Name: assay development for high content quantification of sod1 mutant protein aggregate formation in living cells
Uploaded: 2017-10-04T12:15:00
Description: Watch this Scientific Journal Video about Assay Development for High Content Quantification of Sod1 Mutant Protein Aggregate Formation in Living Cells at JoVE.com

This work was supported by a grant funded by the Korean government (MSIP) (NRF-2014K1A4A7A01074642), and the National Research Foundation of Korea (NRF) individual scientist support program (NRF-2013M3A9B5076486/NRF-2015R1D1A1A09057239).

1. Lentivirus production
NOTE: The production and manipulation of lentiviral vectors was carried out according to the National Institutes of Health (NIH) guidelines for research involving recombinant DNA. The plasmid encoding the wild-type and A4V mutant SOD1 tagged with enhanced YFP (SOD1WT-YFP and SOD1A4V-YFP) are described in Kim et al.11 Both gene fusion products were amplified using the PCR primer pair 5&#8242;-ATCGTCTAGACACCATGGCGACGAAGGTCGTGTGC-3&#8242; an...

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I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disulfide+bond+mediates+aggregation,+toxicity,+and+ubiquitylation+of+familial+amyotrophic+lateral+sclerosis-linked+mutant+SOD1.">Disulfide bond mediates aggregation, toxicity, and ubiquitylation of familial amyotrophic lateral sclerosis-linked mutant SOD1.</a> J Biol Chem. 282 (38), 28087-28095 (2007).</li><li>Juneja, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prognosis+in+familial+amyotrophic+lateral+sclerosis:+progression+and+survival+in+patients+with+glu100gly+and+ala4val+mutations+in+Cu,Zn+superoxide+dismutase.">Prognosis in familial amyotrophic lateral sclerosis: progression and survival in patients with glu100gly and ala4val mutations in Cu,Zn superoxide dismutase.</a> Neurology. 48 (1), 55-57 (1997).</li><li>Kaur, S. 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R., Rashid, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mutant+SOD1+mediated+pathogenesis+of+Amyotrophic+Lateral+Sclerosis.">Mutant SOD1 mediated pathogenesis of Amyotrophic Lateral Sclerosis.</a> Gene. 577 (2), 109-118 (2016).</li><li>de Bruyns, A., Geiling, B., Dankort, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Construction+of+Modular+Lentiviral+Vectors+for+Effective+Gene+Expression+and+Knockdown.">Construction of Modular Lentiviral Vectors for Effective Gene Expression and Knockdown.</a> Methods Mol Biol. 1448, 3-21 (2016).</li><li>Sirven, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+Transgene+Expression+in+Cord+Blood+CD34+-Derived+Hematopoietic+Cells,+Including+Developing+T+Cells+and+NOD/SCID+Mouse+Repopulating+Cells,+Following+Transduction+with+Modified+TRIP+Lentiviral+Vectors.">Enhanced Transgene Expression in Cord Blood CD34+-Derived Hematopoietic Cells, Including Developing T Cells and NOD/SCID Mouse Repopulating Cells, Following Transduction with Modified TRIP Lentiviral Vectors.</a> Mol Ther. 3 (4), 438-448 (2001).</li><li>Wu, C., Lu, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-titre+retroviral+vector+system+for+efficient+gene+delivery+into+human+and+mouse+cells+of+haematopoietic+and+lymphocytic+lineages.">High-titre retroviral vector system for efficient gene delivery into human and mouse cells of haematopoietic and lymphocytic lineages.</a> J gen virol. 91 (Pt 8), 1909-1918 (2010).</li><li>Irshad, H., Veillard, A., Roux, L., Racoceanu, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+for+nuclei+detection,+segmentation,+and+classification+in+digital+histopathology:+A+review-current+status+and+future+potential.">Methods for nuclei detection, segmentation, and classification in digital histopathology: A review-current status and future potential.</a> IEEE Rev Biomed Eng. 7, 97-114 (2014).</li><li>Purschke, M., Rubio, N., Held, K. 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There are two main approaches for generating stable cell lines. The first takes several weeks and requires transient transfection and resistance selection of the genomic integrated plasmid DNA vectors. The second takes a matter of hours through the use of lentivirus, making this protocol amenable to the effective expression of target protein in multiple cell lines with limited effort. The TRIP-CMV vector19 was a sustained vector to use, with conserved transduction efficiency and stable transgene e...

Protein aggregation is a biological process by which misfolded proteins group up and may act as causative agents in neurodegenerative diseases (amyloidosis). Characterizing protein aggregation is essential in understanding the role of aggregates in cellular dysfunction as well as in facilitating the discovery of new factors that influence the onset of the pathology. The visualization of fluorescence-tagged proteins in living cells is a powerful method which may aid in the development of assays applicable to high content screening (HCS)1,2,3,4.
Amyotrophic lateral sclerosis (ALS) is regarded as a proteopathic disease caused by the presence of misfolded proteins with the propensity to aggregate and accumulate in motor neurons in both familial ALS (fALS) and sporadic ALS (sALS)5,6. A subset of ~20% of fALS cases are associated with dominant mutations in the gene encoding the cytosolic antioxidant enzyme copper-zinc superoxide dismutase type 1 (SOD1)7,8. Several potential causes for this genetically derived dysfunction have been proposed, including changes in the structure and function of SOD1 variants, such as aberrant stability, increased unfolding rate, and propensity to aggregate9,10. Notably, the only verified and potentially toxic property shared by both ALS-linked SOD1 variants and wild-type (WT) SOD1 is an increased propensity to form compartmentalized protein aggregates or proteinaceous inclusions11,12. Misfolded mutant SOD1, is persistently polyubiquitinated and degraded by the ubiquitin-proteasome system. As a result, a low level of inhibition of proteasome activity leads to the accumulation of mutant SOD1 aggregates13,14, which form amorphous structures composed of soluble components that can exchange with soluble mutant SOD1 in the cytosol15. In particular, SOD1 mutant A4V (alanine at codon 4 changed to valine) is the most common ALS-causing mutation, and leads to rapid neurodegeneration with an average survival time of less than 2 years after disease onset16. Biochemically, SOD1 A4V has an increased tendency to monomerize, aggregate, and form amyloid pores; its pore-like aggregates are similar to amyloid pores of other disease-linked mutant forms, such as &#945;-synuclein and &#946;-amyloid protein17. To study the dynamics of SOD1-aggregate accumulation, methods for monitoring soluble and insoluble SOD1 aggregate forms remain to be developed.
We have previously shown, using live-cell imaging and HEK-293 cells transiently transfected with fluorescent protein-tagged SOD1, that ALS-associated mutations impair SOD1 dimerization and aggregation11. Although transient expression systems can provide useful information about the biological outcome of short-term gene overexpression, methods providing stable integration of desired genes may be preferred for assay development. As such, lentiviral vectors offer the ability to confer long-term and regulated gene expression on mammalian cells 18. In this study, we focused on the generation of stable cell lines transduced with recombinant lentivirus bearing WT and mutant SOD1 tagged with yellow fluorescent protein (YFP). Using live-cell imaging microscopy and automated quantification of SOD1 aggregation, we triggered and quantified SOD1 aggregation events upon inhibition of the proteasome.

<table>
	<tbody>
		<tr>
			<td>ALLN (C20H37N3O4)</td>
			<td>Millipore</td>
			<td>208719</td>
			<td></td>
		</tr>
		<tr>
			<td>MG132 (C26H41N3O5)</td>
			<td>Sigma-Aldrich</td>
			<td>C2211</td>
			<td></td>
		</tr>
		<tr>
			<td>Epoxomicin (C28H50N4O7)</td>
			<td>Sigma-Aldrich</td>
			<td>E3652</td>
			<td></td>
		</tr>
		<tr>
			<td>Hoechst 33342</td>
			<td>Invitrogen</td>
			<td>H-3570</td>
			<td></td>
		</tr>
		<tr>
			<td>Opera</td>
			<td>Perkin Elmer</td>
			<td>OP-QEHS-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Opera EvoShell software</td>
			<td>Perkin Elmer</td>
			<td>Ver 1.8.1</td>
			<td></td>
		</tr>
		<tr>
			<td>Operetta</td>
			<td>Perkin Elmer</td>
			<td>OPRT1288</td>
			<td></td>
		</tr>
		<tr>
			<td>Harmony Imaging software</td>
			<td>Perkin Elmer</td>
			<td>Ver 3.0.0</td>
			<td></td>
		</tr>
		<tr>
			<td>Columbus Image analysis software</td>
			<td>Perkin Elmer</td>
			<td>Ver 2.3.2</td>
			<td></td>
		</tr>
		<tr>
			<td>CyBi Hummingwell liquid handling</td>
			<td>CyBio AG</td>
			<td>OL 3387 3 0110</td>
			<td></td>
		</tr>
	</tbody>
</table>

assay development for high content quantification of sod1 mutant protein aggregate formation in living cells

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that can be caused by inherited mutations in the gene encoding copper-zinc superoxide dismutase 1 (SOD1). The structural instability of SOD1 and the detection of SOD1-positive inclusions in familial-ALS patients supports a potential causal role for misfolded and/or aggregated SOD1 in ALS pathology. In this study, we describe the development of a cell-based assay designed to quantify the dynamics of SOD1 aggregation in living cells by high content screening approaches. Using lentiviral vectors, we generated stable cell lines expressing wild-type and mutant A4V SOD1 tagged with yellow fluorescent protein and found that both proteins were expressed in the cytosol without any sign of aggregation. Interestingly, only SOD1 A4V stably expressed in HEK-293, but not in U2OS or SH-SY5Y cell lines, formed aggregates upon proteasome inhibitor treatment. We show that it is possible to quantify aggregation based on dose-response analysis of various proteasome inhibitors, and to track aggregate-formation kinetics by time-lapse microscopy. Our approach introduces the possibility of quantifying the effect of ALS mutations on the role of SOD1 in aggregate formation as well as screening for small molecules that prevent SOD1 A4V aggregation.

Generating stable cell line using lentivirus: The overall strategy for monitoring SOD1 protein aggregates is illustrated in Figure 1. In a first step, we generated a lentiviral expression vector for SOD1 stable gene delivery into cell lines (Step 1). Two lentiviral vectors encoding YFP-tagged SOD1 WT and SOD1 A4V (SOD1WT-YFP and SOD1A4V-YFP, respectively) with packing and envelope plasmids were prepared (Figure 2A</strong...

Watch this Scientific Journal Video about Assay Development for High Content Quantification of Sod1 Mutant Protein Aggregate Formation in Living Cells at JoVE.com

Assay Development for High Content Quantification of Sod1 Mutant Protein Aggregate Formation in Living Cells

We describe a method to quantify the aggregation of misfolded proteins. Our protocol details lentiviral induced stable cell line generation, automated confocal imaging, and image analysis of protein aggregates. As an illustrative application, we studied the effect of small molecules in promoting SOD1 aggregation in a time- and dose-dependent manner.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that can be caused by inherited mutations in the gene encoding copper-zinc ...

The overall goal of this experiment is to develop an assay for studying the effect of small molecules in modulating the aggregation of misfolded proteins in a time and dose dependent manner. This method can help answer the key questions for development of cellular assay, and it's use is for high-content screening techniques. The main advantage of this technique is to provide a simple method to detect and quantify protein aggregation occurring in several neurodegenerative disorders.The implication of this technique extends towards potential therapy of neurodegenerative diseases, such as ALS, because it proposes a simple method that allow to develop cellular assay and perform screening for small molecule moderators. To start virus production, prior to plasmid transfection split HEK-293 T-cells at 30 to 40%confluence in a 10 centimeter tissue culture dish and 10 milliliters of cell culture medium. Incubate the culture plate in a 5%carbon dioxide incubator at 37 degrees Celsius overnight.On the following day, prepare DNA transfection solution with packaging plasmids lentiviral vector, 125 microliters of one molar calcium chloride and add distilled water to adjust the volume to 500 microliters. Gently add 500 microliters of 0.05 molar HEPS buffer and incubate for 10 minutes at room temperature. After that, replace HEK-293 T-cell medium with 10 milliliters pre-warmed antibiotic-free fresh culture medium mixed with one milliliter of DNA transfection solution.Incubate at 37 degrees Celsius and 5%carbon dioxide incubator over night. Replace cell supernatent with fresh culture medium on the following day and incubate again overnight. Finally, on the following day harvest the supernatent and transfer to a 15 milliliter tube.To remove the dead cells and debris, centrifuge the tube at 500 times g for five minutes. To further purify the supernatent, pass it through a 0.45 micrometer filter using a 60-milliliter syringe. Then, immediately dispense the filtered supernatent into 300-microliter single use aliquots.To prepare the cells for transduction, split them to be infected at 60%confluence in a six-well tissue culture plate in two milliliters of DMAM supplemented with 10%FBS. Incubate the cells in a 37-degree Celsius incubator at 5%carbon dioxide overnight. On the following day, thaw one aliquot of the frozen lentivirus on ice for each use.Meanwhile, warm the cell culture medium containing the serum compatible with the cell line of interest. Once the virus is fully thawed, dilute it in DMEM in new 1.5 milliliter micro-centrifuge tubes. Then adjust the volume to one milliliter with reduced serum medium.Next, add two microliters of polybrene to one milliliter of virus per medium and mix well by pipetting. Add one milliliter of this mixture to the cells and incubate at 37 degrees Celsius for 24 hours. After incubation, remove the virus containing medium and replace it with normal DMEM supplemented with 10%FBS and return the cells to the incubator.Monitor the cell growth and change the medium every two days When the cells reach confluence, expand each well of the six-well dish into a 10-centimeter tissue culture plate. Move the plates to the incubator. Finally, save 1.5 times 10 to the 4th cells per well and 50 microliters of DMEM on 384 well assay plates.Then check the expression level of the YFP-tagged protein under the microscope. If the expression shows signal-to-noise ratio equal or greater than three, prepare cell stock for the corresponding cell line. For the compound transfer, on a 384-well storage polypropylene plate, add serial dilutions of compounds by the standard one to three dilution series.Then, using a liquid handler equipped with a 384-capillary head, distribute 0.25 microliters of proteasome inhibitors on empty, flat-bottomed black 384-well assay plates. Then seed 1.5 times 10 to the 4th cells on these plates. Incubate at 37 degrees Celsius and 5%carbon dioxide for 24 hours.Prior to imaging the cell line treated with proteasome inhibitors, add 10 microliters of pre-warmed DMEM with staining solution and incubate at room temperature for 10 minutes. After staining, start the automated microscope operating software by selecting the microscope tab. First, select the configuration tab and then select 20 times objective in the correct plate type.To allow proper focus with different plate types, make sure that the caller is set to the correct value on the objective. Next, select exposure one. Set focus height to zero micrometers, then select focus.Once it is focused, expose camera one. To optimize the exposure plane, adjust the focus height and click on take height. Change exposure times and laser power for a maximum pixel intensity of approximately 3000 and save exposure parameters.Select experiment definition tab, create a layout and sublayout. Next, drag and drop the relevant layout exposure, reference image, skew crop file, and sublayout. Then, save the experiment.Finally, select automatic experiment tab and acquire images. For two-channel images, first select the software algorithm to segment the primary objects, such as nuclei, cytosol, and aggregates. First, distribute 0.25 microliters of proteasome inhibitor dissolved in 100%DMSO or DMSO on 384-well flat-bottomed plates.On the same plate, manually seed 1.5 times 10 to the 4th cells per well in 50-microliters of DMEM. Then set up the microscope system environmental control unit to 37 degrees Celsius and 5%carbon dioxide. Operate the microscope in wide-field florescence mode and as software settings, choose LWD 20 times objective non-confocal mode, four fields per well, and capture interval of one hour.Then, select the appropriate algorithm to segment the primary object such as cytosol and aggregates. Adjust background threshold and contrast parameters if required. The tested cell lines transduced with SOD-1 wild type and SOD-1 A4V mutant remained healthy, showed high expression levels, and longterm wide phi-labeling irrespective of the SOD form.Treatment with proteasome inhibitor ALLN for 24 hours promoted the accumulation of SOD-1 A4V YFP aggregates in HEK-293 cells but not in SOD-1 Wild Type YFP transduced cells. Furthermore, there were very low levels of aggregation in U2 OS and SH-SY5Y cell lines SOD-1 A4V YFP transduced with the same vectors. After seeding the cells in the presence or absence of ALLN, they were monitored for aggregate formation for a period of 50 hours.ALLN aggregate formation reached a plateau at 24 hours and remained stable over the next 12 hours. Furthermore, cell density significantly decreased after 28 hours as a result of the cytotoxic effect of ALLN, while cell number increased in the DMSO-treated negative control. SOD-1 A4V YFP cells cultured in the presence of proteasome inhibitors for 24 hours were stained with Hoechst solution.The relative toxicity for three different proteasome inhibitors was quatified by measuring the number of adherent cell lines remaining in the well labeled with Hoechst dye. The total cell number decreased in response to increased dose of protease inhibitors. Inversely, the percentage of cells expressing SOD-1 A4V aggregates increased with the concentration of protease inhibitor.When doing this process it is important to remember that the cell quality will drastically influence your result. So it's important to determine that the cells are microplasma free and are healthy all along the steps. Following this process, another imaging method can be used in order to answer additional questions regarding the degradation of protein or the interaction of the protein with others using resonance energy transfer.After watching this video, you should have a good understanding of how to generate the tools to test the fate of protein in multiple living cells using high-content image analysis. So this method can provide insight into protein aggregation as it occurs in simple cellular models. It can also be applied to other systems such as neuron differentiated from patient specific induced pluripotent stem cells.

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Neuroscience

High Sensitivity 5-hydroxymethylcytosine Detection in Balb/C Brain Tissue

DNA hydroxymethylation is a long known modification of DNA, but has recently become a focus in epigenetic research. Mammalian DNA is enzymatically modified at the 5th carbon position of cytosine (C) residues to 5-mC, predominately in the context of CpG dinucleotides. 5-mC is amenable to enzymatic oxidation to 5-hmC by the Tet family of enzymes, which are believed to be involved in development and disease. Currently, the biological role of 5-hmC is not fully understood, but is generating a lot of interest due to its potential as a biomarker. This is due to several groundbreaking studies identifying 5-hydroxymethylcytosine in mouse embryonic stem (ES) and neuronal cells. Research techniques, including bisulfite sequencing methods, are unable to easily distinguish between 5-mC and 5-hmC . A few protocols exist that can measure global amounts of 5-hydroxymethylcytosine in the genome, including liquid chromatography coupled with mass spectrometry analysis or thin layer chromatography of single nucleosides digested from genomic DNA. Antibodies that target 5-hydroxymethylcytosine also exist, which can be used for dot blot analysis, immunofluorescence, or precipitation of hydroxymethylated DNA, but these antibodies do not have single base resolution.In addition, resolution depends on the size of the immunoprecipitated DNA and for microarray experiments, depends on probe design. Since it is unknown exactly where 5-hydroxymethylcytosine exists in the genome or its role in epigenetic regulation, new techniques are required that can identify locus specific hydroxymethylation. The EpiMark 5-hmC and 5-mC Analysis Kit provides a solution for distinguishing between these two modifications at specific loci. The EpiMark 5-hmC and 5-mC Analysis Kit is a simple and robust method for the identification and quantitation of 5-methylcytosine and 5-hydroxymethylcytosine within a specific DNA locus. This enzymatic approach utilizes the differential methylation sensitivity of the isoschizomers MspI and HpaII in a simple 3-step protocol. Genomic DNA of interest is treated with T4-BGT, adding a glucose moeity to 5-hydroxymethylcytosine. This reaction is sequence-independent, therefore all 5-hmC will be glucosylated; unmodified or 5-mC containing DNA will not be affected. This glucosylation is then followed by restriction endonuclease digestion. MspI and HpaII recognize the same sequence (CCGG) but are sensitive to different methylation states. HpaII cleaves only a completely unmodified site: any modification (5-mC, 5-hmC or 5-ghmC) at either cytosine blocks cleavage. MspI recognizes and cleaves 5-mC and 5-hmC, but not 5-ghmC. The third part of the protocol is interrogation of the locus by PCR. As little as 20 ng of input DNA can be used. Amplification of the experimental (glucosylated and digested) and control (mock glucosylated and digested) target DNA with primers flanking a CCGG site of interest (100-200 bp) is performed. If the CpG site contains 5-hydroxymethylcytosine, a band is detected after glucosylation and digestion, but not in the non-glucosylated control reaction. Real time PCR will give an approximation of how much hydroxymethylcytosine is in this particular site. In this experiment, we will analyze the 5-hydroxymethylcytosine amount in a mouse Babl/C brain sample by end point PCR.

The EpiMark 5-hmC and 5-mC Analysis Kit can be used to analyze and quantitate 5-methylcytosine and 5-hydroxymethylcytosine within a spe cific locus. The kit distinguishes 5-mC from 5-hmC by the addition of glucose to the hydroxyl group of 5-hmC via an enzymatic reaction utilizing &beta;-glucosyltransferase (T4-BGT). When 5-hmC occurs In the context of CCGG, this modification converts a cleavable MspI site to a non-cleavable site.

DNA hydroxymethylation is a long known modification of DNA, but has recently become a focus in epigenetic research.   Mammalian DNA is enzymatically ...

Preparation of Living Isolated Vertebrate Photoreceptor Cells for Fluorescence Imaging

In the vertebrate retina, phototransduction, the conversion of light to an electrical signal, is carried out by the rod and cone photoreceptor cells1-4. Rod photoreceptors are responsible for vision in dim light, cones in bright light. Phototransduction takes place in the outer segment of the photoreceptor cell, a specialized compartment that contains a high concentration of visual pigment, the primary light detector. The visual pigment is composed of a chromophore, 11-cis retinal, attached to a protein, opsin. A photon absorbed by the visual pigment isomerizes the chromophore from 11-cis to all-trans. This photoisomerization brings about a conformational change in the visual pigment that 
initiates a cascade of reactions culminating in a change in membrane potential, and bringing about the transduction of the light stimulus to an electrical signal. The 
recovery of the cell from light stimulation involves the deactivation of the intermediates activated by light, and the reestablishment of the membrane potential. Ca2+ modulates the activity of several of the enzymes involved in phototransduction, and its concentration is reduced upon light stimulation. In this way, Ca2+ plays an important role in the recovery of the cell from light stimulation and its adaptation to background light.
Another essential part of the recovery process is the regeneration of the visual pigment that has been destroyed during light-detection by the 
photoisomerization of its 11-cis chromophore to all-trans5-7. This regeneration begins with the release of all-trans retinal by 
the photoactivated pigment, leaving behind the apo-protein opsin. The released all-trans retinal is rapidly reduced in a reaction utilizing NADPH to all-
trans retinol, and opsin combines with fresh 11-cis retinal brought into the outer segment to reform the visual pigment. All-trans retinol is 
then transferred out of the outer segment and into neighboring cells by the specialized carrier Interphotoreceptor Retinoid Binding Protein (IRBP).
Fluorescence imaging of single photoreceptor cells can be used to study their physiology and cell biology. Ca2+-sensitive fluorescent dyes can be used to examine in detail the interplay between outer 
segment Ca2+ changes and response to light8-12 as well as the role of inner segment Ca2+ stores in Ca2+ homeostasis13,14. 
Fluorescent dyes can also be used for measuring Mg2+ concentration15, pH, and as tracers of aqueous and membrane compartments16. 
Finally, the intrinsic fluorescence of all-trans retinol (vitamin A) can be used to monitor the kinetics of its formation and removal in single 
photoreceptor cells17-19.

A method is described for the preparation of single living photoreceptor cells from different vertebrate species for fluorescence imaging. The method can be used to image the fluorescence of endogenous fluorophores, such as NADH or vitamin A, or that of exogenously added fluorescent dyes sensitive to Ca2+ or other factors.

In the vertebrate retina, phototransduction, the conversion of light to an electrical signal, is carried out by the rod and cone photoreceptor cells1-4.  ...

A Quantitative Cell Migration Assay for Murine Enteric Neural Progenitors

Neural crest cells (NCC) are a transient and multipotent cell population that originates from the dorsal neural tube and migrates extensively throughout the developing vertebrate embryo. In addition to providing peripheral glia and neurons, NCC generate melanocytes as well as most of the cranio-facial skeleton. NCC migration and differentiation is controlled by a combination of their axial origin along the neural tube and their exposure to regionally distinct extracellular cues. Such contribution of extracellular ligands is especially evident during the formation of the enteric nervous system (ENS), a complex interconnected network of neural ganglia that locally controls (among other things) gut muscle movement and intestinal motility. Most of the ENS is derived from a small initial pool of NCC that undertake a long journey in order to colonize - in a rostral to caudal fashion - the entire length of the prospective gut. Among several signaling pathways known to influence enteric NCC colonization, GDNF/RET signaling is recognized as the most important. Indeed, spatiotemporally controlled secretion of the RET ligand GDNF by the gut mesenchyme is chiefly responsible for the attraction and guidance of RET-expressing enteric NCC to and within the embryonic gut. Here, we describe an ex vivo cell migration assay, making use of a transgenic mouse line possessing fluorescently labeled NCC, which allows precise quantification of enteric NCC migration potential in the presence of various growth factors, including GDNF.

We present an ex vivo cell migration assay that allows precise quantification of enteric neural crest cell migration potential in the presence of various growth factors.

Neural crest cells (NCC) are a transient and multipotent cell population that originates from the dorsal neural tube and migrates extensively throughout ...

A High Content Imaging Assay for Identification of Botulinum Neurotoxin Inhibitors

Synaptosomal-associated protein-25 (SNAP-25) is a component of the soluble NSF attachment protein receptor (SNARE) complex that is essential for synaptic neurotransmitter release. Botulinum neurotoxin serotype A (BoNT/A) is a zinc metalloprotease that blocks exocytosis of neurotransmitter by cleaving the SNAP-25 component of the SNARE complex. Currently there are no licensed medicines to treat BoNT/A poisoning after internalization of the toxin by motor neurons. The development of effective therapeutic measures to counter BoNT/A intoxication has been limited, due in part to the lack of robust high-throughput assays for screening small molecule libraries. Here we describe a high content imaging (HCI) assay with utility for identification of BoNT/A inhibitors. Initial optimization efforts focused on improving the reproducibility of inter-plate results across multiple, independent experiments. Automation of immunostaining, image acquisition, and image analysis were found to increase assay consistency and minimize variability while enabling the multiparameter evaluation of experimental compounds in a murine motor neuron system.

Botulinum neurotoxin is one of the most potent toxins among Category-A biothreat agents, yet a post-exposure therapeutic is not available. The high content imaging approach is a powerful methodology for identifying novel inhibitors as it enables multiparameter screening using biologically relevant motor neurons, the primary target of this toxin.

Synaptosomal-associated protein-25 (SNAP-25) is a component of the soluble NSF attachment protein receptor (SNARE) complex that is essential for synaptic ...

Straightforward Assay for Quantification of Social Avoidance in Drosophila melanogaster

Drosophila melanogaster is an emerging model to study different aspects of social interactions. For example, flies avoid areas previously occupied by stressed conspecifics due to an odorant released during stress known as the Drosophila stress odorant (dSO). Through the use of the T-maze apparatus, one can quantify the avoidance of the dSO by responder flies in a very affordable and robust assay. Conditions necessary to obtain a strong performance are presented here. A stressful experience is necessary for the flies to emit dSO, as well as enough emitter flies to cause a robust avoidance response to the presence of dSO. Genetic background, but not their group size, strongly altered the avoidance of the dSO by the responder flies. Canton-S and Elwood display a higher performance in avoiding the dSO than Oregon and Samarkand strains. This behavioral assay will allow identification of mechanisms underlying this social behavior, and the assessment of the influence of genes and environmental conditions on both emission and avoidance of the dSO. Such an assay can be included in batteries of simple diagnostic tests used to identify social deficiencies of mutants or environmental conditions of interest.

Straightforward Assay for Quantification of Social Avoidance in Drosophila melanogaster

Here, we present a protocol to quantify the avoidance of stressed individuals. This paradigm is powerful yet user-friendly and can be used to assess the influence of genes and environment on one kind of social interaction in Drosophila melanogaster.

Drosophila melanogaster is an emerging model to study different aspects of social interactions. For example, flies avoid areas previously occupied by ...

High-resolution Quantification of Odor-guided Behavior in Drosophila melanogaster Using the Flywalk Paradigm

In their natural environment, insects such as the vinegar fly Drosophila melanogaster are bombarded with a huge amount of chemically distinct odorants. To complicate matters even further, the odors detected by the insect nervous system usually are not single compounds but mixtures whose composition and concentration ratios vary. This leads to an almost infinite amount of different olfactory stimuli which have to be evaluated by the nervous system.
To understand which aspects of an odor stimulus determine its evaluation by the fly, it is therefore desirable to efficiently examine odor-guided behavior towards many odorants and odor mixtures. To directly correlate behavior to neuronal activity, behavior should be quantified in a comparable time frame and under identical stimulus conditions as in neurophysiological experiments. However, many currently used olfactory bioassays in Drosophila neuroethology are rather specialized either towards efficiency or towards resolution.
Flywalk, an automated odor delivery and tracking system, bridges the gap between efficiency and resolution. It allows the determination of exactly when an odor packet stimulated a freely walking fly, and to determine the animal&#180;s dynamic behavioral reaction.

High-resolution Quantification of Odor-guided Behavior in Drosophila melanogaster Using the Flywalk Paradigm

The automated tracking system Flywalk is used for high-resolution quantification of odor-guided behavior in Drosophila melanogaster.

In their natural environment, insects such as the vinegar fly Drosophila melanogaster are bombarded with a huge amount of chemically distinct odorants. To ...

Novel Assay for Cold Nociception in Drosophila Larvae

How organisms sense and respond to noxious temperatures is still poorly understood. Further, the mechanisms underlying sensitization of the sensory machinery, such as in patients experiencing peripheral neuropathy or injury-induced sensitization, are not well characterized. The genetically tractable Drosophila model has been used to study the cells and genes required for noxious heat detection, which has yielded multiple conserved genes of interest. Little is known however about the cells and receptors important for noxious cold sensing. Although, Drosophila does not survive prolonged exposure to cold temperatures (&#8804;10 &#186;C), and will avoid cool, preferring warmer temperatures in behavioral preference assays, how they sense and possibly avoid noxious cold stimuli has only recently been investigated.
Here we describe and characterize the first noxious cold (&#8804;10 &#186;C) behavioral assay in Drosophila. Using this tool and assay, we show an investigator how to qualitatively and quantitatively assess cold nociceptive behaviors. This can be done under normal/healthy culture conditions, or presumably in the context of disease, injury or sensitization. Further, this assay can be applied to larvae selected for desired genotypes, which might impact thermosensation, pain, or nociceptive sensitization. Given that pain is a highly conserved process, using this assay to further study&#160;thermal nociception will likely glean important understanding of pain processes in other species, including vertebrates.

Novel Assay for Cold Nociception in Drosophila Larvae

Here we demonstrate a novel assay to study cold nociception in Drosophila larvae. This assay utilizes a custom-built Peltier probe capable of applying a focal noxious cold stimulus and results in quantifiable cold-specific behaviors. This technique will allow further cellular and molecular dissection of cold nociception.

How organisms sense and respond to noxious temperatures is still poorly understood. Further, the mechanisms underlying sensitization of the sensory ...

High-throughput Analysis of Locomotor Behavior in the Drosophila Island Assay

Advances in next-generation sequencing technologies contribute to the identification of (candidate) disease genes for movement disorders and other neurological diseases at an increasing speed. However, little is known about the molecular mechanisms that underlie these disorders. The genetic, molecular, and behavioral toolbox of Drosophila melanogaster makes this model organism particularly useful to characterize new disease genes and mechanisms in a high-throughput manner. Nevertheless, high-throughput screens require efficient and reliable assays that, ideally, are cost-effective and allow for the automatized quantification of traits relevant to these disorders. The island assay is a cost-effective and easily set-up method to evaluate Drosophila locomotor behavior. In this assay, flies are thrown onto a platform from a fixed height. This induces an innate motor response that enables the flies to escape from the platform within seconds. At present, quantitative analyses of filmed island assays are done manually, which is a laborious undertaking, particularly when performing large screens.
This manuscript describes the &#34;Drosophila Island Assay&#34; and &#34;Island Assay Analysis&#34; algorithms for&#160;high-throughput, automated data processing and quantification of island assay data. In the setup, a simple webcam connected to a laptop collects an image series of the platform while the assay is performed. The &#34;Drosophila Island Assay&#34; algorithm developed for the open-source software Fiji processes these image series and quantifies, for each experimental condition, the number of flies on the platform over time. The &#34;Island Assay Analysis&#34; script, compatible with the free software R, was developed to automatically process the obtained data and to calculate whether treatments/genotypes are statistically different. This greatly improves the efficiency of the island assay and makes it a powerful readout for basic locomotion and flight behavior. It can thus be applied to large screens investigating fly locomotor ability, Drosophila models of movement disorders, and drug efficacy.

High-throughput Analysis of Locomotor Behavior in the Drosophila Island Assay

The island assay is a relatively new, cost-effective assay that can be used to evaluate the basic locomotor behavior of Drosophila melanogaster. This manuscript describes algorithms for automatic data processing and objective quantification of island assay data, making this assay a sensitive, high-throughput readout for large genetic or pharmacological screens.

Advances in next-generation sequencing technologies contribute to the identification of (candidate) disease genes for movement disorders and other ...

High-resolution Confocal Imaging of the Blood-brain Barrier: Imaging, 3D Reconstruction, and Quantification of Transcytosis

The blood-brain barrier (BBB) is a dynamic multicellular interface that regulates the transport of molecules between the circulation and the brain. Transcytosis across the BBB regulates the delivery of hormones, metabolites, and therapeutic antibodies to the brain parenchyma. Here, we present a protocol that combines immunofluorescence of free-floating sections with laser scanning confocal microscopy and image analysis to visualize subcellular organelles within endothelial cells at the BBB. Combining this data-set with 3D image analysis software allows for the semi-automated segmentation and quantification of capillary volume and surface area, as well as the number and intensity of intracellular organelles at the BBB. The detection of mouse endogenous immunoglobulin (IgG) within intracellular vesicles and their quantification at the BBB is used to illustrate the method. This protocol can potentially be applied to the investigation of the mechanisms controlling BBB transcytosis of different molecules in vivo.

Here we present a microscopy-based protocol for high-resolution imaging and a three-dimensional reconstruction of the mouse neurovascular unit and blood-brain barrier using brain free-floating sections. This method allows for the visualization, analysis, and quantification of intracellular organelles at the BBB.

The blood-brain barrier (BBB) is a dynamic multicellular interface that regulates the transport of molecules between the circulation and the brain. ...

A Temperature Gradient Assay to Determine Thermal Preferences of Drosophila Larvae

Many animals, including the fruit fly, Drosophila melanogaster, are capable of discriminating minute differences in&#160;environmental temperature, which enables them to seek out their preferred thermal landscape. To define the temperature preferences of larvae over a defined linear range, we developed an assay using a temperature gradient. To establish a single-directional gradient, two aluminum blocks are connected to independent water baths, each of which controls the temperature of individual blocks. The two blocks set the lower and upper limits of the gradient. The temperature gradient is established by placing an agarose-coated aluminum plate over the two water-controlled blocks so that the plate spans the distance between them. The ends of the aluminum plate that is set on the top of the water blocks defines the minimum and maximum temperatures, and the regions in-between the two blocks form a linear temperature gradient. The gradient assay can be applied to&#160;larvae of different ages and can be used to identify mutants that exhibit phenotypes, such as those with mutations affecting genes encoding TRP channels and opsins, which are required for temperature discrimination.

A Temperature Gradient Assay to Determine Thermal Preferences of Drosophila Larvae

Here, we present a protocol to determine the preferred environmental temperature of Drosophila larvae using a continuous thermal gradient.

Many animals, including the fruit fly, Drosophila melanogaster, are capable of discriminating minute differences in&#160;environmental temperature, which ...