultrafast+universal+RNA-seq+aligner.">STAR: ultrafast universal RNA-seq aligner.</a> Bioinformatics. 29 (1), 15-21 (2013).</li><li>Li, H., 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=The+Sequence+Alignment/Map+format+and+SAMtools.">The Sequence Alignment/Map format and SAMtools.</a> Bioinformatics. 25 (16), 2078-2079 (2009).</li><li>. Convert chromosome names in a bigWig file Available from: <a target="_blank" href="https://gist.github.com/dpryan79/39c70b4429dd4559d88fb079b8669721">https://gist.github.com/dpryan79/39c70b4429dd4559d88fb079b8669721</a> (2019)</li><li>Love, M. I., Huber, W., Anders, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Moderated+estimation+of+fold+change+and+dispersion+for+RNA-seq+data+with+DESeq2.">Moderated estimation of fold change and dispersion for RNA-seq data with DESeq2.</a> Genome Biol. 15 (12), 550 (2014).</li><li>Eden, E., Navon, R., Steinfeld, I., Lipson, D., Yakhini, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GOrilla:+a+tool+for+discovery+and+visualization+of+enriched+GO+terms+in+ranked+gene+lists.">GOrilla: a tool for discovery and visualization of enriched GO terms in ranked gene lists.</a> BMC Bioinformatics. 10, 48 (2009).</li><li>Yu, G., Wang, L. G., Han, Y., He, Q. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=clusterProfiler:+an+R+package+for+comparing+biological+themes+among+gene+clusters.">clusterProfiler: an R package for comparing biological themes among gene clusters.</a> Omics. 16 (5), 284-287 (2012).</li><li>Kretz, 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=Control+of+somatic+tissue+differentiation+by+the+long+non-coding+RNA+TINCR.">Control of somatic tissue differentiation by the long non-coding RNA TINCR.</a> Nature. 493 (7431), 231-235 (2013).</li><li>Mullegama, S. V., 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=Nucleic+Acid+Extraction+from+Human+Biological+Samples.">Nucleic Acid Extraction from Human Biological Samples.</a> Methods in Molecular Biology. 1897, 359-383 (2019).</li><li>Ma, 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=A+comparison+between+whole+transcript+and+3'+RNA+sequencing+methods+using+Kapa+and+Lexogen+library+preparation+methods.">A comparison between whole transcript and 3' RNA sequencing methods using Kapa and Lexogen library preparation methods.</a> BMC Genomics. 20 (1), 9 (2019).</li><li>Chao, H. P., 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=Systematic+evaluation+of+RNA-Seq+preparation+protocol+performance.">Systematic evaluation of RNA-Seq preparation protocol performance.</a> BMC Genomics. 20 (1), 571 (2019).</li><li>Podnar, J., Deiderick, H., Huerta, G., Hunicke-Smith, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Next-Generation+Sequencing+RNA-Seq+Library+Construction.">Next-Generation Sequencing RNA-Seq Library Construction.</a> Current Protocols in Molecular Biology. 106, 21 (2014).</li><li>Haque, A., Engel, J., Teichmann, S. A., Lonnberg, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+practical+guide+to+single-cell+RNA-sequencing+for+biomedical+research+and+clinical+applications.">A practical guide to single-cell RNA-sequencing for biomedical research and clinical applications.</a> Genome Medicine. 9 (1), 75 (2017).</li><li>Oyola, S. O., 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=Optimizing+Illumina+next-generation+sequencing+library+preparation+for+extremely+AT-biased+genomes.">Optimizing Illumina next-generation sequencing library preparation for extremely AT-biased genomes.</a> BMC Genomics. 13, 1 (2012).</li><li>Quail, M. A., 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=Optimal+enzymes+for+amplifying+sequencing+libraries.">Optimal enzymes for amplifying sequencing libraries.</a> Nature Methods. 9 (1), 10-11 (2011).</li><li>Quail, M. A., 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=A+tale+of+three+next+generation+sequencing+platforms:+comparison+of+Ion+Torrent,+Pacific+Biosciences+and+Illumina+MiSeq+sequencers.">A tale of three next generation sequencing platforms: comparison of Ion Torrent, Pacific Biosciences and Illumina MiSeq sequencers.</a> BMC Genomics. 13, 341 (2012).</li><li>Ross, M. 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=Characterizing+and+measuring+bias+in+sequence+data.">Characterizing and measuring bias in sequence data.</a> Genome Biology. 14 (5), 51 (2013).</li><li>. ARMOR Available from: <a target="_blank" href="https://github.com/csoneson/ARMOR">https://github.com/csoneson/ARMOR</a> (2019)</li><li>. snakemake-workflows Available from: <a target="_blank" href="https://github.com/vanheeringen-lab/snakemake-workflows">https://github.com/vanheeringen-lab/snakemake-workflows</a> (2019)</li></ol>

The authors have nothing to disclose.

This work describes a method for inducing human keratinocyte differentiation and subsequent characterization using RNA-seq analyses. In the current literature, many studies on human keratinocyte differentiation use two other methods, with a high calcium concentration or with serum&#160;as methods to induce differentiation2,3,23. A previous report carefully compared these three different methods3 and showe...

Human primary keratinocytes derived from the human skin are often used as a cellular model to study the biology of the epidermis1,2,3,4. The stratification of the epidermis can be modeled by keratinocyte differentiation, either in a 2D submerged monolayer fashion or 3D air-lift organotypic model2,3,5,6,7. Although 3D models have become increasingly important to assess the epidermal structure and function, 2D differentiation models are still widely used, due to their convenience and the possibility to generate large numbers of cells for analyses.
Various conditions have been applied for inducing keratinocyte differentiation in 2D, including addition of serum, high concentration of calcium, lower temperature and inhibition of epidermal growth factor receptors2,3. Each of these methods has been validated by a number of keratinocyte differentiation marker genes and shown to be effective in assessing keratinocyte differentiation, including under pathological conditions. However, these induction conditions also show differences in their differentiation efficiency and kinetics when specific panels of marker genes are examined2,3.
One of these methods involves keratinocyte contact inhibition and depletion of growth factors in the culture medium8. It has been shown that keratinocytes can differentiate spontaneously when cells reach full density. &#160;Excluding growth factors in the culture medium can further enhance differentiation. The method combining contact inhibition and depleting growth factors has been shown to generate differentiated keratinocytes with gene expression patterns similar to the normal stratified epidermis when using several epidermal markers3, suggesting that this model is suitable for studying normal keratinocyte differentiation. Recently, two comprehensive gene expression analyses of keratinocyte differentiation using this model have been reported9,10. Researchers validated this model at the molecular level and showed that it can be used to study normal and diseased keratinocyte differentiation.
This protocol describes the procedure for the in vitro differentiation method and molecular analysis of differentiated cells using RNA-seq. It also illustrates characterization of the transcriptome of cells on differentiation day 0 (proliferation stage), day 2, day 4, and day 7 (early, middle, and late differentiation, respectively). It is shown that differentiated keratinocytes display gene expression patterns that largely resemble cells during epidermal stratification. To examine whether this method can be used for studying skin pathology, we applied the same experimental and analysis pipeline to investigate keratinocytes carrying mutations of the transcription factor p63 that are derived from patients with ectrodactyly, ectodermal displasia and cleft lip/palate (EEC) syndrome11,12. This protocol focuses on the in vitro differentiation of keratinocytes as well as subsequent bioinformatic analysis of RNA-seq. Other steps in the complete procedure such as RNA extraction, RNA-seq sample preparation and library construction, are well documented and can be easily followed, especially when using many commonly used commercial kits. Therefore, these steps are only briefly described in the protocol. The data show that this pipeline is suitable for studying molecular events during epidermal differentiation in healthy and diseased keratinocytes.

<table border="0" cellpadding="0" cellspacing="0" style="width:892px;" width="892">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:397px;">Bioanalyzer 2100</td>
			<td style="width:231px;">Agilent</td>
			<td style="width:200px;">G2929BA</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Bovine pituitary extract (BPE)</td>
			<td>Lonza</td>
			<td></td>
			<td>Part of the bulletKit</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">CFX96 Real-Time system</td>
			<td>Bio-Rad</td>
			<td></td>
			<td>qPCR machine</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Dulbecco&#39;s Phosphate-Buffered Saline (DPBS)</td>
			<td>Sigma-Aldrich</td>
			<td>D8537</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Epidermal Growth Factor (EGF)</td>
			<td>Lonza</td>
			<td></td>
			<td>Part of the bulletKit</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ethanolamine &#62;= 98%</td>
			<td>Sigma-Aldrich</td>
			<td>E9508</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">High Sensitivity DNA chips</td>
			<td>Agilent</td>
			<td>5067-4626</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Hydrocortison</td>
			<td>Lonza</td>
			<td></td>
			<td>Part of the bulletKit</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Insulin</td>
			<td>Lonza</td>
			<td></td>
			<td>Part of the bulletKit</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">iQ SYBR Green Kit</td>
			<td>BioRad</td>
			<td>170-8886</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">iScript cDNA synthesis</td>
			<td>Bio rad</td>
			<td>1708890</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">KAPA Library Quant Kit</td>
			<td>Roche</td>
			<td>07960255001</td>
			<td>Low concentration measure kit</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">KAPA RNA HyperPrep Kit with RiboErase</td>
			<td>Roche</td>
			<td>KK8540</td>
			<td>RNAseq kit</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">KGM Gold Keratinocyte Growth Medium BulletKit</td>
			<td>Lonza</td>
			<td>192060</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Nanodrop</td>
			<td>deNovix</td>
			<td>DS-11 FX (model)</td>
			<td>Nanodrop and Qbit for DNA and RNA measurements</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">NEXTflex DNA barcodes -24</td>
			<td>Illumnia</td>
			<td>NOVA-514103</td>
			<td>6 bp long primers</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Penicillin-Streptomycin</td>
			<td>Gibco</td>
			<td>15140122</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">RNA Pico Chip</td>
			<td>Agilent</td>
			<td>5067-1513</td>
			<td></td>
		</tr>
	</tbody>
</table>

characterization of in vitro differentiation of human primary keratinocytes by rna-seq analysis

Human primary keratinocytes are often used as in vitro models for studies on epidermal differentiation and related diseases. Methods have been reported for in vitro differentiation of keratinocytes cultured in two-dimensional (2D) submerged manners using various induction conditions. Described here is a procedure for 2D in vitro keratinocyte differentiation method by contact inhibition and subsequent molecular characterization by RNA-seq. In brief, keratinocytes are grown in defined keratinocyte medium supplemented with growth factors until they are fully confluent. Differentiation is induced by close contacts between the keratinocytes and further stimulated by excluding growth factors in the medium. Using RNA-seq analyses, it is shown that both 1) differentiated keratinocytes exhibit distinct molecular signatures during differentiation and 2) the dynamic gene expression pattern largely resembles cells during epidermal stratification. As for comparison to normal keratinocyte differentiation, keratinocytes carrying mutations of the transcription factor p63 exhibit altered morphology and molecular signatures, consistent with their differentiation defects. In conclusion, this protocol details the steps for 2D in vitro keratinocyte differentiation and its molecular characterization, with an emphasis on bioinformatic analysis of RNA-seq data. Because RNA extraction and RNA-seq procedures have been well-documented, it is not the focus of this protocol. The experimental procedure of in vitro keratinocyte differentiation and bioinformatic analysis pipeline can be used to study molecular events during epidermal differentiation in healthy and diseased keratinocytes.

Normal keratinocyte differentiation and RNA-seq analysis 
In this experiment, keratinocyte lines derived from five individuals were used for differentiation and RNA-seq analyses. Figure 1 summarizes the experimental procedure of differentiation and RNA-seq analysis results. An overview of in vitro differentiation procedures of normal keratinocytes and cell morphology changes during differentiation are illustrated in Figure 1A. Principle com...

Watch this Scientific Journal Video about Characterization of In Vitro Differentiation of Human Primary Keratinocytes by RNA-Seq Analysis at JoVE.com

Characterization of In Vitro Differentiation of Human Primary Keratinocytes by RNA-Seq Analysis

Presented here is a stepwise procedure for in vitro differentiation of human primary keratinocytes by contact inhibition followed by characterization at the molecular level by RNA-seq analysis.

Human primary keratinocytes are often used as in vitro models for studies on epidermal differentiation and related diseases. Methods have been reported ...

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6.0K Views.  Radboud University, Nijmegen, The Netherlands. Presented here is a stepwise procedure for in vitro differentiation of human primary keratinocytes by contact inhibition followed by characterization at the molecular level by RNA-seq analysis.

Video: Characterization of In Vitro Differentiation of Human Primary Keratinocytes by RNA-Seq Analysis

Parallel Measurement of Circadian Clock Gene Expression and Hormone Secretion in Human Primary Cell Cultures

Circadian clocks are functional in all light-sensitive organisms, allowing for an adaptation to the external world by anticipating daily environmental changes. Considerable progress in our understanding of the tight connection between the circadian clock and most aspects of physiology has been made in the field over the last decade. However, unraveling the molecular basis that underlies the function of the circadian oscillator in humans stays of highest technical challenge. Here, we provide a detailed description of an experimental approach for long-term (2-5 days) bioluminescence recording and outflow medium collection in cultured human primary cells. For this purpose, we have transduced primary cells with a lentiviral luciferase reporter that is under control of a core clock gene promoter, which allows for the parallel assessment of hormone secretion and circadian bioluminescence. Furthermore, we describe the conditions for disrupting the circadian clock in primary human cells by transfecting siRNA targeting CLOCK. Our results on the circadian regulation of insulin secretion by human pancreatic islets, and myokine secretion by human skeletal muscle cells, are presented here to illustrate the application of this methodology. These settings can be used to study the molecular makeup of human peripheral clocks and to analyze their functional impact on primary cells under physiological or pathophysiological conditions.

Here, we describe settings to monitor in parallel circadian bioluminescence and the secretory activity of human islet cells and primary myotubes. For this, we employed lentiviral gene delivery of a luciferase core clock reporter, followed by in vitro synchronization and collection of outflow medium by continuous cell perifusion.

Circadian clocks are functional in all light-sensitive organisms, allowing for an adaptation to the external world by anticipating daily environmental ...

Analysis of the Ambient Particulate Matter-induced Chromosomal Aberrations Using an In Vitro System

Exposure to particulate matter (PM) is a major world health concern, which may damage various cellular components, including the nuclear genetic material. To assess the impact of PM on nuclear genetic integrity, structural chromosomal aberrations are scored in the metaphase spreads of mouse RAW264.7 macrophage cells. PM is collected from ambient air with a high volume total suspended particles sampler. The collected material is solubilized and filtered to retain the water-soluble, fine portion. The particles are characterized for chemical composition by nuclear magnetic resonance (NMR) spectroscopy. Different concentrations of particle suspension are added onto an in vitro culture of RAW264.7 mouse macrophages for a total exposure time of 72 hr, along with untreated control cells. At the end of exposure, the culture is treated with colcemid to arrest cells in metaphase. Cells are then harvested, treated with hypotonic solution, fixed in acetomethanol, dropped onto glass slides and finally stained with Giemsa solution. Slides are examined to assess the structural chromosomal aberrations (CAs) in metaphase spreads at 1,000X magnification using a bright-field microscope. 50 to 100 metaphase spread are scored for each treatment group. This technique is adapted for the detection of structural chromosomal aberrations (CAs), such as chromatid-type breaks, chromatid-type exchanges, acentric fragments, dicentric and ring chromosomes, double minutes, endoreduplication, and Robertsonian translocations in vitro after exposure to PM. It is a powerful method to associate a well-established cytogenetic endpoint to epigenetic alterations.

Analysis of the Ambient Particulate Matter-induced Chromosomal Aberrations Using an In Vitro System

This protocol describes techniques for the quantification and characterization of chromosomal aberrations in vitro in RAW264.7 mouse macrophages after treatment with ambient air particulate matter.

Exposure to particulate matter (PM) is a major world health concern, which may damage various cellular components, including the nuclear genetic material. ...

Analysis of Cap-binding Proteins in Human Cells Exposed to Physiological Oxygen Conditions

Translational control is a focal point of gene regulation, especially during periods of cellular stress. Cap-dependent translation via the eIF4F complex is by far the most common pathway to initiate protein synthesis in eukaryotic cells, but stress-specific variations of this complex are now emerging. Purifying cap-binding proteins with an affinity resin composed of Agarose-linked m7GTP (a 5' mRNA cap analog) is a useful tool to identify factors involved in the regulation of translation initiation. Hypoxia (low oxygen) is a cellular stress encountered during fetal development and tumor progression, and is highly dependent on translation regulation. Furthermore, it was recently reported that human adult organs have a lower oxygen content (physioxia 1-9% oxygen) that is closer to hypoxia than the ambient air where cells are routinely cultured. With the ongoing characterization of a hypoxic eIF4F complex (eIF4FH), there is increasing interest in understanding oxygen-dependent translation initiation through the 5' mRNA cap. We have recently developed a human cell culture method to analyze cap-binding proteins that are regulated by oxygen availability. This protocol emphasizes that cell culture and lysis be performed in a hypoxia workstation to eliminate exposure to oxygen. Cells must be incubated for at least 24 hr for the liquid media to equilibrate with the atmosphere within the workstation. To avoid this limitation, pre-conditioned media (de-oxygenated) can be added to cells if shorter time points are required. Certain cap-binding proteins require interactions with a second base or can hydrolyze the m7GTP, therefore some cap interactors may be missed in the purification process. Agarose-linked to enzymatically resistant cap analogs may be substituted in this protocol. This method allows the user to identify novel oxygen-regulated translation factors involved in cap-dependent translation.

Here, we present human cell culture protocols to analyze translation initiation factors that bind the 5' cap of mRNA during physiological oxygen conditions. This method utilizes an Agarose-linked m7GTP cap analog and is suitable to investigate cap-binding factors and their interacting partners.

Translational control is a focal point of gene regulation, especially during periods of cellular stress. Cap-dependent translation via the eIF4F complex ...

Genome Editing and Directed Differentiation of hPSCs for Interrogating Lineage Determinants in Human Pancreatic Development

Interrogating gene function in self-renewing or differentiating human pluripotent stem cells (hPSCs) offers a valuable platform towards understanding human development and dissecting disease mechanisms in a dish. To capitalize on this potential application requires efficient genome-editing tools to generate hPSC mutants in disease-associated genes, as well as in vitro hPSC differentiation protocols to produce disease-relevant cell types that closely recapitulate their in vivo counterparts. An efficient genome-editing platform for hPSCs named iCRISPR has been developed through the TALEN-mediated targeting of a Cas9 expression cassette in the AAVS1 locus. Here, the protocols for the generation of inducible Cas9 hPSC lines using cells cultured in a chemically defined medium and a feeder-free condition are described. Detailed procedures for using the iCRISPR system for gene knockout or precise genetic alterations in hPSCs, either through non-homologous end joining (NHEJ) or via precise nucleotide alterations using a homology-directed repair (HDR) template, respectively, are included. These technical procedures include descriptions of the design, production, and transfection of CRISPR guide RNAs (gRNAs); the measurement of the CRISPR mutation rate by T7E1 or RFLP assays; and the establishment and validation of clonal mutant lines. Finally, we chronicle procedures for hPSC differentiation into glucose-responsive pancreatic &#946;-like cells by mimicking in vivo pancreatic embryonic development. Combining iCRISPR technology with directed hPSC differentiation enables the systematic examination of gene function to further our understanding of pancreatic development and diabetes disease mechanisms.

Protocols to generate hPSC mutant lines using the iCRISPR platform and to differentiate hPSCs into glucose-responsive &#946;-like cells are described. Combining genome editing technology with hPSC-directed differentiation provides a powerful platform for the systematic analysis of the role of lineage determinants in human development and disease progression.

Interrogating gene function in self-renewing or differentiating human pluripotent stem cells (hPSCs) offers a valuable platform towards understanding ...

Kinetics of Lagging-strand DNA Synthesis In Vitro by the Bacteriophage T7 Replication Proteins

Here we provide protocols for the kinetic examination of lagging-strand DNA synthesis in vitro by the replication proteins of bacteriophage T7. The T7 replisome is one of the simplest replication systems known, composed of only four proteins, which is an attractive feature for biochemical experiments. Special emphasis is placed on the synthesis of ribonucleotide primers by the T7 primase-helicase, which are used by DNA polymerase to initiate DNA synthesis. Because the mechanisms of DNA replication are conserved across evolution, these protocols should be applicable, or useful as a conceptual springboard, to investigators using other model systems. The protocols described here are highly sensitive and an experienced investigator can perform these experiments and obtain data for analysis in about a day. The only specialized piece of equipment required is a rapid-quench flow instrument, but this piece of equipment is relatively common and available from various commercial sources. The major drawbacks of these assays, however, include the use of radioactivity and the relative low throughput.

Kinetics of Lagging-strand DNA Synthesis In Vitro by the Bacteriophage T7 Replication Proteins

We describe sensitive, gel-based discontinuous assays to examine the kinetics of lagging-strand initiation using the replication proteins of bacteriophage T7.

Here we provide protocols for the kinetic examination of lagging-strand DNA synthesis in vitro by the replication proteins of bacteriophage T7. The T7 ...

Mapping Genome-wide Accessible Chromatin in Primary Human T Lymphocytes by ATAC-Seq

Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq) is a method used for the identification of open (accessible) regions of chromatin. These regions represent regulatory DNA elements (e.g., promoters, enhancers, locus control regions, insulators) to which transcription factors bind. Mapping the accessible chromatin landscape is a powerful approach for uncovering active regulatory elements across the genome. This information serves as an unbiased approach for discovering the network of relevant transcription factors and mechanisms of chromatin structure that govern gene expression programs. ATAC-seq is a robust and sensitive alternative to DNase I hypersensitivity analysis coupled with next-generation sequencing (DNase-seq) and formaldehyde-assisted isolation of regulatory elements (FAIRE-seq) for genome-wide analysis of chromatin accessibility and to the sequencing of micrococcal nuclease-sensitive sites (MNase-seq) to determine nucleosome positioning. We present a detailed ATAC-seq protocol optimized for human primary immune cells i.e. CD4+ lymphocytes (T helper 1 (Th1) and Th2 cells). This comprehensive protocol begins with cell harvest, then describes the molecular procedure of chromatin tagmentation, sample preparation for next-generation sequencing, and also includes methods and considerations for the computational analyses used to interpret the results. Moreover, to save time and money, we introduced quality control measures to assess the ATAC-seq library prior to sequencing. Importantly, the principles presented in this protocol allow its adaptation to other human immune and non-immune primary cells and cell lines. These guidelines will also be useful for laboratories which are not proficient with next-generation sequencing methods.

Assay for Transposase-Accessible Chromatin coupled with high-throughput sequencing (ATAC-seq) is a genome-wide method to uncover accessible chromatin. This is a step-by-step ATAC-seq protocol, from molecular to the final computational analysis, optimized for human lymphocytes (Th1/Th2). This protocol can be adopted by researchers without prior experience in next-generation sequencing methods.

Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq) is a method used for the identification of open (accessible) regions ...

Differentiation, Maintenance, and Analysis of Human Retinal Pigment Epithelium Cells: A Disease-in-a-dish Model for BEST1 Mutations

Although over 200 genetic mutations in the human BEST1 gene have been identified and linked to retinal degenerative diseases, the pathological mechanisms remain elusive mainly due to the lack of a good in vivo model for studying BEST1 and its mutations under physiological conditions. BEST1 encodes an ion channel, namely BESTROPHIN1 (BEST1), which functions in retinal pigment epithelium (RPE); however, the extremely limited accessibility to native human RPE cells represents a major challenge for scientific research. This protocol describes how to generate human RPEs bearing BEST1 disease-causing mutations by induced differentiation from human pluripotent stem cells (hPSCs). As hPSCs are self-renewable, this approach allows researchers to have a steady source of hPSC-RPEs for various experimental analyses, such as immunoblotting, immunofluorescence, and patch clamp, and thus provides a very powerful disease-in-a-dish model for BEST1-associated retinal conditions. Notably, this strategy can be applied to study RPE (patho)physiology and other genes of interest natively expressed in RPE.

Differentiation, Maintenance, and Analysis of Human Retinal Pigment Epithelium Cells: A Disease-in-a-dish Model for BEST1 Mutations

Here we present a protocol to differentiate retinal pigment epithelium (RPE) cells from human pluripotent stem cells bearing patient-derived mutations. The mutant cell lines may be used for functional analyses including immunoblotting, immunofluorescence, and patch clamp. This disease-in-a-dish approach circumvents the difficulty of obtaining native human RPE cells.

Although over 200 genetic mutations in the human BEST1 gene have been identified and linked to retinal degenerative diseases, the pathological mechanisms ...

Isolation, Characterization and MicroRNA-based Genetic Modification of Human Dental Follicle Stem Cells

To date, several stem cell types at different developmental stages are in the focus for the treatment of degenerative diseases. Yet, certain aspects, such as initial massive cell death and low therapeutic effects, impaired their broad clinical translation. Genetic engineering of stem cells prior to transplantation emerged as a promising method to optimize therapeutic stem cell effects. However, safe and efficient gene delivery systems are still lacking. Therefore, the development of suitable methods may provide an approach to resolve current challenges in stem cell-based therapies.
The present protocol describes the extraction and characterization of human dental follicle stem cells (hDFSCs) as well as their non-viral genetic modification. The postnatal dental follicle unveiled as a promising and easily accessible source for harvesting adult multipotent stem cells possessing high proliferation potential. The described isolation procedure presents a simple and reliable method to harvest hDFSCs from impacted wisdom teeth. Also this protocol comprises methods to define stem cell characteristics of isolated cells. For genetic engineering of hDFSCs, an optimized cationic lipid-based transfection strategy is presented enabling highly efficient microRNA introduction without causing cytotoxic effects. MicroRNAs are suitable candidates for transient cell manipulation, as these small translational regulators control the fate and behavior of stem cells without the hazard of stable genome integration. Thus, this protocol represents a safe and efficient procedure for engineering of hDFSCs that may become important for optimizing their therapeutic efficacy.

This protocol describes the transient genetic engineering of dental stem cells extracted from the human dental follicle. The applied non-viral modification strategy may become a basis for the improvement of therapeutic stem cell products.

To date, several stem cell types at different developmental stages are in the focus for the treatment of degenerative diseases. Yet, certain aspects, such ...

Improving Small RNA-seq: Less Bias and Better Detection of 2'-O-Methyl RNAs

The study of small RNAs (sRNAs) by next-generation sequencing (NGS) is challenged by bias issues during library preparation. Several types of sRNA such as plant microRNAs (miRNAs) carry a 2&#39;-O-methyl (2&#39;-OMe) modification at their 3&#39;&#160;terminal nucleotide. This modification adds another difficulty as it inhibits 3&#39;&#160;adapter ligation. We previously demonstrated that modified versions of the &#39;TruSeq (TS)&#39;&#160;protocol have less bias and an improved detection of 2&#39;-OMe RNAs. Here we describe in detail protocol &#39;TS5&#39;, which showed the best overall performance. TS5 can be followed either using homemade reagents or reagents from the TS kit, with equal performance.

We present a detailed small RNA library reparation protocol with less bias than standard methods and an increased sensitivity for 2&#39;-O-methyl RNAs. This protocol can be followed using homemade reagents to save cost or using kits for convenience.

The study of small RNAs (sRNAs) by next-generation sequencing (NGS) is challenged by bias issues during library preparation. Several types of sRNA such as ...

Investigation of the Transcriptional Role of a RUNX1 Intronic Silencer by CRISPR/Cas9 Ribonucleoprotein in Acute Myeloid Leukemia Cells

The bulk of the human genome (~98%) is comprised of non-coding sequences. Cis-regulatory elements (CREs) are non-coding DNA sequences that contain binding sites for transcriptional regulators to modulate gene expression. Alterations of CREs have been implicated in various diseases including cancer. While promoters and enhancers have been the primary CREs for studying gene regulation, very little is known about the role of silencer, which is another type of CRE that mediates gene repression. Originally identified as an adaptive immunity system in prokaryotes, CRISPR/Cas9 has been exploited to be a powerful tool for eukaryotic genome editing. Here, we present the use of this technique to delete an intronic silencer in the human RUNX1 gene and investigate the impacts on gene expression in OCI-AML3 leukemic cells. Our approach relies on electroporation-mediated delivery of two preassembled Cas9/guide RNA (gRNA) ribonucleoprotein (RNP) complexes to create two double-strand breaks (DSBs) that flank the silencer. Deletions can be readily screened by fragment analysis. Expression analyses of different mRNAs transcribed from alternative promoters help evaluate promoter-dependent effects. This strategy can be used to study other CREs and is particularly suitable for hematopoietic cells, which are often difficult to transfect with plasmid-based methods. The use of a plasmid- and virus-free strategy allows simple and fast assessments of gene regulatory functions.

Investigation of the Transcriptional Role of a RUNX1 Intronic Silencer by CRISPR/Cas9 Ribonucleoprotein in Acute Myeloid Leukemia Cells

Direct delivery of preassembled Cas9/guide RNA ribonucleoprotein complexes is a fast and efficient means for genome editing in hematopoietic cells. Here, we utilize this approach to delete a RUNX1 intronic silencer and examine the transcriptional responses in OCI-AML3 leukemic cells.

The bulk of the human genome (~98%) is comprised of non-coding sequences. Cis-regulatory elements (CREs) are non-coding DNA sequences that contain binding ...