Name: an optogenetic method to control and analyze gene expression patterns in cell-to-cell interactions
Uploaded: 2018-03-22T14:00:00
Description: Watch this Scientific Journal Video about An Optogenetic Method to Control and Analyze Gene Expression Patterns in Cell-to-cell Interactions at JoVE.com

This work was supported by JST, PRESTO (A.I.), Core Research for Evolutional Science and Technology (JPMJCR12W2 (R.K.)), Grant-in-Aid for Scientific Research on Innovative Areas (Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan 26119708 (A.I.) and 16H06480 (R.K.)), Scientific Research (A) (Japan Society for the Promotion of Science (JSPS) 24240049 (R.K.)), and Young Scientists (A) (JSPS 15H05326 (A.I.)), and a Grant-in-Aid for Scientific Research on Innovative Areas &#34;Fluorescence Live imaging&#34; of the MEXT, Japan, and Platform for Dynamic Approaches to Living System from the MEXT, Japan.

1. Generation of Stable Cell Lines by the Tol2 System
<ol>
	<li>Transfect plasmid vectors (Figure 1A) of Tol2-based optogenetic modules together with the transposase (Tol2) expression vector (pCAGGS-mT2TP) into C2C12 cells. In all steps, culture cells with DMEM medium supplemented with 10% fetal bovine serum (FBS) and penicillin-streptomycin at 37 &#176;C (Table 1), in the presence of 5% CO2, otherwise denoted.
	<ol>
		<li>Count trypsinized cells with a cell-cou...

<ol>
	<li>Hubaud, A., Pourquie, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Signalling+dynamics+in+vertebrate+segmentation.">Signalling dynamics in vertebrate segmentation.</a> Nat. Rev. Mol. Cell Biol. 15, 709-721 (2014).</li><li>Maroto, M., Dale, J. K., Dequeant, M. L., Petit, A. C., Pourqui&#233;, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synchronised+cycling+gene+oscillations+in+presomitic+mesoderm+cells+require+cell-cell+contact.">Synchronised cycling gene oscillations in presomitic mesoderm cells require cell-cell contact.</a> Int. J. Dev. Biol. 49, 309-315 (2005).</li><li>Masamizu, Y., Ohtsuka, T., Takashima, Y., Nagahara, H., Takenaka, Y., Yoshikawa, K., Okamura, H., Kageyama, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+imaging+of+the+somite+segmentation+clock:+revelation+of+unstable+oscillators+in+the+individual+presomitic+mesoderm+cell.">Real-time imaging of the somite segmentation clock: revelation of unstable oscillators in the individual presomitic mesoderm cell.</a> Proc. Natl. Acad. Sci. USA. 103, 1313-1318 (2006).</li><li>Tsiairis, C., Aulehla, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-Organization+of+Embryonic+Genetic+Oscillators+into+Spatiotemporal+Wave+Patterns.">Self-Organization of Embryonic Genetic Oscillators into Spatiotemporal Wave Patterns.</a> Cell. 164, 656-667 (2016).</li><li>Jiang, Y. J., Aerne, B. L., Smithers, L., Haddon, C., Ish-Horowicz, D., Lewis, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Notch+signalling+and+the+synchronization+of+the+somite+segmentation+clock.">Notch signalling and the synchronization of the somite segmentation clock.</a> Nature. 408, 475-479 (2000).</li><li>Delaune, E. A., Fran&#231;ois, P., Shih, N. P., Amacher, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-cell-resolution+imaging+of+the+impact+of+Notch+signaling+and+mitosis+on+segmentation+clock+dynamics.">Single-cell-resolution imaging of the impact of Notch signaling and mitosis on segmentation clock dynamics.</a> Dev. Cell. 23, 995-1005 (2012).</li><li>Dale, J. K., Maroto, M., Dequeant, M. L., Malapert, P., McGrew, M., Pourqui&#233;, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Periodic+inhibition+by+Lunatic+Fringe+underlies+the+chick+Segmentation+Clock.">Periodic inhibition by Lunatic Fringe underlies the chick Segmentation Clock.</a> Nature. 421, 275-278 (2003).</li><li>Okubo, Y., Sugawara, T., Abe-Koduka, N., Kanno, J., Kimura, A., Saga, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lfng+regulates+the+synchronized+oscillation+of+the+mouse+segmentation+clock+via+trans-repression+of+Notch+signalling.">Lfng regulates the synchronized oscillation of the mouse segmentation clock via trans-repression of Notch signalling.</a> Nat. Commun. 3, 1141 (2012).</li><li>Shimojo, H., Isomura, A., Ohtsuka, T., Kori, H., Miyachi, H., Kageyama, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oscillatory+control+of+Delta-like1+in+cell+interactions+regulates+dynamic+gene+expression+and+tissue+morphogenesis.">Oscillatory control of Delta-like1 in cell interactions regulates dynamic gene expression and tissue morphogenesis.</a> Genes Dev. 30, 102-116 (2016).</li><li>Isomura, A., Ogushi, F., Kori, H., Kageyama, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optogenetic+perturbation+and+bioluminescence+imaging+to+analyze+cell-to-cell+transfer+of+oscillatory+information.">Optogenetic perturbation and bioluminescence imaging to analyze cell-to-cell transfer of oscillatory information.</a> Genes Dev. 31, 524-535 (2017).</li><li>Wang, X., Chen, X., Yang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatiotemporal+control+of+gene+expression+by+a+light-switchable+transgene+system.">Spatiotemporal control of gene expression by a light-switchable transgene system.</a> Nat. Meth. 9, 266-269 (2012).</li><li>Imayoshi, I., Isomura, A., Harima, Y., Kawaguchi, K., Kori, H., Miyachi, H., Fujiwara, T. K., Ishidate, F., Kageyama, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oscillatory+control+of+factors+determining+multipotency+and+fate+in+mouse+neural+progenitors.">Oscillatory control of factors determining multipotency and fate in mouse neural progenitors.</a> Science. 342, 1203-1208 (2013).</li><li>Kawakami, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tol2:+a+versatile+gene+transfer+vector+in+vertebrates.">Tol2: a versatile gene transfer vector in vertebrates.</a> Genome Biol. 8, S7 (2007).</li><li>Yagita, K., Yamanaka, I., Emoto, N., Kawakami, K., Shimada, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+monitoring+of+circadian+clock+oscillations+in+primary+cultures+of+mammalian+cells+using+Tol2+transposon-mediated+gene+transfer+strategy.">Real-time monitoring of circadian clock oscillations in primary cultures of mammalian cells using Tol2 transposon-mediated gene transfer strategy.</a> BMC Biotechnology. 10, 3 (2010).</li><li>Filonov, G. 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We showed a method to control gene expression dynamics with a periodicity of 2 to 3 h. This time-scale is much shorter than the ones in other conventional systems, including the Tet-On system and the original LightOn system. Key parameters to reach the ultradian time-scales are half-lives of photo-induced molecular products, mRNAs, and proteins. These kinetic parameters may depend on cell types and species. For tuning the kinetics, replacing Hes1 3&#39;UTR sequences with others is a straight-forward way, because it does ...

Cell-to-cell communications play critical roles in embryonic patterning in developmental processes. In vertebrate embryos, the metameric structures called somites are formed along the anterior-posterior body axis with a precise temporal accuracy under the control of a time-keeping clock, called the segmentation clock1. During this process, a group of presomitic mesoderm (PSM) cells are periodically converted into somites in a synchronous manner. This process involves synchronized oscillatory gene expression and PSM cells that oscillate in phase form the same somites. The period of the oscillatory gene expression is around 2 to 3 h in mice and about 30 min in zebrafish. When dissociated, PSM cells lose the synchrony2,3, but when they are re-aggregated, they can self-organize and recover the population synchrony4, suggesting that cell-cell coupling is a key for the synchronized oscillations.
Extensive efforts revealed that signaling molecules in the Delta-Notch pathway are tightly connected to the synchronized oscillations of the segmentation clock genes. Either pharmacological inhibitors or genetic mutations of Notch signaling desynchronize the population of the oscillators. In zebrafish, mutants of Notch signaling components, such as DeltaC, DeltaD, and Notch1a, display asynchronous oscillations5,6. In chick or mouse embryos, not only the Notch ligand Delta-like1 (Dll1) but also the Notch Modulator Lunatic fringe (Lfng) is required for synchronized oscillations7,8,9. However, it has been difficult to test the functional capability of such molecules for dynamic information transfer from cell to cell, because temporal resolutions of conventional perturbation of gene regulation dynamics were not sufficient to investigate the processes of timescales of 2&#8211;3 h (ultradian rhythms).
We have recently developed an integrated method to control and monitor gene expression patterns in mammalian cells10. This technology enables induction of gene expression pulses by periodic light illumination on ultradian time-scales. This protocol represents the methods to establish photosensitive cell-lines and observe dynamic responses of reporter cells by live-cell luminescence monitoring in the contexts of cell-to-cell communications. This method is applicable to the analysis of many other signaling pathways.

<table border="0" cellpadding="0" cellspacing="0" width="695">
	<tbody>
		<tr height="19">
			<td height="19" style="height:19px;width:207px;">FACS</td>
			<td style="width:237px;">Becton, Dickinson and Company</td>
			<td style="width:180px;">FACSAriaII SORP</td>
			<td style="width:71px;"></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Camera</td>
			<td>Andor</td>
			<td>iKon M-934</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Microscope</td>
			<td>Olympus</td>
			<td>IX-81 ZDC</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">PMT device</td>
			<td>Churitsu eletric corp.</td>
			<td>CL24B-LIC/B</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Blue LED illuminator</td>
			<td>OptoCode</td>
			<td>LEDB-SBOXH</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">DMEM</td>
			<td>Nacalai</td>
			<td>08459-35&#160;</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Penicillin-streptomycin</td>
			<td>Nacalai</td>
			<td>26253-84</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Fetal bovine serum</td>
			<td>Sigma</td>
			<td>172012</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">KRYSTAL24 (black 24 well plate )</td>
			<td>Hi-tech</td>
			<td>303012</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">D-Luciferin Potassium Salt</td>
			<td>Nacalai</td>
			<td>20028-24&#160;</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Light meter</td>
			<td>LI-COR Biosciences</td>
			<td>LI-250A</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">anti-HA-Peroxidase antibody</td>
			<td>Roche</td>
			<td>clone 3F10</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">anti-Actin-Peroxidase antibody</td>
			<td>Wako</td>
			<td>clone 2F3</td>
			<td></td>
		</tr>
	</tbody>
</table>

an optogenetic method to control and analyze gene expression patterns in cell-to-cell interactions

Cells should respond properly to temporally changing environments, which are influenced by various factors from surrounding cells. The Notch signaling pathway is one of such essential molecular machinery for cell-to-cell communications, which plays key roles in normal development of embryos. This pathway involves a cell-to-cell transfer of oscillatory information with ultradian rhythms, but despite the progress in molecular biology techniques, it has been challenging to elucidate the impact of multicellular interactions on oscillatory gene dynamics. Here, we present a protocol that permits optogenetic control and live monitoring of gene expression patterns in a precise temporal manner. This method successfully revealed that intracellular and intercellular periodic inputs of Notch signaling entrain intrinsic oscillations by frequency tuning and phase shifting at the single-cell resolution. This approach is applicable to the analysis of the dynamic features of various signaling pathways, providing a unique platform to test a functional significance of dynamic gene expression programs in multicellular systems.

We adapted the LightOn system11,12, which enables photo-induced gene expression in mammalian cells, to the study of genetic oscillators with 2- to 3-h periodicity. This system comprises of two parts: the photo-inducible transcriptional activator hGAVPO and a UAS-promoter cassette to drive transcription of arbitrary genes of interest. To accelerate the pulsatile kinetics of photo-induced gene expression, the polyA sequence in the U...

Watch this Scientific Journal Video about An Optogenetic Method to Control and Analyze Gene Expression Patterns in Cell-to-cell Interactions at JoVE.com

An Optogenetic Method to Control and Analyze Gene Expression Patterns in Cell-to-cell Interactions

Here, we present a protocol to analyze cell-to-cell transfer of oscillatory information by optogenetic control and live monitoring of gene expression. This approach provides a unique platform to test a functional significance of dynamic gene expression programs in multicellular systems.

Cells should respond properly to temporally changing environments, which are influenced by various factors from surrounding cells. The Notch signaling ...

The overall goal of this experiment is to observe cell-to-cell transfer of oscillatory information by optogenetic control and live monitoring of gene expression. This method can help answer key questions of how cells communicate with each other through the Notch signaling pathway, particularly of how cells transmit the oscillatory information to each other. The main advantage of this technique is that we can control and monitor gene expression dynamics with very high precision.Demonstrating the procedure will be Akihiro Isomura, a research fellow from my laboratory who developed this new technology. To transfect plasmid vectors of Tol2-based optogenetic modules together with the transposase expression vector into C2C12 cells, first count trypsinized cells with a cell counter. Plate 50, 000 C2C12 cells per well in a 12-well plate one day before transfection.Then, co-transfect 0.375 micrograms of Tol2-based optogenetic vectors, 0.125 micrograms of a drug selection vector, and 0.5 micrograms of the transposase expression vector by using the lipofection reagent. Trypsinize the transfected cells, and plate them into 100-millimeter culture dishes one day after transfection. Exchange the culture medium for the transfected cells to culture medium supplemented with 100 milligrams per milliliter hygromycin.Culture the cells for three days to eliminate untransfected cells. Note that medium change is not necessary. Next, trypsinize the transfected cells, and purify a population of cells expressing fluorescent proteins for selection by sorting the receiver and photo-sensitive cells, as detailed in the text protocol.Set up two types of incubators with or without light sources for a light-induced condition or a dark condition. Use a light meter to set up the light intensity of a blue-LED transilluminator. Measure the light intensity after closing the door.Program timings and duration of light illumination by loading a control script to a single-board microcontroller that allows programmable schedules for illumination. Count the trypsinized cells with a cell counter, and plate 100, 000 photo-sensitive sender cells carrying pAI218 and pAI170 on 35-millimeter-diameter plastic culture dishes. Set the dishes in separate incubators for dark and light conditions.After setting up the dishes, keep the doors of the incubators closed until collecting the cell lysates. One and a half days after plating, start light illumination. Don't expose cells to uncontrolled light to avoid undesirable photo-stimulation.So, do this step without opening the door. Note that opening the door here is only for demonstration. About two days after plating, move sample dishes from incubators to ice in 30-minute intervals, and start preparation of cell lysates for further analysis.To monitor the cellular responses upon optical stimulation by PMT in real-time, first trypsinize and count the numbers of sender and receiver cells with standard methods. Prepare a one-milliliter total volume suspension of 25, 000 receiver and 125, 000 sender cells. Plate the mixed cells in each well of 24-well black plates with culture medium containing one-millimolar luciferin.Analyze the cells on a plate reader for the luciferase assay to confirm that the output signals are not too high for the recording system. Next, set the plate on the recording system, and start a recording program. For example, start light illumination at 18 hours after setting the recording.For real-time imaging of single-cell responses under the control of optogenetic perturbation, first plate 50, 000 receiver and 250, 000 sender cells onto 27-millimeter-diameter-glass-base 35-millimeter-diameter dishes. Ensure that mixing ratios and total cell number are correctly adjusted. One day after plating, exchange medium with two milliliters of the recording medium.Set the glass-base dish on an inverted microscope equipped with an environmental chamber at 37 degrees Celsius and 5%carbon dioxide. Set up a cooled CCD camera. Ensure that the temperature of the CCD sensor is cooled down to the destination value.Set parameters for multi-dimensional time-lapse window in automatic acquisition software to capture images with five-minute intervals and more than 288 times. In the multi-dimensional time-lapse window, select a luminescence channel. Ensure that the readout mode is set to the slow 50-kilohertz readout mode, which is critical for reducing readout noises to detect weakly emitting bioluminescent light.In the multi-dimensional time-lapse window, select fluorescence channels. Ensure that the readout mode is set to the fast one megahertz mode to reduce the time required for fluorescence imaging. Finally, set two-by-two binning with 400-millisecond exposure.Next, select a journal tab to set up schedules to stimulate the cells with periodic blue-light illumination. Click the plus button to add a new journal setup. Select a journal file from a journal box, choose multiple time points, and set values in initial point and interval boxes to schedule for stimulation.Ensure that the specified journal file includes sequential protocols for selecting illumination, shutter opening, delay, shutter closing, and delay. Next, set up schedules to stimulate cells with periodic blue-light illumination. Finally, start time-lapse recording by clicking the Acquire button.Finally, extract single-cell traces of luminescence channels from time-lapse movies, as described in the text protocol. Representative results of optogenetic sender-receiver assays are shown here. The photo-inducible sender cells produced oscillatory patterns of Delta ligand expression in the presence of periodic blue-light illumination, as expected.When receiver cells are co-cultured with the photo-sensitive sender cells and exposed to repetitive light illumination, a real-time bioluminescence recording system detects cyclic responses of receiver cells in various conditions of mixing ratios. Moreover, time-lapse microscopy with repetitive light illumination also reveals the synchronized responses of receiver cells at the single-cell level. After its development, this technique paved the way for researchers in the field of cell biology to explore how dynamic information of gene expression is transferred in cell-cell interactions.

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Genetics

Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions

Gene deletion plays an important role in the analysis of gene function. One of the most efficient methods to disrupt genes in a targeted manner is the replacement of the entire gene with a selectable marker via homologous recombination. During homologous recombination, exchange of DNA takes place between sequences with high similarity. Therefore, linear genomic sequences flanking a target gene can be used to specifically direct a selectable marker to the desired integration site. Blunt ends of the deletion construct activate the cell&#39;s DNA repair systems and thereby promote integration of the construct either via homologous recombination or by non-homologous-end-joining. In organisms with efficient homologous recombination, the rate of successful gene deletion can reach more than 50% making this strategy a valuable gene disruption system. The smut fungus Ustilago maydis is a eukaryotic model microorganism showing such efficient homologous recombination. Out of its about 6,900 genes, many have been functionally characterized with the help of deletion mutants, and repeated failure of gene replacement attempts points at essential function of the gene. Subsequent characterization of the gene function by tagging with fluorescent markers or mutations of predicted domains also relies on DNA exchange via homologous recombination. Here, we present the U. maydis strain generation strategy in detail using the simplest example, the gene deletion.

Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions

We describe a robust gene replacement strategy to genetically manipulate the smut fungus Ustilago maydis. This protocol explains how to generate deletion mutants to investigate infection phenotypes. It can be extended to modify genes in any desired way, e.g., by adding a sequence encoding a fluorescent protein tag.

Gene deletion plays an important role in the analysis of gene function. One of the most efficient methods to disrupt genes in a targeted manner is the ...

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 ...

Optogenetic Random Mutagenesis Using Histone-miniSOG in C. elegans

Forward genetic screening in model organisms is the workhorse to discover functionally important genes and pathways in many biological processes. In most mutagenesis-based screens, researchers have relied on the use of toxic chemicals, carcinogens, or irradiation, which requires designated equipment, safety setup, and/or disposal of hazardous materials. We have developed a simple approach to induce heritable mutations in C. elegans using germline-expressed histone-miniSOG, a light-inducible potent generator of reactive oxygen species. This mutagenesis method is free of toxic chemicals and requires minimal laboratory safety and waste management. The induced DNA modifications include single-nucleotide changes and small deletions, and complement those caused by classical chemical mutagenesis. This methodology can also be used to induce integration of extrachromosomal transgenes. Here, we provide the details of the LED setup and protocols for standard mutagenesis and transgene integration.

Optogenetic Random Mutagenesis Using Histone-miniSOG in C. elegans

Genetically-encoded histone-miniSOG induces genome-wide heritable mutations in a blue&#160;light-dependent manner. This mutagenesis method is simple, fast, free of toxic chemicals, and well-suited for forward genetic screening and transgene integration.

Forward genetic screening in model organisms is the workhorse to discover functionally important genes and pathways in many biological processes. In most ...

Single-cell Gene Expression Using Multiplex RT-qPCR to Characterize Heterogeneity of Rare Lymphoid Populations

Gene expression heterogeneity is an interesting feature to investigate in lymphoid populations. Gene expression in these cells varies during cell activation, stress, or stimulation. Single-cell multiplex gene expression enables the simultaneous assessment of tens of genes1,2,3. At the single-cell level, multiplex gene expression determines population heterogeneity4,5. It allows for the distinction of population heterogeneity by determining both the probable mix of diverse precursor stages among mature cells and also the diversity of cell responses to stimuli.
Innate lymphoid cells (ILC) have been recently described as a population of innate effectors of the immune response6,7. In this protocol, cell heterogeneity of the ILC hepatic compartment is investigated during homeostasis.
Currently, the most widely used technique to assess gene expression is RT-qPCR. This method measures gene expression only one gene at a time. Additionally, this method cannot estimate heterogeneity of gene expression, since multiple cells are needed for one test. This leads to the measurement of the average gene expression of the population. When assessing large numbers of genes, RT-qPCR becomes a time-, reagent-, and sample-consuming method. Hence, the trade-offs limit the number of genes or cell populations that can be evaluated, increasing the risk of missing the global picture.
This manuscript describes how single-cell multiplex RT-qPCR can be used to overcome these limitations. This technique has benefited from recent microfluidics technological advances1,2. Reactions occurring in multiplex RT-qPCR chips do not exceed the nanoliter-level. Hence, single-cell gene expression, as well as simultaneous multiple gene expression, can be performed in a reagent-, sample-, and cost-effective manner. It is possible to test cell gene signature heterogeneity at the clonal level between cell subsets within a population at different developmental stages or under different conditions4,5. Working on rare populations with large numbers of conditions at the single-cell level is no longer a restriction.

This protocol describes how to assess the expression of a large array of genes at the clonal level. Single-cell RT-qPCR produces highly reliable results with a strong sensitivity for hundreds of samples and genes.

Gene expression heterogeneity is an interesting feature to investigate in lymphoid populations. Gene expression in these cells varies during cell ...

Single-cell Gene Expression Profiling Using FACS and qPCR with Internal Standards

Gene expression measurements from bulk populations of cells can obscure the considerable transcriptomic variation of individual cells within those populations. Single-cell gene expression measurements can help assess the role of noise in gene expression, identify correlations in the expression of pairs of genes, and reveal subpopulations of cells that respond differently to a stimulus. Here, we describe a procedure to measure the expression of up to 96 genes in single mammalian cells isolated from a population growing in tissue culture. Cells are sorted into lysis buffer by fluorescence-activated cell sorting (FACS), and the mRNA species of interest are reverse-transcribed and amplified. Gene expression is then measured using a microfluidic real-time PCR machine, which performs up to 96 qPCR assays on up to 96 samples at a time. We also describe the generation and use of PCR amplicon standards to enable the estimation of the absolute number of each transcript. Compared with other methods of measuring gene expression in single cells, this approach allows for the quantification of more distinct transcripts than RNA FISH at a lower cost than RNA-Seq.

We describe a method to sort single mammalian cells and to quantify the expression of up to 96 target genes of interest in each cell. This method includes the use of internal qPCR standards to enable the estimation of absolute transcript counts.

Gene expression measurements from bulk populations of cells can obscure the considerable transcriptomic variation of individual cells within those ...

Studying Cell Cycle-regulated Gene Expression by Two Complementary Cell Synchronization Protocols

The gene expression program of the cell cycle represents a critical step for understanding cell cycle-dependent processes and their role in diseases such as cancer. Cell cycle-regulated gene expression analysis depends on cell synchronization into specific phases. Here we describe a method utilizing two complementary synchronization protocols that is commonly used for studying periodic variation of gene expression during the cell cycle. Both procedures are based on transiently blocking the cell cycle in one defined point. The synchronization protocol by hydroxyurea (HU) treatment leads to cellular arrest in late G1/early S phase, and release from HU-mediated arrest provides a cellular population uniformly progressing through S and G2/M. The synchronization protocol by thymidine and nocodazole (Thy-Noc) treatment blocks cells in early mitosis, and release from Thy-Noc mediated arrest provides a synchronized cellular population suitable for G1 phase and S phase-entry studies. Application of both procedures requires monitoring of the cell cycle distribution profiles, which is typically performed after propidium iodide (PI) staining of the cells and flow cytometry-mediated analysis of DNA content. We show that the combined use of two synchronization protocols is a robust approach to clearly determine the transcriptional profiles of genes that are differentially regulated in the cell cycle (i.e. E2F1 and E2F7), and consequently to have a better understanding of their role in cell cycle processes. Furthermore, we show that this approach is useful for the study of mechanisms underlying drug-based therapies (i.e. mitomycin C, an anticancer agent), because it allows to discriminate genes that are responsive to the genotoxic agent from those solely affected by cell cycle perturbations imposed by the agent.

We report two cell synchronization protocols that provide a context for studying events related to specific phases of the cell cycle. We show that this approach is useful for analyzing the regulation of specific genes in an unperturbed cell cycle or upon exposure to agents affecting the cell cycle.

The gene expression program of the cell cycle represents a critical step for understanding cell cycle-dependent processes and their role in diseases such ...

Sample Preparation and Analysis of RNASeq-based Gene Expression Data from Zebrafish

The analysis of global gene expression changes is a valuable tool for identifying novel pathways underlying observed phenotypes. The zebrafish is an excellent model for rapid assessment of whole transcriptome from whole animal or individual cell populations due to the ease of isolation of RNA from large numbers of animals. Here a protocol for global gene expression analysis in zebrafish embryos using RNA sequencing (RNASeq) is presented. We describe preparation of RNA from whole embryos or from cell populations obtained using cell sorting in transgenic animals. We also describe an approach for analysis of RNASeq data to identify enriched pathways and Gene Ontology (GO) terms in global gene expression data sets. Finally, we provide a protocol for validation of gene expression changes using quantitative reverse transcriptase PCR (qRT-PCR). These protocols can be used for comparative analysis of control and experimental sets of zebrafish to identify novel gene expression changes, and provide molecular insight into phenotypes of interest.

This protocol presents an approach for whole transcriptome analysis from zebrafish embryos, larvae, or sorted cells. We include isolation of RNA, pathway analysis of RNASeq data, and qRT-PCR-based validation of gene expression changes.

The analysis of global gene expression changes is a valuable tool for identifying novel pathways underlying observed phenotypes. The zebrafish is an ...

Measuring Gene Expression in Bombarded Barley Aleurone Layers with Increased Throughput

The aleurone layer of barley grains is an important model system for hormone-regulated gene expression in plants. In aleurone cells, genes required for germination or early seedling development are activated by gibberellin (GA), while genes associated with stress responses are activated by abscisic acid (ABA). The mechanisms of GA and ABA signaling can be interrogated by introducing reporter gene constructs into aleurone cells via particle bombardment, with the resulting transient expression measured using enzyme assays. An improved protocol is reported that partially automates and streamlines the grain homogenization step and the enzyme assays, allowing significantly more throughput than existing methods. Homogenization of the grain samples is carried out using an automated tissue homogenizer, and GUS (&#946;-glucuronidase) assays are carried out using a 96-well plate system. Representative results using the protocol suggest that phospholipase D activity may play an important role in the activation of HVA1 gene expression by ABA, through the transcription factor TaABF1.

An improved protocol is presented for the measurement of transient gene expression from reporter constructs in barley aleurone cells after particle bombardment. The combination of automated grain grinding with 96-well plate enzyme assays provides high throughput for the procedure.

The aleurone layer of barley grains is an important model system for hormone-regulated gene expression in plants. In aleurone cells, genes required for ...

A Method to Study the C924T Polymorphism of the Thromboxane A2 Receptor Gene

The thromboxane A2 receptor (TBXA2R) gene is a member of the G-protein coupled superfamily with seven-transmembrane regions. It is involved in atherogenesis progression, ischemia, and myocardial infarction. Here we present a methodology of patient genotyping to investigate the post-transcriptional role of the C924T polymorphism (rs4523) situated at the 3&#39; region of the TBXA2 receptor gene. This method relies on DNA extraction from whole blood, polymerase chain reaction (PCR) amplification of the TBXA2 gene portion containing the C924T mutation, and identification of wild type and/or mutant genotypes using a restriction digest analysis, specifically a restriction fragment length polymorphism (RFLP) on agarose gel. In addition, the results were confirmed by sequencing the TBXA2R gene. This method features several potential advantages, such as high efficiency and the rapid identification of the C924T polymorphism by PCR and restriction enzyme analysis. This approach allows a predictive study for plaque formation and atherosclerosis progression by analyzing patient genotypes for the TBXA2R C924T polymorphism. Application of this method has the potential to identify subjects who are more susceptible to atherothrombotic processes, in particular subjects in a high-risk, aspirin-treated group.

In the present study, we describe a methodology to analyze the C924T genotype. The protocol consists of three phases: DNA extraction, amplification by polymerase chain reaction (PCR), and analysis of the restriction fragment length polymorphism (RFLP) on agarose gel.

The thromboxane A2 receptor (TBXA2R) gene is a member of the G-protein coupled superfamily with seven-transmembrane regions. It is involved in ...

An Ecdysone Receptor-based Singular Gene Switch for Deliberate Expression of Transgene with Robustness, Reversibility, and Negligible Leakiness

Precise control of transgene expression is desirable in biological and clinical studies. However, because the binary feature of currently employed gene switches requires the transfer of two therapeutic expression units concurrently into a single cell, the practical application of the system for gene therapy is limited. To simplify the transgene expression system, we generated a gene switch designated as pEUI(+) encompassing a complete set of transgene expression modules in a single vector. Comprising of the GAL4 DNA-binding domain and modified EcR (GvEcR), a minimal VP16 activation domain fused with a GAL4 DNA-binding domain, as well as a modified Drosophila ecdysone receptor (EcR), the newly developed singular gene switch is highly responsive to the administration of a chemical inducer in a time- and dosage-dependent manner. The pEUI(+) vector is a potentially powerful tool for improving the control of transgene expression in both biological research and pre-clinical studies. Here, we present a detailed protocol for modulation of a transient and stable transgene expression using pEUI(+) vector by the treatment of tebufenozide (Teb). Additionally, we share important guidelines for the use of Teb as a chemical inducer.

Here, we present a protocol for the modulation of transgene expression using pEUI(+) singular gene switch by tebufenozide treatment.

Precise control of transgene expression is desirable in biological and clinical studies. However, because the binary feature of currently employed gene ...