We thank Chris Webster for performing the preliminary experiments shown in Figure 3 of the representative results and Jason Watts and Chris Webster for helpful comments on the manuscript. Funding for this study was provided by a grant from the National Institutes of Health (USA) (R01DK074114) to JLW. Some nematode strains used in this work were provided by the Caenorhabditis Genetics Center, which is funded by the NIH Office of Research Infrastructure Programs (P40 OD010440).

Polyunsaturated fatty acids are sensitive to heat, light and oxygen. Therefore, care must be taken when preparing fatty acid supplementation plates such that fatty acids are not exposed to excess heat and light. NGM media containing 0.1% Tergitol (NP-40) is autoclaved and partially cooled, after which fatty acid sodium salts are added with constant stirring. The plates are allowed to dry in the dark. Uptake of fatty acids by C. elegans cultured on these plates can then be monitored by gas chromatography.
1. Preparation of Fatty Acid Supplemented Media
<ol>
	<li>Measure out media components into an appropriately sized flask. Per 1 L, add 17 g Bacto-agar, 2.5 g tryptone, 3 g NaCl, 1 ml&#160;5 mg/ml cholesterol dissolved in ethanol, and 10 ml&#160;10% Tergitol dissolved in water.</li>
	<li>Add 80% of final desired volume of Millipore water and autoclave the media along with empty glass bottles (equal to the number of different fatty acid concentrations to be tested), as well as appropriate graduated cylinders.</li>
	<li>Cool media in a water bath set to 55 &#176;C. While the media is cooling prepare the working stock solution of the fatty acid sodium salt by breaking open the glass vial, using safety precautions and ensuring glass particles do not mix in with the fatty acids. Weigh out enough fatty acid to make a 100 mM working stock.</li>
	<li>Bring the fatty acid solution to a final concentration of 100 mM with purified water. Fully dissolving the fatty acid sodium salt typically takes about 20-30 min. Purge the working stock of fatty acid with argon or nitrogen, because contact with an inert gas prevents oxidation. Cap the vial and store the working stock in the dark until media has cooled.</li>
	<li>(Optional) If RNAi media is desired, measure ampicillin and Isopropyl &#946;-D-1-thiogalactopyranoside (IPTG) solutions here.</li>
	<li>When the agar has cooled to 55 &#176;C add per 1 L: 1 ml of 1 M MgSO4, 1 ml of 1 M CaCl2, and 25 ml of phosphate buffer (108.3 g KH2PO4 and 35.6 g K2HPO4 per 1 L autoclaved). Add the filter sterilized ampicillin and IPTG solutions if making RNAi plates. For all types of plates, add sterile water to bring the final media volume to 1 L.</li>
	<li>Near a flame, transfer media to an autoclaved and appropriately sized graduated cylinder and then add warm sterile water to desired volume. Transfer media back to initial flask and mix by stirring.</li>
	<li>Near a flame, transfer media into a number of bottles equal to the number of concentrations to be tested by measuring with an autoclaved and appropriately sized graduated cylinder. Maintain the aliquoted media as liquid using a water bath until the fatty acid working stock has fully dissolved.</li>
	<li>Place one bottle on a stir plate and stir until the media is warm to the touch, but not hot. Make sure to leave yourself enough time to stir in the fatty acid stock solution and pour plates before the media begins to solidify. If stir plate has temperature control, set it to 55 &#176;C.</li>
	<li>Dilute the 100 mM fatty acid working stock into the media for the final concentration desired. Stir media until the white precipitate is in solution (approximately 1 min). Media may still be slightly cloudy afterwards.</li>
	<li>(Optional) If RNAi media is desired add ampicillin to 0.1 mg/ml and IPTG to 2 mM final concentration.</li>
	<li>Pour media using an automated pipette aid and a sterile 25 ml pipette, adding 8 ml of media per 60 mm plate or 25 ml of media per 100 mm plate. Repeat fatty acid addition and plate pouring steps for the remaining bottles.</li>
	<li>After the agar has solidified, cover the fatty acid-supplemented plates with a box or store at room temperature in a well-vented drawer to protect from light oxidation.</li>
	<li>Seed E. coli&#160;OP50 onto plates two days after plates have dried. For 60 mm plates, pipette 300 &#181;l of an overnight OP50 culture (grown at 37 &#176;C). If RNAi plates were poured, seed with 300 &#181;l of RNAi bacteria after the plates have dried for four days. Plate drying time may need to be adjusted due to differences in humidity in various lab environments.</li>
	<li>Incubate the plates in a dark environment at room temperature while the bacterial lawn is drying.</li>
</ol>
2. Inducing Germ Cell Destruction by Supplementation of DGLA
<ol>
	<li>C. elegans grown on plates containing 0.3 mM DGLA (20:3n-6) become sterile due to the destruction of germ cells in both larval stage and adult nematodes.
	<ol>
		<li>Prepare a synchronized population of L1 larvae by treating gravid hermaphrodites with alkaline hypochlorite solution(for a 10 ml&#160;solution: 0.5 ml&#160;of 5M NaOH, 2.5 ml&#160;of household bleach, and 7 ml&#160;H2O). Gently rock the gravid hermaphrodites in this solution until the adult worms dissolve. Eggs will be preserved, and can be pelleted by low speed centrifugation.</li>
		<li>Wash egg preparation 3 times in M9 buffer (3 g KH2PO4, 6 g Na2HPO4, 5 g NaCl, 1 ml 1 M MgSO4, H2O to 1 L. Add MgSO4 after autoclaving). To provide enough oxygen, resuspend the eggs in a 15 ml&#160;plastic tube to a final volume of 5 ml&#160;of M9 buffer and rock on a shaker overnight.</li>
		<li>L1 larvae should be added to the supplemented plates two days after seeding with OP50, or one day after plating the RNAi bacteria. Incubate worms at 20 &#176;C for three days or until they reach the adult stage.</li>
	</ol>
	</li>
	<li>Adult worms can be scored for sterility using a dissecting microscope with high enough magnification to visualize embryos developing in the uterus. Successful germ cell loss will appear as a clear uterus void of eggs.</li>
	<li>Worms can also be scored by fixing and staining with the nucleic acid dye diamindinophenylindole (DAPI), which facilitates the visualization of nuclei in germ cells and developing embryos. A rapid DAPI stain is achieved by picking worms into a drop of M9 buffer on a watchglass9.
	<ol>
		<li>Flood watch-glass with 1 ml of a 0.2 ng/m.&#160;DAPI in 95% ethanol solution, let sit for approximately 5 min.</li>
		<li>Pick worms into a drop of VectaShield on a slide, and then cover with a coverslip.</li>
		<li>Seal coverslip and store at 4 &#176;C in the dark overnight for optimum staining, however slides can also be viewed immediately. Score for presence or absence of germ cell nuclei using a fluorescence microscope equipped with a UV lamp and filter.</li>
	</ol>
	</li>
</ol>
3. Confirming Fatty Acid Uptake by Gas Chromatography
Overall fatty acid composition of C. elegans can be determined by producing fatty acid methyl esters (FAMEs) which are then separated and quantified using gas chromatography4.
<ol>
	<li>Collect 500-1,000 adult worms by washing them off of the plates with water and transferring to a silanized 13 mm x 100 mm glass screw top tube.</li>
	<li>Let worms settle by gravity, and then remove as much water as possible with a glass Pasteur pipette.</li>
	<li>Wash worms once with water, and then again remove as much water as possible.</li>
	<li>FAMEs are formed by adding 1 ml&#160;of 2.5 % H2SO4 in methanol, and then heating at 70 &#176;C for 1 hr in a water bath.</li>
	<li>Remove the tubes from the water bath and cool for 1 min.</li>
	<li>Extract FAMEs by adding 1.5 ml&#160;water and 0.25 ml&#160;of hexane.</li>
	<li>Recap tubes and shake vigorously.</li>
	<li>Centrifuge tubes in a tabletop clinical centrifuge for 1 min&#160;at maximum speed to separate hexane from aqueous solvent.</li>
	<li>Transfer hexane (top layer) to a GC vial insert within a GC vial, being careful not to transfer any of the aqueous phase. For GC analysis, 1-2 &#956;l of FAMEs in hexane is injected onto a polar capillary gas chromatography column suitable for FAMEs analysis. The Agilent 7890 GC injector is set at 250 &#176;C, with a flow rate of 1.4 ml/min, and the GC oven is programmed for an initial temperature of 130 &#176;C, which is held for 1 min. Subsequently, the temperature is ramped 10 &#176;C/min until 190 &#176;C, and then ramped again at 5 &#176;C/min until 210 &#176;C and held for an additional 1 min.</li>
	<li>To ensure that uptake of DGLA has occurred, analyze FAMEs by flame ionization detection (FID) or mass spectrometry (MS) detection, using authentic standards for the identification of the C. elegans fatty acids.</li>
</ol>

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The authors declare that they have no competing financial interests.

Here we describe a method of supplementation of C. elegans with dietary unsaturated fatty acids. As mentioned above, care must be taken in the preparation of PUFA supplemented plates because the reactive nature of the double bonds in PUFAs causes these fatty acids to be sensitive to oxidation through heat and light11. To avoid oxidation, it is important to add the PUFA to the liquid agar medium after the media has cooled to 55 &#176;C and stores plates in a dark environment.
<p class="jove_content...

Fatty acids are essential structural components of membranes as well as efficient energy storage molecules. Additionally, fatty acids can be cleaved from cellular membranes by lipases and be enzymatically modified to produce signaling effectors1. Naturally occurring polyunsaturated fatty acids (PUFAs) contain two or more cis double bonds. The omega-3 fatty acids and the omega-6 fatty acids are distinguished from each other based on the positions of double bonds with respect to the methyl end of the fatty acid. Healthy diets require both omega-6 and omega-3 fatty acids. However, Western diets are particularly rich in omega-6 fatty acids and poor in omega-3 fatty acids. A high omega-6 to omega-3 fatty acid ratio is associated with increased risk of cardiovascular and inflammatory diseases, however, the precise beneficial and detrimental functions of specific fatty acids are not well understood2. The roundworm Caenorhabditis elegans is useful in studying fatty acid function because it synthesizes all of the enzymes necessary to produce a range of omega-6 and omega-3 fatty acids, including an omega-3 desaturase, an activity that is absent in most animals3,4 . Mutants lacking fatty acid desaturase enzymes fail to produce specific PUFAs, leading to a range of developmental and neurological defects4-6.
To study the physiological effects of dietary fatty acids, we have developed a biochemical assay compatible with genetic analysis using both mutant and RNAi knock-down techniques in C. elegans. Supplementation with specific PUFAs is achieved by adding a fatty acid sodium salt solution to the agar medium prior to pouring. This results in PUFA uptake by the E. coli food source, where it accumulates in the bacterial membranes. C. elegans ingest the PUFA-containing bacteria, and this dietary supplementation is sufficient to rescue the defects of PUFA-deficient mutants. Supplementation of most fatty acids has no detrimental effects on wild type animals, however, specific omega-6 fatty acids, especially dihomo-gamma linolenic acid (DGLA, 20:3n-6) cause a permanent destruction of C. elegans germ cells7,8 .
Gas chromatography is used to monitor the uptake of the supplemented fatty acid in the bacterial food source (either OP50 or HT115) as well as in the nematodes. The addition of the detergent Tergitol (NP-40) in the media allows for even distribution of fatty acids through the entire plate and more efficient uptake of the fatty acids by the E. coli and the nematodes. We have found that unsaturated fatty acids are readily taken up by bacteria and C. elegans, but the uptake of saturated fatty acids is much less efficient. This article will describe step-by-step how to supplement the agar media with fatty acids, as well as how to monitor fatty acid uptake in the nematode using gas chromatography.

<table border="0" cellpadding="0" cellspacing="0" width="765">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Bacto-Agar</td>
			<td style="width:128px;">Difco</td>
			<td style="width:155px;">214010</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Tryptone</td>
			<td style="width:128px;">Difco</td>
			<td style="width:155px;">211705</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">NaCl</td>
			<td style="width:128px;">J.T. Baker</td>
			<td style="width:155px;">3624-05</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Tergitol</td>
			<td style="width:128px;">Sigma</td>
			<td style="width:155px;">NP40S-500mL</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Cholesterol</td>
			<td style="width:128px;">Sigma</td>
			<td style="width:155px;">C8667-25G</td>
			<td style="width:275px;">(5 mg/mL in ethanol)</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">MgSO4</td>
			<td style="width:128px;">J.T. Baker</td>
			<td style="width:155px;">2504-01</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">CaCl2</td>
			<td style="width:128px;">J.T. Baker</td>
			<td style="width:155px;">1311-01</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">K2HPO4</td>
			<td style="width:128px;">J.T. Baker</td>
			<td style="width:155px;">3254-05</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">KH2PO4</td>
			<td style="width:128px;">J.T. Baker</td>
			<td style="width:155px;">3246-05</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:208px;">Sodium dihomogamma linolenate</td>
			<td style="width:128px;">NuCHEK</td>
			<td style="width:155px;">S-1143</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:208px;">Warm sterile Millipore water</td>
			<td style="width:128px;"></td>
			<td style="width:155px;"></td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:208px;">Sterile water for collecting worms</td>
			<td style="width:128px;"></td>
			<td style="width:155px;"></td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:208px;">Nuclease-free Water for DGLA stock solution</td>
			<td style="width:128px;">Ambion</td>
			<td style="width:155px;">AM9932</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:208px;">Ampicillin</td>
			<td style="width:128px;">Fisher Scientific</td>
			<td style="width:155px;">BP1760-25</td>
			<td style="width:275px;">100 mg/ml in water (for RNAi plates)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:208px;">Isopropyl-beta-D-thiogalactopyranoside (IPTG)</td>
			<td style="width:128px;">Gold Biotechnology</td>
			<td style="width:155px;">12481C100</td>
			<td style="width:275px;">1 M in water (for RNAi plates)</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">HSO4</td>
			<td style="width:128px;">J.T. Baker</td>
			<td style="width:155px;">9681-03</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Methanol</td>
			<td style="width:128px;">Fisher Scientific</td>
			<td style="width:155px;">A452-4</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Hexane</td>
			<td style="width:128px;">Fisher Scientific</td>
			<td style="width:155px;">H302-4</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;">diamindinophenylindole (DAPI)</td>
			<td style="width:128px;">Sigma</td>
			<td style="width:155px;">D9542</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:208px;">VectaShield</td>
			<td style="width:128px;">Vector Laboratories</td>
			<td style="width:155px;">H-1000</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Glass Flask</td>
			<td style="width:128px;">Corning</td>
			<td style="width:155px;">4980-2L</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:208px;">Autoclaveable Glass bottles with stirbars</td>
			<td style="width:128px;">Fisherbrand</td>
			<td style="width:155px;">FB-800</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:208px;">Autoclaveable Glass Graduated Cylinder</td>
			<td style="width:128px;">Fisherbrand</td>
			<td style="width:155px;">08-557</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Stir Plate</td>
			<td style="width:128px;">VWR</td>
			<td style="width:155px;">97042-642</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:208px;">Waterbath at 55+ &#176;C</td>
			<td style="width:128px;">Precision Scientific Inc.</td>
			<td style="width:155px;">66551</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Screwcap Brown Glass Vial</td>
			<td style="width:128px;">Sun SRI</td>
			<td style="width:155px;">200 494</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Argon gas tank</td>
			<td style="width:128px;"></td>
			<td style="width:155px;"></td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Automated Pipette aid</td>
			<td style="width:128px;">Pipette-Aid</td>
			<td style="width:155px;">P-90297</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:208px;">Sterile Serological Pipettes (25 ml)</td>
			<td style="width:128px;">Corning</td>
			<td style="width:155px;">4489</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Bunsen Burner</td>
			<td style="width:128px;">VWR</td>
			<td style="width:155px;">89038-534</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Dissection microscope</td>
			<td style="width:128px;">Leica</td>
			<td style="width:155px;">TLB3000</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Silanized glass tube</td>
			<td style="width:128px;">Thermo Scientific</td>
			<td style="width:155px;">STT-13100-S</td>
			<td>for FAMEs derivitization</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:208px;">PTFE Screw caps</td>
			<td style="width:128px;">Kimble-Chase</td>
			<td style="width:155px;">1493015D</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Clinical tabletop centrifuge</td>
			<td style="width:128px;">IEC</td>
			<td style="width:155px;"></td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">GC Crimp Vial</td>
			<td style="width:128px;">SUN SRi</td>
			<td style="width:155px;">200 000</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">GC Vial Insert</td>
			<td style="width:128px;">SUN SRi</td>
			<td style="width:155px;">200 232</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">GC Vial cap</td>
			<td style="width:128px;">SUN SRi</td>
			<td style="width:155px;">200 100</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Gas Chromatograph</td>
			<td style="width:128px;">Agilent</td>
			<td style="width:155px;">7890A</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Mass Spectrometry Detector</td>
			<td style="width:128px;">Agilent</td>
			<td style="width:155px;">5975C</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:208px;">Column for gas chromatography</td>
			<td style="width:128px;">Suppelco</td>
			<td style="width:155px;">SP 2380</td>
			<td>30 m x 0.25 mm fused silica capillary column</td>
		</tr>
	</tbody>
</table>

dietary supplementation of polyunsaturated fatty acids in caenorhabditis elegans

Fatty acids are essential for numerous cellular functions. They serve as efficient energy storage molecules, make up the hydrophobic core of membranes, and participate in various signaling pathways. Caenorhabditis elegans synthesizes all of the enzymes necessary to produce a range of omega-6 and omega-3 fatty acids. This, combined with the simple anatomy and range of available genetic tools, make it an attractive model to study fatty acid function. In order to investigate the genetic pathways that mediate the physiological effects of dietary fatty acids, we have developed a method to supplement the C. elegans diet with unsaturated fatty acids. Supplementation is an effective means to alter the fatty acid composition of worms and can also be used to rescue defects in fatty acid-deficient mutants. Our method uses nematode growth medium agar (NGM) supplemented with fatty acidsodium salts. The fatty acids in the supplemented plates become incorporated into the membranes of the bacterial food source, which is then taken up by the C. elegans that feed on the supplemented bacteria. We also describe a gas chromatography protocol to monitor the changes in fatty acid composition that occur in supplemented worms. This is an efficient way to supplement the diets of both large and small populations of C. elegans, allowing for a range of applications for this method.

Supplementation of the C. elegans diet is limited by the ability of the bacterial food source to uptake and incorporate fatty acid into the bacterial membrane. To determine the ability of E. coli OP50 to assimilate various fatty acids into its membranes, OP50 was plated onto media with no supplement, 0.1 mM and 0.3 mM concentrations of stearic acid (18:0), sodium oleate (18:1n-9), and sodium DGLA (20:3n-6). Plates were dried at room temperature for 2 days in the dark, and incubated at 20 &#176;C for 3 d...

Watch this Scientific Journal Video about Dietary Supplementation of Polyunsaturated Fatty Acids in Caenorhabditis elegans at JoVE.com

Dietary Supplementation of Polyunsaturated Fatty Acids in Caenorhabditis elegans

Caenorhabditis elegans is a useful model to explore the functions of polyunsaturated fatty acids in development and physiology. This protocol describes an efficient method of supplementing the C. elegans diet with polyunsaturated fatty acids.

Dietary Supplementation of Polyunsaturated Fatty Acids in Caenorhabditis elegans

Fatty acids are essential for numerous cellular functions. They serve as efficient energy storage molecules, make up the hydrophobic core of membranes, ...

dietary-supplementation-polyunsaturated-fatty-acids-caenorhabditis

Research

JoVE Journal

Biology

17.0K Views.  Washington State University. Caenorhabditis elegans is a useful model to explore the functions of polyunsaturated fatty acids in development and physiology. This protocol describes an efficient method of supplementing the C. elegans diet with polyunsaturated fatty acids. 

Video: Dietary Supplementation of Polyunsaturated Fatty Acids in Caenorhabditis elegans

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 ...

Solid Plate-based Dietary Restriction in Caenorhabditis elegans

Reduction of food intake without malnutrition or starvation is known to increase lifespan and delay the onset of various age-related diseases in a wide range of species, including mammals. It also causes a decrease in body weight and fertility, as well as lower levels of plasma glucose, insulin, and IGF-1 in these animals. This treatment is often referred to as dietary restriction (DR) or caloric restriction (CR). The nematode Caenorhabditis elegans has emerged as an important model organism for studying the biology of aging. Both environmental and genetic manipulations have been used to model DR and have shown to extend lifespan in C. elegans. However, many of the reported DR studies in C. elegans were done by propagating animals in liquid media, while most of the genetic studies in the aging field were done on the standard solid agar in petri plates. Here we present a DR protocol using standard solid NGM agar-based plate with killed bacteria.

Solid Plate-based Dietary Restriction in Caenorhabditis elegans

Here we present a protocol for performing solid plate-based dietary restriction in C. elegans with killed bacteria.

Reduction of food intake without malnutrition or starvation is known to increase lifespan and delay the onset of various age-related diseases in a wide ...

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 ...

Prostaglandin Extraction and Analysis in Caenorhabditis elegans

Caenorhabditis elegans is emerging as a powerful animal model to study the biology of lipids1-9. Prostaglandins are an important class of eicosanoids, which are lipid signals derived from polyunsaturated fatty acids (PUFAs)10-14. These signalling molecules are difficult to study because of their low abundance and reactive nature. The characteristic feature of prostaglandins is a cyclopentane ring structure located within the fatty acid backbone. In mammals, prostaglandins can be formed through cyclooxygenase enzyme-dependent and -independent pathways10,15. C. elegans synthesizes a wide array of prostaglandins independent of cyclooxygenases6,16,17. A large class of F-series prostaglandins has been identified, but the study of eicosanoids is at an early stage with ample room for new discoveries. Here we describe a procedure for extracting and analyzing prostaglandins and other eicosanoids. Charged lipids are extracted from mass worm cultures using a liquid-liquid extraction technique and analyzed by liquid chromatography coupled to electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The inclusion of deuterated analogs of prostaglandins, such as PGF2 &alpha;-d4 as an internal standard is recommended for quantitative analysis. Multiple reaction monitoring or MRM can be used to quantify and compare specific prostaglandin types between wild-type and mutant animals. Collision-induced decomposition or MS/MS can be used to obtain information on important structural features. Liquid chromatography mass spectrometry (LC-MS) survey scans of a selected mass range, such as m/z 315-360 can be used to evaluate global changes in prostaglandin levels. We provide examples of all three analyses. These methods will provide researchers with a toolset for discovering novel eicosanoids and delineating their metabolic pathways.

Prostaglandin Extraction and Analysis in Caenorhabditis elegans

In this paper, we describe an optimized procedure for extracting and analyzing prostaglandins and other eicosanoids from C. elegans using LC-MS/MS.

Caenorhabditis elegans is emerging as a powerful animal model to study the biology of lipids1-9. Prostaglandins are an important class of eicosanoids, ...

Cultivation of Caenorhabditis elegans in Three Dimensions in the Laboratory

The use of genetic model organisms such as Caenorhabditis elegans has led to seminal discoveries in biology over the last five decades. Most of what we know about C. elegans is limited to laboratory cultivation of the nematodes that may not necessarily reflect the environments they normally inhabit in nature. Cultivation of C. elegans in a 3D habitat that is more similar to the 3D matrix that worms encounter in rotten fruits and vegetative compost in nature could reveal novel phenotypes and behaviors not observed in 2D. In addition, experiments in 3D can address how phenotypes we observe in 2D are relevant for the worm in nature. Here, a new method in which C. elegans grows and reproduces normally in three dimensions is presented. Cultivation of C. elegans in Nematode Growth Tube-3D (NGT-3D) can allow us to measure the reproductive fitness of C. elegans strains or different conditions in a 3D environment. We also present a novel method, termed Nematode Growth Bottle-3D (NGB-3D), to cultivate C. elegans in 3D for microscopic analysis. These methods allow scientists to study C. elegans biology in conditions that are more reflective of the environments they encounter in nature. These can help us to understand the overlying evolutionary relevance of the physiology and behavior of C. elegans we observe in the laboratory.

Cultivation of Caenorhabditis elegans in Three Dimensions in the Laboratory

We present a simple method to construct 3D nematode cultivation systems called NGT-3D and NGB-3D. These can be used to study nematode fitness and behaviors in habitats that are more similar to natural Caenorhabditis elegans habitats than the standard 2D laboratory C. elegans culture plates.

The use of genetic model organisms such as Caenorhabditis elegans has led to seminal discoveries in biology over the last five decades. Most of what we ...

Measurement of Oxygen Consumption Rates in Intact Caenorhabditis elegans

Optimal mitochondrial function is critical for healthy cellular activity, particularly in cells that have high energy demands like those in the nervous system and muscle. Consistent with this, mitochondrial dysfunction has been associated with a myriad of neurodegenerative diseases and aging in general. Caenorhabditis elegans have been a powerful model system for elucidating the many intricacies of mitochondrial function. Mitochondrial respiration is a strong indicator of mitochondrial function and recently developed respirometers offer a state-of-the-art platform to measure respiration in cells. In this protocol, we provide a technique to analyze live, intact C. elegans. This protocol spans a period of ~7 days and includes steps for (1) growing and synchronization of C. elegans, (2) preparation&#160;of compounds to be injected and hydration of probes, (3) drug loading and cartridge equilibration, (4) preparation of worm assay plate and assay run, and (5) post-experiment data analysis.

Measurement of Oxygen Consumption Rates in Intact Caenorhabditis elegans

Mitochondrial respiration is critical for organismal survival; therefore, oxygen consumption rate is an excellent indicator of mitochondrial health. In this protocol, we describe the use of a commercially available respirometer to measure basal and maximal oxygen consumption rates in live, intact, and freely-motile Caenorhabditis elegans.

Optimal mitochondrial function is critical for healthy cellular activity, particularly in cells that have high energy demands like those in the nervous ...

Purification and Analysis of Caenorhabditis elegans Extracellular Vesicles

The secretion of small membrane-bound vesicles into the external environment is a fundamental physiological process of all cells. These extracellular vesicles (EVs) function outside the cell to regulate global physiological processes by transferring proteins, nucleic acids, metabolites, and lipids between tissues. EVs reflect the physiological state of their cells of origin. EVs are implicated to have fundamental roles in virtually every aspect of human health. Thus, EV protein and genetic cargos are being increasingly analyzed for biomarkers of health and disease. However, the EV field still lacks a tractable invertebrate model system that permits the study of EV cargo composition. C. elegans is well suited for EV research because it actively secretes EVs outside of its body into its external environment, permitting facile isolation. This article provides all the necessary information for generating, purifying, and quantifying these environmentally secreted C. elegans EVs including how to work quantitatively with very large populations of age-synchronized worms, purifying EVs, and a flow cytometry protocol that directly measures the number of intact EVs in the purified sample. Thus, the large library of genetic reagents available for C. elegans research can be tapped into for investigating the impacts of genetic pathways and physiological processes on EV cargo composition.

Purification and Analysis of Caenorhabditis elegans Extracellular Vesicles

This article presents methods for generating, purifying, and quantifying Caenorhabditis elegans extracellular vesicles.

The secretion of small membrane-bound vesicles into the external environment is a fundamental physiological process of all cells. These extracellular ...

Quantifying Tissue-Specific Proteostatic Decline in Caenorhabditis elegans

The ability to maintain proper function and folding of the proteome (protein homeostasis) declines during normal aging, facilitating the onset of a growing number of age-associated diseases. For instance, proteins with polyglutamine expansions are prone to aggregation, as exemplified with the huntingtin protein and concomitant onset of Huntington&#8217;s disease. The age-associated deterioration of the proteome has been widely studied through the use of transgenic Caenorhabditis elegans expressing polyQ repeats fused to a yellow fluorescent protein (YFP). This polyQ::YFP transgenic animal model facilitates the direct quantification of the age-associated decline of the proteome through imaging the progressive formation of fluorescent foci (i.e., protein aggregates) and subsequent onset of locomotion defects that develop as a result of the collapse of the proteome. Further, the expression of the polyQ::YFP transgene can be driven by tissue-specific promoters, allowing the assessment of proteostasis across tissues in the context of an intact multicellular organism. This model is highly amenable to genetic analysis, thus providing an approach to quantify aging that is complementary to lifespan assays. We describe how to accurately measure polyQ::YFP foci formation within either neurons or body wall muscle during aging, and the subsequent onset of behavioral defects. Next, we highlight how these approaches can be adapted for higher throughput, and potential future applications using other emerging strategies for C. elegans genetic analysis.

Quantifying Tissue-Specific Proteostatic Decline in Caenorhabditis elegans

Proteostatic decline is a hallmark of aging, facilitating the onset of neurodegenerative diseases. We outline a protocol to quantifiably measure proteostasis in two different Caenorhabditis elegans tissues through heterologous expression of polyglutamine repeats fused to a fluorescent reporter. This model allows rapid in vivo genetic analysis of proteostasis.

The ability to maintain proper function and folding of the proteome (protein homeostasis) declines during normal aging, facilitating the onset of a ...

Automating Aggregate Quantification in Caenorhabditis elegans

A rise in the prevalence of neurodegenerative protein conformational diseases (PCDs) has fostered a great interest in this subject over the years. This increased attention has called for the diversification and improvement of animal models capable of reproducing disease phenotypes observed in humans with PCDs. Though murine models have proven invaluable, they are expensive and are associated with laborious, low-throughput methods. Use of the Caenorhabditis elegans nematode model to study PCDs has been justified by its relative ease of maintenance, low cost, and rapid generation time, which allow for high-throughput applications. Additionally, high conservation between the C. elegans and human genomes makes this model an invaluable discovery tool. Nematodes that express fluorescently tagged tissue-specific polyglutamine (polyQ) tracts exhibit age- and polyQ length-dependent aggregation characterized by fluorescent foci. Such reporters are often employed as proxies to monitor changes in proteostasis across tissues. Manual aggregate quantification is time-consuming, limiting experimental throughput. Furthermore, manual foci quantification can introduce bias, as aggregate identification can be highly subjective. Herein, a protocol consisting of worm culturing, image acquisition, and data processing was standardized to support high-throughput aggregate quantification using C. elegans that express intestine-specific polyQ. By implementing a C. elegans-based image processing pipeline using CellProfiler, an image analysis software, this method has been optimized to separate and identify individual worms and enumerate their respective aggregates. Though the concept of automation is not entirely unique, the need to standardize such procedures for reproducibility, elimination of bias from manual counting, and increase throughput is high. It is anticipated that these methods can drastically simplify the screening process of large bacterial, genomic, or drug libraries using the C. elegans model.

Automating Aggregate Quantification in Caenorhabditis elegans

The following protocol describes the development and optimization of a high-throughput workflow for worm culturing, fluorescence imaging, and automated image processing to quantify polyglutamine aggregates as an assessment of changes in proteostasis.

A rise in the prevalence of neurodegenerative protein conformational diseases (PCDs) has fostered a great interest in this subject over the years. This ...