We thank Ueli Grossniklaus (University of Z&#252;rich) for technical and financial support. We are thankful to Valeria Gagliardini, Christof Eichenberger, Arturo Bolanos and Peter Kopf for general lab support. This research was funded by the University of Z&#252;rich, grants from the Swiss National Foundation to CB (31003A_130722) and Ueli Grossniklaus (31003A_141245 and 31003AB-126006), and the Agence Nationale de la Recherche to DG (Programme ANR-BLANC-2012).

The procedure is described in the workflow in Figure 1, and the setup for dissection and embedding of tissues are presented in Figure 2.
1. Tissue Fixation
<ol>
	<li>Collect 20-30 carpels in a microfuge tube containing freshly made BVO fixative buffer on ice.</li>
	<li>Fix the tissue 30 min with gentle shaking at room temperature.</li>
	<li>Spin the tubes containing the carpels in fixative in a benchtop microcentrifuge 1 min at 400 x g.</li>
	<li>Remove carefully the fixative buffer and add 1 ml of PBT, place the tubes on ice.</li>
</ol>
2. Dissection and Embedding
<ol>
	<li>Prepare five Eppendorf tubes with each 200 &#956;l of a freshly made, 5% acrylamide mix.</li>
	<li>Prepare five Superfrost slides pre-cleaned with 70% ethanol and labeled with a pencil.</li>
	<li>Thaw one aliquot of 20% APS and 20% NaPS each, on ice.</li>
	<li>Take 4-5 carpels with a cut-end tip, place them on a clean slide, remove the excess of liquid.</li>
	<li>Make longitudinal cuts with a fine needle and detach the carpel walls to release rows of ovules as shown Figure 2, avoid drying by covering with PBS (not more than 10 &#956;l).</li>
	<li>Quickly add and mix 12 &#956;l NaPS, 12 &#956;l APS with an aliquot of 200 &#956;l acrylamide mix.</li>
	<li>Add 30 &#956;l of the activated acrylamide onto the dissected ovules.</li>
	<li>Cover with a 20 x 20 mm coverslip, let polymerize at room temperature, 45-60 min.</li>
	<li>Remove the coverslip using a razor blade. At this stage, the samples can be kept overnight at 4 &#176;C in a Coplin jar containing PBS.</li>
</ol>
3. Tissue Processing
NOTE: All steps except 3.2.1, 3.2.3, 3.3.2 and 3.4.3 are carried out in Coplin jars with 80 ml solution under the chemical hood at room temperature. Slides are transferred with a flat-tip forceps.
<ol>
	<li>Tissue clarification and fixation:
	<ol>
		<li>Incubate 5 min in methanol.</li>
		<li>Incubate 5 min in ethanol.</li>
		<li>Incubate 30 min in ethanol:xylene (1:1).</li>
		<li>Incubate 5 min in ethanol.</li>
		<li>Incubate 5 min in methanol.</li>
		<li>Incubate 15 min in methanol and PBT (1:1), complemented with 2.5% formaldehyde.</li>
		<li>Rinse 2 x 10 min in PBT. At this stage, slides can be kept overnight at 4 &#176;C.</li>
	</ol>
	</li>
	<li>Cell wall digestion:
	<ol>
		<li>Thaw an aliquot of the cell wall digestion mix on ice.</li>
		<li>Take a slide from the Coplin jar, drain the excess of liquid by placing it vertically on a paper towel.</li>
		<li>Add 100&#160;&#956;l of cell wall digestion mix over the acrylamide pad and cover with a 23 x 46 mm coverslip. Repeat for the other slides. Incubate for 2 hr at 37 &#176;C in a moist chamber (described in Materials).</li>
		<li>Wash the slides 2 x 5 min in PBT.</li>
	</ol>
	</li>
	<li>RNase A treatment:
	<ol>
		<li>Take a slide from the Coplin jar, drain the excess of liquid as before.</li>
		<li>Incubate each slide with 100 &#956;l of RNAseA at 100 &#956;g/ml in PBS with 1% Tween-20 for 1 hr at 37 &#176;C in a moist chamber.</li>
		<li>Wash the slides for 2 x 5 min in PBT.</li>
	</ol>
	</li>
	<li>Post-fixation and permeabilization:
	<ol>
		<li>Post-fix for 20 min in freshly made PBT-F.</li>
		<li>Rinse the slides for 10 min in PBT.</li>
		<li>Permeabilize for 2 hr in PBS with 2% Tween-20 at 4 &#176;C.</li>
		<li>Rinse the slides for 2 x 5 min in PBT.</li>
	</ol>
	</li>
</ol>
4. Immunostaining
NOTE: For this step, the optimal concentration of the primary antibody has to be tested by using different dilutions (1:200, 1:500, 1:1000) of the antibodies.
<ol>
	<li>Incubate each slide with 100&#160;&#956;l of primary antibody diluted in PBS with 0.2% Tween-20 for 12-24 hr at 4 &#176;C.</li>
	<li>Wash the slides in PBT for 2-4 hr at room temperature under gentle shaking.</li>
	<li>Apply the secondary antibody 1:200 in PBS + 0.2% Tween-20 for 24 hr at 4 &#176;C.</li>
	<li>Wash slides in PBT for 1 hr at room temperature under gentle shaking.</li>
	<li>Counterstain with 10 &#956;g/ml propidium iodide in PBS for 15 min, then rinse 15 min in PBS under gentle shaking, at room temperature.</li>
	<li>Mount in anti-fading liquid mountant supplemented with 10 &#956;g/ml propidium iodide. Let the mounting medium harden for 1 hr before acquiring images by CLSM.</li>
</ol>
5. Quantitative Imaging
<ol>
	<li>Image acquisition:
	<ol>
		<li>Acquire high resolution images using CLSM, ideally using a resonance scanning mode, which allows better preservation of fluorescent signals over prolonged imaging23, and a 63X glycerol immersion lens.</li>
		<li>Test the acquisition parameters such as laser intensity, gain, pinhole, voxel size and zoom factor at the beginning of the experiment to define a standard acquisition procedure to strictly follow throughout all slides for consistent quantitative measurements.</li>
		<li>Verify the absence of cross-talk between fluorochromes. If present, set up a sequential scan. Acquire transmission images separately and not simultaneously.</li>
		<li>Perform serial, three-dimensional image acquisition with highest possible resolution in the x and y dimensions and with 2x oversampling in the z dimension (Nyquist&#8217;s rule).</li>
	</ol>
	</li>
	<li>Image processing:
	<ol>
		<li>Reconstruct serial images in three-dimensions using commercial or open source software.</li>
		<li>Define contour surfaces around each nucleus (or cell) of interest in 3D.</li>
		<li>Quantify fluorescence in each channel as the sum of pixel intensities in each object.</li>
		<li>Export the data to Excel for statistical analyses. Normalize antibody signals against e.g. DNA staining signals.</li>
	</ol>
	</li>
</ol>

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The authors declare that they have no competing financial interests.

In flowering plants, the female reproductive lineage is surrounded by several cell layers including the nucellus and the ovule teguments, thus rendering cytological staining in whole-mount technically challenging. Here we present an efficient protocol enabling the preparation and processing of a large number of ovules suitable for cytological staining such as immunostaining, DNA staining and fluorescence in situ hybridization in whole-mount. We successfully used it for the analysis of the female reproductive ger...

In flowering plants, the establishment of reproductive lineages begins with the differentiation of SMCs, female MMC and male microspore mother cell. The MMC develops from a sub-epidermal nucellar cell at the distal tip of the ovule primordium, and the microspore mother cell develops from sporogenous tissue in the anther locule, which are located deep inside the floral organs1. SMCs undergo meiosis to produce haploid spores, which then give rise to the gametophytes upon mitosis. The female gametophyte, or embryo sac, consists of one egg cell, one central cell, two synergids and three antipodals. The male gametophyte, or pollen, is composed of one vegetative cell and two sperm cells. While the male gametophyte remains a relatively accessible object-of-study, the female gametophyte is embedded inside the ovule, itself enclosed in the flower carpel, and thus poses specific challenges to molecular and cytological analyses. Recently, however, laser-assisted microdissection offered an elegant solution allowing transcriptomic analyses in the MMC and female gametophytic cells2-4. In addition to candidate gene expression analyses, using e.g. RNA in situ hybridization or reporter gene assays, cytological analyses allows investigating the dynamics of endogenous cellular components using specific direct cellular staining or indirect immunostaining. Particularly, cytogenetic staining using FISH and DNA staining, together with immunostaining of chromatin modifications or chromatin components are central approaches to elucidate chromatin dynamics and nuclear organization in Arabidopsis5. Typically, meiosis entails specific chromosome dynamics which has been well investigated in plant male meiocytes6,7; further large-scale, cell-specific chromatin reorganization, likely reflecting dynamic epigenetic reprogramming has been described during pollen development8-10. By contrast, due to the relative inaccessibility of the female meiocyte and gametophyte, these investigations remain technically difficult to apply, and often require sectioning or manual dissection and enzymatic digestion (see below). In addition, the prevalent lack of optical clarity in whole-mount is an obstacle to high-resolution imaging of reproductive cells in intact ovules.
A classical method for cytological analysis of chromosome organization in whole-mount ovules uses Feulgen&#8217;s staining11-13. It involves acid hydrolysis (using hypochlorous acid) of the DNA which results in protein denaturation and thus causes destruction of the chromatin structure. Alternatively, chromosome organization in female meiocytes and gametophytic cells can be observed using DAPI staining and immunostaining on semi-thin sections or dissected embryo sacs and MMC (for instance see14-18). Clearly, however, manual dissection and sectioning can be labor intensive and impedes on the qualitative and quantitative analysis of a large number of chromatin epitopes.
Here we provide an efficient protocol to prepare a large number of Arabidopsis ovules suitable for a variety of downstream cytological staining in whole-mount. In brief, flower buds are incubated in a fixative solution, rows of ovules are dissected from the carpel and embedded in acrylamide on slide as done for pollen meiocytes19,20. The embedded ovules are further cleared and fixed in methanol, ethanol, and xylene before cell wall digestion and permeabilization. Possible variations of these steps are discussed. The samples can then be used for DNA staining, immunostaining, and FISH. The preparation mode is efficient and allows for parallel experimental set-up (up to 16 slides can be prepared in a day for different downstream analysis). The treatments described enable homogeneous signals in whole-mount and well preserved histological, cellular, and nuclear organization in reproductive cells and surrounding nucellar cells which benefit qualitative and quantitative comparisons between cell types. Calibrated, CLSM-based high-resolution imaging followed by 3-dimensional reconstruction enables meaningful quantitative measurements of fluorescent signals. We successfully used this procedure to analyze chromatin dynamics in the differentiating MMC21 and developing female gametophyte22; we present here representative results of heterochromatin analysis, chromatin immunostaining, GFP immunostaining and FISH in whole-mount ovules. We further believe that our protocol will be suitable for other plant tissues and species.

<table border="0" cellpadding="0" cellspacing="0" width="993">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;"><a name="RANGE!A1:D39">Name of Material/ Equipment</a></td>
			<td style="width:135px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:481px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Solutions</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">BVO Fixation Buffer (based on32)</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:481px;">2mM EGTA, pH7.5, 1% (v/v) Formaldehyde,10% DMSO, 1&#215; PBS, 0.1% Tween-20</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PBT</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:481px;">1&#215; PBS, 0.1% Tween-20</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PBT-F</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:481px;">1&#215; PBT, 2.5% (v/v) formaldehyde</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">30% acrylamide:bisacrylamide&#160;</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:481px;">3g acrylamide, 0.33g bisacrylamide, 1&#215; PBS (prepare 10ml, store at 4&#176;C)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">200mL&#160; 5% acrylamide mix in PBS&#160;</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:481px;">34mL 30% acrylamide:bisacrylamide, 166mL 1&#215; PBS (make fresh from 30% stock)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">20% ammoniumpersulfte&#160;</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:481px;">0.2g ammoniumpersulfte, 1mL sterile water (prepare aliquots with 1mL and store at -20&#176;C)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">20% sodium sulfite&#160;</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:481px;">0.2g sodium sulfite, 1mL sterile water (prepare aliquots with 1mL and store at -20&#176;C)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cell wall enzyme mix</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:481px;">0.5% (w/v) cellulase, 1% (w/v) driselase, 0.5% (w/v) pectolyase</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;"></td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Reagents and Materials</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Formaldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>F1635</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DMSO</td>
			<td>Sigma</td>
			<td>D5879</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tris</td>
			<td>Amaresco</td>
			<td>0497</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethanol</td>
			<td>Schaurlau</td>
			<td>ET00102500</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Methanol</td>
			<td>Schaurlau</td>
			<td>ME03062500</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Xylene</td>
			<td>ROTH</td>
			<td>4436.1</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cellulase</td>
			<td>Sigma</td>
			<td>1794</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Driselase</td>
			<td>Sigma</td>
			<td>D8037</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">pectolyase</td>
			<td>Sigma</td>
			<td>P5936</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tween-20</td>
			<td>Merck</td>
			<td>8.22184.0500</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">EGTA</td>
			<td>Sigma</td>
			<td>E-4378</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">acrylamide</td>
			<td>Sigma</td>
			<td>A-3553</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">bisacrylamide</td>
			<td>Sigma</td>
			<td>M2022</td>
			<td style="width:481px;">toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ammoniumpersulfate</td>
			<td>Sigma</td>
			<td>A9164</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium sulfite</td>
			<td>Fluka</td>
			<td>71988</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Anti-trimethyl-Histone H3 (Lys4)</td>
			<td>Upstate</td>
			<td>07-473</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Anti- monomethyl-Histone H3 (Lys27)</td>
			<td>Upstate</td>
			<td>07-448</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Alexa Fluor 488~goat ~anti ~rabbit (H+L)</td>
			<td>Molecular Probe</td>
			<td>A11008</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ProlongGold</td>
			<td>Invitrogen</td>
			<td>P36934</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Propidium iodide</td>
			<td>Sigma</td>
			<td>P4170</td>
			<td style="width:481px;">toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DAPI</td>
			<td>Sigma</td>
			<td>D9542</td>
			<td style="width:481px;">toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RNAse A</td>
			<td>Roche</td>
			<td>10109169001</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Coplin jar</td>
			<td>Huber &#38; CO</td>
			<td>10.055</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Forceps</td>
			<td>DUMONT BIOLOGY</td>
			<td style="width:119px;"></td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Shaker</td>
			<td>Heidolph</td>
			<td>543-12310-00-0</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="38">
			<td height="38" style="height:39px;">Moist chamber</td>
			<td style="width:135px;"></td>
			<td style="width:119px;"></td>
			<td style="width:481px;">A plastic box with damp paper towel inside, a plastic support is put into the box for supporting the slides and keep slides from the water.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Superfrost Plus slide</td>
			<td>Thermo Fisher</td>
			<td>J1800AMNZ</td>
			<td style="width:481px;">Menzel-Gl&#228;ser</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FISH Tag DNA KIt</td>
			<td>Invitrogen</td>
			<td>F32947</td>
			<td style="width:481px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">GFP booster</td>
			<td style="width:135px;">Chromotek</td>
			<td style="width:119px;"></td>
			<td style="width:481px;"></td>
		</tr>
	</tbody>
</table>

an efficient method for quantitative, single-cell analysis of chromatin modification and nuclear architecture in whole-mount ovules in arabidopsis

In flowering plants, the somatic-to-reproductive cell fate transition is marked by the specification of spore mother cells (SMCs) in floral organs of the adult plant. The female SMC (megaspore mother cell, MMC) differentiates in the ovule primordium and undergoes meiosis. The selected haploid megaspore then undergoes mitosis to form the multicellular female gametophyte, which will give rise to the gametes, the egg cell and central cell, together with accessory cells. The limited accessibility of the MMC, meiocyte and female gametophyte inside the ovule is technically challenging for cytological and cytogenetic analyses at single cell level. Particularly, direct or indirect immunodetection of cellular or nuclear epitopes is impaired by poor penetration of the reagents inside the plant cell and single-cell imaging is demised by the lack of optical clarity in whole-mount tissues.
Thus, we developed an efficient method to analyze the nuclear organization and chromatin modification at high resolution of single cell in whole-mount embedded Arabidopsis ovules. It is based on dissection and embedding of fixed ovules in a thin layer of acrylamide gel on a microscopic slide. The embedded ovules are subjected to chemical and enzymatic treatments aiming at improving tissue clarity and permeability to the immunostaining reagents. Those treatments preserve cellular and chromatin organization, DNA and protein epitopes. The samples can be used for different downstream cytological analyses, including chromatin immunostaining, fluorescence in situ hybridization (FISH), and DNA staining for heterochromatin analysis. Confocal laser scanning microscopy (CLSM) imaging, with high resolution, followed by 3D reconstruction allows for quantitative measurements at single-cell resolution.

We provide a robust protocol for large-scale preparation and processing of Arabidopsis ovules suitable for cytological staining in whole-mount. Thanks to the embedding, the ovules retain a 3-dimensional structure (Figure 3). Furthermore, the tissue processing including optical clarification enables imaging subcellular structures at high-resolution. Figure 4 shows DNA staining in whole-mount ovule primordia where heterochromatin appears as bright, well defined conspicuous foci (n...

Watch this Scientific Journal Video about An Efficient Method for Quantitative, Single-cell Analysis of Chromatin Modification and Nuclear Architecture in Whole-mount Ovules in Arabidopsis at JoVE.com

An Efficient Method for Quantitative, Single-cell Analysis of Chromatin Modification and Nuclear Architecture in Whole-mount Ovules in Arabidopsis

We provide here an efficient and reliable protocol for immunostaining, Fluorescence in&#160;situ Hybridization, DNA staining followed by quantitative, high-resolution imaging in whole-mount Arabidopsis thaliana ovules. This method was successfully used to analyze chromatin modifications and nuclear architecture.

An Efficient Method for Quantitative, Single-cell Analysis of Chromatin Modification and Nuclear Architecture in Whole-mount Ovules in Arabidopsis

In flowering plants, the somatic-to-reproductive cell fate transition is marked by the specification of spore mother cells (SMCs) in floral organs of the ...

an-efficient-method-for-quantitative-single-cell-analysis-chromatin

Research

JoVE Journal

Biology

13.1K Views.  University of Zürich. We provide here an efficient and reliable protocol for immunostaining, Fluorescence in situ Hybridization, DNA staining followed by quantitative, high-resolution imaging in whole-mount Arabidopsis thaliana ovules. This method was successfully used to analyze chromatin modifications and nuclear architecture.

Video: An Efficient Method for Quantitative, Single-cell Analysis of Chromatin Modification and Nuclear Architecture in Whole-mount Ovules in Arabidopsis

Double Whole Mount in situ Hybridization of Early Chick Embryos

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ideal tool for studying  gene expression in brain, neural tube, somite and heart primordia formation. This video demonstrates the different steps in 2-color whole mount in situ hybridization; First, the embryo is dissected from the egg and fixed in paraformaldehyde. Second, the embryo is processed for prehybridization. The embryo is then hybridized with two different probes, one coupled to DIG, and one coupled to FITC.  Following overnight hybridization, the embryo is incubated with DIG coupled antibody. Color reaction for DIG substrate is performed, and the region of interest appears blue. The embryo is then incubated with FITC coupled antibody. The embryo is processed for color reaction with FITC, and the region of interest appears red. Finally, the embryo is fixed and processed for phtograph and sectioning. A troubleshooting guide is also presented.

This video demonstrates 2-color whole mount in situ hybridization, a method by which the spatial and temporal expression pattern of 2 different genes can be visualized in young chick embryos. This method was originally introduced by David Wilkinson, Domingos Henrique, Phil Ingham and David Ish -Horowicz.

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ...

Method for Whole Mount Antibody Staining in Chick

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ideal tool for studying antibody expression in developing brain, neural tube and somite. This video demonstrates the different steps in whole-mount antibody staining using HRP conjugated secondary antibodies; First, the embryo is dissected from the egg and fixed in paraformaldehyde. Second, endogenous peroxidase is inactivated; The embryo is then exposed to primary antibody. After several washes, the embryo is incubated with secondary antibody conjugated to HRP. Peroxidase activity is revealed using reaction with diaminobenzidine substrate. Finally, the embryo is fixed and processed for photography and sectioning. The advantage of this method over the use of fluorescent antibodies is that embryos can be processed for wax sectioning, thus enabling the study of antigen sites in cross section. This method was originally introduced by Jane Dodd and Tom Jessell 1.

This video demonstrates whole mount immunohistochemistry, a method by which the spatial and temporal expression pattern of an antigen can be visualized in young chick embryos. This method was originally introduced by Jane Dodd and Tom Jessell.

Single-cell Suction Recordings from Mouse Cone Photoreceptors

Rod and cone photoreceptors in the retina are responsible for light detection. In darkness, cyclic nucleotide-gated (CNG) channels in the outer segment are open and allow cations to flow steadily inwards across the membrane, depolarizing the cell. Light exposure triggers the closure of the CNG channels, blocks the inward cation current flow, and thus results in cell hyperpolarization. Based on the polarity of photoreceptors, a suction recording method was developed in 1970s that, unlike the classic patch-clamp technique, does not require penetrating the plasma membrane 1. Drawing the outer segment into a tightly-fitting glass pipette filled with extracellular solution allows recording the current changes in individual cells upon test-flash exposure. However, this well-established "outer-segment-in (OS-in)" suction recording is not suitable for mouse cone recordings, because of the low percentage of cones in the mouse retina (3%) and the difficulties in identifying the cone outer segments. Recently, an inner-segment-in (IS-in) recording configuration was developed to draw the inner segment/nuclear region of the photoreceptor into the recording pipette 2,3. In this video, we will show how to record from individual mouse cone photoresponses using single-cell suction electrode.

We will show how to record flash responses from single mouse cones using a suction electrode.

Rod and cone photoreceptors in the retina are responsible for light detection. In darkness, cyclic nucleotide-gated (CNG) channels in the outer segment ...

Hi-C: A Method to Study the Three-dimensional Architecture of Genomes.

The three-dimensional folding of chromosomes compartmentalizes the genome and and can bring distant functional elements, such as promoters and enhancers, into close spatial proximity 2-6. Deciphering the relationship between chromosome organization and genome activity will aid in understanding genomic processes, like transcription and replication. However, little is known about how chromosomes fold. Microscopy is unable to distinguish large numbers of loci simultaneously or at high resolution. To date, the detection of chromosomal interactions using chromosome conformation capture (3C) and its subsequent adaptations required the choice of a set of target loci, making genome-wide studies impossible 7-10.
We developed Hi-C, an extension of 3C that is capable of identifying long range interactions in an unbiased, genome-wide fashion. In Hi-C, cells are fixed with formaldehyde, causing interacting loci to be bound to one another by means of covalent DNA-protein cross-links. When the DNA is subsequently fragmented with a restriction enzyme, these loci remain linked. A biotinylated residue is incorporated as the 5' overhangs are filled in. Next, blunt-end ligation is performed under dilute conditions that favor ligation events between cross-linked DNA fragments. This results in a genome-wide library of ligation products, corresponding to pairs of fragments that were originally in close proximity to each other in the nucleus. Each ligation product is marked with biotin at the site of the junction. The library is sheared, and the junctions are pulled-down with streptavidin beads. The purified junctions can subsequently be analyzed using a high-throughput sequencer, resulting in a catalog of interacting fragments.
Direct analysis of the resulting contact matrix reveals numerous features of genomic organization, such as the presence of chromosome territories and the preferential association of small gene-rich chromosomes. Correlation analysis can be applied to the contact matrix, demonstrating that the human genome is segregated into two compartments: a less densely packed compartment containing open, accessible, and active chromatin and a more dense compartment containing closed, inaccessible, and inactive chromatin regions. Finally, ensemble analysis of the contact matrix, coupled with theoretical derivations and computational simulations, revealed that at the megabase scale Hi-C reveals features consistent with a fractal globule conformation.

The Hi-C method allows unbiased, genome-wide identification of chromatin interactions (1). Hi-C couples proximity ligation and massively parallel sequencing. The resulting data can be used to study genomic architecture at multiple scales: initial results identified features such as chromosome territories, segregation of open and closed chromatin, and chromatin structure at the megabase scale.

The three-dimensional folding of chromosomes compartmentalizes the genome and and can bring distant functional elements, such as promoters and enhancers, ...

Visualization and Analysis of mRNA Molecules Using Fluorescence In Situ Hybridization in Saccharomyces cerevisiae

The Fluorescence in situ Hybridization (FISH) method allows one to detect nucleic acids in the native cellular environment. Here we provide a protocol for using FISH to quantify the number of mRNAs in single yeast cells. Cells can be grown in any condition of interest and then fixed and made permeable. Subsequently, multiple single-stranded deoxyoligonucleotides conjugated to fluorescent dyes are used to label and visualize mRNAs. Diffraction-limited fluorescence from single mRNA molecules is quantified using a spot-detection algorithm to identify and count the number of mRNAs per cell. While the more standard quantification methods of northern blots, RT-PCR and gene expression microarrays provide information on average mRNAs in the bulk population, FISH facilitates both the counting and localization of these mRNAs in single cells at single-molecule resolution.

Visualization and Analysis of mRNA Molecules Using Fluorescence In Situ Hybridization in Saccharomyces cerevisiae

This protocol describes an experimental procedure for performing Fluorescence in situ Hybridization (FISH) for counting mRNAs in single cells at single-molecule resolution.

The Fluorescence in situ Hybridization (FISH) method allows one to detect nucleic acids in the native cellular environment. Here we provide a protocol for ...

Measuring Spatial and Temporal Ca2+ Signals in Arabidopsis Plants

Developmental and environmental cues induce Ca2+ fluctuations in plant cells. Stimulus-specific spatial-temporal Ca2+ patterns are sensed by cellular Ca2+ binding proteins that initiate Ca2+ signaling cascades. However, we still know little about how stimulus specific Ca2+ signals are generated. The specificity of a Ca2+ signal may be attributed to the sophisticated regulation of the activities of Ca2+ channels and/or transporters in response to a given stimulus. To identify these cellular components and understand their functions, it is crucial to use systems that allow a sensitive and robust recording of Ca2+ signals at both the tissue and cellular levels. Genetically encoded Ca2+ indicators that are targeted to different cellular compartments have provided a platform for live cell confocal imaging of cellular Ca2+ signals. Here we describe instructions for the use of two Ca2+ detection systems: aequorin based FAS (film adhesive seedlings) luminescence Ca2+ imaging and case12 based live cell confocal fluorescence Ca2+ imaging. Luminescence imaging using the FAS system provides a simple, robust and sensitive detection of spatial and temporal Ca2+ signals at the tissue level, while live cell confocal imaging using Case12 provides simultaneous detection of cytosolic and nuclear Ca2+ signals at a high resolution.

Measuring Spatial and Temporal Ca2+ Signals in Arabidopsis Plants

Ca2+ signaling regulates diverse biological processes in plants. Here we present approaches for monitoring abiotic stress induced spatial and temporal Ca2+ signals in Arabidopsis cells and tissues using the genetically encoded Ca2+ indicators Aequorin or Case12.

Developmental and environmental cues induce Ca2+ fluctuations in plant cells. Stimulus-specific spatial-temporal Ca2+ patterns are sensed by cellular Ca2+ ...

A Whole Mount In Situ Hybridization Method for the Gastropod Mollusc Lymnaea stagnalis

Whole mount in situ hybridization (WMISH) is a technique that allows for the spatial resolution of nucleic acid molecules (often mRNAs) within a &#39;whole mount&#39; tissue preparation, or developmental stage (such as an embryo or larva) of interest. WMISH is extremely powerful because it can significantly contribute to the functional characterization of complex metazoan genomes, a challenge that is becoming more of a bottleneck with the deluge of next generation sequence data. Despite the conceptual simplicity of the technique much time is often needed to optimize the various parameters inherent to WMISH experiments for novel model systems; subtle differences in the cellular and biochemical properties between tissue types and developmental stages mean that a single WMISH method may not be appropriate for all situations. We have developed a set of WMISH methods for the re-emerging gastropod model Lymnaea stagnalis that generate consistent and clear WMISH signals for a range of genes, and across all developmental stages. These methods include the assignment of larvae of unknown chronological age to an ontogenetic window, the efficient removal of embryos and larvae from their egg capsules, the application of an appropriate Proteinase-K treatment for each ontogenetic window, and hybridization, post-hybridization and immunodetection steps. These methods provide a foundation from which the resulting signal for a given RNA transcript can be further refined with probe specific adjustments (primarily probe concentration and hybridization temperature).

A Whole Mount In Situ Hybridization Method for the Gastropod Mollusc Lymnaea stagnalis

The goal of this protocol is to provide users with a set of methods for the high-throughput decapsulation of Lymnaea stagnalis embryos and larvae in preparation for whole mount in situ hybridization, and for subsequent pre- and post-hybridization treatments.

Whole mount in situ hybridization (WMISH) is a technique that allows for the spatial resolution of nucleic acid molecules (often mRNAs) within a ...

CUBIC Protocol Visualizes Protein Expression at Single Cell Resolution in Whole Mount Skin Preparations

The skin is essential for our survival. The outer epidermal layer consists of the interfollicular epidermis, which is a stratified squamous epithelium covering most of our body, and epidermal appendages such as the hair follicles and sweat glands. The epidermis undergoes regeneration throughout life and in response to injury. This is enabled by K14-expressing basal epidermal stem/progenitor cell populations that are tightly regulated by multiple regulatory mechanisms active within the epidermis and between epidermis and dermis. This article describes a simple method to clarify full thickness mouse skin biopsies, and visualize K14 protein expression patterns, Ki67 labeled proliferating cells, Nile Red labeled sebocytes, and DAPI nuclear labeling at single cell resolution in 3D. This method enables accurate assessment and quantification of skin anatomy and pathology, and of abnormal epidermal phenotypes in genetically modified mouse lines. The CUBIC protocol is the best method available to date to investigate molecular and cellular interactions in full thickness skin biopsies at single cell resolution.

This report describes a CUBIC protocol to clarify full thickness mouse skin biopsies, and visualize protein expression patterns, proliferating cells, and sebocytes at the single cell resolution in 3D. This method enables accurate assessment of skin anatomy and pathology, and of abnormal epidermal phenotypes in genetically modified mouse lines.

The skin is essential for our survival. The outer epidermal layer consists of the interfollicular epidermis, which is a stratified squamous epithelium ...

Visualization of 3D White Adipose Tissue Structure Using Whole-mount Staining

Adipose tissue is an important metabolic organ with high plasticity and is responsive to environmental stimuli and nutrient status. As such, various techniques have been developed to study the morphology and biology of adipose tissue. However, conventional visualization methods are limited to studying the tissue in 2D sections, failing to capture the 3D architecture of the whole organ. Here we present whole-mount staining, an immunohistochemistry method that preserves intact adipose tissue morphology with minimal processing steps. Hence, the structures of adipocytes and other cellular components are maintained without distortion, achieving the most representative 3D visualization of the tissue. In addition, whole-mount staining can be combined with lineage tracing methods to determine cell fate decisions. However, this technique has some limitations to providing accurate information regarding deeper parts of adipose tissue. To overcome this limitation, whole-mount staining can be further combined with tissue clearing techniques to remove the opaqueness of tissue and allow for complete visualization of entire adipose tissue anatomy using light-sheet fluorescent microscopy. Therefore, a higher resolution and more accurate representation of adipose tissue structures can be captured with the combination of these techniques.

The focus of the present study is to demonstrate the whole-mount immunostaining and visualization technique as an ideal method for 3D imaging of adipose tissue architecture and cellular component.

Adipose tissue is an important metabolic organ with high plasticity and is responsive to environmental stimuli and nutrient status. As such, various ...

An Easy and Flexible Inoculation Method for Accurately Assessing Powdery Mildew-Infection Phenotypes of Arabidopsis and Other Plants

Reducing crop losses due to fungal diseases requires improved understanding of the mechanisms governing plant immunity and fungal pathogenesis, which in turn requires accurate determination of disease phenotypes of plants upon infection with a particular fungal pathogen. However, accurate disease phenotyping with unculturable biotrophic fungal pathogens such as powdery mildew is not easy to achieve and can be a rate-limiting step of a research project. Here, we have developed a safe, efficient, and easy-to-operate disease phenotyping system using the Arabidopsis-powdery mildew interaction as an example. This system mainly consists of three components: (i) a wooden inoculation box fitted with a removable lid mounted with a stainless steel or nylon mesh of ~50 &#181;m pores for inoculating a flat of plants with fungal spores, (ii) a transparent plastic chamber with a small front opening for minimizing spore escape while conducting inoculation inside, and (iii) a spore-dislodging and distribution method for even and effective inoculation. The protocols described here include the steps and parameters for making the inoculation box and the plastic chamber at a low cost, and a video demonstration of how to use the system to enable even inoculation with powdery mildew spores, thereby improving accuracy and reproducibility of disease phenotyping.

We present a protocol for constructing a simple spore-distribution system consisting of an inoculation box with a ~50 &#181;m mesh and a transparent plastic chamber. This can be used to evenly inoculate plants with powdery mildew spores, thereby enabling accurate and reproducible assessment of disease phenotypes of plants under study.

Reducing crop losses due to fungal diseases requires improved understanding of the mechanisms governing plant immunity and fungal pathogenesis, which in ...