This work was supported by the following grants: F31-DK113666 (AWW), K01-DK102868 (AMZ), K08-DK106478 (KJW), and P30-DK050306 (Pilot grant to KJW).

All methods that involve the use of mice are consistent with the guidelines provided by the IACUC of the Penn Office of Animal Welfare at the University of Pennsylvania.
1. Reagent Preparation
<ol>
	<li>Cycloheximide
	<ol>
		<li>To make 500 &#181;L of 0.1 g/mL cycloheximide, suspend 50 mg of cycloheximide in 500 &#181;L of methanol. 
		CAUTION: Cycloheximide is extremely toxic to the environment and can cause congenital malformation. All wastes and buff...

<ol>
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K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liver+regeneration+after+partial+hepatectomy:+critical+analysis+of+mechanistic+dilemmas.">Liver regeneration after partial hepatectomy: critical analysis of mechanistic dilemmas.</a> The American Journal of Pathology. 176 (1), 2-13 (2010).</li><li>Grompe, M., 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=Loss+of+fumarylacetoacetate+hydrolase+is+responsible+for+the+neonatal+hepatic+dysfunction+phenotype+of+lethal+albino+mice.">Loss of fumarylacetoacetate hydrolase is responsible for the neonatal hepatic dysfunction phenotype of lethal albino mice.</a> Genes &amp; Development. 7 (12A), 2298-2307 (1993).</li><li>Wangensteen, K. J., 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=A+facile+method+for+somatic,+lifelong+manipulation+of+multiple+genes+in+the+mouse+liver.">A facile method for somatic, lifelong manipulation of multiple genes in the mouse liver.</a> Hepatology. 47 (5), 1714-1724 (2008).</li><li>Wang, A. W., 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=TRAP-seq+identifies+cystine/glutamate+antiporter+as+a+driver+of+recovery+from+liver+injury.">TRAP-seq identifies cystine/glutamate antiporter as a driver of recovery from liver injury.</a> The Journal of Clinical Investigation. 128 (6), 2297-2309 (2018).</li><li>Heiman, M., Kulicke, R., Fenster, R. J., Greengard, P., Heintz, 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+type-specific+mRNA+purification+by+translating+ribosome+affinity+purification+(TRAP).">Cell type-specific mRNA purification by translating ribosome affinity purification (TRAP).</a> Nature Protocols. 9 (6), 1282-1291 (2014).</li><li>Agilent Technologies. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Agilent RNA 6000 Pico: User Manual. , (2016).</li><li>NEBNext. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> NEBNext Ultra RNA Library Prep Kit for Illumina: User Manual. , (2018).</li><li>NanoDrop. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 2000/2000c Spectrophotomerter: User Manual. , (2009).</li><li>Liu, J., 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=Cell-specific+translational+profiling+in+acute+kidney+injury.">Cell-specific translational profiling in acute kidney injury.</a> The Journal of Clinical Investigation. 124 (3), 1242-1254 (2014).</li><li>Lu, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+glutathione+synthesis.">Regulation of glutathione synthesis.</a> Molecular Aspects of Medicine. 30 (1-2), 42-59 (2009).</li><li>Wang, A. W., 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+dynamic+chromatin+architecture+of+the+regenerating+liver.">The dynamic chromatin architecture of the regenerating liver.</a> bioRxiv. , (2019).</li><li>Zahm, A. M., 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=A+high-content+in+vivo+screen+to+identify+microRNA+epistasis+in+the+repopulating+mouse+liver.">A high-content in vivo screen to identify microRNA epistasis in the repopulating mouse liver.</a> bioRxiv. , (2019).</li><li>Stork, C., Zheng, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome-Wide+Profiling+of+RNA-Protein+Interactions+Using+CLIP-Seq.">Genome-Wide Profiling of RNA-Protein Interactions Using CLIP-Seq.</a> Methods in Molecular Biology. 1421, 137-151 (2016).</li><li>Zhao, X., 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=Glutathione+antioxidant+pathway+activity+and+reserve+determine+toxicity+and+specificity+of+the+biliary+toxin+biliatresone+in+zebrafish.">Glutathione antioxidant pathway activity and reserve determine toxicity and specificity of the biliary toxin biliatresone in zebrafish.</a> Hepatology. 64 (3), 894-907 (2016).</li><li>Halpern, K. B., 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=Single-cell+spatial+reconstruction+reveals+global+division+of+labour+in+the+mammalian+liver.">Single-cell spatial reconstruction reveals global division of labour in the mammalian liver.</a> Nature. 542 (7641), 352-356 (2017).</li><li>Camp, J. G., 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=Multilineage+communication+regulates+human+liver+bud+development+from+pluripotency.">Multilineage communication regulates human liver bud development from pluripotency.</a> Nature. 546 (7659), 533-538 (2017).</li><li>Wang, Y. J., Kaestner, K. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-Cell+RNA-Seq+of+the+Pancreatic+Islets--a+Promise+Not+yet+Fulfilled?.">Single-Cell RNA-Seq of the Pancreatic Islets--a Promise Not yet Fulfilled?.</a> Cell Metabolism. 29 (3), 539-544 (2019).</li></ol>

TRAP-seq is a technique for cell type-specific isolation of translating mRNA via epitope-tagged ribosomes and presents an alternative to FACS approaches, as it circumvents limitations such as time requirements of FACS9. Instead, TRAP allows rapid and efficient isolation of RNA directly from bulk tissues, helping to avoid any alterations in gene expression. TRAP-seq is especially well-suited for use in the repopulating Fah-/- mouse liver, as hepatocyte expansion following remova...

As the main metabolic organ in vertebrates, the liver is responsible for glucose homeostasis, serum protein synthesis, bile acid secretion, and xenobiotic metabolism and detoxification. The liver possesses an extraordinary capacity to regenerate the injured parenchyma upon exposure to toxins to prevent immediate liver failure1. However, failure of regeneration can occur in the setting of acetaminophen or alcohol overconsumption, which can lead to acute liver failure2. Furthermore, chronic liver injury caused by viral hepatitis infection, fatty liver disease, and steatohepatitis can cause liver fibrosis, cirrhosis, and hepatocellular carcinoma3. The only available curative treatment for end-stage liver disease is transplantation but is limited by organ shortage, preventing efficient treatment for all patients4. A better understanding of the recovery process after toxic liver injury is therefore crucial for the development of treatments to stimulate regeneration sufficient to rescue function in the diseased organ.
The most broadly applied model system for the study of liver regeneration is partial hepatectomy in rodents, in which a large proportion of the liver is resected to stimulate rapid hepatocyte expansion5. However, partial hepatectomy does not recapitulate hepatocyte expansion following toxic liver injury due to the lack of immune cell infiltration and hepatocyte cell necrosis often observed in the setting of acute liver injury in humans6. A more suitable system to model this form of organ renewal is the Fah-/- mouse, which lacks functional fumarylacetoacetate hydrolase (FAH) required for proper tyrosine metabolism and develops severe liver damage leading to death7. These mice can be maintained in a healthy state indefinitely by treatment with the drug nitisinone in the drinking water. Alternatively, FAH expression can be restored by transgene delivery to a subset of hepatocytes, which will expand to repopulate the liver upon nitisinone removal8.
To profile the gene expression changes of repopulating hepatocytes, a tool to specifically isolate replicating hepatocytes in the Fah-/- mouse without contamination from the neighboring injured hepatocytes and other cell types is required. Unfortunately, fluorescence-assisted cell sorting (FACS) of hepatocytes is difficult since (1) the fragility of repopulating hepatocytes leads to poor recovery after liver perfusion, (2) replicating hepatocytes are highly variable in size, making isolation of a pure population by FACS difficult, and (3) the procedure time from liver perfusion to RNA isolation is greater than 2 h, hence gene expression profiles may undergo substantial artificial changes before samples are acquired9.
Alternatively, the expression of epitope-tagged ribosomes specifically in repopulating hepatocytes allows for the rapid isolation of actively translating mRNA bound by ribosomes using affinity purification immediately after organ harvest, with bulk liver tissue lysates. Here, we describe a protocol to perform translating-ribosome affinity purification (TRAP)10 followed by high-throughput RNA-sequencing (TRAP-seq), to specifically isolate and profile mRNA in repopulating hepatocytes in the Fah-/- mouse9. Coexpression of green fluorescent protein-tagged ribosomal protein (GFP:RPL10A) with FAH allows affinity purification of translating mRNA bound by polysomes containing GFP:RPL10A. This method avoids any cell dissociation steps, such as liver perfusion to isolate fragile repopulating hepatocytes. Instead, it utilizes lysis of whole organ tissue and antibodies to rapidly extract the RNA specifically from the target cells. Finally, isolation of abundant, high-quality mRNA via TRAP-seq enables downstream applications such as sequencing analysis to profile the dynamic change of gene expression during the repopulation process.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>10 mL Tissue Grinder, Potter-Elv, Coated</td>
			<td>DWK Life Sciences (Wheaton)</td>
			<td>358007</td>
			<td></td>
		</tr>
		<tr>
			<td>Absolutely RNA Miniprep Kit</td>
			<td>Agilent</td>
			<td>400800</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-GFP antibodies</td>
			<td>Memorial Sloan-Kettering Antibody &#38; Bioresource Core</td>
			<td colspan="2">GFP Ab #19C8 and GFP Ab #19F7</td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin, IgG-Free, Protease-Free</td>
			<td>Jackson ImmunoResearch</td>
			<td>001-000-162</td>
			<td></td>
		</tr>
		<tr>
			<td>cOmplete, Mini, EDTA-free Protease Inhibitor Cocktail</td>
			<td>Roche</td>
			<td>11836170001</td>
			<td></td>
		</tr>
		<tr>
			<td>Cycloheximide</td>
			<td>Millipore Sigma</td>
			<td>C7698</td>
			<td></td>
		</tr>
		<tr>
			<td>Deoxycholic acid, DOC</td>
			<td>Millipore Sigma</td>
			<td>D2510</td>
			<td></td>
		</tr>
		<tr>
			<td>D-Glucose, Dextrose</td>
			<td>Fisher Scientific</td>
			<td>D16</td>
			<td></td>
		</tr>
		<tr>
			<td>DL-Dithiothreitol</td>
			<td>Millipore Sigma</td>
			<td>D9779</td>
			<td></td>
		</tr>
		<tr>
			<td>Dynabeads MyOne Streptavidin T1</td>
			<td>Thermo Fisher Scientific</td>
			<td>65602</td>
			<td></td>
		</tr>
		<tr>
			<td>Fisherbrand Petri Dishes with Clear Lid</td>
			<td>Fisher Scientific</td>
			<td>FB0875712</td>
			<td></td>
		</tr>
		<tr>
			<td>HBSS (10x), calcium, magnesium, no phenol red</td>
			<td>Thermo Fisher Scientific</td>
			<td>14065-056</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES, 1M Solution, pH 7.3, Molecular Biology Grade, Ultrapure, Thermo Scientific</td>
			<td>Thermo Fisher Scientific</td>
			<td>AAJ16924AE</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium chloride, MgCl2&#160;</td>
			<td>Millipore Sigma</td>
			<td>M8266</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Fisher Scientific</td>
			<td>A452</td>
			<td></td>
		</tr>
		<tr>
			<td>NanoDrop 2000/2000c Spectrophotometer</td>
			<td>Thermo Fisher Scientific</td>
			<td>VV-83061-00</td>
			<td></td>
		</tr>
		<tr>
			<td>NEBNext Poly(A) mRNA Magnetic Isolation Module</td>
			<td>New England BioLabs</td>
			<td>E7490S</td>
			<td></td>
		</tr>
		<tr>
			<td>NEBNext Ultra RNA Library Prep Kit for Illumina</td>
			<td>New England BioLabs</td>
			<td>E7530S</td>
			<td></td>
		</tr>
		<tr>
			<td>Nonylphenyl polyethylene glycol, NP-40. IGEPAL CA-630</td>
			<td>Millipore Sigma</td>
			<td>I8896</td>
			<td></td>
		</tr>
		<tr>
			<td>Nuclease-Free Water, not DEPC-Treated</td>
			<td>Ambion</td>
			<td>AM9932</td>
			<td></td>
		</tr>
		<tr>
			<td>Overhead Stirrer</td>
			<td>DWK Life Sciences (Wheaton)</td>
			<td>903475</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS Buffer (10x), pH 7.4</td>
			<td>Ambion</td>
			<td>AM9625</td>
			<td></td>
		</tr>
		<tr>
			<td>Pierce Recombinant Protein L, Biotinylated</td>
			<td>Thermo Fisher Scientific</td>
			<td>29997</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium chloride, KCl</td>
			<td>Millipore Sigma</td>
			<td>P4504</td>
			<td></td>
		</tr>
		<tr>
			<td>RNA 6000 Pico Kit &#38; Reagents</td>
			<td>Agilent</td>
			<td>5067-1513</td>
			<td></td>
		</tr>
		<tr>
			<td>RNaseZap RNase Decontamination Solution</td>
			<td>Invitrogen</td>
			<td>AM9780</td>
			<td></td>
		</tr>
		<tr>
			<td>RNasin Ribonuclease Inhibitors</td>
			<td>Promega</td>
			<td>N2515</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium azide, NaN3</td>
			<td>Millipore Sigma</td>
			<td>S2002</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium bicarbonate, NaHCO3</td>
			<td>Millipore Sigma</td>
			<td>S6297</td>
			<td></td>
		</tr>
		<tr>
			<td>SUPERase&#183;In RNase Inhibitor</td>
			<td>Invitrogen</td>
			<td>AM2694</td>
			<td></td>
		</tr>
	</tbody>
</table>

cell type-specific gene expression profiling in the mouse liver

Liver repopulation after injury is a crucial feature of mammals which prevents immediate organ failure and death after exposure of environmental toxins. A deeper understanding of the changes in gene expression that occur during repopulation could help identify therapeutic targets to promote the restoration of liver function in the setting of injuries. Nonetheless, methods to isolate specifically the repopulating hepatocytes are inhibited by a lack of cell markers, limited cell numbers, and the fragility of these cells. The development of translating ribosome affinity purification (TRAP) technology in conjunction with the Fah-/- mouse model to recapitulate repopulation in the setting of liver injury allows gene expression profiling of the repopulating hepatocytes. With TRAP, cell type-specific translating mRNA is rapidly and efficiently isolated. We developed a method that utilizes TRAP with affinity-based isolation of translating mRNA from hepatocytes that selectively express the green fluorescent protein (GFP)-tagged ribosomal protein (RP), GFP:RPL10A. TRAP circumvents the long time period required for fluorescence-activated cell sorting that could change the gene expression profile. Furthermore, since only the repopulating hepatocytes express the GFP:RPL10A fusion protein, the isolated mRNA is devoid of contamination from the surrounding injured hepatocytes and other cell types in the liver. The affinity-purified mRNA is of high quality and allows downstream PCR- or high-throughput sequencing-based analysis of gene expression.

To profile gene expression in repopulating hepatocytes of the Fah-/- mouse, Gfp:Rpl10a fusion and Fah transgenes are co-delivered within a transposon-containing plasmid8 (TRAP vector) to livers by hydrodynamic injection (Figure 1A). The removal of nitisinone induces a toxic liver injury that creates a selection pressure for hepatocytes stably expressing FAH to repopulate the injure...

Watch this Scientific Journal Video about Cell Type-specific Gene Expression Profiling in the Mouse Liver at JoVE.com

Cell Type-specific Gene Expression Profiling in the Mouse Liver

Translating ribosome affinity purification (TRAP) enables rapid and efficient isolation of cell type-specific translating mRNA. Here, we demonstrate a method that combines hydrodynamic tail-vein injection in a mouse model of liver repopulation and TRAP to examine the expression profile of repopulating hepatocytes.

Liver repopulation after injury is a crucial feature of mammals which prevents immediate organ failure and death after exposure of environmental toxins. A ...

With TRAP-seq, we can isolate the RNA from specific cell types, such as the hepatocytes repopulating in injured liver to analyze the gene expression changes occurring in those cells. It does not require any steps to remove unwanted cells from the tissue. The cell type-specific RNA is isolated by affinity purification from whole organ lysates.This technique helps us determine how specific cells respond to injuries, which could help identify new strategies or drugs to fight liver disease. This could be used to identify how liver cells respond to different types of liver injuries. Currently, there are few options for severe acute liver injuries and this method will help to clue us in to new treatments.This method originated in the brain. In the liver, we envisioned it could be used to examine dynamic changes in a variety of cell types, the hepatocytes, biliary duct cells, Kupffer cells, and endothelial cells to name a few. Demonstrating the procedure will be Amber Wang, a graduate student and my mentee.To begin, resuspend magnetic beads by gentle pipetting. Collect the beads on a magnetic stand for more than one minute and remove the supernatant. Then, remove the microcentrifuge tube from the magnetic stand and add one milliliter of PBS, followed by pipetting up and down to wash the beads.Place the tube back on the magnetic stand for more than one minute to collect the beads and remove the PBS. To prepare protein L-coated beads, add 16 microliters of biotinylated protein L to the resuspended and washed magnetic beads and add 1X PBS to make the final volume one milliliter, if using a 1.5-milliliter microcentrifuge tube, or 1.5 milliliters, if using a two-milliliter microcentrifuge tube. Incubate the magnetic beads with biotinylated protein L for 35 minutes at room temperature on a tube rotator.Then, place the tube on the magnetic stand for more than one minute and remove the supernatant to collect the protein L-coated beads. Remove the microcentrifuge tube from the magnetic stand and add one milliliter of PBS with 3%BSA buffer, followed by gentle pipetting at least five times to wash the protein L-coated beads. Again, place the tube on the magnetic stand for more than one minute and remove the supernatant to collect the coated beads.Repeat the BSA washing another four times. Next, add 50 micrograms of antibodies for GFP antibody 19C8 and GFP antibody 19F7 each into the protein L-coated beads, and incubate for one hour at four degrees Celsius on a tube rotator. To collect the affinity matrix, place the tube on the magnetic stand for more than one minute and remove the supernatant.Take the tube away from the magnetic stand and add one milliliter of low-salt buffer. Gently pipet up-and-down to wash the affinity matrix and repeat the low-salt buffer washing another two times. Resuspend the beads in 200 microliters of low-salt buffer, to make 200 microliters of affinity matrix.First, set up the tissue grinder so that the PTFE glass tubes can be placed on ice during homogenization. Fill four milliliters of cold lysis buffer into the PTFE glass tubes. Lay the liver on a Petri dish.Use a knife to isolate 200 to 500 milligrams of liver pieces and move into the PTFE glass tubes. Place the remaining liver tissue into a pre-chilled microcentrifuge tube and flash freeze in liquid nitrogen. Homogenize the samples in a motor-driven homogenizer, starting at 300 rpm for at least five strokes to dissociate hepatocytes from the liver structure.Lower the glass tube each time. Prevent aeration, which could cause protein denaturation, by keeping the pestle below the solution. Then, raise the speed to 900 rpm to fully homogenize the liver tissues for at least 12 full strokes.Transfer the lysate into labeled and pre-chilled tubes with no more than one milliliter of lysate each. To start nuclear lysis, centrifuge the liver lysate at 2, 000 times g at four degrees Celsius for 10 minutes, then transfer the supernatant to a new pre-chilled microcentrifuge tube on ice. Add 1/9th of the supernatant volume of 10%NP-40 into the microcentrifuge tube on ice and mix the solution by gently inverting the tube.Quickly spin down the microcentrifuge tubes with a mini centrifuge and add 1/9th of the sample volume of 10%DOC. Mix by gently inverting the microcentrifuge tubes and quickly spin down the microcentrifuge tubes and incubate on ice for five minutes. Centrifuge the nuclear lysate at 20, 000 times g at four degrees Celsius for 10 minutes and transfer the supernatant to new pre-chilled microcentrifuge tubes on ice.For each tube, take out 1%of the total volume of the supernatant as a pre-immunoprecipitation control. Place the pre-immunoprecipitation controls on a tube rotator at four degrees Celsius overnight. Take extra care to gently resuspend the affinity matrix by pipetting, then add 200 microliters to each sample.Incubate the lysates at four degrees Celsius overnight with gentle mixing on a tube rotator. To isolate RNA, quickly spin down the tubes containing the lysates in the mini centrifuge and collect the beads by placing on the magnetic rack for at least one minute. Collect the supernatant in additional microcentrifuge tubes.Add one milliliter of fresh high-salt buffer to each tube, followed by gentle pipetting at least five times without introducing bubbles. Collect the beads on the magnetic stand on ice for over one minute and remove the supernatant. Repeat the washing steps another four times.Then, remove the microcentrifuge tubes from the magnetic stand and place at room temperature for five minutes to warm up. Resuspend the beads in 100 microliters of lysis buffer with 0.7 microliters of beta-mercaptoethanol to release bound RNA from the affinity matrix. Vortex the tubes for at least five seconds at the highest speed and quickly spin down.Then, incubate the tubes at room temperature for 10 minutes. Place the tubes on the magnetic stand for at least one minute, then collect the supernatant and proceed immediately to RNA cleanup according to the RNA purification protocol in the kit. To achieve maximum quality of the isolated RNA, perform all optional steps, including DNase digestion and all RNA elution steps, including the recommended preheating of the elution buffer to 60 degrees Celsius.In this study, GFP-L10A fusion and Fah transgenes were co-delivered within a transposon-containing plasmid trap vector to livers by hydrodynamic injection. The removal of nitisinone induced a toxic liver injury. Immunofluorescence staining confirmed the coexpression of the FAH and GFP-L10A fusion protein and the repopulating hepatocytes after two weeks of liver repopulation.The quiescent sample produced the highest yield of fusion protein, since all hepatocytes express GFP-L10A after AAV8-TBG-Cre injection. Conversely, barely any RNA was detectable in wild-type controls that did not have the GFP-L10A transgene, indicating the TRAP procedure is highly specific and has a low background. When TRAP was used on liver tissue undergoing repopulation with GFP-L10A transduced hepatocytes, abundant high-quality RNA was obtained.In contrast, no RNA trace was detected via Bioanalyzer for the negative control sample. Gsta1 expression was induced by over tenfold in repopulating hepatocytes as compared to quiescent hepatocytes, while no threshold cycle values was detected with TRAP-isolated RNA from the wild type mouse due to the lack of input RNA. When homogenizing the tissue, make sure to move the pestle slowly to prevent aeration.After isolating the RNA, high-throughput sequencing or qPCR can be performed to analyze gene expression. With TRAP-seq, we now have a method to specifically isolate RNA from repopulating hepatocytes and analyze the change in gene expression during liver repopulation. This allows us to identify genes that are altered during this process and potential therapeutic targets for the treatment of liver injury.Cycloheximide and DTT, which are present in several buffers, are both toxic. Waste should be collected and discarded according to institutional guidelines.

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7.5K Views.  University of Pennsylvania. With TRAP-seq, we can isolate the RNA from specific cell types, such as the hepatocytes repopulating in injured liver to analyze the gene expression changes occurring in those cells. It does not require any steps to remove unwanted cells from the tissue. The cell type-specific RNA is isolated by affinity purification from whole organ lysates.This technique helps us determine how specific cells respond to injuries, which could help identify new strategies or drugs to fight liver disease...