Name: mouse adipose tissue collection and processing for rna analysis
Uploaded: 2018-01-31T14:00:00
Description: Watch this Scientific Journal Video about Mouse Adipose Tissue Collection and Processing for RNA Analysis at JoVE.com

This work was supported by Diabetes Canada.

Care of the mice used in the procedures complied with standards for the care and use of experimental animals set by the Canadian Council for the Protection of Animals. All procedures were approved by the University Animal Care and Use Committee at the CHUM Research Center.
1. Necropsy and Adipose Tissue Collection from Male Mice
<ol>
	<li>Make experimental groups according to study objectives. In this study, samples were collected from two groups of male mice on a C57Bl/6 background (n=12-14...

<ol>
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Following HF-diet feeding, obese mice were found to have increased body and white adipose tissue weights compared to mice fed a N diet. RNA extracted using phenol solution yielded samples with good purity. Leptin is an adipokine primarily produced by adipose tissue and is known to correlate positively with fat mass16. As expected, leptin mRNA expression increased in obese mice in concomitance with their fat mass.
This method has several critical steps. The major one is ...

Obesity is a worldwide epidemic which can lead to complications such as type 2 diabetes1. Diet-induced obese and genetically modified animal models are frequently used for research in obesity and its associated complications. Traditionally, white adipose tissue is known as a storage compartment for excess energy and is mostly composed of lipids while brown adipose tissue converts energy into heat2,3. Adipose tissue is dynamic and will expand and shrink depending on many factors such as food intake and physical activity. Hence, to determine contributing factors to these changes, adequate adipose tissue collection and handling are required4.
Among white adipose tissues, it is generally accepted that subcutaneous and visceral fat depots have different properties such as anatomical localization and function2,5. Consequently, to avoid conflicting results or large variability, attention needs to be taken to avoid cross-contamination between these different fat depots when collecting fat pads.
Moreover, there are three major challenges when isolating RNA or protein from mice white adipose tissue. First, collecting fat pads in obese mice is not an easy task as the border which separates different white fat depots is not always clear, in contrast to other organs such as the kidneys and heart6. Second, because of the high lipid content of adipose tissue, during RNA or protein isolation, a layer of lipids floats on top and prevents direct access to the sample. Third, as opposed to brown adipose tissue or other tissues, white adipose tissue has considerably lower RNA and protein content and this is of major concern when using young mice, mice fed a normal (N) diet and mice which are expected to have low fat masses (i.e. KO models, treatment with drugs, exercise training, etc.)7,8.
Therefore, choosing the appropriate method to isolate the RNA from adipose tissue is critical. Alternative methods to phenol/chloroform extraction are commercial kits. They are typically based on an initial phenol extraction step, followed by RNA purification on a column9. However, those kits are typically more expensive and give samples of lower yield, while the RNA quality might be variable but are less time consuming. However, one of the biggest advantages to phenol solution/chloroform extraction described here is the possibility of isolating RNA, DNA, and protein from a single sample10. Since mice fat pads are usually small and give small quantity of RNA and proteins (especially in lean mouse models), these protocols maximize the data one can get out of a small sample.
The objective of this paper is to describe in detail a method to ensure adequate sample collection from three mice white adipose tissue depots as well as quantity and quality of RNA isolation. RNA obtained by following this protocol can be used to perform real-time PCR assays. This protocol is not intended for RNA isolation from cultured primary adipocytes.

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			<td height="21" style="height:21px;width:457px;">1 mL seringes</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">1X TE solution (10 mM Tris-HCl and 1 mM EDTA&#8226;Na2. pH 8.0)</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:457px;">22 G needles</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:457px;">26 G needles</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:457px;">75% Ethanol</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Block heater (dry bath)</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Chloroform</td>
			<td>Sigma</td>
			<td>C2432-500mL</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">dATP&#160;&#160;&#160;</td>
			<td style="width:189px;">Thermo scientific</td>
			<td style="width:189px;">R0141</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">dCTP&#160;&#160;</td>
			<td style="width:189px;">Thermo scientific</td>
			<td style="width:189px;">R0151</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">dGTP&#160;&#160;</td>
			<td style="width:189px;">Thermo scientific</td>
			<td style="width:189px;">R0161</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">DNase I (1 U/&#181;l)&#160;</td>
			<td style="width:189px;">Thermo scientific</td>
			<td style="width:189px;">EN0521</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">dTTP&#160;</td>
			<td style="width:189px;">Thermo scientific</td>
			<td style="width:189px;">R0171</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Faststart Universal SYBR green Master (Rox)</td>
			<td style="width:189px;">Roche</td>
			<td style="width:189px;">4913922001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Faststart universal SYBR green master (Rox) fluorescent dye&#160;</td>
			<td style="width:189px;">Roche</td>
			<td style="width:189px;">4913914001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Filtered tips</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Forceps&#160;</td>
			<td style="width:189px;">Instrumentarium</td>
			<td>HB275</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Gauze</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Hammer</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">High fat rodent diet</td>
			<td>Bio-Serv, Frenchtown, NJ</td>
			<td style="width:189px;">F3282</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Isopropanol&#160;</td>
			<td>Laboratoire MAT</td>
			<td>IH-0101</td>
			<td></td>
		</tr>
		<tr height="39">
			<td height="39" style="height:39px;width:457px;">Leptin forward PCR primer (5&#8217;-GGGCTTCACCCCATTCTGA-3&#8217;) 10 uM</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="39">
			<td height="39" style="height:39px;width:457px;">Leptin reverse PCR primer (5&#8217;-GGCTATCTGCAGCACATTTTG-3&#8217;) 10 uM</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Liquid nitrogen</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Maxima Reverse Transcriptase (enzyme and 5x buffer)</td>
			<td style="width:189px;">Thermo scientific</td>
			<td style="width:189px;">EP0742</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Nanopure water (referred as ultrapure water)</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Nitrile examination gloves</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Nitrile gloves</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="39">
			<td height="39" style="height:39px;width:457px;">Normal rodent diet</td>
			<td style="width:189px;">Harlan Laboratories, Madison, WI</td>
			<td style="width:189px;">Harlan 2018</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">P1000 pipetman</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">P2 pipetman</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:457px;">P20 pipetman</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:457px;">P200 pipetman</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Phenol solution (TRIzol)&#160;</td>
			<td style="width:189px;">Ambion Life Technologies</td>
			<td style="width:189px;">15598018</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Pre-identified aluminium foil</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Quartz spectrophotometer cuvette</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Rack for PCR tube strips</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Racks for RT-PCR tube strips</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Random hexamers&#160;</td>
			<td style="width:189px;">Invitrogen</td>
			<td style="width:189px;">58875</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:457px;">Real-time PCR Rotor Gene system&#160;</td>
			<td style="width:189px;">Corbett research</td>
			<td style="width:189px;">RG-3000 Rotor-Gene thermal cycler</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Refrigerated bench-top centrifuge</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">RiboLock RNase Inhibitor&#160;</td>
			<td style="width:189px;">Thermo scientific</td>
			<td style="width:189px;">EO0381</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">RNase-free 1.5 mL eppendorf tubes</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">RNase-free 1.5 mL screw cap tubes</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RNase-free PCR tube strips (0.2 mL) and caps</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">RNase-free water&#160;</td>
			<td style="width:189px;">Hyclone</td>
			<td style="width:189px;">SH30538.02</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">RT-PCR machine</td>
			<td style="width:189px;">Qiagen</td>
			<td style="width:189px;">Rotor-Gene Corbett 3000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">RT-PCR tube strips (0.1 mL) and caps</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="39">
			<td height="39" style="height:39px;width:457px;">S16 forward PCR primer (5&#8217;-ATCTCAAAGGCCCTGGTAGC-3&#8217;) 10 uM</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="39">
			<td height="39" style="height:39px;width:457px;">S16 reverse PCR primer (5&#8217; ACAAAGGTAAACCCCGATCG-3&#8217;) 10 uM</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Spectrophotometer</td>
			<td style="width:189px;">Biochrom</td>
			<td style="width:189px;">Ultrospec 3100 pro</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Stainless steel mortar and pestle</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="77">
			<td height="77" style="height:77px;width:457px;">Surgical pads</td>
			<td style="width:189px;">Home made a foam board wrapped in a disposable absorbent underpad</td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Surgical scissors&#160;</td>
			<td style="width:189px;">Intrumentarium</td>
			<td style="width:189px;">130.450.11</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Thermal cycler</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Thermal cycler&#160;</td>
			<td style="width:189px;">Biometra</td>
			<td style="width:189px;">Thermocycler</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Vortex mixer</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:457px;">Weighing spatula</td>
			<td style="width:189px;"></td>
			<td style="width:189px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

mouse adipose tissue collection and processing for rna analysis

Compared to other tissues, white adipose tissue has a considerably less RNA and protein content for downstream applications such as real-time PCR and Western Blot, since it mostly contains lipids. RNA isolation from adipose tissue samples is also challenging as extra steps are required to avoid these lipids. Here, we present a procedure to collect three anatomically different white adipose tissues from mice, to process these samples and perform RNA isolation. We further describe the synthesis of cDNA and gene expression experiments using real-time PCR. The hereby described protocol allows the reduction of contamination from the animal's hair and blood on fat pads as well as cross-contamination between different fat pads during tissue collection. It has also been optimized to ensure adequate quantity and quality of the RNA extracted. This protocol can be widely applied to any mouse model where adipose tissue samples are required for routine experiments such as real-time PCR but is not intended for isolation from primary adipocytes cell culture.

Following the necropsy procedure, three white adipose tissues were collected and weighted from the two groups of mice (N and HF diet-fed mice). As expected, mice on the HF diet had increased final body weight and weight gain compared to littermates on N diet (Table 1). These observations were accompanied by more than a 2-fold increase in the weight of the PGF, PRF, and SCF in obese mice compared to those on N diet.
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Watch this Scientific Journal Video about Mouse Adipose Tissue Collection and Processing for RNA Analysis at JoVE.com

Mouse Adipose Tissue Collection and Processing for RNA Analysis

The purpose of this paper is to present a step-by-step procedure to collect different white adipose tissues from mice, process the fat samples and extract RNA.

Compared to other tissues, white adipose tissue has a considerably less RNA and protein content for downstream applications such as real-time PCR and ...

The overall goal of this procedure is to ensure adequate sample collection of white adipose tissue depots from different mice, and to isolate a high amount of good-quality RNA from the tissue. This method can answer key questions in the fields of metabolism, biochemistry and molecular biology that, for example, pertain to gene expression in adipose tissue from treated or genetically-modified mice. The main advantage of this technique is that it allows for the isolation of high amounts of good-quality RNA from adipose tissue which typically has low RNA content.Demonstrating the procedure will be Emilie Pepin, a research assistant from my laboratory. After euthanizing a mouse, cut the skin over the linea alba according to the text protocol, then make two incisions of approximately two centimeters from the middle of the ribcage towards the right arm and close to the genital organs above the right hind limb. Stretch one corner of the opened skin and use a 22-gauge needle to pin it down on the pad.Then, pin down the other corner. Using surgical scissors positioned against the skin as flat as possible, carry out blunt dissection of the abdominal subcutaneous fat, or SCF, then transfer it to a precut piece of aluminum foil. Repeat the dissection for the left side of the animal.Then, pull both the left and right collected fat pads in the aluminum foil and use liquid nitrogen to freeze the sample. To get access to the visceral adipose tissue, cut the abdominal muscle along the linea alba. Then, make an incision in the abdominal muscles from the genitals towards the back of the mouse on both sides.The fat around the reproductive organs is the perigonadal fat, or PGF. Detach the left and right fat pads from the epididymis, the testes and the ductus deferens and transfer it to the pre-labeled aluminum foil. Then, freeze the sample in liquid nitrogen.Starting with the left-hand side, expose the kidneys by moving the gut away from the abdominal cavity to the right-hand side. The adipose tissue seen here surrounding the kidney and the adrenal glands is the perirenal fat, or PRF. Isolate and remove the adrenal glands before collecting the PRF.This can be tedious as they are just a bit pinker than the adipose tissue. Now, isolate the PRF from the back muscular wall and cut the ureter, the renal artery and vein which separates the PRF and kidney from the rest of the body. Then, isolate the PRF from the kidney by cutting and removing the renal capsule.After isolating the right PRF, transfer the sample to the aluminum foil with the tissue from the left side and use liquid nitrogen to freeze the samples. Chill 1.5-milliliter RNase-free conical tubes, a mortar and pestle and a spatula in liquid nitrogen according to the text protocol. Put the adipose tissue sample in the mortar then use a few layers of brown paper to lift the pestle from the liquid nitrogen and fit it into the mortar.While holding the pestle with the paper, use the hammer to hit the top of the pestle once or twice. Next, grind the sample using a rotating motion until a fine powder is obtained. Then, remove the pestle, retrieve the spatula from the liquid nitrogen and use it to transfer the sample into the corresponding pre-chilled 1.5-milliliter conical tube.Dip the spatula back into liquid nitrogen from time to time to prevent the sample from melting. Also, keep the conical tube on dry ice to prevent the sample from thawing. Fill the conical tube to approximately 2/3 capacity with ground sample for adequate RNA yield.Then, prepare the remaining samples according to the text protocol. Under a chemical hood and while wearing a lab coat, gloves and safety glasses, remove a ground sample from liquid nitrogen. Slowly open the tube, and add 500 microliters of phenol solution.Close the lid of the tube and vortex at maximum speed for about five seconds, then slowly and carefully open the tube to release the pressure from the nitrogen. The sound of air coming out of the tube will be heard. Pipette an additional 500 microliters of phenol solution into the tube.Then, vortex and slowly open it as before. Vortex the sample until it is completely dissolved. Then, open the tube to release pressure before processing additional samples.Once all samples have been processed, briefly vortex them at maximum speed and incubate them at room temperature for five minutes. Centrifuge the tubes at 12, 000 times G and four degrees Celsius for 10 minutes. Then, bring the tubes back to room temperature.To avoid contamination, for each sample, use a P1000 pipette with a filtered tip to isolate as much RNA as possible from the middle pink layer by piercing the lipid phase near the side of the tube. Dispense the RNA into the new conical tubes without touching the sides of the tubes to prevent transferring lipids present on the outside of the tip. Add 200 microliters of pure chloroform to each sample and mix the tubes by inversion for 15 seconds.Then, after incubating the samples at room temperature for 10 minutes, centrifuge the tubes at 12, 000 times G and four degrees Celsius for 15 minutes and bring the tubes back to room temperature. For each sample, use a P1000 pipette and filtered tips to transfer as much aqueous transparent RNA-containing top phase as possible to the second set of corresponding conical tubes. Next, add 500 microliters of 100%isopropanol to each sample and mix the tubes by inversion for 15 seconds.Then, incubate the samples at room temperature for 10 minutes. Centrifuge the tubes at 12, 000 times G and four degrees Celsius for 10 minutes before bringing the tubes back to room temperature. Discard the isopropanol by pouring it out of each tube.Now, add one milliliter of 75%ethanol to each sample and briefly vortex the tubes at maximum speed. Then, centrifuge the samples at 7, 500 times G and four degrees Celsius for five minutes. After spinning the samples and bringing them to room temperature, discard the 75%ethanol by inverting each tube and lighting tapping them against brown paper to remove any residual ethanol.Leave the lid open and air-dry the RNA pellet for about 15 to 20 minutes. After evaluating the size of the RNA pellets, add 10 to 25 microliters of RNase-free water to each sample. Incubate the samples in a heat block at 60 degrees Celsius for five minutes.Then, briefly vortex the tubes. Incubate the samples in the same heat block for an additional five minutes. Then, quickly spin all the samples and immediately place them on ice.Carry out RT-PCR for gene expression in adipose tissue according to the text protocol. As expected, mice on the high fat diet had increased body weight and weight gain compared to litter mates on the normal diet. These observations were accompanied by a more than two-fold increase in the weight of the PGF, PRF and SCF in obese mice compared to those on the normal diet.This table shows that for each white adipose tissue, RNA isolation by phenol solution produced samples with an OD260 over OD280 of around 2.0 which is considered pure for RNA. As seen in this bar graph, realtime PCR data showed that leptin mRNA expression was significantly higher in PGF, PRF and SCF of obese mice compared to those on a normal diet. The differences observed in leptin mRNA expression were not due to a variation of s16, the reference gene used to normalize the results between the two groups of mice as CT values were not altered.Once mastered, this technique can be done in four hours if it is performed properly. While attempting this procedure, it's important to remember to work in an RNase-free environment during the RNA extraction procedure. Following this procedure, other methods like realtime PCR amplification can be performed in order to answer additional questions like gene expression modifications.After its development, this technique paved the way for researchers in the field of metabolism to explore adipose tissue modulations related to obesity and diabetes in rodents. After watching this video, you should have a good understanding of how to isolate different fat pads and isolate RNA from them. Don't forget that working with the phenol solution can be extremely hazardous, and precautions such as wearing a lab coat and gloves should always be taken while performing this procedure.

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Research

JoVE Journal

Biochemistry

Experimental Design for Laser Microdissection RNA-Seq: Lessons from an Analysis of Maize Leaf Development

Genes with important roles in development frequently have spatially and/or temporally restricted expression patterns. Often these gene transcripts are not detected or are not identified as differentially expressed (DE) in transcriptomic analyses of whole plant organs. Laser Microdissection RNA-Seq (LM RNA-Seq) is a powerful tool to identify genes that are DE in specific developmental domains. However, the choice of cellular domains to microdissect and compare, and the accuracy of the microdissections are crucial to the success of the experiments. Here, two examples illustrate design considerations for transcriptomics experiments; a LM RNA-seq analysis to identify genes that are DE along the maize leaf proximal-distal axis, and a second experiment to identify genes that are DE in liguleless1-R (lg1-R) mutants compared to wild-type. Key elements that contributed to the success of these experiments were detailed histological and in situ hybridization analyses of the region to be analyzed, selection of leaf primordia at equivalent developmental stages, the use of morphological landmarks to select regions for microdissection, and microdissection of precisely measured domains. This paper provides a detailed protocol for the analysis of developmental domains by LM RNA-Seq. The data presented here illustrate how the region selected for microdissection will affect the results obtained.

Many developmentally important genes have cell- or tissue-specific expression patterns. This paper describes LM RNA-seq experiments to identify genes that are differentially expressed at the maize leaf blade-sheath boundary and in lg1-R mutants compared to wild-type. The experimental considerations discussed here apply to transcriptomic analyses of other developmental phenomena.

Genes with important roles in development frequently have spatially and/or temporally restricted expression patterns. Often these gene transcripts are not ...

An Efficient Method for the Isolation of Highly Purified RNA from Seeds for Use in Quantitative Transcriptome Analysis

Plant seeds accumulate large amounts of storage reserves comprising biodegradable organic matter. Humans rely on seed storage reserves for food and as industrial materials. Gene expression profiles are powerful tools for investigating metabolic regulation in plant cells. Therefore, detailed, accurate gene expression profiles during seed development are required for crop breeding. Acquiring highly purified RNA is essential for producing these profiles. Efficient methods are needed to isolate highly purified RNA from seeds. Here, we describe a method for isolating RNA from seeds containing large amounts of oils, proteins, and polyphenols, which have inhibitory effects on high-purity RNA isolation. Our method enables highly purified RNA to be obtained from seeds without the use of phenol, chloroform, or additional processes for RNA purification. This method is applicable to Arabidopsis, rapeseed, and soybean seeds. Our method will be useful for monitoring the expression patterns of low level transcripts in developing and mature seeds.

We have succeeded in establishing a method for RNA isolation from plant seeds containing large amounts of oils, proteins, and polyphenols, which have inhibitory effects on high-purity RNA isolation. Our method is suitable for monitoring the expression of genes with low level transcripts in seeds.

Plant seeds accumulate large amounts of storage reserves comprising biodegradable organic matter. Humans rely on seed storage reserves for food and as ...

Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs

Translation initiation is the rate-limiting step of protein synthesis and represents a key point at which cells regulate their protein output. Regulation of protein synthesis is the key to cellular stress-response, and dysregulation is central to many disease states, such as cancer. For instance, although cellular stress leads to the inhibition of global translation by attenuating cap-dependent initiation, certain stress-response proteins are selectively translated in a cap-independent manner. Discreet RNA regulatory elements, such as cellular internal ribosome entry sites (IRESes), allow for the translation of these specific mRNAs. Identification of such mRNAs, and the characterization of their regulatory mechanisms, have been a key area in molecular biology. Toeprinting is a method for the study of RNA structure and function as it pertains to translation initiation. The goal of toeprinting is to assess the ability of in vitro transcribed RNA to form stable complexes with ribosomes under a variety of conditions, in order to determine which sequences, structural elements, or accessory factors are involved in ribosome binding&#8212;a pre-cursor for efficient translation initiation. Alongside other techniques, such as western analysis and polysome profiling, toeprinting allows for a robust characterization of mechanisms for the regulation of translation initiation.

Toeprinting aims to measure the ability of in vitro transcribed RNA to form translation initiation complexes with ribosomes under a variety of conditions. This protocol describes a method for toeprinting mammalian RNA and can be used to study both cap-dependent and IRES-driven translation.

Translation initiation is the rate-limiting step of protein synthesis and represents a key point at which cells regulate their protein output. Regulation ...

Capture and Identification of RNA-binding Proteins by Using Click Chemistry-assisted RNA-interactome Capture (CARIC) Strategy

A comprehensive identification of RNA-binding proteins (RBPs) is key to understanding the posttranscriptional regulatory network in cells. A widely used strategy for RBP capture exploits the polyadenylation [poly(A)] of target RNAs, which mostly occurs on eukaryotic mature mRNAs, leaving most binding proteins of non-poly(A) RNAs unidentified. Here we describe the detailed procedures of a recently reported method termed click chemistry-assisted RNA-interactome capture (CARIC), which enables the transcriptome-wide capture of both poly(A) and non-poly(A) RBPs by combining the metabolic labeling of RNAs, in vivo UV cross-linking, and bioorthogonal tagging.

Capture and Identification of RNA-binding Proteins by Using Click Chemistry-assisted RNA-interactome Capture CARIC Strategy

A detailed protocol for applying the click chemistry-assisted RNA-interactome capture (CARIC) strategy to identify proteins binding to both coding and noncoding RNAs is presented.

A comprehensive identification of RNA-binding proteins (RBPs) is key to understanding the posttranscriptional regulatory network in cells. A widely used ...

Studying RNA Interactors of Protein Kinase RNA-Activated during the Mammalian Cell Cycle

Protein kinase RNA-activated (PKR) is a member of the innate immune response proteins and recognizes the double-stranded secondary structure of viral RNAs. When bound to viral double-stranded RNAs (dsRNAs), PKR undergoes dimerization and subsequent autophosphorylation. Phosphorylated PKR (pPKR) becomes active and induces phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2&#945;) to suppress global translation. Increasing evidence suggests that PKR can be activated under physiological conditions such as during the cell cycle or under various stress conditions without infection. However, our understanding of the RNA activators of PKR is limited due to the lack of a standardized experimental method to capture and analyze PKR-interacting dsRNAs. Here, we present an experimental protocol to specifically enrich and analyze PKR bound RNAs during the cell cycle using HeLa cells. We utilize the efficient crosslinking activity of formaldehyde to fix PKR-RNA complexes and isolate them via immunoprecipitation. PKR co-immunoprecipitated RNAs can then be further processed to generate a high-throughput sequencing library. One major class of PKR-interacting cellular dsRNAs is mitochondrial RNAs (mtRNAs), which can exist as intermolecular dsRNAs through complementary interaction between the heavy-strand and the light-strand RNAs. To study the strandedness of these duplex mtRNAs, we also present a protocol for strand-specific qRT-PCR. Our protocol is optimized for the analysis of PKR-bound RNAs, but it can be easily modified to study cellular dsRNAs or RNA-interactors of other dsRNA binding proteins.

We present experimental approaches for studying RNA-interactors of double-stranded RNA binding protein kinase RNA-activated (PKR) during the mammalian cell cycle using HeLa cells. This method utilizes formaldehyde to crosslink RNA-PKR complexes and immunoprecipitation to enrich PKR-bound RNAs. These RNAs can be further analyzed through high-throughput sequencing or qRT-PCR.

Protein kinase RNA-activated (PKR) is a member of the innate immune response proteins and recognizes the double-stranded secondary structure of viral ...

Rapid and Cost-Effective RNA Extraction of Rat Pancreatic Tissue

Regardless of the extraction method, optimized RNA extraction of tissues and cell lines are carried out in four stages: 1) homogenization, 2) effective denaturation of proteins from RNA, 3) ribonuclease inactivation, and 4) removal of contamination from DNA, proteins, and carbohydrates. However, it is very laborious to maintain the integrity of RNA when there are high levels of RNase in the tissue. Spontaneous autolysis makes it very difficult to extract RNA from pancreatic tissue without damaging it. Thus, a practical RNA extraction method is needed to maintain the integrity of pancreatic tissues during the extraction process. An experimental and comparative study of existing protocols was carried out by obtaining 20-30 mg of rat pancreatic tissues in less than 2 minutes and extracting the RNA. The results were assessed by electrophoresis. The experiments were carried out three times for generalization of the results. Immersing pancreatic tissue in RNA stabilization reagent at -80 &#176;C for 24 h yielded high integrity RNA, when the RNA extraction reagent was used as the reagent. The results obtained were comparable to the results obtained from commercial kits with spin column bindings.

The purity and integrity of the isolated RNA is a vital step in RNA dependent assays. Here, we present a practical, rapid, and inexpensive method to extract RNA from a small quantity of undamaged pancreatic tissue.

Regardless of the extraction method, optimized RNA extraction of tissues and cell lines are carried out in four stages: 1) homogenization, 2) effective ...

RNA Blot Analysis for the Detection and Quantification of Plant MicroRNAs

MicroRNAs (miRNAs) are a class of endogenously expressed non-coding, ~21 nt small RNAs involved in the regulation of gene expression in both plants and animals. Most miRNAs act as negative switches of gene expression targeting key genes. In plants, primary miRNAs (pri-miRNAs) transcripts are generated by RNA polymerase II, and they form varying lengths of stable stem-loop structures called pre-miRNAs. An endonuclease, Dicer-like1, processes the pre-miRNAs into miRNA-miRNA* duplexes. One of the strands from miRNA-miRNA* duplex is selected and loaded onto Argonaute 1 protein or its homologs to mediate the cleavage of target mRNAs. Although miRNAs are key signaling molecules, their detection is often carried out by less than optimal PCR-based methods instead of a sensitive northern blot analysis. We describe a simple, reliable, and extremely sensitive northern method that is ideal for the quantification of miRNA levels with very high sensitivity, literally from any plant tissue. Additionally, this method can be used to confirm the size, stability and the abundance of miRNAs and their precursors.

This method demonstrates use of the northern hybridization technique to detect miRNAs from total RNA extract.

MicroRNAs (miRNAs) are a class of endogenously expressed non-coding, ~21 nt small RNAs involved in the regulation of gene expression in both plants and ...

Optical Tweezers to Study RNA-Protein Interactions in Translation Regulation

RNA adopts diverse structural folds, which are essential for its functions and thereby can impact diverse processes in the cell. In addition, the structure and function of an RNA can be modulated by various trans-acting factors, such as proteins, metabolites or other RNAs. Frameshifting RNA molecules, for instance, are regulatory RNAs located in coding regions, which direct translating ribosomes into an alternative open reading frame, and thereby act as gene switches. They may also adopt different folds after binding to proteins or other trans-factors. To dissect the role of RNA-binding proteins in translation and how they modulate RNA structure and stability, it is crucial to study the interplay and mechanical features of these RNA-protein complexes simultaneously.&#160;This work illustrates how to employ single-molecule-fluorescence-coupled optical tweezers to explore the conformational and thermodynamic landscape of RNA-protein complexes at a high resolution. As an example, the interaction of the SARS-CoV-2 programmed ribosomal frameshifting element with the trans-acting factor short isoform of zinc-finger antiviral protein is elaborated. In addition, fluorescence-labeled ribosomes were monitored using the confocal unit, which would ultimately enable the study of translation elongation. The fluorescence coupled OT assay can be widely applied to explore diverse RNA-protein complexes or trans-acting factors regulating translation and could facilitate studies of RNA-based gene regulation.

This protocol presents a complete experimental workflow for studying RNA-protein interactions using optical tweezers. Several possible experimental setups are outlined including the combination of optical tweezers with confocal microscopy.

RNA adopts diverse structural folds, which are essential for its functions and thereby can impact diverse processes in the cell. In addition, the ...

Routine Collection of High-Resolution cryo-EM Datasets Using 200 KV Transmission Electron Microscope

Cryo-electron microscopy (cryo-EM) has been established as a routine method for protein structure determination during the past decade, taking an ever-increasing share of published structural data. Recent advances in TEM technology and automation have boosted both the speed of data collection and quality of acquired images while simultaneously decreasing the required level of expertise for obtaining cryo-EM maps at sub-3 &#197; resolutions. While most of such high-resolution structures have been obtained using state-of-the-art 300 kV cryo-TEM systems, high-resolution structures can be also obtained with 200 kV cryo-TEM systems, especially when equipped with an energy filter. Additionally, automation of microscope alignments and data collection with real-time image quality assessment reduces system complexity and assures optimal microscope settings, resulting in increased yield of high-quality images and overall throughput of data collection. This protocol demonstrates the implementation of recent technological advances and automation features on a 200 kV cryo-transmission electron microscope and shows how to collect data for the reconstruction of 3D maps that are sufficient for de novo atomic model building. We focus on best practices, critical variables, and common issues that must be considered to enable the routine collection of such high-resolution cryo-EM datasets. Particularly the following essential topics are reviewed in detail: i) automation of microscope alignments, ii) selection of suitable areas for data acquisition, iii) optimal optical parameters for high-quality, high-throughput data collection, iv) energy filter tuning for zero-loss imaging, and v) data management and quality assessment. Application of the best practices and improvement of achievable resolution using an energy filter will be demonstrated on the example of apo-ferritin that was reconstructed to 1.6 &#197;, and Thermoplasma acidophilum 20S proteasome reconstructed to 2.1-&#197; resolution using a 200 kV TEM equipped with an energy filter and a direct electron detector.

High-resolution cryo-EM maps of macromolecules can be also achieved by using 200 kV TEM microscopes. This protocol shows the best practices for setting accurate optics alignments, data acquisition schemes, and selection of imaging areas that are all essential for the successful collection of high-resolution datasets using a 200 kV TEM.

Cryo-electron microscopy (cryo-EM) has been established as a routine method for protein structure determination during the past decade, taking an ...

An Optimized Quantitative Pull-Down Analysis of RNA-Binding Proteins Using Short Biotinylated RNA

Protein-RNA interactions regulate gene expression and cellular functions at transcriptional and post-transcriptional levels. For this reason, identifying the binding partners of an RNA of interest remains of high importance to unveil the mechanisms behind many cellular processes. However, RNA molecules might interact transiently and dynamically with some RNA-binding proteins (RBPs), especially with non-canonical ones. Hence, improved methods to isolate and identify such RBPs are greatly needed.
To identify the protein partners of a known RNA sequence efficiently and quantitatively, we developed a method based on the pull-down and characterization of all interacting proteins, starting from cellular total protein extract. We optimized the protein pull-down using biotinylated RNA pre-loaded on streptavidin-coated beads. As a proof of concept, we employed a short RNA sequence known to bind the neurodegeneration-associated protein TDP-43 and a negative control of a different nucleotide composition but the same length. After blocking the beads with yeast tRNA, we loaded the biotinylated RNA sequences on the streptavidin beads and incubated them with the total protein extract from HEK 293T cells. After incubation and several washing steps to remove nonspecific binders, we eluted the interacting proteins with a high-salt solution, compatible with the most commonly used protein quantification reagents and with sample preparation for mass spectrometry. We quantified the enrichment of TDP-43 in the pull-down performed with the known RNA binder compared to the negative control by mass spectrometry. We used the same technique to verify the selective interactions of other proteins computationally predicted to be unique binders of our RNA of interest or of the control. Finally, we validated the protocol by western blot via the detection of TDP-43 with an appropriate antibody. 
This protocol will allow the study of the protein partners of an RNA of interest in near-to-physiological conditions, helping uncover unique and unpredicted protein-RNA interactions.

Here, we present an optimized in vitro method to uncover, quantify, and validate protein interactors of specific RNA sequences, using total protein extract from human cells, streptavidin beads coated with biotinylated RNA, and mass spectrometry analysis.

Protein-RNA interactions regulate gene expression and cellular functions at transcriptional and post-transcriptional levels. For this reason, identifying ...