Name: in situ monitoring of transiently formed molecular chaperone assemblies in bacteria, yeast, and human cells
Uploaded: 2019-09-02T15:00:00
Description: Watch this Scientific Journal Video about In Situ Monitoring of Transiently Formed Molecular Chaperone Assemblies in Bacteria, Yeast, and Human Cells at JoVE.com

NBN is supported by a special Recruitment Grant from the Monash University Faculty of Medicine Nursing and Health Sciences with funding from the State Government of Victoria and the Australian Government. We thank Bernd Bukau (ZMBH, Heidelberg University, Germany) and Harm H. Kampinga (Department of Biomedical Sciences of Cells &#38; Systems, University of Groningen, The Netherlands) for their invaluable support and sharing of reagents, Holger Lorenz (ZMBH Imaging Facility, Heidelberg University, Germany) for his support with confocal microscopy and image processing, and Claire Hirst (ARMI, Monash University, Australia) for critical reading of the manuscript.

1. HeLa Cell Preparation
<ol>
	<li>Prepare the following materials: PBS (137 mM NaCl, 2.7 mM KCl, 10 mM Na2HPO4, 1.8 mM KH2PO4), pH 7.4; DMEM, supplemented with 10% FCS and 1% Pen-Strep; 4% paraformaldehyde in PBS; 0.5% Triton-X100 in PBS; TBS-T (150 mM NaCl, 20 mM Tris, 0.05% Tween), pH 7.4; 0.0001% sterile poly-L-Lysine solution; 10-well diagnostic slides; a humid chamber; tissue paper; and Coplin slide-staining jars. 
	NOTE: To ensure optimal fixation...

<ol>
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Co-immunoprecipitation and co-localization based approaches have been used as long-standing methods to characterize protein assembles. The detection of transiently formed specific chaperone complexes is a major challenge with such conventional methods, and as a result, previous findings are largely restricted to qualitative&#160; interpretations. The cell lysis-based co-immunoprecipitation techniques often require cross-linking to stabilize protein-protein interactions.&#160;Cell lysis increases the risk of disrupting tr...

A vast amount of genomic information remains uninterpretable due to our incomplete understanding of cellular interactomes. Conventional protein-protein interaction detection methodologies such as protein co-immunoprecipitation with/without chemical cross-linking and protein co-localization, though widely used, pose a range of disadvantages. Some&#160; of the main disadvantages include poor quantification of the interactions and the potential introduction of non-native binding events.&#160;In comparison, emerging proximity-based techniques provide an alternative and a powerful approach for capturing protein interactions in cells. The proximity ligation assay (PLA)1, now available as a proprietary kit, employs&#160;antibodies to specifically target protein complexes based on the proximity of the interacting subunits.
PLA is initiated by the&#160; formation of a scaffold consisting of primary and secondary antibodies with small DNA tags (PLA probes) on the surface of the targeted protein complex (Figure 1, steps 1-3). Next, determined by the proximity of the DNA tags, a circular DNA molecule is generated via hybridization with connector oligonucleotides (Figure 1, step 4). The formation of the circular DNA is completed by a DNA ligation step. The newly formed circular piece of DNA serves as a template for the subsequent&#160;rolling circle amplification (RCA)-based polymerase chain reaction (PCR) primed by one of the conjugated oligonucleotide tags. This generates a single-stranded concatemeric DNA-molecule attached to the protein complex via the antibody scaffold (Figure 1, step 6). The concatemeric DNA molecule is visualized using fluorescently labeled oligonucleotides that hybridize to multiple unique sequences scattered across the amplified DNA&#160;(Figure 1, step 7)2. The generated PLA signal, which appears as a fluorescent dot (Figure 1, step 7), corresponds to the location of the targeted protein complex in the cell. As a result, the assay could detect protein complexes with high spatial accuracy. The technique is not limited to simply capturing protein interactions, but could also be utilized to detect single molecules or protein modifications on proteins with high sensitivity1,2.
Hsp70 forms a highly versatile chaperone system fundamentally important for maintaining cellular protein homeostasis by participating in an array of&#160;housekeeping and stress-associated functions. Housekeeping activities of the Hsp70 chaperone system include&#160;de novo protein folding, protein translocation across cellular membranes, assembly and disassembly of protein complexes, regulation of protein activity and linking different protein folding/quality control machineries3. The same chaperone system also refolds misfolded/unfolded proteins, prevents protein aggregation, promotes protein disaggregation and cooperates with cellular proteases to degrade terminally misfolded/damaged proteins to facilitate cellular repair after proteotoxic stresses4,5. To achieve this functional diversity, the Hsp70 chaperone relies on partnering co-chaperones of the JDP family and nucleotide exchange factors (NEFs) that fine-tune the Hsp70&#8217;s ATP-dependent allosteric control of substrate binding and release3,6. Further, the JDP co-chaperones play a vital role in&#160;selecting&#160;substrates for&#160;this versatile chaperone system.&#160;Members of this family are subdivided into three classes (A, B and C) based on their structural homology to the prototype JDP, the E. coli DnaJ. Class A JDPs contain an N-terminal J-domain, which interacts with Hsp70, a glycine-phenylalanine rich region, a substrate binding region consisting of a Zinc finger-like region (ZFLR) and two &#946;-barrel domains, and a C-terminal dimerization domain. JDPs with an N-terminal J-domain and a glycine-phenylalanine rich region, but lacking the ZFLR, fall into class B. In general, members of these two classes are&#160;involved in chaperoning functions. Members falling under the catchall class C, which contains JDPs that only share the J-domain4, recruit Hsp70s to perform a variety of non-chaperoning functions. The important role of JDPs as interchangeable substrate recognition &#8220;adaptors&#8221; of the Hsp70 system is reflected by an expansion of the family members during evolution. For example, humans have over 42 distinct JDP members4. These JDPs function as monomers, homodimers and/or homo/hetero oligomers4,5. Recently, a functional cooperation via transient complex formation between class A (e.g., H. sapiens&#160;DNAJA2; S. cerevisiae Ydj1) and class B (e.g., H. sapiens DNAJB1; S. cerevisiae Sis1) eukaryotic JDPs was reported to promote efficient recognition of amorphous protein aggregates in vitro7,8. These mixed class JDP complexes presumably assemble on the surface of aggregated proteins to facilitate the formation of Hsp70- and Hsp70+Hsp100-based protein disaggregases7,8,9,10. The critical evidence to support the existence of these transiently formed mixed class JDP complexes in eukaryotic cells was provided with PLA8.
PLA is increasingly employed for assessing protein interactions in metazoa, primarily in mammalian cells. Here, we report the successful expansion of this&#160;technique to monitor transiently formed chaperone complexes in eukaryotic and prokaryotic unicellular organisms such as the budding yeast S. cerevisiae and the bacterium E. coli.&#160;Importantly, this expansion highlights the potential use of PLA in detecting and analyzing microbes that infect human and animal cells.

<table>
	<tbody>
		<tr>
			<td>37% Formaldehyde</td>
			<td>Merck</td>
			<td>103999</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Sigma-Aldrich</td>
			<td>32201</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-DNAJA2 antibody</td>
			<td>Abcam</td>
			<td>ab157216</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-DNAJB1 Antibody</td>
			<td>Enzo Life Sciences</td>
			<td>ADI-SPA-450</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-DnaK antibody</td>
			<td>In house</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>anti-mCherry antibody</td>
			<td>Abcam</td>
			<td>ab125096</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-Sis1 Antibody</td>
			<td>Cosmo Bio Corp</td>
			<td>COP-080051</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-Ydj1 antibody</td>
			<td>StressMarq Biosciences</td>
			<td>&#160;SMC-150,</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-YFP antibody</td>
			<td>In house</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Coplin slide-staining jar</td>
			<td>Sigma-Aldrich</td>
			<td>S5516</td>
			<td></td>
		</tr>
		<tr>
			<td>Diagnostic slides</td>
			<td>Marienfeld</td>
			<td>1216530</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Thermo-Fischer</td>
			<td>31966021</td>
			<td></td>
		</tr>
		<tr>
			<td>DuoLink In Situ Detection Reagents Orange</td>
			<td>Sigma-Aldrich</td>
			<td>DUO92007</td>
			<td></td>
		</tr>
		<tr>
			<td>DuoLink In Situ Mounting Medium + DAPI</td>
			<td>Sigma-Aldrich</td>
			<td>DUO82040</td>
			<td></td>
		</tr>
		<tr>
			<td>DuoLink In Situ PLA Probe Anti-Mouse MINUS</td>
			<td>Sigma-Aldrich</td>
			<td>DUO92004</td>
			<td></td>
		</tr>
		<tr>
			<td>DuoLink In Situ PLA Probe Anti-Rabbit PLUS</td>
			<td>Sigma-Aldrich</td>
			<td>DUO92002</td>
			<td></td>
		</tr>
		<tr>
			<td>DuoLink In Situ Wash Buffers, Fluorescence</td>
			<td>Sigma-Aldrich</td>
			<td>DUO82049</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Calf Serum</td>
			<td>Thermo-Fischer</td>
			<td>10082147</td>
			<td></td>
		</tr>
		<tr>
			<td>Lysozyme</td>
			<td>Sigma-Aldrich</td>
			<td>62971</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Sigma-Aldrich</td>
			<td>32213</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>P6148</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>Thermo-Fischer</td>
			<td>15070063</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly-L-Lysine</td>
			<td>Sigma-Aldrich</td>
			<td>P47-07</td>
			<td></td>
		</tr>
		<tr>
			<td>Sorbitol</td>
			<td>Sigma-Aldrich</td>
			<td>S7547</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton-X100</td>
			<td>Merck</td>
			<td>108643</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin</td>
			<td>Thermo-Fischer</td>
			<td>25300096</td>
			<td></td>
		</tr>
		<tr>
			<td>Tween-20</td>
			<td>Sigma-Aldrich</td>
			<td>P1379</td>
			<td></td>
		</tr>
		<tr>
			<td>Zymolase 100T / / Lyticase</td>
			<td>United States Biological</td>
			<td>Z1004</td>
			<td></td>
		</tr>
	</tbody>
</table>

in situ monitoring of transiently formed molecular chaperone assemblies in bacteria, yeast, and human cells

J-domain proteins (JDPs) form the largest and the most diverse co-chaperone family in eukaryotic cells. Recent findings show that specific members of the JDP family could form transient heterocomplexes in eukaryotes to fine-tune substrate selection for the 70 kDa heat shock protein (Hsp70) chaperone-based protein disaggregases. The JDP complexes target acute/chronic stress induced aggregated proteins and presumably help assemble the disaggregases by recruiting multiple Hsp70s to the surface of protein aggregates. The extent of the protein quality control (PQC) network formed by these physically interacting JDPs remains largely uncharacterized in vivo. Here, we describe a microscopy-based in situ protein interaction assay named the proximity ligation assay (PLA), which is able to robustly capture&#160;these transiently formed chaperone complexes in distinct cellular compartments of eukaryotic cells. Our work expands the employment of PLA from human cells to yeast (Saccharomyces cerevisiae) and bacteria (Escherichia coli), thus rendering an important tool to monitor the dynamics of transiently formed protein assemblies in both prokaryotic and eukaryotic cells.

Our previous in vitro studies using purified proteins revealed that a subset of human class A and class B JDPs form transient mixed class JDP complexes to efficiently target a broad range of aggregated proteins and possibly facilitate the assembly of Hsp70-based protein disaggregases7. We employed PLA to determine whether mixed class (A+B) JDP complexes occur in&#160;human cervical cancer cells (HeLa). Human JDPs DNAJA2 (class A) and DNAJB1 (class B) were targeted with highly specific primary anti...

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In Situ Monitoring of Transiently Formed Molecular Chaperone Assemblies in Bacteria, Yeast, and Human Cells

Cognate J-domain proteins cooperate with the Hsp70 chaperone to assist in a myriad of biological processes ranging from protein folding to degradation. Here, we describe an in situ proximity ligation assay, which allows the monitoring of these transiently formed chaperone machineries in bacterial, yeast and human cells.

J-domain proteins (JDPs) form the largest and the most diverse co-chaperone family in eukaryotic cells. Recent findings show that specific members of the ...

This method captures transient protein interactions in organisms like bacteria and yeast and in different cell types. Here we monitor transiently formed specific chaperone complexes that are involved in cellular proteostasis. The main advantage of this technique is the ability to generate information on dynamics and sub-cellular localization of protein assemblies in prokaryotic and eukaryotic cells.Adaptations of this technique in unicellular organisms like bacteria and yeast, allows researchers to use it as a powerful tool to investigate diseases related to microbial infections. This technique could potentially be employed to analyze protein interactions in almost all organisms by simply changing the conditions at the sample preparation phase of the protocol. It is important to select good quality antibodies that are specific and tested in either immunohistochemistry, immunofluorescence, ELISA, or immunoprecipitations.Begin by pre-treating 10-well diagnostic slides with poly-L-Lysine. Add 100 microliters of sterile and filtered 0.0001%poly-L-Lysine to each well, and incubate the slides for 30 minutes in a sterile laminar flow hood. Then, wash each well with 50 microliters of sterile water to remove excess poly-L-Lysine.Add approximately 15, 000 cells per well depending on the cell type, and grow the cells in a sterile humid incubator at 37 degrees Celsius with 5%carbon dioxide to a 60 to 80%confluency. After 24 hours, remove the growth medium by placing a tissue paper at the edge of each well, and wash the cells three times with 50 microliters of PBS. Then fix the cells by adding 50 microliters of freshly prepared 4%paraformaldehyde in PBS to each well and incubating the slide at room temperature for 10 minutes.After fixation, wash the slide three times by submerging the slide in a slide-staining jar with PBS. To permeabilize the membranes of the attached cells, submerge the slide in 100 milliliters of 0.5%Triton-X100 in PBS, and incubate the cells for 10 minutes at room temperature. Then wash the slides three times in TBS-T.After the last wash, remove excess buffer with a tissue paper. Grow and dilute S.cerevisiae cells according to manuscript directions, then transfer them to a 50-milliliter centrifuge tube and pellet by centrifugation at 665 times g for three minutes. Remove the supernatant and resuspend the cells in five milliliters of fresh medium.Then add 550 microliters of 37%formaldehyde for a final concentration of 4%and incubate the culture at room temperature for 15 minutes to fix the cells. After the incubation, pellet the cells, remove the supernatant, and resuspend the pellet in one milliliter of freshly prepared 4%paraformaldehyde in wash buffer. Incubate the cells at room temperature for 45 minutes.Meanwhile, prepare the diagnostic slides by adding 100 microliters of 0.0001%poly-L-Lysine solution to each well and incubating the slides for 30 minutes at room temperature. Then wash away the excess poly-L-Lysine with ultrapure water and let the slides air-dry. After the incubation step, wash the cells twice with one milliliter of wash buffer by centrifugation.Remove the supernatant and resuspend the cells in wash buffer. Pellet the cells after the last wash, and remove the supernatant and resuspend the cells in one milliliter of wash buffer containing 1.2 molar sorbitol. To digest the cell wall, pellet the cells again and resuspend the cells in 250 microliters of freshly prepared Lyticase solution.Incubate the cells at 30 degrees Celsius for 15 minutes with gentle shaking. After the digestion step, wash the cells three times in wash buffer and resuspend the cells in 250 microliters of wash buffer containing 1.2 molar sorbitol. Add 20 microliters of re-suspended cells to each poly-L-Lysine-coated well, and allow the fixed and permeabilized cells to attach for 30 minutes.Wash the wells three times with 50 microliters of wash buffer to remove non-adherent cells, and proceed with the proximity ligation assay. Initiate the proximity ligation assay, or PLA protocol, by adding a drop of the blocking buffer to each well and incubate the slide in a humid chamber for 30 minutes at 37 degrees Celsius. Remove the blocking buffer by placing a tissue paper at the edge of each well, and wash the cells twice in 100 milliliters of wash buffer A.Next, add 40 microliters of the primary antibody solution to each well, and incubate the slide for 60 minutes at 37 degrees Celsius in a humid chamber.Remove the primary antibody solution and wash the slides twice in wash buffer A.After the wash, add 40 microliters of the secondary antibody solution to each well and incubate the slide for 60 minutes at 37 degrees Celsius in a humid chamber. Then remove the solution and wash the slides twice in wash buffer A.Then add 40 microliters of the DNA ligation mixture which contains the connector oligonucleotides and DNA ligase, to each well, and incubate the slide in the humid chamber at 37 degrees Celsius for 30 minutes. After incubation, remove the ligation mixture and wash the slides twice with wash buffer A.Add 40 microliters of DNA amplification mixture which contains the DNA polymerase and the fluorescently labeled oligonucleotides to each well, and incubate for 100 minutes in the humid chamber at 37 degrees Celsius.Remove the amplification mixture and wash the slides in 100 milliliters of wash buffer B for 10 minutes per wash. Then wash the slides in 100 milliliters of wash buffer B diluted one to 100 in ultrapure water. Add 20 microliters of DAPI-containing mounting medium per well.Cover the wells of the slide with a cover slip and seal with nail polish. This protocol was successfully used to monitor transient chaperone assemblies formed between distinct J-domain proteins and Hsp70 chaperone and J-domain proteins in HeLa, S.cerevisiae, and E.coli cells. Human class A and class B J-domain proteins were targeted with highly specific primary antibodies.Each of the red fluorescent puncti represents a protein complex formed between two distinct J-domain proteins in HeLa cells. Similar mixed-class J-domain protein complexes are also observed in the unicellular eukaryote S.cerevisiae, or baker's yeast. Some of the fluorescent puncti generated from PLA were more difficult to resolve as individual foci, due to the small cell size.Complex formation between class A and B J-domain proteins were not observed in E.coli cells, which is consistent with biochemical studies performed with purified proteins. But other chaperone assemblies involving J-domain proteins and the Hsp70 chaperone were captured using the PLA protocol. Technical controls lacking a primary antibody against one of the interacting J-domain proteins or chaperones in the otherwise complete PLA reactions showed little or no fluorescence puncti formation in the cells, indicating a lack of false positive signal amplification.To obtain reliable results using the proximity ligation assay, verify beforehand that the antibodies used are of sufficient quality. Furthermore, take precaution in avoiding over-digestion of cells containing a cell wall.

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Research

JoVE Journal

Biology

Using Whole Mount in situ Hybridization to Link Molecular and Organismal Biology

Whole mount in situ hybridization (WISH) is a common technique in molecular biology laboratories used to study gene expression through the localization of specific mRNA transcripts within whole mount specimen. This technique (adapted from Albertson and Yelick, 2005) was used in an upper level undergraduate Comparative Vertebrate Biology laboratory classroom at Syracuse University. The first two thirds of the Comparative Vertebrate Biology lab course gave students the opportunity to study the embryology and gross anatomy of several organisms representing various chordate taxa primarily via traditional dissections and the use of models. The final portion of the course involved an innovative approach to teaching anatomy through observation of vertebrate development employing molecular techniques in which WISH was performed on zebrafish embryos. A heterozygous fibroblast growth factor 8 a (fgf8a) mutant line, ace, was used. Due to Mendelian inheritance, ace intercrosses produced wild type, heterozygous, and homozygous ace/fgf8a mutants in a 1:2:1 ratio. RNA probes with known expression patterns in the midline and in developing anatomical structures such as the heart, somites, tailbud, myotome, and brain were used. WISH was performed using zebrafish at the 13 somite and prim-6 stages, with students performing the staining reaction in class. The study of zebrafish embryos at different stages of development gave students the ability to observe how these anatomical structures changed over ontogeny. In addition, some ace/fgf8a mutants displayed improper heart looping, and defects in somite and brain development. The students in this lab observed the normal development of various organ systems using both external anatomy as well as gene expression patterns. They also identified and described embryos displaying improper anatomical development and gene expression (i.e., putative mutants).
For instructors at institutions that do not already own the necessary equipment or where funds for lab and curricular innovation are limited, the financial cost of the reagents and apparatus may be a factor to consider, as will the time and effort required on the part of the instructor regardless of the setting. Nevertheless, we contend that the use of WISH in this type of classroom laboratory setting can provide an important link between developmental genetics and anatomy. As technology advances and the ability to study organismal development at the molecular level becomes easier, cheaper, and increasingly popular, many evolutionary biologists, ecologists, and physiologists are turning to research strategies in the field of molecular biology. Using WISH in a Comparative Vertebrate Biology laboratory classroom is one example of how molecules and anatomy can converge within a single course. This gives upper level college students the opportunity to practice modern biological research techniques, leading to a more diversified education and the promotion of future interdisciplinary scientific research.

Using Whole Mount in situ Hybridization to Link Molecular and Organismal Biology

Whole mount in situ hybridization (WISH) was used in an upper level undergraduate Comparative Vertebrate Biology course in addition to vertebrate dissections. This gave students the opportunity to study gene expression patterns as well as gross anatomy, linking the study of molecular and organismal biology within one course.

Whole mount in situ hybridization (WISH) is a common technique in molecular biology laboratories used to study gene expression through the localization of ...

A Fluorescence Microscopy Assay for Monitoring Mitophagy in the Yeast Saccharomyces cerevisiae

Autophagy is important for turnover of cellular components under a range of different conditions. It serves an essential homeostatic function as well as a quality control mechanism that can target and selectively degrade cellular material including organelles1-4. For example, damaged or redundant mitochondria (Fig. 1), not disposed of by autophagy, can represent a threat to cellular homeostasis and cell survival. In the yeast, Saccharomyces cerevisiae, nutrient deprivation (e.g., nitrogen starvation) or damage can promote selective turnover of mitochondria by autophagy in a process termed mitophagy 5-9.
We describe a simple fluorescence microscopy approach to assess autophagy. For clarity we restrict our description here to show how the approach can be used to monitor mitophagy in yeast cells. The assay makes use of a fluorescent reporter, Rosella, which is a dual-emission biosensor comprising a relatively pH-stable red fluorescent protein linked to a pH-sensitive green fluorescent protein. The operation of this reporter relies on differences in pH between the vacuole (pH ~ 5.0-5.5) and mitochondria (pH ~ 8.2) in living cells. Under growing conditions, wild type cells exhibit both red and green fluorescence distributed in a manner characteristic of the mitochondria. Fluorescence emission is not associated with the vacuole. When subjected to nitrogen starvation, a condition which induces mitophagy, in addition to red and green fluorescence labeling the mitochondria, cells exhibit the accumulation of red, but not green fluorescence, in the acidic vacuolar lumen representing the delivery of mitochondria to the vacuole. Scoring cells with red, but not green fluorescent vacuoles can be used as a measure of mitophagic activity in cells5,10-12.

A Fluorescence Microscopy Assay for Monitoring Mitophagy in the Yeast Saccharomyces cerevisiae

A robust approach to monitor the delivery of organelles to the acidic lumen of the yeast vacuole for degradation and recycling is described. The method relies on the specific labeling of target organelles with a genetically encoded dual-emission fluorescence pH-biosensor, and visualization of individual cells using fluorescence microscopy.

Autophagy is important for turnover of cellular components under a range of different conditions. It serves an essential homeostatic function as well as a ...

Long-term Lethal Toxicity Test with the Crustacean Artemia franciscana

Our research activities target the use of biological methods for the evaluation of environmental quality, with particular reference to saltwater/brackish water and sediment. The choice of biological indicators must be based on reliable scientific knowledge and, possibly, on the availability of standardized procedures. In this article, we present a standardized protocol that used the marine crustacean Artemia to evaluate the toxicity of chemicals and/or of marine environmental matrices. Scientists propose that the brine shrimp (Artemia) is a suitable candidate for the development of a standard bioassay for worldwide utilization. A number of papers have been published on the toxic effects of various chemicals and toxicants on brine shrimp (Artemia). The major advantage of this crustacean for toxicity studies is the overall availability of the dry cysts; these can be immediately used in testing and difficult cultivation is not demanded1,2. Cyst-based toxicity assays are cheap, continuously available, simple and reliable and are thus an important answer to routine needs of toxicity screening, for industrial monitoring requirements or for regulatory purposes3. The proposed method involves the mortality as an endpoint. The numbers of survivors were counted and percentage of deaths were calculated. Larvae were considered dead if they did not exhibit any internal or external movement during several seconds of observation4. This procedure was standardized testing a reference substance (Sodium Dodecyl Sulfate); some results are reported in this work. This article accompanies a video that describes the performance of procedural toxicity testing, showing all the steps related to the protocol.

Long-term Lethal Toxicity Test with the Crustacean Artemia franciscana

This study concerns the development and standardization of a valuable methodological protocol to determine long-term (14 days) lethal toxicity exerted by chemical substances, industrial wastewater or sewage and liquid environmental samples on the saltwater crustacean, Artemia franciscana.

Our research activities target the use of biological methods for the evaluation of environmental quality, with particular reference to saltwater/brackish ...

Reprogramming Human Somatic Cells into Induced Pluripotent Stem Cells (iPSCs) Using Retroviral Vector with GFP

Human embryonic stem cells (hESCs) are pluripotent and an invaluable cellular sources for in vitro disease modeling and regenerative medicine1. It has been previously shown that human somatic cells can be reprogrammed to pluripotency by ectopic expression of four transcription factors (Oct4, Sox2, Klf4 and Myc) and become induced pluripotent stem cells (iPSCs)2-4 . Like hESCs, human iPSCs are pluripotent and a potential source for autologous cells. Here we describe the protocol to reprogram human fibroblast cells with the four reprogramming factors cloned into GFP-containing retroviral backbone4. Using the following protocol, we generate human iPSCs in 3-4 weeks under human ESC culture condition. Human iPSC colonies closely resemble hESCs in morphology and display the loss of GFP fluorescence as a result of retroviral transgene silencing. iPSC colonies isolated mechanically under a fluorescence microscope behave in a similar fashion as hESCs. In these cells, we detect the expression of multiple pluripotency genes and surface markers.

Reprogramming Human Somatic Cells into Induced Pluripotent Stem Cells iPSCs Using Retroviral Vector with GFP

A method to generate human induced pluripotent stem cells (iPSCs) via retrovirus-mediated ectopic expression of OCT4, SOX2, KLF4 and MYC is described. A practical way to identify human iPSC colonies based on GFP expression is also discussed.

Human embryonic stem cells (hESCs) are pluripotent and an invaluable cellular sources for in vitro disease modeling and regenerative medicine1. It has ...

Measurement of Vacuolar and Cytosolic pH In Vivo in Yeast Cell Suspensions

Vacuolar and cytosolic pH are highly regulated in yeast cells and occupy a central role in overall pH homeostasis. We describe protocols for ratiometric measurement of pH in vivo using pH-sensitive fluorophores localized to the vacuole or cytosol. Vacuolar pH is measured using BCECF, which localizes to the vacuole in yeast when introduced into cells in its acetoxymethyl ester form. Cytosolic pH is measured with a pH-sensitive GFP expressed under control of a yeast promoter, yeast pHluorin. Methods for measurement of fluorescence ratios in yeast cell suspensions in a fluorimeter are described. Through these protocols, single time point measurements of pH under different conditions or in different yeast mutants have been compared and changes in pH over time have been monitored. These methods have also been adapted to a fluorescence plate reader format for high-throughput experiments. Advantages of ratiometric pH measurements over other approaches currently in use, potential experimental problems and solutions, and prospects for future use of these techniques are also described.

Measurement of Vacuolar and Cytosolic pH In Vivo in Yeast Cell Suspensions

Vacuolar and cytosolic pH can be measured in live yeast (S. cerevisiae) cells using ratiometric fluorescent dyes localized to specific cellular compartments. We describe procedures for measuring vacuolar pH with BCECF-AM, which localizes to the vacuole in yeast, and cytosolic pH with a cytosolic ratiometric pH-sensitive GFP (yeast pHluorin).

Vacuolar and  cytosolic pH are highly regulated in yeast cells and occupy a central role in  overall pH homeostasis. We describe  protocols for ...

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 ...

Efficient Generation Human Induced Pluripotent Stem Cells from Human Somatic Cells with Sendai-virus

A few years ago, the establishment of human induced pluripotent stem cells (iPSCs) ushered in a new era in biomedicine. Potential uses of human iPSCs include modeling pathogenesis of human genetic diseases, autologous cell therapy after gene correction, and personalized drug screening by providing a source of patient-specific and symptom relevant cells. However, there are several hurdles to overcome, such as eliminating the remaining reprogramming factor transgene expression after human iPSCs production. More importantly, residual transgene expression in undifferentiated human iPSCs could hamper proper differentiations and misguide the interpretation of disease-relevant in vitro phenotypes. With this reason, integration-free and/or transgene-free human iPSCs have been developed using several methods, such as adenovirus, the piggyBac system, minicircle vector, episomal vectors, direct protein delivery and synthesized mRNA. However, efficiency of reprogramming using integration-free methods is quite low in most cases.
Here, we present a method to isolate human iPSCs by using Sendai-virus (RNA virus) based reprogramming system. This reprogramming method shows consistent results and high efficiency in cost-effective manner.

Here, we present our established method to reprogram human somatic cells into transgene-free human iPSCs with Sendai virus, which shows consistent outcome and enhanced efficiency.

A few years ago, the establishment of human induced pluripotent stem cells (iPSCs) ushered in a new era in biomedicine. Potential uses of human iPSCs ...

Profiling Individual Human Embryonic Stem Cells by Quantitative RT-PCR

Heterogeneity of stem cell population hampers detailed understanding of stem cell biology, such as their differentiation propensity toward different lineages. A single cell transcriptome assay can be a new approach for dissecting individual variation. We have developed the single cell qRT-PCR method, and confirmed that this method works well in several gene expression profiles. In single cell level, each human embryonic stem cell, sorted by OCT4::EGFP positive cells, has high expression in OCT4, but a different level of NANOG expression. Our single cell gene expression assay should be useful to interrogate population heterogeneities.

Single cell gene expression assay is needed for understanding stem cell heterogeneities.

Heterogeneity of stem cell population hampers detailed understanding of stem cell biology, such as their differentiation propensity toward different ...

A Graphical User Interface for Software-assisted Tracking of Protein Concentration in Dynamic Cellular Protrusions

Filopodia are dynamic, finger-like cellular protrusions associated with migration and cell-cell communication. In order to better understand the complex signaling mechanisms underlying filopodial initiation, elongation and subsequent stabilization or retraction, it is crucial to determine the spatio-temporal protein activity in these dynamic structures. To analyze protein function in filopodia, we recently developed a semi-automated tracking algorithm that adapts to filopodial shape-changes, thus allowing parallel analysis of protrusion dynamics and relative protein concentration along the whole filopodial length. Here, we present a detailed step-by-step protocol for optimized cell handling, image acquisition and software analysis. We further provide instructions for the use of optional features during image analysis and data representation, as well as troubleshooting guidelines for all critical steps along the way. Finally, we also include a comparison of the described image analysis software with other programs available for filopodia quantification. Together, the presented protocol provides a framework for accurate analysis of protein dynamics in filopodial protrusions using image analysis software.

We present a software solution for semi-automated tracking of relative protein concentration along the length of dynamic cellular protrusions.

Filopodia are dynamic, finger-like cellular protrusions associated with migration and cell-cell communication. In order to better understand the complex ...

A Simple Fluorescence-based Reporter Assay to Identify Cellular Components Required for Ricin Toxin A Chain (RTA) Trafficking in Yeast

Bacterial and plant A/B toxins exploit the natural trafficking pathways in eukaryotic cells to reach their intracellular target(s) in the cytosol and to ultimately kill. Such A/B toxins generally consist of an enzymatically active Asubunit (e.g., ricin toxin A (RTA)) and one or more cell binding Bsubunit(s), which are responsible for toxin binding to specific cell surface receptors. Our current knowledge of how A/B toxins are capable of efficiently intoxicating cells helped scientists to understand fundamental cellular mechanisms, like endocytosis and intracellular protein sorting in higher eukaryotic cells. From a medical point of view, it is likewise important to identify the major toxin trafficking routes to find adequate treatment solutions for patients or to eventually develop therapeutic toxin-based applications for cancer therapy.
Since genome-wide analyses of A/B toxin trafficking in mammalian cells is complex, time-consuming, and expensive, several studies on A/B toxin transport have been performed in the yeast model organism Saccharomyces cerevisiae. Despite being less complex, fundamental cellular processes in yeast and higher eukaryotic cells are similar and very often results obtained in yeast can be transferred to the mammalian situation.
Here, we describe a fast and easy to use reporter assay to analyze the intracellular trafficking of RTA in yeast. An essential advantage of the new assay is the opportunity to investigate not only RTA retro-translocation from the endoplasmic reticulum (ER) into the cytosol, but rather endocytosis and retrograde toxin transport from the plasma membrane into the ER. The assay makes use of a reporter plasmid that allows indirect measurement of RTA toxicity through fluorescence emission of the green fluorescent protein (GFP) after in vivo translation. Since RTA efficiently prevents the initiation of protein biosynthesis by 28S rRNA depurination, this assay allows the identification of host cell proteins involved in intracellular RTA transport through the detection of changes in fluorescence emission.

A Simple Fluorescence-based Reporter Assay to Identify Cellular Components Required for Ricin Toxin A Chain RTA Trafficking in Yeast

In the manuscript, we describe the use of a yeast-based fluorescence reporter assay to identify cellular components involved in the trafficking and killing processes of the cytotoxic A subunit of the plant toxin ricin (RTA).

Bacterial and plant A/B toxins exploit the natural trafficking pathways in eukaryotic cells to reach their intracellular target(s) in the cytosol and to ...