Name: assessment of de novo protein synthesis rates in caenorhabditis elegans
Uploaded: 2020-09-12T13:00:00
Description: Watch this Scientific Journal Video about Assessment of de novo Protein Synthesis Rates in Caenorhabditis elegans at JoVE.com

We thank Chaniotakis M. and Kounakis K. for video recording and editing. K.P. is funded by a grant from the Hellenic Foundation for Research and Innovation (HFRI) and the General Secretariat for Research and Technology (GSRT). N.T. is funded by grants from the European Research Council (ERC &#8211; GA695190 &#8211; MANNA), the European Commission Framework Programmes, and the Greek Ministry of Education.

NOTE: Both transcriptional and translational fusions to fluorophores can be used to evaluate de novo protein translation in several tissues. Protein synthesis rates can be assessed for multiple protein families that localized in different cellular compartments, including cytoplasm, mitochondria and nucleus7. The following strains are used to monitor global and neuronal protein synthesis rates, N2;Ex[pife-2GFP, pRF4], ife-2(ok306);Ex[pife-2</e...

<ol>
	<li>Syntichaki, P., Troulinaki, K., Tavernarakis, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=eIF4E+function+in+somatic+cells+modulates+ageing+in+Caenorhabditis+elegans.">eIF4E function in somatic cells modulates ageing in Caenorhabditis elegans.</a> Nature. 445 (7130), 922-926 (2007).</li><li>Charmpilas, N., Daskalaki, I., Papandreou, M. E., Tavernarakis, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+synthesis+as+an+integral+quality+control+mechanism+during+ageing.">Protein synthesis as an integral quality control mechanism during ageing.</a> Ageing Research Reviews. 23, 75-89 (2015).</li><li>Li, G. W., Burkhardt, D., Gross, C., Weissman, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantifying+absolute+protein+synthesis+rates+reveals+principles+underlying+allocation+of+cellular+resources.">Quantifying absolute protein synthesis rates reveals principles underlying allocation of cellular resources.</a> Cell. 157 (3), 624-635 (2014).</li><li>Dermit, M., Dodel, M., Mardakheh, F. K. <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+monitoring+and+measurement+of+protein+translation+in+time+and+space.">Methods for monitoring and measurement of protein translation in time and space.</a> Molecular Biosystems. 13 (12), 2477-2488 (2017).</li><li>Iwasaki, S., Ingolia, N. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Growing+Toolbox+for+Protein+Synthesis+Studies.">The Growing Toolbox for Protein Synthesis Studies.</a> Trends in Biochemical Sciences. 42 (8), 612-624 (2017).</li><li>Corsi, A. K., Wightman, B., Chalfie, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Transparent+Window+into+Biology:+A+Primer+on+Caenorhabditis+elegans.">A Transparent Window into Biology: A Primer on Caenorhabditis elegans.</a> Genetics. 200 (2), 387-407 (2015).</li><li>Kourtis, N., Tavernarakis, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell-specific+monitoring+of+protein+synthesis+in+vivo.">Cell-specific monitoring of protein synthesis in vivo.</a> PLoS One. 4 (2), 4547 (2009).</li><li>Parker, R., Sheth, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=P+bodies+and+the+control+of+mRNA+translation+and+degradation.">P bodies and the control of mRNA translation and degradation.</a> Molecular Cell. 25 (5), 635-646 (2007).</li><li>Rieckher, M., Markaki, M., Princz, A., Schumacher, B., Tavernarakis, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maintenance+of+Proteostasis+by+P+Body-Mediated+Regulation+of+eIF4E+Availability+during+Aging+in+Caenorhabditis+elegans.">Maintenance of Proteostasis by P Body-Mediated Regulation of eIF4E Availability during Aging in Caenorhabditis elegans.</a> Cell Reports. 25 (1), 199-211 (2018).</li><li>Reits, E. A., Neefjes, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+fixed+to+FRAP:+measuring+protein+mobility+and+activity+in+living+cells.">From fixed to FRAP: measuring protein mobility and activity in living cells.</a> Nature Cell Biology. 3 (6), 145-147 (2001).</li><li>Keith, S. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Graded+Proteasome+Dysfunction+in+Caenorhabditis+elegans+Activates+an+Adaptive+Response+Involving+the+Conserved+SKN-1+and+ELT-2+Transcription+Factors+and+the+Autophagy-Lysosome+Pathway.">Graded Proteasome Dysfunction in Caenorhabditis elegans Activates an Adaptive Response Involving the Conserved SKN-1 and ELT-2 Transcription Factors and the Autophagy-Lysosome Pathway.</a> PLoS Genetics. 12 (2), 1005823 (2016).</li><li>Kumsta, C., 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=The+autophagy+receptor+p62/SQST-1+promotes+proteostasis+and+longevity+in+C.+elegans+by+inducing+autophagy.">The autophagy receptor p62/SQST-1 promotes proteostasis and longevity in C. elegans by inducing autophagy.</a> Nature Communications. 10 (1), 5648 (2019).</li><li>Gregersen, N., Bolund, L., Bross, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+misfolding,+aggregation,+and+degradation+in+disease.">Protein misfolding, aggregation, and degradation in disease.</a> Molecular Biotechnology. 31 (2), 141-150 (2005).</li></ol>

Protein synthesis modulation is essential for organismal homeostasis. During ageing, global as well as specific protein synthesis is perturbed. Recent studies reveal the fact that protein translation balance directly controls senescence and aging is not merely a byproduct of the aging process. In particular, core components of the translation machinery such as eukaryotic initiation factor 4E (eIF4E), which facilitates mRNA capping during translation initiation, and thus the rate of cap-dependent protein translation, indu...

Protein synthesis and degradation is essential for organismal homeostasis. A multitude of age-related diseases are instigated by defective protein production1,2. In order to measure global protein translation rates, there are biochemical techniques such as ribosomal profiling, which involves deep sequencing of ribosome-protected mRNA fragments to monitor expression as well as novel protein synthesis3. This method, besides being an indirect readout of translational rates, as increased RNA association to ribosomes does not necessarily mean increased translation, has technical disadvantages, such as high cost and a requirement of a large amount of starting material. On the other hand, proteomics-based methods allow for direct protein quantification by pulse metabolic profiling followed by mass spectrometry analysis4,5. However, this is a semi-quantitative approach with limited temporal resolution that cannot be easily used in vivo. Moreover, labelling of the protein can be unequally distributed in the animal/tissue of interest. Importantly, both these methods can conceal tissue-specific or cell-specific variations in protein translation rates in whole animals or tissues, respectively.
Caenorhabditis elegans is an easy-to-use model organism that can be grown in large numbers6. Additionally, its genetic amenability and transparency allow for live imaging in vivo. This protocol describes the methodology to detect protein synthesis rates using fluorescence recovery after photobleaching (FRAP). We take advantage of the transgenic expression of fluorescent proteins, either in the whole organism or in specific tissues/cells. Transgenic animals may either express GFP using the promoter of a gene, which is widely/globally expressed or a tissue-specific promoter to target specific cell types. This technique can be extended to a specific promoter to examine protein synthesis rates of a specific protein.

<table>
	<tbody>
		<tr>
			<td>Agar</td>
			<td>Sigma-Aldrich</td>
			<td>5040</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>Biozym</td>
			<td>8,40,004</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose pads 2%</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Calcium chloride dehydrate (CaCl2&#8729;2H2O)</td>
			<td>Sigma-Aldrich</td>
			<td>C5080</td>
			<td></td>
		</tr>
		<tr>
			<td>Cholesterol</td>
			<td>SERVA Electrophoresis</td>
			<td>17101.01</td>
			<td></td>
		</tr>
		<tr>
			<td>cycloheximide</td>
			<td>Sigma-Aldrich</td>
			<td>C-7698</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting stereomicroscope</td>
			<td>Nikon Corporation</td>
			<td></td>
			<td>SMZ645</td>
		</tr>
		<tr>
			<td>edc-3(ok1427);Ex[punc-119GFP, pRF4]</td>
			<td>Tavernarakis lab</td>
			<td></td>
			<td>Maintain animals at 20 &#176;C</td>
		</tr>
		<tr>
			<td>Epifluorescence microscope</td>
			<td>Zeiss</td>
			<td></td>
			<td>Axio Imager Z2</td>
		</tr>
		<tr>
			<td>Escherichia coli OP50 strain</td>
			<td>Caenorhabditis Genetics Center (CGC)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescence dissecting stereomicroscope</td>
			<td>Zeiss</td>
			<td></td>
			<td>SteREO Lumar V12</td>
		</tr>
		<tr>
			<td>Greiner Petri dishes (60 x 15 mm)</td>
			<td>Sigma-Aldrich</td>
			<td>P5237</td>
			<td></td>
		</tr>
		<tr>
			<td>ife-2(ok306);Ex[pife-2GFP, pRF4]</td>
			<td>Tavernarakis lab</td>
			<td></td>
			<td>Maintain animals at 20 &#176;C</td>
		</tr>
		<tr>
			<td>image analysis software</td>
			<td>Fiji</td>
			<td></td>
			<td>https://fiji.sc</td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>EMD Millipore</td>
			<td>1,37,010</td>
			<td></td>
		</tr>
		<tr>
			<td>K2HPO4</td>
			<td>EMD Millipore</td>
			<td>1,04,873</td>
			<td></td>
		</tr>
		<tr>
			<td>LB liquid medium</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>M9 buffer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium sulfate (MgSO4)</td>
			<td>Sigma-Aldrich</td>
			<td>M7506</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope slides (75 x 25 x 1 mm)</td>
			<td>Marienfeld, Lauda-Koenigshofen</td>
			<td>10 006 12</td>
			<td></td>
		</tr>
		<tr>
			<td>Microsoft Office 2011 Excel software package</td>
			<td>Microsoft Corporation, Redmond, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>N2;Ex[pife-2GFP; pRF4]</td>
			<td>Tavernarakis lab</td>
			<td></td>
			<td>Maintain animals at 20 &#176;C</td>
		</tr>
		<tr>
			<td>N2;Ex[psod-3GFP; pRF4]</td>
			<td>Tavernarakis lab</td>
			<td></td>
			<td>Maintain animals at 20 &#176;C</td>
		</tr>
		<tr>
			<td>N2;Ex[punc-119GFP; pRF4]</td>
			<td>Tavernarakis lab</td>
			<td></td>
			<td>Maintain animals at 20 &#176;C</td>
		</tr>
		<tr>
			<td>Na2HPO4</td>
			<td>EMD Millipore</td>
			<td>1,06,586</td>
			<td></td>
		</tr>
		<tr>
			<td>Nematode growth medium (NGM) agar plates</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nystatin stock solution</td>
			<td>Sigma-Aldrich</td>
			<td>N3503</td>
			<td></td>
		</tr>
		<tr>
			<td>Peptone</td>
			<td>BD, Bacto</td>
			<td>211677</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride (NaCl)</td>
			<td>EMD Millipore</td>
			<td>1,06,40,41,000</td>
			<td></td>
		</tr>
		<tr>
			<td>Standard equipment for preparing agar plates (autoclave, Petri dishes, etc.)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Standard equipment for maintaining worms (platinum wire pick, incubators, etc.).</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>statistical analysis software</td>
			<td>GraphPad Software Inc., San Diego, USA</td>
			<td></td>
			<td>GraphPad Prism software package</td>
		</tr>
		<tr>
			<td>Streptomycin</td>
			<td>Sigma-Aldrich</td>
			<td>S6501</td>
			<td></td>
		</tr>
		<tr>
			<td>UV Crosslinker</td>
			<td>Vilber Lourmat BIO-LINK BLX 254</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Worm pick</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

assessment of de novo protein synthesis rates in caenorhabditis elegans

Maintaining a healthy proteome is essential for cell and organismal homeostasis. Perturbation of the balance between protein translational control and degradation instigates a multitude of age-related diseases. Decline of proteostasis quality control mechanisms is a hallmark of ageing. Biochemical methods to detect de novo protein synthesis are still limited, have several disadvantages and cannot be performed in live cells or animals. Caenorhabditis elegans, being transparent and easily genetically modified, is an excellent model to monitor protein synthesis rates by using imaging techniques. Here, we introduce and describe a method to measure de novo protein synthesis in vivo utilizing fluorescence recovery after photobleaching (FRAP). Transgenic animals expressing fluorescent proteins in specific cells or tissues are irradiated by a powerful light source resulting in fluorescence photobleaching. In turn, assessment of fluorescence recovery signifies new protein synthesis in cells and/or tissues of interest. Hence, the combination of transgenic nematodes, genetic and/or pharmacological interventions together with live imaging of protein synthesis rates can shed light on mechanisms mediating age-dependent proteostasis collapse.

Using the procedure presented here, wild type and mutant transgenic nematodes expressing the following somatic reporters, pife-2GFP, psod-3GFP and punc-119GFP, were used to assess protein synthesis rates according to the respective protocols. Particularly, wild type and ife-2 mutant worms expressing cytoplasmic GFP throughout their somatic tissues by using the ife-2 promoter were compared before, immediat...

Watch this Scientific Journal Video about Assessment of de novo Protein Synthesis Rates in Caenorhabditis elegans at JoVE.com

Assessment of de novo Protein Synthesis Rates in Caenorhabditis elegans

Here, we introduce and describe a nonradioactive and noninvasive method to assess de novo protein synthesis in vivo, utilizing the nematode Caenorhabditis elegans and fluorescence recovery after photobleaching (FRAP). This method can be combined with genetic and/or pharmacological screens to identify novel modulators of protein synthesis.

Assessment of de novo Protein Synthesis Rates in Caenorhabditis elegans

Maintaining a healthy proteome is essential for cell and organismal homeostasis. Perturbation of the balance between protein translational control and ...

The rate of protein synthesis is perturbed during disease and aging. Fluorescence recovery after photobleaching, or FRAP, allows the measurement of rate of protein synthesis in vivo. We use transparent C.elegans worms, which express GFP, as a model to monitor the novel protein synthesis after photobleaching.We provide practical guidelines to measure fluorescence recovery by using transgenic worms, which express GFP under different promoters, either widely expressed or in specific cells or tissues. Also, this method offers protein synthesis speed monitoring in real time. Use a dissecting stereomicroscope to assess the developmental stages and growth of wild-type and mutant transgenic nematodes.Pick 10 L4 larvae of wild-type and mutant transgenic animals carrying the desired fluorescent reporter onto nematode growth media plates seeded with E.coli. Incubate and grow the nematodes at the standard temperature of 20 degrees Celsius. Four days later, the plate contains a mixed population of transgenic worms.Select and transfer 15 L4 larvae of each strain on freshly seeded OP50 NGM plates. Perform FRAP assay, and monitor protein synthesis rate on day one of adulthood. The next day, prepare and use cycloheximide-containing NGM plates as a positive control.Kill bacteria by exposing the seeded NGM plates for 15 minutes with UV light. Add cycloheximide on the top of bacterial-seeded plates too 500 microgram per mL final concentration in the agar volume. Allow plates to dry.Transfer transgenic nematodes expressing GFP on vehicle and cycloheximide-containing plates. Incubate animals for two hours at the standard temperature of 20 degrees Celsius. Pick and transfer one-day adult transgenic animals to individual NGM plates seeded with a 20 microliters OP50 drop in the center.Remove the lid and place each plate under a 20H objective lens of an epifluorescent microscope. Focus and capture a reference image before photobleaching. Photobleach each sample for 10 minutes.Capture an image after photobleaching. Keep animals in individual NGM plates, and let them to recover. Image and record the recovery of each fluorescent reporter every one hour for at least six hours at an epifluorescent stereomicroscope.Prepare 2%agarose pads, and add 10 microliters drop of M9 buffer at the center of the agarose pad. Transfer five transgenic nematodes expressing pan-neuronal cytoplasmic GFP into a drop of M9 buffer. Use an eyelash to spread the liquid.Animals display reduced movements within two minutes because of M9 absorbance into the agar. Change nematode's position by using an eyelash pick. Place the sample at the 40H objective lens of an epifluorescent microscope without using a cover slip.Focus and capture a reference image. Photobleach a targeted area of interest for 90 seconds. Capture an image after photobleaching.Add a 10 microliters drop of M9 buffer on photobleached nematodes. Let the animals to recover for five minutes. Use the eyelash pick or a pipette to transfer the nematodes to individual NGM plates seeded with 20 microliters OP50 drop in the center.Capture an image of each sample every one hour under an epifluorescent stereomicroscope. Wild-type and fe-2 mutant worms expressing cytoplasmic GFP throughout their somatic tissues by using the fe-2 promoter were compared before, immediately after photobleaching, and five hours post-recovery. Wild-type animals fully recovered while fe-2 mutants had the minis recovery capacity.Thus wild type worms initiate the normal protein synthesis after photobleaching, while worms lacking mRNA translation initiation factor fe-2 are unable to do so, indicating that the rate of fluorescent recovery illustrates the rate of protein synthesis in vivo. Cycloheximide, a specific inhibitor of mRNA translation can be used as a positive control for protein translation inhibition. Indeed, cycloheximide-treated transgenic animals expressing cytoplasmic GFP under the promoter do not recover their fluorescence upon photobleaching.mRNA processing bodies affect the rate of protein translation. Wild-type and edc-3 mutant nematodes expressing GFP pan-neuronally were examined for their recovery capacity upon targeted photobleaching at the head region. Fluorescent recovery is much slower in edc-3-deficient animals compared to wild-type worms.Protein synthesis modulation is essential for organismal homeostasis. During aging, global as well as specific protein synthesis is perturbed. Protein translation balance directly controls senescence and aging.Specifically, core components of the translation machinery as well as P-body interacting components accelerate the aging process. Perturbation of translation initiation decelerates aging. Hence, measuring global protein synthesis rates by FRAP is a direct readout of the aging process.

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Biology

Osmotic Avoidance in Caenorhabditis elegans: Synaptic Function of Two Genes, Orthologues of Human NRXN1 and NLGN1, as Candidates for Autism

Neurexins and neuroligins are cell adhesion molecules present in excitatory and inhibitory synapses, and they are required for correct neuron network function1. These proteins are found at the presynaptic and postsynaptic membranes 2. Studies in mice indicate that neurexins and neurologins have an essential role in synaptic transmission 1. Recent reports have shown that altered neuronal connections during the development of the human nervous system could constitute the basis of the etiology of numerous cases of autism spectrum disorders 3.
Caenorhabditis elegans could be used as an experimental tool to facilitate the study of the functioning of synaptic components, because of its simplicity for laboratory experimentation, and given that its nervous system and synaptic wiring has been fully characterized. In C. elegans nrx-1 and nlg-1 genes are orthologous to human NRXN1 and NLGN1 genes which encode alpha-neurexin-1 and neuroligin-1 proteins, respectively. In humans and nematodes, the organization of neurexins and neuroligins is similar in respect to functional domains.
The head of the nematode contains the amphid, a sensory organ of the nematode, which mediates responses to different stimuli, including osmotic strength. The amphid is made of 12 sensory bipolar neurons with ciliated dendrites and one presynaptic terminal axon 4. Two of these neurons, named ASHR and ASHL are particularly important in osmotic sensory function, detecting water-soluble repellents with high osmotic strength 5. The dendrites of these two neurons lengthen to the tip of the mouth and the axons extend to the nerve ring, where they make synaptic connections with other neurons determining the behavioral response 6.
To evaluate the implications of neurexin and neuroligin in high osmotic strength avoidance, we show the different response of C. elegans mutants defective in nrx-1 and nlg-1 genes, using a method based on a 4M fructose ring 7. The behavioral phenotypes were confirmed using specific RNAi clones 8. In C. elegans, the dsRNA required to trigger RNAi can be administered by feeding 9. The delivery of dsRNA through food induces the RNAi interference of the gene of interest thus allowing the identification of genetic components and network pathways.

Osmotic Avoidance in Caenorhabditis elegans: Synaptic Function of Two Genes, Orthologues of Human NRXN1 and NLGN1, as Candidates for Autism

Neurexins and neuroligins are membrane-neuron adhesion proteins which perform essential roles in synaptic differentiation and transmission. Neuroligin deficient mutants of C. elegans are defective in detecting osmotic strength, but when they also contain a mutation in the gene coding neurexin, they recover the wild type phenotype.

Neurexins and neuroligins are cell adhesion molecules present in excitatory and inhibitory synapses, and they are required for correct neuron network ...

Isolation and In vitro Activation of Caenorhabditis elegans Sperm

Males and hermaphrodites are the two naturally found sexual forms in the nematode C. elegans. The amoeboid sperm are produced by both males and hermaphrodites. In the earlier phase of gametogenesis, the germ cells of hermaphrodites differentiate into limited number of sperm - around 300 - and are stored in a small 'bag' called the spermatheca. Later on, hermaphrodites continually produce oocytes1. In contrast, males produce exclusively sperm throughout their adulthood. The males produce so much sperm that it accounts for &gt;50% of the total cells in a typical adult worm2. Therefore, isolating sperm from males is easier than from that of hermaphrodites.
Only a small proportion of males are naturally generated due to spontaneous non-disjunction of X chromosome3. Crossing hermaphrodites with males or more conveniently, the introduction of mutations to give rise to Him (High Incidence of Males) phenotype are some of strategies through which one can enrich the male population3.
Males can be easily distinguished from hermaphrodites by observing the tail morphology4. Hermaphrodite's tail is pointed, whereas male tail is rounded with mating structures.
Cutting the tail releases vast number of spermatids stored inside the male reproductive tract. Dissection is performed under a stereo microscope using 27 gauge needles. Since spermatids are not physically connected with any other cells, hydraulic pressure expels internal contents of male body, including spermatids2.
Males are directly dissected on a small drop of 'Sperm Medium'. Spermatids are sensitive to alteration in the pH. Hence, HEPES, a compound with good buffering capacity is used in sperm media. Glucose and other salts present in sperm media help maintain osmotic pressure to maintain the integrity of sperm.
Post-meiotic differentiation of spermatids into spermatozoa is termed spermiogenesis or sperm activation. Shakes5, and Nelson6 previously showed that round spermatids can be induced to differentiate into spermatozoa by adding various activating compounds including Pronase E. Here we demonstrate in vitro spermiogenesis of C. elegans spermatids using Pronase E.
Successful spermiogenesis is pre-requisite for fertility and hence the mutants defective in spermiogenesis are sterile. Hitherto several mutants have been shown to be defective specifically in spermiogenesis process7. Abnormality found during in vitro activation of novel Spe (Spermatogenesis defective) mutants would help us discover additional players participating in this event.

Isolation and In vitro Activation of Caenorhabditis elegans Sperm

A protocol for isolating and activating spermatids from male C. elegans is described here. Cutting the posterior end of male releases spermatids. The spermatids can be activated by addition of protease.

Males and hermaphrodites are the two naturally found sexual forms in the nematode C. elegans. The amoeboid sperm are produced by both males and ...

Time-lapse Microscopy of Early Embryogenesis in Caenorhabditis elegans

Caenorhabditis elegans has often been used as a model system in studies of early developmental processes. The transparency of the 
embryos, the genetic resources, and the relative ease of transformation are qualities that make C. elegans an excellent model for early embryogenesis. Laser-based 
confocal microscopy and fluorescently labeled tags allow researchers to follow specific cellular structures and proteins in the developing embryo. For example, 
one can follow specific organelles, such as lysosomes or mitochondria, using fluorescently labeled dyes. These dyes can be delivered to the early embryo by means 
of microinjection into the adult gonad. Also, the localization of specific proteins can be followed using fluorescent protein tags. Examples are presented here 
demonstrating the use of a fluorescent lysosomal dye as well as fluorescently tagged histone and ubiquitin proteins. The labeled histone is used to visualize 
the DNA and thus identify the stage of the cell cycle. GFP-tagged ubiquitin reveals the dynamics of ubiquitinated vesicles in the early embryo. Observations 
of labeled lysosomes and GFP:: ubiquitin can be used to determine if there is colocalization between ubiquitinated vesicles and lysosomes. A technique for 
the microinjection of the lysosomal dye is presented. Techniques for generating transgenenic strains are presented elsewhere (1, 2). For imaging, embryos 
are cut out of adult hermaphrodite nematodes and mounted onto 2% agarose pads followed by time-lapse microscopy on a standard laser scanning confocal 
microscope or a spinning disk confocal microscope. This methodology provides for the high resolution visualization of early embryogenesis.

Time-lapse Microscopy of Early Embryogenesis in Caenorhabditis elegans

This article describes a technique for the visualization of the early events of embryogenesis in the nematode Caenorhabditis elegans.

Caenorhabditis elegans has often been used as a model system in studies of early developmental processes.  The transparency of the 
embryos, the genetic ...

Basic Caenorhabditis elegans Methods: Synchronization and Observation

Research into the molecular and developmental biology of the nematode Caenorhabditis elegans was begun in the early seventies by Sydney Brenner and it has since been used extensively as a model organism 1. C. elegans possesses key attributes such as simplicity, transparency and short life cycle that have made it a suitable experimental system for fundamental biological studies for many years 2. Discoveries in this nematode have broad implications because many cellular and molecular processes that control animal development are evolutionary conserved 3.
C. elegans life cycle goes through an embryonic stage and four larval stages before animals reach adulthood. Development can take 2 to 4 days depending on the temperature. In each of the stages several characteristic traits can be observed. The knowledge of its complete cell lineage 4,5 together with the deep annotation of its genome turn this nematode into a great model in fields as diverse as the neurobiology 6, aging 7,8, stem cell biology 9 and germ line biology 10. 
An additional feature that makes C. elegans an attractive model to work with is the possibility of obtaining populations of worms synchronized at a specific stage through a relatively easy protocol. The ease of maintaining and propagating this nematode added to the possibility of synchronization provide a powerful tool to obtain large amounts of worms, which can be used for a wide variety of small or high-throughput experiments such as RNAi screens, microarrays, massive sequencing, immunoblot or in situ hybridization, among others. 
Because of its transparency, C. elegans structures can be distinguished under the microscope using Differential Interference Contrast microscopy, also known as Nomarski microscopy. The use of a fluorescent DNA binder, DAPI (4',6-diamidino-2-phenylindole), for instance, can lead to the specific identification and localization of individual cells, as well as subcellular structures/defects associated to them.

Basic Caenorhabditis elegans Methods: Synchronization and Observation

The easiness of maintaining and propagating the nematode C. elegans make it a nice model organism to work with. The possibility of synchronizing worms allows the work with a significant amount of subjects at the same developmental stage, what facilitates the study of one particular process in many animals.

Research into the molecular and developmental biology of the nematode Caenorhabditis elegans was begun in the early seventies by Sydney Brenner and it has ...

Biochemical and High Throughput Microscopic Assessment of Fat Mass in Caenorhabditis Elegans

The nematode C. elegans has emerged as an important model for the study of conserved genetic pathways regulating fat metabolism as it relates to human obesity and its associated pathologies. Several previous methodologies developed for the visualization of C. elegans triglyceride-rich fat stores have proven to be erroneous, highlighting cellular compartments other than lipid droplets. Other methods require specialized equipment, are time-consuming, or yield inconsistent results. We introduce a rapid, reproducible, fixative-based Nile red staining method for the accurate and rapid detection of neutral lipid droplets in C. elegans. A short fixation step in 40% isopropanol makes animals completely permeable to Nile red, which is then used to stain animals. Spectral properties of this lipophilic dye allow it to strongly and selectively fluoresce in the yellow-green spectrum only when in a lipid-rich environment, but not in more polar environments. Thus, lipid droplets can be visualized on a fluorescent microscope equipped with simple GFP imaging capability after only a brief Nile red staining step in isopropanol. The speed, affordability, and reproducibility of this protocol make it ideally suited for high throughput screens. We also demonstrate a paired method for the biochemical determination of triglycerides and phospholipids using gas chromatography mass-spectrometry. This more rigorous protocol should be used as confirmation of results obtained from the Nile red microscopic lipid determination. We anticipate that these techniques will become new standards in the field of C. elegans metabolic research.

Biochemical and High Throughput Microscopic Assessment of Fat Mass in Caenorhabditis Elegans

We present robust biochemical and microscopic methods for studying Caenorhabditis elegans lipid stores. A rapid, simple, fixing-staining procedure for fluorescent lipid droplet imaging leverages the spectral properties of the lipophilic dye Nile red. We then present biochemical measurement of triglycerides and phospholipids using solid phase extraction and gas chromatography-mass spectrometry.

The nematode C. elegans has emerged as an important  model for the study of conserved genetic pathways regulating fat metabolism as  it relates to human ...

Protein WISDOM: A Workbench for In silico De novo Design of BioMolecules

The aim of de novo protein design is to find the amino acid sequences that will fold into a desired 3-dimensional structure with improvements in specific properties, such as binding affinity, agonist or antagonist behavior, or stability, relative to the native sequence. Protein design lies at the center of current advances drug design and discovery. Not only does protein design provide predictions for potentially useful drug targets, but it also enhances our understanding of the protein folding process and protein-protein interactions. Experimental methods such as directed evolution have shown success in protein design. However, such methods are restricted by the limited sequence space that can be searched tractably. In contrast, computational design strategies allow for the screening of a much larger set of sequences covering a wide variety of properties and functionality. We have developed a range of computational de novo protein design methods capable of tackling several important areas of protein design. These include the design of monomeric proteins for increased stability and complexes for increased binding affinity.
To disseminate these methods for broader use we present Protein WISDOM (<a href="http://www.proteinwisdom.org" target="_blank">http://www.proteinwisdom.org</a>), a tool that provides automated methods for a variety of protein design problems. Structural templates are submitted to initialize the design process. The first stage of design is an optimization sequence selection stage that aims at improving stability through minimization of potential energy in the sequence space. Selected sequences are then run through a fold specificity stage and a binding affinity stage. A rank-ordered list of the sequences for each step of the process, along with relevant designed structures, provides the user with a comprehensive quantitative assessment of the design. Here we provide the details of each design method, as well as several notable experimental successes attained through the use of the methods.

Protein WISDOM: A Workbench for In silico De novo Design of BioMolecules

We developed computational de novo protein design methods capable of tackling several important areas of protein design. To disseminate these methods we present Protein WISDOM, an online tool for protein design (<a href="http://www.proteinwisdom.org" target="_blank">http://www.proteinwisdom.org</a>). Starting from a structural template, design of monomeric proteins for increased stability and complexes for increased binding affinity can be performed.

The aim of de novo protein design is to find the amino acid sequences that will fold into a desired 3-dimensional structure with improvements in specific ...

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the function and regulation of protein folding was studied in vitro, in isolated tissue culture cells and in unicellular organisms. Recent studies have uncovered links between protein homeostasis (proteostasis), metabolism, development, aging, and temperature-sensing. These findings have led to the development of new tools for monitoring protein folding in the model metazoan organism Caenorhabditis elegans. In our laboratory, we combine behavioral assays, imaging and biochemical approaches using temperature-sensitive or naturally occurring metastable proteins as sensors of the folding environment to monitor protein misfolding. Behavioral assays that are associated with the misfolding of a specific protein provide a simple and powerful readout for protein folding, allowing for the fast screening of genes and conditions that modulate folding. Likewise, such misfolding can be associated with protein mislocalization in the cell. Monitoring protein localization can, therefore, highlight changes in cellular folding capacity occurring in different tissues, at various stages of development and in the face of changing conditions. Finally, using biochemical tools ex vivo, we can directly monitor protein stability and conformation. Thus, by combining behavioral assays, imaging and biochemical techniques, we are able to monitor protein misfolding at the resolution of the organism, the cell, and the protein, respectively.

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

To study the relationship between protein homeostasis, stress and aging, we monitored changes in protein folding by following protein dysfunction, protein localization in the cell and protein stability at the organismal, cellular and protein levels, using the genetically tractable metazoan Caenorhabditis elegans as a model system.

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the ...

Methods to Study Changes in Inherent Protein Aggregation with Age in Caenorhabditis elegans

In the last decades, the prevalence of neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD), has grown. These age-associated disorders are characterized by the appearance of protein aggregates with fibrillary structure in the brains of these patients. Exactly why normally soluble proteins undergo an aggregation process remains poorly understood. The discovery that protein aggregation is not limited to disease processes and instead part of the normal aging process enables the study of the molecular and cellular mechanisms that regulate protein aggregation, without using ectopically expressed human disease-associated proteins. Here we describe methodologies to examine inherent protein aggregation in Caenorhabditis elegans through complementary approaches. First, we examine how to grow large numbers of age-synchronized C. elegans to obtain aged animals and we present the biochemical procedures to isolate highly-insoluble-large aggregates. In combination with a targeted genetic knockdown, it is possible to dissect the role of a gene of interest in promoting or preventing age-dependent protein aggregation by using either a comprehensive analysis with quantitative mass spectrometry or a candidate-based analysis with antibodies. These findings are then confirmed by in vivo analysis with transgenic animals expressing fluorescent-tagged aggregation-prone proteins. These methods should help clarify why certain proteins are prone to aggregate with age and ultimately how to keep these proteins fully functional.

Methods to Study Changes in Inherent Protein Aggregation with Age in Caenorhabditis elegans

The goal of the method presented here is to explore protein aggregation during normal aging in the model organism C. elegans. The protocol represents a powerful tool to study the highly insoluble large aggregates that form with age and to determine how changes in proteostasis impact protein aggregation.

In the last decades, the prevalence of neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD), has grown. These ...

De Novo Generation of Somatic Stem Cells by YAP/TAZ

Here we present protocols to isolate primary differentiated cells and turn them into stem/progenitor cells (SCs) of the same lineage by transient expression of the transcription factor YAP. With this method, luminal differentiated (LD) cells of the mouse mammary gland are converted into cells that exhibit molecular and functional properties of mammary SCs. YAP also turns fully differentiated pancreatic exocrine cells into pancreatic duct-like progenitors. Similarly, to endogenous, natural SCs, YAP-induced stem-like cells ("ySCs") can be eventually expanded as organoid cultures long term in vitro, without further need of ectopic YAP/TAZ, as ySCs are endowed with a heritable self-renewing SC-like state. 
The reprogramming procedure presented here offers the possibility to generate and expand in vitro progenitor cells of various tissue sources starting from differentiated cells. The straightforward expansion of somatic cells ex vivo has implications for regenerative medicine, for understanding mechanisms of tumor initiation and, more in general, for cell and developmental biology studies.

De Novo Generation of Somatic Stem Cells by YAP/TAZ

Availability of somatic SCs is crucial for regenerative medicine, disease modeling and to gain insight into SC properties. Here we present experimental strategies to reprogram, in vitro, differentiated adult cells into their corresponding expandable tissue-specific stem/progenitor cells by the transient expression of the single transcriptional co-activator YAP.

Here we present protocols to isolate primary differentiated cells and turn them into stem/progenitor cells (SCs) of the same lineage by transient ...

Detecting Protein Subcellular Localization by Green Fluorescence Protein Tagging and 4',6-Diamidino-2-phenylindole Staining in Caenorhabditis elegans

In this protocol, a green fluorescence protein (GFP) fusion protein and 4',6-diamidino-2-phenylindole (DAPI) staining are used to track protein subcellular localization changes; in particular, a nuclear translocation under a heat stress condition. Proteins react correspondingly to external and internal signals. A common mechanism is to change its subcellular localization. This article describes a protocol to track protein localization that does not require an antibody, radioactive labeling, or a confocal microscope. In this article, GFP is used to tag the target protein EXL-1 in C. elegans, a member of the chloride intracellular channel proteins (CLICs) family, including mammalian CLIC4. An integrated translational exl-1::gfp transgenic line (with a promoter and a full gene sequence) was created by transformation and &#947;-radiation, and stably expresses the gene and gfp. Recent research showed that upon heat stress, not oxidative stress, EXL-1::GFP accumulates in the nucleus. Overlapping the GFP signal with both the nuclei structure and the DAPI signals confirms the EXL-1 subcellular localization changes under stress. This protocol presents two different fixation methods for DAPI staining: ethanol fixation and acetone fixation. The DAPI staining protocol presented in this article is fast and efficient and preserves both the GFP signal and the protein subcellular localization changes. This method only requires a fluorescence microscope with Nomarski, a FITC filter, and a DAPI filter. It is suitable for a small laboratory setting, undergraduate student research, high school student research, and biotechnology classrooms.

Detecting Protein Subcellular Localization by Green Fluorescence Protein Tagging and 4&#039;,6-Diamidino-2-phenylindole Staining in Caenorhabditis elegans

This protocol demonstrates how to track a protein nuclear translocation under heat stress by using a green fluorescence protein (GFP) fusion protein as a marker and 4',6-diamidino-2-phenylindole (DAPI) staining. The DAPI staining protocol is fast and preserves the GFP and protein subcellular localization signals.