We thank Satoshi Kishigami, Sayaka Wakayama, Hiroaki Nagatomo, Satoshi Kamimura, and Kana Kishida for providing critical comments and technical support. This work was partially funded by the Ministry of Education, Culture, Sports, Science and Technology program for promoting the reform of national universities to M.O.; the Japan Society for the Promotion of Science (16H02593), Asada Science Foundation, and the Takeda Science Foundation to T.W. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the University of Yamanashi. The protocol was approved by the Committee on the Ethics of Animal Experiments of the University of Yamanashi (Permit Number: A24-50). All surgeries were performed under tribromoethanol anesthesia, and all efforts were made to minimize suffering. An illustrated overview of the procedures and time-table are shown in Figure 1 and <strong...

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	<li>Burton, A., Torres-Padilla, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epigenetic+reprogramming+and+development:+a+unique+heterochromatin+organization+in+the+preimplantation+mouse+embryo.">Epigenetic reprogramming and development: a unique heterochromatin organization in the preimplantation mouse embryo.</a> Brief Funct Genomics. 9, 444-454 (2010).</li><li>Okada, Y., Yamaguchi, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epigenetic+modifications+and+reprogramming+in+paternal+pronucleus:+sperm,+preimplantation+embryo,+and+beyond.">Epigenetic modifications and reprogramming in paternal pronucleus: sperm, preimplantation embryo, and beyond.</a> Cell Mol Life Sci. 74, 1957-1967 (2017).</li><li>Ooga, M., Fulka, H., Hashimoto, S., Suzuki, M. G., Aoki, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+chromatin+structure+in+mouse+preimplantation+embryos+by+fluorescent+recovery+after+photobleaching.">Analysis of chromatin structure in mouse preimplantation embryos by fluorescent recovery after photobleaching.</a> Epigenetics. 11, 85-94 (2016).</li><li>Meshorer, E., 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=Hyperdynamic+plasticity+of+chromatin+proteins+in+pluripotent+embryonic+stem+cells.">Hyperdynamic plasticity of chromatin proteins in pluripotent embryonic stem cells.</a> Dev Cell. 10, 105-116 (2006).</li><li>Boskovic, 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=Higher+chromatin+mobility+supports+totipotency+and+precedes+pluripotency+in+vivo.">Higher chromatin mobility supports totipotency and precedes pluripotency in vivo.</a> Genes Dev. 28, 1042-1047 (2014).</li><li>Yamagata, K., Ueda, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+live-cell+imaging+of+mammalian+preimplantation+development+and+derivation+process+of+pluripotent+stem+cells+from+the+embryos.">Long-term live-cell imaging of mammalian preimplantation development and derivation process of pluripotent stem cells from the embryos.</a> Dev Growth Differ. 55, 378-389 (2013).</li><li>Ooga, M., Wakayama, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FRAP+analysis+of+chromatin+looseness+in+mouse+zygotes+that+allows+full-term+development.">FRAP analysis of chromatin looseness in mouse zygotes that allows full-term development.</a> PLoS One. 12, e0178255 (2017).</li><li>Quinn, P., Begley, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+human+seminal+plasma+and+mouse+accessory+gland+extracts+on+mouse+fertilization+in+vitro.">Effect of human seminal plasma and mouse accessory gland extracts on mouse fertilization in vitro.</a> Australian journal of biological sciences. 37, 147-152 (1984).</li><li>Chatot, C. 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As revealed in this study, the zFRAP analysis does not cause critical damage to full-term development, suggesting this method is a very useful tool to reveal the association between molecular events and the embryonic developmental potential. During reprogramming, into the two-cell like state of ES cells, by which the differential potential of those cells becomes as high as that of two-cell stage embryos, chromatin looseness changes into that comparable with two-cell stage embryos5. Accordingly, it...

After fertilization, the chromatin structure is altered dynamically, and zygotic chromatin structure is then eventually established1,2. During this period, in paternal pronuclei, the dominant chromatin protein is changed from protamine into histone. The resulting chromatin is extremely different from that of sperms and female oocytes in several points (e.g., histone variant composition, histone modification). Thus, formed zygotic chromatin is thought to be important for subsequent embryonic development. However, despite efforts to reveal the details of zygotic chromatin structure over long periods, methods to evaluate the quality of zygotes or to predict their full-term development at the one-cell stage by analyzing their chromatin structure have never been established.
In the previous study, it is discovered that zygotes have an extremely loosened chromatin structure3. Currently, chromatin looseness or openness is believed to be an important factor for cellular differentiation potential in embryonic stem (ES) cells4. ES cells do not exhibit homogeneity in nature, but are rather heterogeneous; in ES cell colonies, some transiently acquire a higher differentiation potential comparable to blastomeres of two-cell stage embryos. During this transition into the two-cell like state, chromatin looseness in ES cells changes into what is comparable with two-cell stage embryos5. Thus, chromatin looseness seems to be important for cellular differentiation potential and it is possible that extensively open chromatin in zygotes is useful for the evaluation of zygotic developmental potential.
Live imaging is a powerful tool that allows for the analysis of molecular events during ontogenesis since this method allows for subsequent development and even full-term development6. As one of the live imaging methods, FRAP analysis has been used to examine chromatin looseness in preimplantation embryos and ES cells3,4,5. If zygotic chromatin looseness can be analyzed without a detrimental effect on full-term development by FRAP analysis, it may be a valuable tool for the evaluation of the quality of embryos at the one-cell stage. However, the effects on full-term development by this experimental method have not been examined. Recently, an experimental system using FRAP to evaluate zygotic chromatin looseness was developed. Because this was a new observation system for zygotes, it was termed as zygotic FRAP (zFRAP). zFRAP did not critically affect full-term development and has been reported elsewhere7. In this report, the protocol of this experimental method is described.

<table border="0" cellpadding="0" cellspacing="0" width="1022">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:260px;">Confocal laser scaning microscope</td>
			<td style="width:208px;">Olympus</td>
			<td style="width:119px;">FV1200</td>
			<td style="width:435px;">FV1000 can be also used for FRAP analysis (reference #7)</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">Thermo plate</td>
			<td style="width:208px;">Tokai Hit</td>
			<td style="width:119px;">TP-110RH26</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">Inverted microscope</td>
			<td style="width:208px;">Olympus</td>
			<td style="width:119px;">IX71</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Micro manupilator</td>
			<td style="width:208px;">Narishige</td>
			<td style="width:119px;">MMO-202ND</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">Pieze Micro Micromanipulator</td>
			<td style="width:208px;">Prime tech</td>
			<td style="width:119px;">PMAS-CT150</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">35 mm culture dish</td>
			<td style="width:208px;">Falcom</td>
			<td style="width:119px;">351008</td>
			<td>35 x 100 mm style; for IVF</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">60 mm culture dish</td>
			<td style="width:208px;">Falcom</td>
			<td style="width:119px;">351007</td>
			<td>60 x 15 mm style; for embryo culture</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">50 mm culture dish</td>
			<td style="width:208px;">Falcom</td>
			<td style="width:119px;">351006</td>
			<td>50 x 9 mm style; for manipulation on the stage</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">50 mm glass bottom dish</td>
			<td style="width:208px;">Matsunami</td>
			<td style="width:119px;">D910400</td>
			<td>50 mm dish, 27 mm &#966; hole size; for FRAP analysis</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">Mineral oil</td>
			<td style="width:208px;">Organic spceiality chemicals</td>
			<td style="width:119px;">625071</td>
			<td>For FRAP analysis on the glass bottom dishes</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">Mineral oil</td>
			<td style="width:208px;">Sigma</td>
			<td style="width:119px;">M8410-1L</td>
			<td>For IVF and embryo culture</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">glass capillary</td>
			<td style="width:208px;">Drummond</td>
			<td style="width:119px;">1-000-1000</td>
			<td>For handling mouse zygotes</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">Borosilicate glass</td>
			<td style="width:208px;">Prime tech</td>
			<td style="width:119px;">B100-75-10-PT</td>
			<td>For microinjection of mRNA</td>
		</tr>
		<tr height="38">
			<td height="38" style="height:38px;width:260px;">Micropipett puller</td>
			<td style="width:208px;">Sutter instrument</td>
			<td style="width:119px;">P-97/IVF</td>
			<td style="width:435px;">For preparation of the injection or holding neadle (out side diameter: 80 &#181;m, inner diameter: 10 &#181;m)&#160;</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">Microforge</td>
			<td style="width:208px;">&#160;Narishige</td>
			<td>MF-900</td>
			<td></td>
		</tr>
		<tr height="38">
			<td height="38" style="height:38px;width:260px;">mMESSAGE MACHINE SP6 Transcription kit</td>
			<td style="width:208px;">Thermo 
			Fisher scientific</td>
			<td style="width:119px;">AM1340</td>
			<td></td>
		</tr>
		<tr height="38">
			<td height="38" style="height:38px;width:260px;">Poly (A) tailing kit</td>
			<td style="width:208px;">Thermo 
			Fisher scientific</td>
			<td style="width:119px;">AM1350</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">PVP solution 10% (PVP-HTF)</td>
			<td style="width:208px;">IrvineSceientific</td>
			<td style="width:119px;">99311</td>
			<td>HEPES buffered HTF containing 10% PVP</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">Sodium HEPES</td>
			<td style="width:208px;">Sigma</td>
			<td style="width:119px;">H3784</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">pTOPO eGFP-H2B</td>
			<td style="width:208px;"></td>
			<td style="width:119px;"></td>
			<td>Template plasmid for eGFP-H2B mRNA (reference #6)</td>
		</tr>
		<tr height="38">
			<td height="38" style="height:38px;width:260px;">NorthernMax Gly Sample loading Dye&#160;</td>
			<td style="width:208px;">Thermo 
			Fisher scientific</td>
			<td style="width:119px;">AM8551</td>
			<td>For electrophoresis of in vitro transcribed mRNA</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">Phenol chloroform isamyl alcohol</td>
			<td style="width:208px;">nacalai tesque</td>
			<td style="width:119px;">25970-14</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">Chloroform</td>
			<td style="width:208px;">nacalai tesque</td>
			<td style="width:119px;">&#160;08401-65</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">Not I</td>
			<td style="width:208px;">TOYOBO</td>
			<td style="width:119px;">NOT-111X</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">Ethachinmate</td>
			<td style="width:208px;">WAKO</td>
			<td style="width:119px;">318-01793</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:260px;">3664 Otical power meter</td>
			<td style="width:208px;">Hioki</td>
			<td style="width:119px;">3664</td>
			<td>&#160;Power meter for laser power</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:260px;">Stereomicmicroscope</td>
			<td style="width:208px;">Olympus</td>
			<td style="width:119px;">SZX16</td>
			<td></td>
		</tr>
	</tbody>
</table>

zygotic fluorescence recovery after photo-bleaching analysis for chromatin looseness that allows full-term development

Live imaging is a powerful tool that allows for the analysis of molecular events during ontogenesis. Recently, chromatin looseness or openness has been shown to be involved in the cellular differentiation potential of pluripotent embryonic stem cells. It was previously reported that compared with embryonic stem cells, zygotes harbor an extremely loosened chromatin structure, suggesting its association with their totipotency. However, until now, it has not been addressed whether this extremely loosened/open chromatin structure is important for embryonic developmental potential. In the present study, to examine this hypothesis, an experimental system in which zygotes that were analyzed by fluorescence recovery after photo-bleaching can develop to term without any significant damage was developed. Importantly, this experimental system needs only a thermos-plate heater in addition to a confocal laser scanning microscope. The findings of this study suggest that fluorescence recovery after photo-bleaching analysis (FRAP) analysis can be used to investigate whether the molecular events in zygotic chromatin are important for full-term development.

zFRAP analysis with eGFP-H2B
Properly produced mRNA encoding eGFP-H2B, which is seen as a shifted band caused by poly A tailing (Figure 2A), was injected into the cytoplasm of zygotes with a 2nd polar body at 1 - 3 h after insemination (Figure 2B). Eight to 12 h after insemination, zygotes with 2 pronuclei showing the expression of eGFP-H2B were collected and subjected to ...

Watch this Scientific Journal Video about Zygotic Fluorescence Recovery After Photo-bleaching Analysis for Chromatin Looseness That Allows Full-term Development at JoVE.com

Zygotic Fluorescence Recovery After Photo-bleaching Analysis for Chromatin Looseness That Allows Full-term Development

Chromatin looseness appears to be involved in the developmental potential of blastomeres. However, it is not known whether chromatin looseness can be used as a reliable index for the developmental potential for embryos. Here, an experimental system in which chromatin looseness-evaluated zygotes can develop to full term has been described.

Live imaging is a powerful tool that allows for the analysis of molecular events during ontogenesis. Recently, chromatin looseness or openness has been ...

The overall goal of this zygotic FRAP or zFRAP is to examine the association between zygotic chromatin looseness and embryonic development potential to term. This method can help answer key questions in the developmental biology field, such as embryonic development. The main advantage of this technique is that it allows the analyzed zygote to develop to full term without significant damage.Visual demonstration of this method is critical as the zFRAP analysis steps are difficult to learn because the experimental condition setting and operation for this analysis are very complex. After preparing eGFP-H2B RNA according to the text protocol, use nuclease-free water to dilute it to 250 nanograms per microliter. In a 60-millimeter dish, place two to three drops each of PVP-HTF, five to six drops of Hepes-buffered CZB, and eGFP-H2B mRNA.Then, use mineral oil to cover the drops. Using a pipette puller, pull borosilicate glass. After breaking the tip, use a microforge to bend the glass pipette to around 30 degrees.Prior to microinjection, confirm that the plate heater on the stage of the micromanipulator is off to prevent killing the zygotes during mRNA injection. Then, using 10%PVP-HTF, wash and coat the inside of the injection needles. Next from the tips fill the glass capillaries with the diluted eGFP-H2B mRNA.Collect the fertilized zygotes with a second polar body, and transfer 20 to 25 of them on to the chamber of the microscope stage. Then, with a holding pipette, hold the zygote and break the zona pellucida and the cytosolic membrane with a piezo drive. Inject about 10 picoliters of mRNA into the cytoplasm of each zygote.Complete the injections within 10 minutes to prevent damage caused by culturing the zygotes outside of the incubator. 10 minutes after microinjection, wash the zygotes in at least three drops of CZB and culture them at 38 degrees Celsius until FRAP analysis. One hour prior to zFRAP analysis, turn on the laser and hot plate attached to the stage of the confocal microscope.Set the temperature to 38 degrees Celsius. On a 60-millimeter glass-bottomed dish, pipette six to 10 microliters of Hepes-buffered CZB medium and cover it with mineral oil. Then, warm the dish on the heater until zygote collection.To make it easy to find the zygote with the confocal microscope, it is important to put the drops throughout the center of the dish. Eight to 12 hours after insemination, collect five to 10 eGFP-H2B expressing zygotes and transfer them to a six to 10-microliter drop of pre-warmed Hepes-buffered CZB medium. To perform a precise quantitative analysis it is important to put the zygote toward the center of the Hepes-buffered CZB drops.Set the bleaching and imaging conditions according to the manufacturer's instructions. For example, under Acquisition Setting, set the scanning speed to four microseconds per pixel and the size to five hundred and twelve. Increase the digital zoom to five, open the DyeList"and choose eGFP"Then, set the observation time to one point six seconds and the number of pictures to 12.Next, start the Stimulus Setting"panel and on UseScanner"click Main"Set the scanning speed to 10 microseconds per pixel. Click Activation in Series"Set PreActivation"to three frames and activation time to five seconds. Then, click Focus x2"and click Stop"Under the stimulus setting panel click Clip Rect"Set the ROI to 40 by 40 pixels.Click Time"and XY"Then, use an optical power meter to access the laser power. It is important to have the lights turned off when measuring the laser. After adjusting the laser gage to set the bleaching and imaging laser power, on the toolbar click Live"and then start Live Plot"Place the oil on the objective lens.Set the chamber on the stage and then find the zygotes in the drops. After finding zygotes, determine the ROI position by clicking Focus x2"And then in the Live Plot"window adjust the HV power gage for the eGFP"channel fluorescence intensity to around 2, 000. To start the zFRAP analysis, click XY"After FRAP analysis, click Series Done"Obtain the FRAP analyzed data, then click on Save As"to save the file 2D View image"as a preferred named file.Use Copy"ROI and Paste"ROI to prepare a reference region and to background respectively. Next, select ROI, REF, and BG, and then in the 2D View"image window, click Series Analysis"Obtain RoFRAP data and then in the Live Plot"window click the Save"button. Carry out data calculations according to the text protocol.Eight to 12 hours after insemination, zygotes with two pronucleai showing the expression of eGFP-H2B"were collected and subjected to zFRAP analysis. After bleaching, the intensity of the eGFP-H2B fluorescent signal recovered slightly because of the inflow of eGFP-H2B into the ROI from the unbleached area in the nucleoplasm. Recovery curves reveal that male pronucleai recovered more quickly and with more mobile fractions than female pronucleai.As demonstrated in these images and graph, after zFRAP analysis, washed and cultured zygotes in CZB medium developed to the blastocyst stage without significant damage. To analyze the full term development, embryos at the two-cell stage were transferred into the ovoducts of pseudo-pregnant mothers. As reported in this table, the birth rate of zFRAP analyzed embryos was slightly, but significantly lower than that of intact embryos but was the same as that of the no zFRAP control.In addition, the pups derived from zFRAP analyzed zygotes seemed healthy and fully developed. While attempting this procedure, it's important to remember to wait for the other expansion. All budget objectorance to avoid focus drift.After watching this video, you should have a good understanding on how to analyze chromatin looseness in zygotes.

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Developmental Biology

7.8K Views.  University of Yamanashi. The overall goal of this zygotic FRAP or zFRAP is to examine the association between zygotic chromatin looseness and embryonic development potential to term. This method can help answer key questions in the developmental biology field, such as embryonic development. The main advantage of this technique is that it allows the analyzed zygote to develop to full term without significant damage.Visual demonstration of this method is critical as the zFRAP analysis steps are difficult to lear...