Name: using fluorescence activated cell sorting to examine cell-type-specific gene expression in rat brain tissue
Uploaded: 2015-05-28T14:00:00
Description: Watch this Scientific Journal Video about Using Fluorescence Activated Cell Sorting to Examine Cell-Type-Specific Gene Expression in Rat Brain Tissue at JoVE.com

The authors would like to acknowledge Lynn Opdenaker at the University of Delaware Center for Translational Research at the Helen F. Graham Cancer Center for technical assistance, as well as Nancy Martin from the Duke University Cancer Institute Flow Cytometry Shared Resource, and Dr. Susan H. Smith for guidance in methods and data collection.

1. Preparation for Tissue Collection (15 &#8211; 30 min)
<ol>
	<li>Fire polish three sets of glass Pasteur pipettes in decreasing diameters and number them &#8220;1&#8221; = approximately 1 mm diameter, &#8220;2&#8221; = approximately 0.75 mm diameter, and &#8220;3&#8221; = approximately 0.50 mm diameter.</li>
	<li>Resuspend lyophilized Enzyme A with all of Buffer A according to the protocol provided with the Neural Dissociation Kit (see Table of Materials). Do not vortex. Aliquot the solution into 50 &#181;l&#160;aliq...

<ol>
	<li>Schwarz, J. M., Smith, S. H., Bilbo, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FACS+analysis+of+neuronal-glial+interactions+in+the+nucleus+accumbens+following+morphine+administration.">FACS analysis of neuronal-glial interactions in the nucleus accumbens following morphine administration.</a> Psychopharmacology. 230 (4), 525-535 (2013).</li><li>Schwarz, J. M., Hutchinson, M. R., Bilbo, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early-life+experience+decreases+drug-induced+reinstatement+of+morphine+CPP+in+adulthood+via+microglial-specific+epigenetic+programming+of+anti-inflammatory+IL-10+expression.">Early-life experience decreases drug-induced reinstatement of morphine CPP in adulthood via microglial-specific epigenetic programming of anti-inflammatory IL-10 expression.</a> J Neurosci. 31 (49), 17835-1523 (2011).</li><li>Herzenberg, L. A., Tung, J., Moore, W. A., Herzenberg, L. A., Parks, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interpreting+flow+cytometry+data:+a+guide+for+the+perplexed.">Interpreting flow cytometry data: a guide for the perplexed.</a> Nature Immunology. 7 (7), 681-685 (2006).</li><li>Guez-Barber, D., 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=FACS+identifies+unique+cocaine-induced+gene+regulation+in+selectively+activated+adult+striatal+neurons.">FACS identifies unique cocaine-induced gene regulation in selectively activated adult striatal neurons.</a> J Neurosci. 31 (11), 4251-4259 (2011).</li><li>Fanous, S., 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=Unique+gene+alterations+are+induced+in+FACS-purified+Fos-positive+neurons+activated+during+cue-induced+relapse+to+heroin+seeking.">Unique gene alterations are induced in FACS-purified Fos-positive neurons activated during cue-induced relapse to heroin seeking.</a> J Neurochem. 124 (1), 100-108 (2013).</li><li>Liu, Q. R., 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=Detection+of+molecular+alterations+in+methamphetamine-activated+Fos-expressing+neurons+from+single+rat+dorsal+striatum+using+fluorescence-activated+cell+sorting+(FACS).">Detection of molecular alterations in methamphetamine-activated Fos-expressing neurons from single rat dorsal striatum using fluorescence-activated cell sorting (FACS).</a> J Neurochem. 128 (1), 173-185 (2013).</li><li>Guez-Barber, D., 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=FACS+purification+of+immunolabeled+cell+types+from+adult+rat+brain.">FACS purification of immunolabeled cell types from adult rat brain.</a> J Neurosci Methods. 203 (1), 10-18 (2012).</li><li>Nolte, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GFAP+promoter-controlled+EGFP-expressing+transgenic+mice:+a+tool+to+visualize+astrocytes+and+astrogliosis+in+living+brain+tissue.">GFAP promoter-controlled EGFP-expressing transgenic mice: a tool to visualize astrocytes and astrogliosis in living brain tissue.</a> Glia. 33 (1), 72-86 (2000).</li><li>Okana, M., Bell, D. W., Haber, D. A., Li, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+methyltransferases+Dnmt3a+and+Dnmt3b+are+essential+for+de+novo+methylation+and+mammalian+development.">DNA methyltransferases Dnmt3a and Dnmt3b are essential for de novo methylation and mammalian development.</a> Cell. 99 (3), 247-257 (1999).</li><li>Bogdanovi&#263;, O., Veenstra, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+methylation+and+methyl-CpG+binding+proteins:+developmental+requirements+and+function.">DNA methylation and methyl-CpG binding proteins: developmental requirements and function.</a> Chromosoma. 118 (5), 549-565 (2009).</li><li>Iwamoto, K., 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=Neurons+show+distinctive+DNA+methylation+profile+and+higher+inter-individual+variations+compared+with+non-neurons.">Neurons show distinctive DNA methylation profile and higher inter-individual variations compared with non-neurons.</a> Genome Res. 21 (5), 688-696 (2011).</li><li>Nishioka, 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=Neuronal+cell-type+specific+DNA+methylation+patterns+of+the+Cacna1c+gene.">Neuronal cell-type specific DNA methylation patterns of the Cacna1c gene.</a> Int J Dev Neurosci. 31 (2), 89-95 (2013).</li><li>Kozlenkov, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differences+in+DNA+methylation+between+human+neuronal+and+glial+cells+are+concentrated+in+enhancers+and+non-CpG+sites.">Differences in DNA methylation between human neuronal and glial cells are concentrated in enhancers and non-CpG sites.</a> Nucleic Acid Res. 42 (1), 109-127 (2014).</li><li>Russo, S. 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=Nuclear+factor+kappa+B+signaling+regulates+neuronal+morphology+and+cocaine+reward.">Nuclear factor kappa B signaling regulates neuronal morphology and cocaine reward.</a> J Neurosci. 29 (11), 3529-3537 (2009).</li><li>Bhatt, D., Ghosh, S. <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+the+NF-&#954;B-Mediated+Transcription+of+Inflammatory+Genes.">Regulation of the NF-&#954;B-Mediated Transcription of Inflammatory Genes.</a> Front Immunol. 5, 71 (2014).</li><li>Okada, S., 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=Flow+cytometric+sorting+of+neuronal+and+glial+nuclei+from+central+nervous+system+tissue.">Flow cytometric sorting of neuronal and glial nuclei from central nervous system tissue.</a> J Cell Physiol. 226 (2), 552-558 (2011).</li></ol>

Similar to many other tissues and systems, the brain is comprised of a heterogeneous cell population that functions together to impact behavior. The analysis of gene expression, protein expression, or epigenetic modifications from individual cells within that heterogeneous population has the potential to reveal information about the function of the system as a whole, to identify cellular processes regulating both normal behavior and disease processes, and to provide cell-type-specific targets for potential therapies. It ...

The purpose of the protocol described below is to isolate individual cell types from a heterogeneous population of neural tissue for the subsequent analysis of cell-type-specific gene expression, protein expression, or even epigenetic markers. The brain is comprised of many cell types that are derived from distinct progenitor cells and that have cell-type-specific properties and functions. Despite these differences, these distinct neural cell types can express similar receptors and intracellular signaling molecules which make the analysis of these more ubiquitous proteins difficult to measure or interpret in a cell-type-specific manner using conventional methods. Neuroscientists must identify the function and activation of these distinct cell types in the brain and how they can individually impact behavior as this will ultimately be the first step to identifying more specific drugs and therapeutic targets for neurological and neuropsychiatric diseases. Despite this overarching goal of neuroscience research, it can been difficult to isolate individual neural cell types from the brain for the analysis of gene or protein expression, the activation of signaling molecules, or the modification of epigenetic markers on DNA. Of the techniques that are currently used, immunohistochemistry can identify the expression of proteins in a cell-type-specific manner when combined with additional staining of a cell-type-specific marker, though this relies on specific antibodies that can properly stain for the proteins of interest and it can be difficult to quantify. In situ hybridization can identify the specific localization of messenger ribonucleic acid (mRNA) in individual cells in the brain, but this is a laborious process that also limits the co-analysis of specific cell types and only allows for the analysis of one or maybe a few genes of interest. Laser capture micro-dissection uses a laser to isolate subpopulations of cells that are visualized via microscopy; however the time-consuming nature of this process and the relatively low yield can significantly limit the subsequent analysis of proteins or mRNA levels, particularly if the expression of these molecules is low to begin with. Fluorescence activated cell sorting (FACS) is a relatively novel technique in the field of neuroscience to isolate individual cell types from the brain for subsequent analysis of gene expression1 and/or epigenetic targets2. This process can also be used to sort specific types of neural cells for subsequent analysis of cell-type-specific gene expression, protein expression, or epigenetic markers. FACS has been used in a number of medical research fields such as cancer and immunology for decades to count and sort different cells based on either physical or biochemical characteristics3. In addition, flow cytometry has classically been used to analyze protein expression on a per cell basis, using specific antibodies. The procedure described below, takes advantage of classical flow cytometry techniques to isolate individual cell types for subsequent analysis of molecular biology endpoints. The flow cytometer can analyze several thousand cells in a second, which makes it a quick and efficient alternative to the techniques described above. In addition, cells can be isolated based on the cellular expression of a specific protein (for example a neurotransmitter receptor) or a combination of two or more proteins (colocalization of multiple proteins in a specific cell type). This allows the user to isolate very selective neural cell types based on their molecular properties to identify their function in the brain.
To perform FACS, neural cells are prepared into a single-cell suspension which is passed through a flow cell that carries and aligns the cells so that they pass single-file through a light beam and lasers for analysis. A computer acquires the data from each cell and plots it on a histogram for analysis of specified parameters (size, granularity, and fluorescence). Based on these parameters, the cells can immediately be sorted into separate tubes for their recollection and subsequent analysis of any endpoint desired. The protocol described below utilizes three antibodies to sort neurons (using a Thymocyte antigen 1, Thy1 antibody), astrocytes (using a glial glutamate transporter, GLT1 antibody), and microglia (using a cluster of differentiation molecule 11B, CD11b antibody). This protocol can be used as described below or modified with different antibodies depending on the cell type that one would like to isolate for his own experiments.
There are a few caveats to consider when determining whether this protocol is appropriate for specific experiments. One major caveat may concern the specific cell type that one would like to isolate. In this protocol, the three antibodies that are used are extracellular antibodies, which allow the experimenter to keep the cell types intact during the staining procedure, thus preserving the integrity of the RNA, DNA and proteins inside. It is possible that one may wish to isolate a specific neural cell type using an antibody that identifies a protein that is only expressed inside that particular cell. For example, one might want to isolate dopaminergic neurons using an antibody to tyrosine hydroxylase or isolate acetylcholine neurons using an antibody for choline acetyltransferase. These proteins are intracellular and thus would require fixation and permeabilization of the cell membrane for subsequent staining with the appropriate antibodies. While this has been done before 4,5, this process may significantly decrease the yield of RNA or DNA from these permeabilized cells. Another caveat may be that not all antibodies are appropriate for FACS. For example, one may currently use an antibody that works very well for western blot, a technique that requires the denaturation of proteins. This antibody may not necessarily be suitable for identification of these cell types using FACS given that the proteins are not denatured at any point in this protocol and thus the antibody may have no way to bind to its inherent antigen. Companies provide specification sheets which identify the applications for which an antibody has been approved. If an antibody has not been approved for flow cytometry, it should not discourage one from trying this protocol with a particular antibody; however, one should be aware that it isn&#8217;t guaranteed to work for FACS. A third caveat of this protocol has to do with the number of cells that one is trying to isolate. FACS is an excellent technique to yield the most cells possible from even a small piece of tissue, but it is also possible that if one would like to isolate a relatively sparse population of cells from a relatively small brain region, the yield from one animal will be inherently low. In this case, it may be necessary to pool the brain tissue from a few animals in the same treatment group in order to yield the number of cells necessary for subsequent analysis; however, a recent publication has used gene-targeted pre-amplification of cDNA for subsequent analysis of gene expression from a small number of activated neurons (5-6%) from a larger set sorted neurons, indicating that it is possible to analyze gene expression from even small subsets of neural cells without pooling large numbers of animals6A final caveat of this technique is that one should have access to a cell sorter that is not too far away. The cell sorter is a complicated machine that requires significant training in order to use it properly. Thus these machines are often run by a qualified technician in a core facility. In addition, the goal of this procedure is to dissociate the neural tissue, stain it for specific antibodies, and immediately take those samples to a sorter within a short period of time (perhaps a half day). This timeframe will help to increase the survival and yield of isolated cells and maintain the integrity of the cells for subsequent processing and analysis. If all of these parameters described above are met, FACS is an excellent method to analyze cell-type specific expression of genes and proteins from neural tissue.
All experiments were performed in accordance with the Institutional Animal Care and Use Committee (IACUC) of the University of Delaware and the National Institutes of Health Guide for the Care and Use of Laboratory Animals.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Neural Dissociation Kit (P)</td>
			<td>Miltenyi Biotec</td>
			<td>130-092-628</td>
			<td></td>
		</tr>
		<tr>
			<td>Myelin Removal Beads II</td>
			<td>Miltenyi Biotec</td>
			<td>130-096-733</td>
			<td></td>
		</tr>
		<tr>
			<td>LS Columns</td>
			<td>Miltenyi Biotec</td>
			<td>130-042-401</td>
			<td></td>
		</tr>
		<tr>
			<td>QuadroMACS Separator</td>
			<td>Miltenyi Biotec</td>
			<td>130-090-976</td>
			<td></td>
		</tr>
		<tr>
			<td>MACS MultiStand</td>
			<td>Miltenyi Biotec</td>
			<td>130-042-303</td>
			<td></td>
		</tr>
		<tr>
			<td>Nylon Mesh Sheet</td>
			<td>Amazon</td>
			<td>CMN-0074-10YD</td>
			<td>40 inch width, 80 micron size mesh</td>
		</tr>
		<tr>
			<td>Fc Block / anti-CD32</td>
			<td>BD Biosciences</td>
			<td>BDB550270</td>
			<td>reactivity for rat</td>
		</tr>
		<tr>
			<td>APC-conjugated CD11b antibody</td>
			<td>Biolegend</td>
			<td>201809</td>
			<td>reactivity for rat</td>
		</tr>
		<tr>
			<td>Rabbit anti-GLT1</td>
			<td>Novus Biologicals</td>
			<td>NBP1-20136</td>
			<td>reactivity for rat or human</td>
		</tr>
		<tr>
			<td>PE-conjugated anti-rabbit secondary antibody</td>
			<td>eBioscience</td>
			<td>1037259</td>
			<td>secondary antibody for anti-GLT1</td>
		</tr>
		<tr>
			<td>FITC-conjugated anti-rat CD90 (Thy1) mouse antibody</td>
			<td>Biolegend</td>
			<td>202504</td>
			<td>reactivity for rat</td>
		</tr>
	</tbody>
</table>

using fluorescence activated cell sorting to examine cell-type-specific gene expression in rat brain tissue

大脑是由四个主要类型的细胞，包括神经元，星形胶质细胞，小胶质细胞和少突胶质细胞。虽然它们不是在大脑中最丰富的细胞类型，神经元是最广泛研究因为它们在影响行为直接作用这些细胞类型。在大脑中的其它细胞类型也影响通过它们产生的信号分子的神经元功能和行为。神经科学家必须了解的细胞类型之间的相互作用在大脑更好地了解这些相互作​​用如何影响神经功能和疾病。迄今为止，分析蛋白质或基因表达的最常见方法是利用整个组织样品均质化，通常是用血，而不考虑的细胞类型。这种方法是用于检查基因或可能影响神经功能和行为表达一般的变化信息的方式;然而，这种分析方法不适合于电池的更深入的了解-type特异性基因表达和细胞 - 细胞通信的对神经功能的影响。行为表观遗传学分析已经日益焦点其中审查的区域如何的脱氧核糖核酸（DNA）的结构影响长期基因表达和行为的修改;然而，该信息可以仅是相关的，如果在给定的鉴别谱系，从而后生标记可存在于个体的神经细胞类型的某些基因的细胞类型特异性的方式进行分析。荧光激活细胞分选如下所述（FACS）技术提供了一种简单而有效的方法，以分离单个神经细胞的基因表达，蛋白质表达，或DNA的表观遗传修饰的随后的分析。这种技术也可以被修改，以在脑中为随后的细胞类型特异性分析隔离更具体的神经细胞类型。

The Importance of Myelin Depletion and Tissue Perfusion
Figure 1 depicts the importance of myelin depletion. Myelin depletion (Steps 5.1 through 5.12 of the protocol above) occurs when the single-cell suspension is incubated in the Myelin Removal Beads, washed, and subsequently passed through the column on the magnetic sorter. The purpose of these steps is to reduce the amount of cellular debris present in each sample. As neurons are dissociated and triturated, it can shear of...

Watch this Scientific Journal Video about Using Fluorescence Activated Cell Sorting to Examine Cell-Type-Specific Gene Expression in Rat Brain Tissue at JoVE.com

Using Fluorescence Activated Cell Sorting to Examine Cell-Type-Specific Gene Expression in Rat Brain Tissue

The goal of this protocol is to use the fluorescence activated cell sorting (FACS) technique to sort specific types of neural cells for subsequent analysis of cell-type-specific gene expression, epigenetic markers, and or protein expression.

在大鼠脑组织用荧光活化细胞分选，以检查细胞类型特异性基因表达

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