Name: analysis of the gap junction-dependent transfer of mirna with 3d-frap microscopy
Uploaded: 2017-06-19T14:00:00
Description: Watch this Scientific Journal Video about Analysis of the Gap Junction-dependent Transfer of miRNA with 3D-FRAP Microscopy at JoVE.com

This work was supported by the Federal Ministry of Education and Research Germany (FKZ 0312138A and FKZ 316159), the State Mecklenburg-Western Pomerania with EU Structural Funds (ESF/IVWM-B34-0030/10 and ESF/IVBM-B35-0010/12), the DFG (DA1296-1), and the German Heart Foundation (F/01/12). In addition, R.D. is supported by the FORUN Program of Rostock University Medical Centre (889001), the DAMP Foundation, and the BMBF (VIP+ 00240).

All steps in this protocol involving neonatal mice were performed per the ethical guidelines for animal care of the Rostock University Medical Centre.
1. Preparation of Cell Culture Dishes and the Medium for Cardiomyocyte Culture
<ol>
	<li>Coat a cell culture plate with 0.1% gelatin in PBS and incubate at 37 &#176;C for 4 h or at 4 &#176;C overnight. Remove the gelatin and allow it to dry under sterile laminar air flow.</li>
	<li>Prepare cell culture medium composed of 50 mL of DMEM suppleme...

<ol>
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miRNAs are key players in cellular physiology and were shown to act as signaling molecules by using&#8212;among others&#8212;GJs as a pathway for intercellular exchange11,12,22. The current protocol presents an in vitro live-cell imaging technique to characterize this GJ-dependent shuttling using fluorescent miRNAs within cell clusters.
The protocol was developed on cardiomyocytes as a cell m...

Small noncoding RNAs are important players in cellular gene regulation. These molecules are composed of 20-25 nucleotides that bind to a specific target mRNA, leading to the blockage of translation or to mRNA degradation1,2. The gene regulatory process undertaken by small RNAs, such as miRNA and siRNA, is a highly conserved mechanism that has been found in many different species3. In particular, miRNA molecules are of crucial importance to a variety of physiological processes, including proliferation, differentiation, and regeneration4,5. In addition, the dysregulation of miRNA expression is attributed to many pathological disorders. Correspondingly, miRNAs have been demonstrated to be suitable as biomarkers for diagnosis and as therapeutic agents for gene therapy6,7.
Gap junctions (GJs) are specialized protein structures in the plasma membrane of two adjacent cells that allow the diffusional exchange of molecules with a molecular weight of up to 1 kD. They have been shown to be important to tissue development, differentiation, cell death, and pathological disorders such as cancer or cardiovascular disease8,9,10. Several molecules have been described as being capable of crossing GJ channels, including ions, metabolites, and nucleotides. Interestingly, GJs were also found to provide a pathway for the intercellular movement of small RNAs11,12. Thus, miRNAs can act not only within the cell in which they are produced, but also within recipient cells. This highlights the role of miRNAs in the intercellular signal transduction system. At the same time, the data demonstrate that gap junctional intercellular communication is closely linked to miRNA function. Because of the significant impact of miRNA and GJs on tissue homeostasis, pathology, and diagnosis, a comprehensive understanding of the function of GJs and the related intercellular dynamics of miRNA will help to clarify the mechanisms of miRNA-based diseases and to develop new strategies for miRNA therapies.
Depending on the extent of gap junctional coupling, the transfer of miRNA molecules between cells can be a very rapid process. Therefore, a methodology that allows the visualization and quantification of the fast intercellular movement of these regulatory signaling molecules is required. Commonly, flow cytometry and molecular biological techniques have been applied to demonstrate the shuttling of small RNAs11,12,13,14. However, as opposed to FRAP microscopy, these approaches lack high temporal resolution, which is mandatory when analyzing the exchange of miRNA via GJs. Moreover, FRAP microscopy is less invasive and therefore represents a powerful and novel live-cell imaging technique to evaluate the GJ-dependent exchange of molecules in several cell types15,16,17.
Here, we present a detailed protocol describing the application of 3D-FRAP to assess miRNA shuttling between cardiomyocytes. For this purpose, cardiomyocytes were transfected with fluorescently labeled miRNA. A cell marked with this miRNA was photobleached, and the gap junctional miRNA re-influx from adjacent cells was recorded in a time-dependent manner. The high temporal resolution of FRAP experiments offers the possibility to perform kinetic studies for the precise evaluation of the intercellular transfer of miRNA and siRNA between living cells. Moreover, as small RNAs can be exchanged via different mechanisms with highly different kinetics, FRAP microscopy can help to clarify the extent to which GJs are involved in the respective shuttling processes18. In addition, 3D-FRAP can be used to investigate physiological and pathological alterations in GJ permeability and its impact on small RNA transfer15,19.

<table border="0" cellpadding="0" cellspacing="0" width="698">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">neonatal NMRI mice</td>
			<td style="width:159px;">Charles River</td>
			<td style="width:119px;"></td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Gelatin</td>
			<td style="width:159px;">Sigma Aldrich</td>
			<td style="width:119px;">G7041</td>
			<td style="width:179px;">0.1% solution in PBS, sterilized</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">PBS</td>
			<td style="width:159px;">Pan Biotech</td>
			<td style="width:119px;">P04-53500</td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Dulbecco&#180;s modified medium</td>
			<td style="width:159px;">Pan Biotech</td>
			<td style="width:119px;">P04-03550</td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Penicillin/Streptomycin</td>
			<td style="width:159px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">15140122</td>
			<td style="width:179px;">100 U/ml, 100&#181;g/ml</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Fetal bovine serum</td>
			<td style="width:159px;">Pan Biotech</td>
			<td style="width:119px;">P30-3306</td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Cell culture plastic</td>
			<td style="width:159px;">TPP</td>
			<td style="width:119px;"></td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Primary Cardiomyocyte Isolation Kit</td>
			<td style="width:159px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">88281</td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:243px;">HBSS</td>
			<td style="width:159px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">88281</td>
			<td style="width:179px;">included in primary cardiomyocyte isolation kit</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Trypan blue</td>
			<td style="width:159px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">15250061</td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:243px;">miRIDIAN Dy547 labeled microRNA Mimic&#160;</td>
			<td style="width:159px;">Dharmacon</td>
			<td style="width:119px;">CP-004500-01-05</td>
			<td style="width:179px;">dissolve in RNAse free water, stock solution 20&#181;M</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:243px;">Sodium phosphate monobasic</td>
			<td style="width:159px;">Sigma</td>
			<td style="width:119px;">S3139</td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Sodium phosphate dibasic</td>
			<td style="width:159px;">Carl Roth</td>
			<td style="width:119px;">T877.2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Potassium chloride</td>
			<td style="width:159px;">Sigma</td>
			<td style="width:119px;">P9333</td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Magnesium chloride</td>
			<td style="width:159px;">Serva</td>
			<td style="width:119px;">28305.01</td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Sodium succinate</td>
			<td style="width:159px;">Carl Roth</td>
			<td style="width:119px;">3195.1</td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">0.05% Trypsin/EDTA solution</td>
			<td style="width:159px;">Merck</td>
			<td style="width:119px;">L2153</td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">4-well- Glass bottom chamber slides</td>
			<td style="width:159px;">IBIDI</td>
			<td style="width:119px;">80827</td>
			<td style="width:179px;">coat with 0.1% gelatin solution</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Amaxa Nucleofector II</td>
			<td style="width:159px;">Lonza</td>
			<td style="width:119px;"></td>
			<td style="width:179px;">program G-009 was used for Electroporation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">LSM 780 ELYRA PS.1 system</td>
			<td style="width:159px;">Zeiss</td>
			<td style="width:119px;"></td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Excel software</td>
			<td style="width:159px;">Microsoft</td>
			<td style="width:119px;"></td>
			<td style="width:179px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">&#945;-actinin antibody</td>
			<td style="width:159px;">Abcam</td>
			<td style="width:119px;">ab9465</td>
			<td style="width:179px;">dilution 1:200</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Connexin43 antibody</td>
			<td style="width:159px;">Santa Cruz</td>
			<td style="width:119px;">sc-9059</td>
			<td style="width:179px;">dilution 1:200</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">goat anti-mouse Alexa 594 antibody</td>
			<td style="width:159px;">Thermo Fisher Scientific</td>
			<td>A-11005</td>
			<td>dilution 1:300</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">goat anti-rabbit Alexa 488 antibody&#160;</td>
			<td style="width:159px;">Thermo Fisher Scientific</td>
			<td>A-11034</td>
			<td>dilution 1:300</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Connexin43 siRNA</td>
			<td style="width:159px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">AM16708 ID158724</td>
			<td>&#160;final concentration 250nM</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Near-IR Live/Dead Cell Stain Kit</td>
			<td style="width:159px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">L10119</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">CellTrace Calcein Red-Orange</td>
			<td style="width:159px;">Thermo Scientific</td>
			<td style="width:119px;">C34851</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">DAPI nuclear stain</td>
			<td style="width:159px;">Thermo Scientific</td>
			<td style="width:119px;">D1306</td>
			<td style="width:179px;"></td>
		</tr>
	</tbody>
</table>

analysis of the gap junction-dependent transfer of mirna with 3d-frap microscopy

Small antisense RNAs, like miRNA and siRNA, play an important role in cellular physiology and pathology and, moreover, can be used as therapeutic agents in the treatment of several diseases. The development of new, innovative strategies for miRNA/siRNA therapy is based on an extensive knowledge of the underlying mechanisms. Recent data suggest that small RNAs are exchanged between cells in a gap junction-dependent manner, thereby inducing gene regulatory effects in the recipient cell. Molecular biological techniques and flow cytometric analysis are commonly used to study the intercellular exchange of miRNA. However, these methods do not provide high temporal resolution, which is necessary when studying the gap junctional flux of molecules. Therefore, to investigate the impact of miRNA/siRNA as intercellular signaling molecules, novel tools are needed that will allow for the analysis of these small RNAs at the cellular level. The present protocol describes the application of three-dimensional fluorescence recovery after photobleaching (3D-FRAP) microscopy to elucidating the gap junction-dependent exchange of miRNA molecules between cardiac cells. Importantly, this straightforward and non-invasive live-cell imaging approach allows for the visualization and quantification of the gap junctional shuttling of fluorescently labeled small RNAs in real time, with high spatio-temporal resolution. The data obtained by 3D-FRAP confirm a novel pathway of intercellular gene regulation, where small RNAs act as signaling molecules within the intercellular network.

Here, we present 3D-FRAP microscopy as a non-invasive technique to study the gap junctional shuttling of fluorescent miRNA within neonatal cardiomyocytes. The isolated cardiomyocytes revealed the typical striated &#945;-actinin pattern and contained large plaques of Cx43 along the cell-cell borders (Figure 1A, white arrowheads), which allowed for the high intercellular flux of molecules. The purity of isolated cardiomyocytes was assessed by the microscopic qu...

Watch this Scientific Journal Video about Analysis of the Gap Junction-dependent Transfer of miRNA with 3D-FRAP Microscopy at JoVE.com

Analysis of the Gap Junction-dependent Transfer of miRNA with 3D-FRAP Microscopy

Here, we describe the application of three-dimensional fluorescence recovery after photobleaching (3D-FRAP) for the analysis of the gap junction-dependent shuttling of miRNA. In contrast to commonly applied methods, 3D-FRAP allows for the quantification of the intercellular transfer of small RNAs in real time, with high spatio-temporal resolution.

Small antisense RNAs, like miRNA and siRNA, play an important role in cellular physiology and pathology and, moreover, can be used as therapeutic agents ...

The overall goal of this procedure is to investigate the gap junction-dependent transfer of micro RNA in living cardiomyocytes. This method can help to address the role of micro RNA for the intercellular signal transaction system. The main advantage of this technique is that the gap junction exchange of micro RNA can be visualized and quantified in life cells with high spatial temporal resolution.After isolating cardiomyocytes according to the text protocol, plate the cells on six well plates at a density of three times 10 to the fifth cells per square centimeter. Incubate the cells overnight at 37 degrees celsius and 5%carbon dioxide. The following day, add 0.5 trypzine to the cells and incubate the cultures for five minutes to detach the cells.Inactivate the trypzine by adding cell culture medium. After counting the cells, centrifuge them at 300 times g for 10 minutes. Then use electroporation buffer to re-suspend the cells at four times 10 to the fifth cells per 100 microliters.Next, mix 100 microliters of cell suspension with fluorescent micro RNA in a tube and load the mixture into an electroporation cuvette. Then carry out electroporation using the G009 program on the electroporator. Add 500 microliters of pre-warmed cell culture medium and transfer the entire volume of cell suspension into a well of a four well glass bottom chamber slide.Culture the cells for one day at 37 degrees celsius, in a 5%carbon dioxide atmosphere. After pre-warming the microscope incubator and turning on the confucal system, insert the chamber slide into the stage sample holder. Use a 1.4 na oil objective and 561 nanometer laser excitation light, at low laser power, with the detection range of 570 to 680 nanometers to find the cluster of transvected cardiomyocytes.Next, in the setup manager, activate the z-stack, time series, bleaching and regions buttons. Then, to define the frap parameters, in the acquisition mode menu, set the frame size to 512 by 512, the line step to one and the scan time to less than one second. In the channels menu, adjust the laser power, offset and gain settings to obtain maximal fluorescence from minimal laser excitation, to avoid intensity saturation.Then, set the pinhole size to two micrometers. Next, in the regions menu, select the roy drawing tool and use the cursor to mark the target cell, the reference cell and the background area. If required, select several target cells for photo bleaching.In the bleaching menu, adjust the photo bleaching settings. Then, in the z-stack menu, define the limits for z-stack acquisition, depending on the thickness of the cells. Adjust the number of z layers to 12 tp 15, then, start the frap experiment and record the fluorescence recovery.To analyze the data, create maximum projection of the acquired z-stacks using microscope specific software, click processing, maximum intensity projection, select file, apply. Finally, copy the fluorescence intensity data at all time points from the target, the background and the reference cell, into a spreadsheet and perform data analysis according to the text protocol. Shown here, are isolate cardiomyocytes with the typical striated alpha actinin pattern and large plaques of connexin43, along the cell to cell borders.Some non-cardiomyocytes were present in the culture. As seen here, by flow cytometry, a 45%transvection efficiency was reached. In addition, a live-dead essay, revealed that the majority of cells demonstrated high viability, which is important when analyzing gap junctional communication.For frap analysis, target cells are selected within a cell cluster and are photo bleached with 100%laser power, leading to reduced micro RNA fluorescence in the selected cells. Quantitative analysis and normalization of the acquired data, showed an average recovery of 20%In this experiment, siRNA mediated knockdown of connexin43, led to reduced protein expression and the inhibition of gap junctional communication. Fluorescence recovery was reduced by more than 50%Indicating that the efficiency of miro RNA transfer is strongly dependent of gap junctional coupling between cells.This figure shows a 3D surface rendering of a frap experiment. Compared to maximum projections, the acquisition of z-stacks can be used to create 3D reconstructions to investigate the localisation and mobility of micro RNA within cells. Once mastered, frap measurements can be done in two to three hours if it is performed properly.While attempting this procedure, it is important to choose target cells which has the similar number of neighboring cells. Moreover, my bleaching parameters and image acquisition conditions should be selected to avoid phototoxic effects. After watching this video, you should have a good understanding of how to use frap microscopy, in order to quantify and visualize the movement of micro RNA within cellular clusters.

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Research

JoVE Journal

Biology

The Xenopus Oocyte Cut-open Vaseline Gap Voltage-clamp Technique With Fluorometry

The cut-open oocyte Vaseline gap (COVG) voltage clamp technique allows for analysis of electrophysiological and kinetic properties of heterologous ion channels in oocytes. Recordings from the cut-open setup are particularly useful for resolving low magnitude gating currents, rapid ionic current activation, and deactivation. The main benefits over the two-electrode voltage clamp (TEVC) technique include increased clamp speed, improved signal-to-noise ratio, and the ability to modulate the intracellular and extracellular milieu.
Here, we employ the human cardiac sodium channel (hNaV1.5), expressed in Xenopus oocytes, to demonstrate the cut-open setup and protocol as well as modifications that are required to add voltage clamp fluorometry capability.
The properties of fast activating ion channels, such as hNaV1.5, cannot be fully resolved near room temperature using TEVC, in which the entirety of the oocyte membrane is clamped, making voltage control difficult. However, in the cut-open technique, isolation of only a small portion of the cell membrane allows for the rapid clamping required to accurately record fast kinetics while preventing channel run-down associated with patch clamp techniques.
In conjunction with the COVG technique, ion channel kinetics and electrophysiological properties can be further assayed by using voltage clamp fluorometry, where protein motion is tracked via cysteine conjugation of extracellularly applied fluorophores, insertion of genetically encoded fluorescent proteins, or the incorporation of unnatural amino acids into the region of interest1. This additional data yields kinetic information about voltage-dependent conformational rearrangements of the protein via changes in the microenvironment surrounding the fluorescent molecule.

The Xenopus Oocyte Cut-open Vaseline Gap Voltage-clamp Technique With Fluorometry

The cut-open Vaseline gap approach is used to obtain low noise recordings of ionic and gating currents from voltage-dependent ion channels expressed in Xenopus oocytes with high resolution of fast channel kinetics. With minor modification, voltage clamp fluorometry can be coupled to the cut-open oocyte protocol.

The cut-open oocyte Vaseline gap (COVG) voltage clamp technique allows for analysis of electrophysiological and kinetic properties of heterologous ion ...

Analysis of Autophagy in Penicillium chrysogenum by Using Starvation Pads in Combination With Fluorescence Microscopy

The study of cellular quality control systems has emerged as a highly dynamic and relevant field of contemporary research. It has become clear that cells possess several lines of defense against damage to biologically relevant molecules like nucleic acids, lipids and proteins. In addition to organelle dynamics (fusion/fission/motility/inheritance) and tightly controlled protease activity, the degradation of surplus, damaged or compromised organelles by autophagy (cellular &#8216;self-eating&#8217;) has received much attention from the scientific community. The regulation of autophagy is quite complex and depends on genetic and environmental factors, many of which have so far not been elucidated. Here a novel method is presented that allows the convenient study of autophagy in the filamentous fungus Penicillium chrysogenum. It is based on growth of the fungus on so-called &#8216;starvation pads&#8217; for stimulation of autophagy in a reproducible manner. Samples are directly assayed by microscopy and evaluated for autophagy induction / progress. The protocol presented here is not limited for use with P. chrysogenum and can be easily adapted for use in other filamentous fungi.

Analysis of Autophagy in Penicillium chrysogenum by Using Starvation Pads in Combination With Fluorescence Microscopy

A convenient and powerful method for studying autophagy in Penicillium chrysogenum by using starvation pads (mixtures of agarose and tap water in a microscope slide containing a central cavity) is presented here.

The study of cellular quality control systems has emerged as a highly dynamic and relevant field of contemporary research. It has become clear that cells ...

Detection of miRNA Targets in High-throughput Using the 3'LIFE Assay

Luminescent Identification of Functional Elements in 3&#8217;UTRs (3&#8217;LIFE) allows the rapid identification of targets of specific miRNAs within an array of hundreds of queried 3&#8217;UTRs. Target identification is based on the dual-luciferase assay, which detects binding at the mRNA level by measuring translational output, giving a functional readout of miRNA targeting. 3&#8217;LIFE uses non-proprietary buffers and reagents, and publically available reporter libraries, making genome-wide screens feasible and cost-effective. 3&#8217;LIFE can be performed either in a standard lab setting or scaled up using liquid handling robots and other high-throughput instrumentation. We illustrate the approach using a dataset of human 3&#8217;UTRs cloned in 96-well plates, and two test miRNAs, let-7c and miR-10b. We demonstrate how to perform DNA preparation, transfection, cell culture and luciferase assays in 96-well format, and provide tools for data analysis. In conclusion 3&#39;LIFE is highly reproducible, rapid, systematic, and identifies high confidence targets.

Detection of miRNA Targets in High-throughput Using the 3&#039;LIFE Assay

Luminescent identification of functional elements in 3&#8217; untranslated regions (3&#8217;UTRs) (3&#8217;LIFE) is a technique to identify functional regulation in 3&#8217;UTRs by miRNAs or other regulatory factors. This protocol utilizes high-throughput methodology such as 96-well transfection and luciferase assays to screen hundreds of putative interactions for functional repression.

Luminescent Identification of Functional Elements in 3&#8217;UTRs (3&#8217;LIFE) allows the rapid identification of targets of specific miRNAs within an ...

Real-time Imaging of Plant Cell Surface Dynamics with Variable-angle Epifluorescence Microscopy

A plant&#8217;s cell surface is its interface for perceiving environmental cues; it responds with cell biological changes such as membrane trafficking and cytoskeletal rearrangement. Real-time and high-resolution image analysis of such intracellular events will increase the understanding of plant cell biology at the molecular level. Variable angle epifluorescence microscopy (VAEM) is an emerging technique that provides high-quality, time-lapse images of fluorescently-labeled proteins on the plant cell surface. In this article, practical procedures are described for VAEM specimen preparation, adjustment of the VAEM optical system, movie capturing and image analysis. As an example of VAEM observation, representative results are presented on the dynamics of PATROL1. This is a protein essential for stomatal movement, thought to be involved in proton pump delivery to plasma membranes in the stomatal complex of Arabidopsis thaliana. VAEM real-time observation of guard cells and subsidiary cells in A. thaliana cotyledons showed that fluorescently-tagged PATROL1 appeared as dot-like structures on plasma membranes for several seconds and then disappeared. Kymograph analysis of VAEM movie data determined the time distribution of the presence (termed &#8216;residence time&#8217;) of the dot-like structures. The use of VAEM is discussed in the context of this example.

The goal of this protocol is to demonstrate how to monitor fluorescently-tagged protein dynamics on plant cell surfaces with variable-angle epifluorescence microscopy, showing blinking dots of GFP-tagged PATROL1, a membrane trafficking protein, in the cell cortex of the stomatal complex in Arabidopsis thaliana.

A plant&#8217;s cell surface is its interface for perceiving environmental cues; it responds with cell biological changes such as membrane trafficking and ...

Biological Sample Preparation by High-pressure Freezing, Microwave-assisted Contrast Enhancement, and Minimal Resin Embedding for Volume Imaging

The described sample preparation technique is designed to combine the best quality of ultrastructural preservation with the most suitable contrast for the imaging modality in a focused ion beam scanning electron microscope (FIB-SEM), which is used to obtain stacks of sequential images for 3D reconstruction and modelling. High-pressure freezing (HPF) allows close to native structural preservation, but the subsequent freeze substitution often does not provide sufficient contrast, especially for a bigger specimen, which is needed for high-quality imaging in the SEM required for 3D reconstruction. Therefore, in this protocol, after the freeze substitution, additional contrasting steps are carried out at room temperature. Although these steps are performed in a microwave, it is also possible to follow traditional bench processing, which requires longer incubation times.The subsequent embedding in minimal amounts of resin allows for faster and more precise targeting and preparation inside the FIB-SEM. This protocol is especially useful for samples that require preparation by high-pressure freezing for a reliable ultrastructural preservation but do not gain enough contrast during the freeze substitution for volume imaging using FIB-SEM. In combination with the minimal resin embedding, this protocol provides an efficient workflow for the acquisition of high-quality volume data.

Here we present a protocol for combining two sample processing techniques, high-pressure freezing and microwave-assisted sample processing, followed by minimal resin embedding for acquiring data with a focused ion beam scanning electron microscope (FIB-SEM). This is demonstrated using a mouse tibial nerve sample and Caenorhabditis elegans.

The described sample preparation technique is designed to combine the best quality of ultrastructural preservation with the most suitable contrast for the ...

Tethered Bilayer Lipid Membranes to Monitor Heat Transfer between Gold Nanoparticles and Lipid Membranes

Here we report a protocol to investigate the heat transfer between irradiated gold nanoparticles (GNPs) and bilayer lipid membranes by electrochemistry using tethered bilayer lipid membranes (tBLMs) assembled on gold electrodes. Irradiated modified GNPs, such as streptavidin-conjugated GNPs, are embedded in tBLMs containing target molecules, such as biotin. By using this approach, the heat transfer processes between irradiated GNPs and model bilayer lipid membrane with entities of interest are mediated by a horizontally focused laser beam. The thermal predictive computational model is used to confirm the electrochemically induced conductance changes in the tBLMs. Under the specific conditions used, detecting heat pulses required specific attachment of the gold nanoparticles to the membrane surface, while unbound gold nanoparticles failed to elicit a measurable response. This technique serves as a powerful detection biosensor which can be directly utilized for the design and development of strategies for thermal therapies that permits optimization of the laser parameters, particle size, particle coatings and composition.

This work outlines a protocol to achieve dynamic, non-invasive monitoring of heat transfer from laser-irradiated gold nanoparticles to tBLMs. The system combines impedance spectroscopy for the real-time measurement of conductance changes across the tBLMs, with a horizontally focused laser beam that drives gold nanoparticle illumination, for heat production.

Here we report a protocol to investigate the heat transfer between irradiated gold nanoparticles (GNPs) and bilayer lipid membranes by electrochemistry ...

Application of Passive Head Motion to Generate Defined Accelerations at the Heads of Rodents

Exercise is widely recognized as effective for various diseases and physical disorders, including those related to brain dysfunction. However, molecular mechanisms behind the beneficial effects of exercise are poorly understood. Many physical workouts, particularly those classified as aerobic exercises such as jogging and walking, produce impulsive forces at the time of foot contact with the ground. Therefore, it was speculated that mechanical impact might be implicated in how exercise contributes to organismal homeostasis. For testing this hypothesis on the brain, a custom-designed ''passive head motion'' (hereafter referred to as PHM) system was developed that can generate vertical accelerations with controlled and defined magnitudes and modes and reproduce mechanical stimulation that might be applied to the heads of rodents during treadmill running at moderate velocities, a typical intervention to test the effects of exercise in animals. By using this system, it was demonstrated that PHM recapitulates the serotonin (5-hydroxytryptamine, hereafter referred to as 5-HT) receptor subtype 2A (5-HT2A) signaling in the prefrontal cortex (PFC) neurons of mice. This work provides detailed protocols for applying PHM and measuring its resultant mechanical accelerations at rodents' heads.

The present protocol describes a custom-designed ''passive head motion'' system, which reproduces mechanical accelerations at rodents' heads generated during their treadmill running at moderate velocities. It allows dissecting mechanical factors/elements from the beneficial effects of physical exercise.

Exercise is widely recognized as effective for various diseases and physical disorders, including those related to brain dysfunction. However, molecular ...

Measurement of Liver Stiffness Using Atomic Force Microscopy Coupled with Polarization Microscopy

Matrix stiffening has been recognized as one of the key drivers of the progression of liver fibrosis. It has profound effects on various aspects of cell behavior such as cell function, differentiation, and motility. However, as these processes are not homogeneous throughout the whole organ, it has become increasingly important to understand changes in the mechanical properties of tissues on the cellular level.
To be able to monitor the stiffening of collagen-rich areas within the liver lobes, this paper presents a protocol for measuring liver tissue elastic moduli with high spatial precision by atomic force microscopy (AFM). AFM is a sensitive method with the potential to characterize local mechanical properties, calculated as Young&#39;s (also referred to as elastic) modulus. AFM coupled with polarization microscopy can be used to specifically locate the areas of fibrosis development based on the birefringence of collagen fibers in tissues. Using the presented protocol, we characterized the stiffness of collagen-rich areas from fibrotic mouse livers and corresponding areas in the livers of control mice.
A prominent increase in the stiffness of collagen-positive areas was observed with fibrosis development. The presented protocol allows for a highly reproducible method of AFM measurement, due to the use of mildly fixed liver tissue, that can be used to further the understanding of disease-initiated changes in local tissue mechanical properties and their effect on the fate of neighboring cells.

We present a protocol to measure the elastic moduli of collagen-rich areas in normal and diseased liver using atomic force microscopy. The simultaneous use of polarization microscopy provides high spatial precision for localizing collagen-rich areas in the liver sections.

Matrix stiffening has been recognized as one of the key drivers of the progression of liver fibrosis. It has profound effects on various aspects of cell ...

Fluorescence Lifetime Macro Imager for Biomedical Applications

This paper presents a new photoluminescence lifetime imager designed to map the molecular oxygen (O2) concentration in different phosphorescent samples ranging from solid-state, O2-sensitive coatings to live animal tissue samples stained with soluble O2-sensitive probes. In particular, the nanoparticle-based near-infrared probe NanO2-IR, which is excitable with a 625 nm light-emitting diode (LED) and emits at 760 nm, was used. The imaging system is based on the Timepix3 camera (Tpx3Cam) and the opto-mechanical adaptor, which also houses an image intensifier. O2 phosphorescence lifetime imaging microscopy (PLIM) is commonly required for various studies, but current platforms have limitations in their accuracy, general flexibility, and usability.
The system presented here is a fast and highly sensitive imager, which is built on an integrated optical sensor and readout chip module, Tpx3Cam. It is shown to produce high-intensity phosphorescence signals and stable lifetime values from surface-stained intestinal tissue samples or intraluminally stained fragments of the large intestine and allows the detailed mapping of tissue O2 levels in about 20 s or less. Initial experiments on the imaging of hypoxia in grafted tumors in unconscious animals are also presented. We also describe how the imager can be re-configured for use with O2-sensitive materials based on Pt-porphyrin dyes using a 390 nm LED for the excitation and a bandpass 650 nm filter for emission. Overall, the PLIM imager was found to produce accurate quantitative measurements of lifetime values for the probes used and respective two-dimensional maps of the O2 concentration. It is also useful for the metabolic imaging of ex vivo tissue models and live animals.

This paper describes the use of a new, fast optical imager for the macroscopic photoluminescence lifetime imaging of long decay emitting samples. The integration, image acquisition, and analysis procedures are described, along with the preparation and characterization of the sensor materials for the imaging and the application of the imager in studying biological samples.

This paper presents a new photoluminescence lifetime imager designed to map the molecular oxygen (O2) concentration in different phosphorescent samples ...

Imaging of Mitochondrial Peroxide in Living Yeast Cells Using mtHyper7

Imaging of mtHyPer7, a Ratiometric Biosensor for Mitochondrial Peroxide, in Living Yeast Cells

Mitochondrial dysfunction, or functional alteration, is found in many diseases and conditions, including neurodegenerative and musculoskeletal disorders, cancer, and normal aging. Here, an approach is described to assess mitochondrial function in living yeast cells at cellular and subcellular resolutions using a genetically encoded, minimally invasive, ratiometric biosensor. The biosensor, mitochondria-targeted HyPer7 (mtHyPer7), detects hydrogen peroxide (H2O2) in mitochondria. It consists of a mitochondrial signal sequence fused to a circularly permuted fluorescent protein and the H2O2-responsive domain of a bacterial OxyR protein. The biosensor is generated and integrated into the yeast genome using a CRISPR-Cas9 marker-free system, for&#160;more consistent expression compared to plasmid-borne constructs.
mtHyPer7 is quantitatively targeted to mitochondria, has no detectable effect on yeast growth rate or mitochondrial morphology, and provides a quantitative readout for mitochondrial H2O2 under normal growth conditions and upon exposure to oxidative stress. This protocol explains how to optimize imaging conditions using a spinning-disk confocal microscope system and perform quantitative analysis using freely available software. These tools make it possible to collect rich spatiotemporal information on mitochondria both within cells and among cells in a population. Moreover, the workflow described here can be used to validate other biosensors.

Author Spotlight: Advancing Mitochondrial Research - mtHyper7 Biosensor for Subcellular Analysis 

Hydrogen peroxide (H2O2) is both a source of oxidative damage and a signaling molecule. This protocol describes how to measure mitochondrial H2O2 using mitochondria-targeted HyPer7 (mtHyPer7), a genetically encoded ratiometric biosensor, in living yeast. It details how to optimize imaging conditions and perform quantitative cellular and subcellular analysis using freely available software.

Mitochondrial dysfunction, or functional alteration, is found in many diseases and conditions, including neurodegenerative and musculoskeletal disorders, ...