This work was funded by the Wellcome Trust through grants to A.P.M [076566/Z/05/Z], J.C.K. [074318] and a core award to the Wellcome Trust Centre for Human Genetics [075491/Z/04].

1) Cell Culture
<ol>
<li>Select cell types expressing the gene of interest.</li>
<li>Select cell lines heterozygous both for DNA risk variants and transcribed coding polymorphism within the gene of interest (Figure 1).</li>
<li>Culture the selected cell lines according to the supplier's specifications and prepare 2 x 10 cm petri dishes for DNA and RNA extraction respectively.</li>
<li>When cells reach 80% confluence start the procedure to harvests cells and isolate DNA and RNA either following the procedure described below or using commercially available kits.</li>
</ol>
2) DNA Extraction
<ol>
<li>Remove media from the dish, wash with PBS and add to the dish 500 &mu;L of a lysis solution (0.6% SDS, 100 mM NaCl, 50 mM Tris, 20 mM EDTA and 50 &mu;g/mL RNase A).</li>
<li>Rock the plate gently for 20 minutes at room temperature.</li>
<li>Scrape the cell lysate into a microcentrifuge tube and incubate at 37 &deg;C overnight.</li>
<li>Add proteinase K to a final concentration of 100 &mu;g/mL and incubate at 37 &deg;C overnight.</li>
<li>Extract the DNA with an equal volume of phenol-chloroform pH 8, repeat, then extract with an equal volume of chloroform/isoamyl alcohol.</li>
<li>Precipitate the DNA with 1/10th volume 3 M NaCl and 2.5 volumes of 100% ethanol.</li>
<li>Leave on ice for 5 min and then spin at 13,000 rpm for 30 min at 4 &deg;C.</li>
<li>Wash the DNA with 70% ethanol, allow to air-dry and resuspend in 200 &mu;L of TE.</li>
<li>Incubate at 65 &deg;C for 10 min and then leave for 2 days at room temperature.</li>
<li>Store at 4 &deg;C or long term at -20 &deg;C.</li>
</ol>
3) RNA Extraction
<ol>
<li>Remove media from the dish, wash with PBS, add 1 mL of TRIzol and incubate for 10 min at room temperature.</li>
<li>Scrape cells, pipette a few times, transfer in a microcentrifuge tube and incubate for 5 min.</li>
<li>Spin for 10 min at 10,000 rpm at 4&deg;C.</li>
<li>Transfer the supernatant in a fresh tube and add 200 &mu;L of chloroform.</li>
<li>Shake and spin for 10 min at 10,000 rpm at 4&deg;C.</li>
<li>Transfer the aqueous phase in a fresh tube and add an equal volume of 70% ethanol.</li>
<li>Load the solution to 1 or 2 (depending on the volume) RNeasy column and spin for 30 sec at maximum speed.</li>
<li>From here follow instruction of the RNeasy kit (Qiagen).</li>
</ol>
4) Nucleic Acid Sample Preparation
<ol>
<li>Quantify DNA and RNA concentration using a NanoDrop Spectrophotometer (Thermo Scientific).</li>
<li>Prepare cDNA from 500-1000 ng of RNA using random decamers and SuperScript III Reverse Transcriptase (Invitrogen) according to the manufacturer's instructions.</li>
</ol>
5) PCR and Primer Extension Assay
<ol>
<li>Design two pairs of PCR primers for each DNA marker, one pair for genomic DNA amplification and the other pair for cDNA amplification (Fig 2). Place forward and reverse primer for cDNA amplification in different exons to avoid genomic contamination. Design primer to obtain a PCR product in the range of 100-500 bp length.</li>
<li>Prepare a 10 &mu;L PCR reaction including 0.5 U Immolase Taq (Bioline) 0.8 mM dNTPs, 2 mM MgCl2, 0.2 M each primer and 20 ng of either cDNA or DNA. Amplify each sample in four independent reactions.</li>
<li>Run the PCR reaction under the conditions optimized for each primer pair keeping cycle number in linear phase of amplification.</li>
<li>Remove PCR primer and dNTPs excess by incubating the PCR product with exonuclease I and Shrimp Alkaline Phosphatase (SAP) at 37 &deg;C for 20 minutes.</li>
<li>Spot each PCR product twice on a 384-well plate, so that 8 measurements will be available for each sample.</li>
<li>Design the extension primer with the Assay Design (Sequenom) software so that the same primer can be used for both genomic and cDNA PCR products. Specify primer length in the range of 14-18 bp and extension mix including combinations of 3ddNTPs (Fig 2).</li>
<li>Carry out the primer extension reaction and MALDI-TOF/MS analysis using the MassARRAY system (Sequenom) according to the manufacturer's instruction.</li>
<li>A typical primer extension reaction include a starting step at 94 &deg;C for 2 min, followed by 40 cycles of 94 &deg;C for 5 s, 52 &deg;C for 5 s and 72 &deg;C for 5 s.</li>
<li>The primer extension products are cleaned with SpectroCLEAN resin and transferred onto microarray (chip) by SpectroPOINT nanolitre dispenser.</li>
<li>The extended oligonucleotides are quantified by MALDI-TOF using a SpectroREADER mass spectrometer.</li>
</ol>
6) Statistical Analysis
<ol>
<li>Check MALDI-TOF/MS results with the MassARRAY Typer software for general quality of the experiment.</li>
<li>Extract the Allelotyping report which includes the peak area data.</li>
<li>For each individual spectrum calculate the ratio between the peak area of allele 1 and allele 2 (peak area ratio).</li>
<li>For each cDNA sample derive a peak area ratio mean and standard deviation, using the corresponding function in Excel, across the 8 measurements.</li>
<li>Derive the same mean peak area ratio across the 8 measurments for genomic DNA.</li>
<li>Divide the cDNA mean ratio by the genomic mean ratio to assess the deviation to the expected 1:1 ratio.</li></ol>
7) Experimental Controls
<ol>
<li>To rule out experimental artifacts, repeat the experiment at least three times.</li>
<li>Whenever possible, design assays for additional DNA markers.</li>
<li>Design multiple PCR primer pairs and extension primers annealing to both forward and reverse strands.</li>
<li>Whenever possible test as negative controls cell lines that are heterozygous for DNA markers but do not carry the DNA risk variants associated with the phenotype (Fig. 1 and Fig. 3)</li>
</ol>
8) Representative Results
An example of allele-specific expression analysis is shown in Figure 3 with examples of mass spectrometry traces. The figure shows the results from the analysis of 4 allele-specific primer extension products carried out on 4 different templates. The top graphs represent the results obtained from the analysis of genomic DNA of two different cell lines, which are both heterozygous for a transcribed coding polymorphism. However, only cell line A is heterozygous for the risk DNA variant (Figure 1). The lower graphs represent the results obtained from the analysis of the cDNA generated from the same cell lines. As a result of experimental artifact the first peak is always higher than the second peak even in the genomic analysis. Therefore, the results from the genomic analysis are used to normalize the cDNA data. After normalization, the allele ratio is significantly different from 1 in cell line A (where the second peak appears lower compared to the other spectra), while it is very close to 1 in cell line B. The data suggest that cell line A carries a DNA variant, in phase with the allele measured by the second peak, which reduces the expression of the gene under analysis. Cell line B provides a very convenient negative control.
<img src="/files/ftp_upload/2279/2279fig1.jpg" alt="Figure 1" /> Figure 1. Cell line selection strategy. Cell lines A and B are heterozygous for a transcribed coding marker (triangle) but only cell line A is heterozygous for risk DNA variant (circle). The blue allele of the risk variant is associated (either with a direct effect or because in close correlation with the actual functional variant) with a lower level of transcription.
<img src="/files/ftp_upload/2279/2279fig2.jpg" alt="Figure 2" /> Figure 2. Allele-specific primer extension assay. This figure show the work-flow of the experimental procedure carried for both cDNA (left) and genomic DNA (right) templates. PCR primers (grey rectangles) are designed to amplify a heterozygous coding polymorphism (triangle). To avoid genomic contamination PCR primers anneal sequences placed in different exons (light blue bars) when amplification is carried out on cDNA template. The PCR product is then used as template for a primer extension reaction carried out with an extension primer, annealing one base next to the polymorphism, and the appropriate mix of three dideoxynucleotide (ddNTPs) terminators (squares) and one deoxynucleotide (circle) to extend the primer of one or two basis respectively. The resulting primer extension products have different masses which allow separation and quantification by MALDI-TOF mass spectrometry. The quantity of product corresponding to the blue allele of the DNA marker is relatively lower to the red allele.
<img src="/files/ftp_upload/2279/2279fig3.jpg" alt="Figure 3" /> 
 Figure 3. Results of an allele-specific expression assay. The figure show the mass spectrometry results from the analysis carried out on the genomic DNA and the cDNA of cell line A and cell line B (Figure 1).

<ol>
	<li>Cookson, W., Liang, L., Abecasis, G., Moffatt, M., Lathrop, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+complex+disease+traits+with+global+gene+expression.">Mapping complex disease traits with global gene expression.</a> Nat Rev Genet. 10, 184-194 (2009).</li><li>Singer-Sam, J., LeBon, J. M., Dai, A., Riggs, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+sensitive,+quantitative+assay+for+measurement+of+allele-specific+transcripts+differing+by+a+single+nucleotide.">A sensitive, quantitative assay for measurement of allele-specific transcripts differing by a single nucleotide.</a> PCR Methods Appl. 1, 160-163 (1992).</li><li>Yan, H., Yuan, W., Velculescu, V. E., Vogelstein, B., Kinzler, K. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Allelic+variation+in+human+gene+expression.">Allelic variation in human gene expression.</a> Science. 297, 1143-11 (2002).</li><li>Ding, C., Cantor, C. R. <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-throughput+gene+expression+analysis+technique+using+competitive+PCR+and+matrix-assisted+laser+desorption+ionization+time-of-flight+MS.">A high-throughput gene expression analysis technique using competitive PCR and matrix-assisted laser desorption ionization time-of-flight MS.</a> Proc Natl Acad Sci U S A. 100, 3059-3064 (2003).</li><li>Gabriel, S., Ziaugra, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SNP+genotyping+using+Sequenom+MassARRAY+7K+platform.">SNP genotyping using Sequenom MassARRAY 7K platform.</a> Curr Protoc Hum Genet Chapter. Chapter 2 (Unit 2), 12-12 (2004).</li><li>Lo, H. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Allelic+variation+in+gene+expression+is+common+in+the+human+genome.">Allelic variation in gene expression is common in the human genome.</a> Genome Res. 13 (8), 1855-1862 (2003).</li><li>Liu, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression-based+discovery+of+variation+in+the+human+glutathione+S-transferase+M3+promoter+and+functional+analysis+in+a+glioma+cell+line+using+allele-specific+chromatin+immunoprecipitation.">Expression-based discovery of variation in the human glutathione S-transferase M3 promoter and functional analysis in a glioma cell line using allele-specific chromatin immunoprecipitation.</a> Cancer Res. 65, 99-104 (2005).</li><li>Knight, J. C., Keating, B. J., Rockett, K. A., Kwiatkowski, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+characterization+of+regulatory+polymorphisms+by+allele-specific+quantification+of+RNA+polymerase+loading.">In vivo characterization of regulatory polymorphisms by allele-specific quantification of RNA polymerase loading.</a> Nat Genet. 33 (4), 469-475 (2003).</li><li>Pastinen, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+survey+of+genetic+and+epigenetic+variation+affecting+human+gene+expression.">A survey of genetic and epigenetic variation affecting human gene expression.</a> Physiol Genomics. 16 (2), 184-193 (2004).</li><li>Francks, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+77-kilobase+region+of+chromosome+6p22.2+is+associated+with+dyslexia+in+families+from+the+United+Kingdom+and+from+the+United+States.">A 77-kilobase region of chromosome 6p22.2 is associated with dyslexia in families from the United Kingdom and from the United States.</a> Am J Hum Genet. 75 (6), 1046-1058 (2004).</li><li>Paracchini, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+chromosome+6p22+haplotype+associated+with+dyslexia+reduces+the+expression+of+KIAA0319,+a+novel+gene+involved+in+neuronal+migration.">The chromosome 6p22 haplotype associated with dyslexia reduces the expression of KIAA0319, a novel gene involved in neuronal migration.</a> Hum Mol Genet. 15 (10), 1659-1666 (2006).</li></ol>

No conflicts of interest declared.

This method enables evaluation of the effect of disease-associated DNA variants on gene expression by assessing in vivo allele-specific difference in transcript level. In this protocol relative transcript abundance is measured by MALDI-TOF but other technologies allowing allele-specific quantification, such as TaqMan6,7, can be used. The major limitation of this approach is the availability of transcribed coding markers. Methods based on the principle described here, but taking advantage of different classes of polymorphisms, have been described. The haploChip assay measures allele-specific expression using markers located within 1 kb of the transcriptional start or end site of a gene which would be present in chromatin immunoprecipitated material isolated with antibodies specific to RNA polymerase II8. Alternatively, intronic SNPs can be used when the template is heteronuclear RNA9.
The specific protocol described here, in combination with the haploChip assay, has been used successfully to identify a candidate gene for dyslexia (or reading disability). Initially a genetic association study identified a DNA sequence associated with dyslexia and which was spanning three genes10. The allele-specific gene expression assay showed that in the presence of the dyslexia-associated DNA variants expression variation was observed for only one of the three genes but not the other two11.

<table border="1">
	<thead>
		<tr>
			<th>Material Name</th>
			<th>Type</th>
			<th>Company</th>
			<th>Catalogue Number</th>
			<th>Comment</th>
		</tr>
	</thead>
	<tbody>
		<tr>
			<td>PBS</td>
			<td>&nbsp;</td>
			<td>Sigma</td>
			<td>P-4417-100TAB</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>SDS</td>
			<td>&nbsp;</td>
			<td>Biorad</td>
			<td>161-0416</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>&nbsp;</td>
			<td>VWR</td>
			<td>27788.366</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Tris</td>
			<td>&nbsp;</td>
			<td>Sigma</td>
			<td>T1503-1KG</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>&nbsp;</td>
			<td>Sigma</td>
			<td>E5134-500G</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>RNase A</td>
			<td>&nbsp;</td>
			<td>Qiagen</td>
			<td>19101</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Proteinase K</td>
			<td>&nbsp;</td>
			<td>Sigma</td>
			<td>P2308-500MG</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Phenol: chloroform</td>
			<td>&nbsp;</td>
			<td>Sigma</td>
			<td>77617</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>&nbsp;</td>
			<td>VWR</td>
			<td>100777C</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>&nbsp;</td>
			<td>Sigma</td>
			<td>32221-2.5L</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Trizol</td>
			<td>&nbsp;</td>
			<td>Invitrogen</td>
			<td>15596-018</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>RNeasy kit</td>
			<td>&nbsp;</td>
			<td>Qiagen</td>
			<td>74104</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>SuperScript III Reverse Transcriptase</td>
			<td>&nbsp;</td>
			<td>Invitrogen</td>
			<td>18080-044</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Immolase Taq</td>
			<td>&nbsp;</td>
			<td>Bioline</td>
			<td>BIO-21048</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>dNTP</td>
			<td>&nbsp;</td>
			<td>Sigma</td>
			<td>DNTP100A</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Exonuclease 1</td>
			<td>&nbsp;</td>
			<td>NEB</td>
			<td>M0293S</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Shrimp Alkaline Phosphatase</td>
			<td>&nbsp;</td>
			<td>GE Healthcare</td>
			<td>E70092Z</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>SpectroCLEAN resin</td>
			<td>&nbsp;</td>
			<td>Sequenom</td>
			<td>10053</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>MassEXTEND ddNTP/dNTP mix </td>
			<td>&nbsp;</td>
			<td>Sequenom</td>
			<td>&nbsp;</td>
			<td>Varies according to assay design</td>
		</tr>
		<tr>
			<td>MassEXTEND thermosequenase </td>
			<td>&nbsp;</td>
			<td>Sequenom</td>
			<td>10052</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Chilled microcentrifuge</td>
			<td>&nbsp;</td>
			<td>Eppendorf</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>NanoDrop Spectrophotometer</td>
			<td>&nbsp;</td>
			<td>Thermo Scientific</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>SpectroPOINT nanolitre dispenser</td>
			<td>&nbsp;</td>
			<td>Sequenom</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>SpectroREADER mass spectrometer</td>
			<td>&nbsp;</td>
			<td>Sequenom</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

an allele-specific gene expression assay to test the functional basis of genetic associations

The number of significant genetic associations with common complex traits is constantly increasing. However, most of these associations have not been understood at molecular level. One of the mechanisms mediating the effect of DNA variants on phenotypes is gene expression, which has been shown to be particularly relevant for complex traits1.
This method tests in a cellular context the effect of specific DNA sequences on gene expression. The principle is to measure the relative abundance of transcripts arising from the two alleles of a gene, analysing cells which carry one copy of the DNA sequences associated with disease (the risk variants)2,3. Therefore, the cells used for this method should meet two fundamental genotypic requirements: they have to be heterozygous both for DNA risk variants and for DNA markers, typically coding polymorphisms, which can distinguish transcripts based on their chromosomal origin (Figure 1). DNA risk variants and DNA markers do not need to have the same allele frequency but the phase (haplotypic) relationship of the genetic markers needs to be understood. It is also important to choose cell types which express the gene of interest. This protocol refers specifically to the procedure adopted to extract nucleic acids from fibroblasts but the method is equally applicable to other cells types including primary cells.
DNA and RNA are extracted from the selected cell lines and cDNA is generated. DNA and cDNA are analysed with a primer extension assay, designed to target the coding DNA markers4. The primer extension assay is carried out using the MassARRAY (Sequenom)5 platform according to the manufacturer's specifications. Primer extension products are then analysed by matrix-assisted laser desorption/ionization time of-flight mass spectrometry (MALDI-TOF/MS). Because the selected markers are heterozygous they will generate two peaks on the MS profiles. The area of each peak is proportional to the transcript abundance and can be measured with a function of the MassARRAY Typer software to generate an allelic ratio (allele 1: allele 2) calculation. The allelic ratio obtained for cDNA is normalized using that measured from genomic DNA, where the allelic ratio is expected to be 1:1 to correct for technical artifacts. Markers with a normalised allelic ratio significantly different to 1 indicate that the amount of transcript generated from the two chromosomes in the same cell is different, suggesting that the DNA variants associated with the phenotype have an effect on gene expression. Experimental controls should be used to confirm the results.

Watch this Scientific Journal Video about An Allele-specific Gene Expression Assay to Test the Functional Basis of Genetic Associations at JoVE.com

An Allele-specific Gene Expression Assay to Test the Functional Basis of Genetic Associations

Genetic associations often remain unexplained at a functional level. This method aims to assess the effect of phenotype-associated genetic markers on gene expression by analyzing cells heterozygous for transcribed SNPs. The technology allows accurate measurement by MALDI-TOF mass spectrometry to quantify allele-specific primer extension products.

The number of significant genetic associations with common complex traits is constantly increasing. However, most of these associations have not been ...

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22.7K Views.  University of Oxford. Genetic associations often remain unexplained at a functional level. This method aims to assess the effect of phenotype-associated genetic markers on gene expression by analyzing cells heterozygous for transcribed SNPs. The technology allows accurate measurement by MALDI-TOF mass spectrometry to quantify allele-specific primer extension products.

Video: An Allele-specific Gene Expression Assay to Test the Functional Basis of Genetic Associations

Light/dark Transition Test for Mice

Although all of the mouse genome sequences have been determined, we do not yet know the functions of most of these genes. Gene-targeting techniques, however, can be used to delete or manipulate a specific gene in mice. The influence of a given gene on a specific behavior can then be determined by conducting behavioral analyses of the mutant mice. As a test for behavioral phenotyping of mutant mice, the light/dark transition test is one of the most widely used tests to measure anxiety-like behavior in mice. The test is based on the natural aversion of mice to brightly illuminated areas and on their spontaneous exploratory behavior in novel environments. The test is sensitive to anxiolytic drug treatment. The apparatus consists of a dark chamber and a brightly illuminated chamber. Mice are allowed to move freely between the two chambers. The number of entries into the bright chamber and the duration of time spent there are indices of bright-space anxiety in mice. To obtain phenotyping results of a strain of mutant mice that can be readily reproduced and compared with those of other mutants, the behavioral test methods should be as identical as possible between laboratories. The procedural differences that exist between laboratories, however, make it difficult to replicate or compare the results among laboratories. Here, we present our protocol for the light/dark transition test as a movie so that the details of the protocol can be demonstrated. In our laboratory, we have assessed more than 60 strains of mutant mice using the protocol shown in the movie. Those data will be disclosed as a part of a public database that we are now constructing.

Visualization of the protocol will facilitate understanding of the details of the entire experimental procedure, allowing for standardization of the protocols used across laboratories and comparisons of the behavioral phenotypes of various strains of mutant mice assessed using this test.

The light/dark transition test is one of the most widely used tests to measure anxiety-like behavior in mice. Here, we present a movie that shows detailed procedures on how we conduct the test.

Although all of the mouse genome sequences have been determined, we do not yet know the functions of most of these genes. Gene-targeting techniques, ...

The Preparation of Primary Hematopoietic Cell Cultures From Murine Bone Marrow for Electroporation

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser MXcell  electroporation system and Gene Pulser  electroporation buffer were specifically developed to transfect nucleic acids into mammalian cells and difficult-to-transfect cells, such as primary and stem cells.This video demonstrates how to establish primary hematopoietic cell cultures from murine bone marrow, and then prepare them for electroporation in the MXcell system. We begin by isolating femur and tibia. Bone marrow from both femur and tibia are then harvested and cultures are established. Cultured bone marrow cells are then transfected and analyzed.

This procedure describes how to establish primary hematopoietic cell cultures from murine bone marrow and is followed by transfection using the Gene Pulser MXCell electroporation system.

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser ...

Spinal Cord Electrophysiology

The neonatal mouse spinal cord is a model for studying the development of neural circuitries and locomotor movement. We demonstrate the spinal cord dissection and preparation of recording bath artificial cerebrospinal fluid used for locomotor studies. Once dissected, the spinal cord ventral nerve roots can be attached to a recording electrode to record the electrophysiologic signals of the central pattern generating circuitry within the lumbar cord.

A demonstration of the isolation of neonatal mouse spinal cord for electrophysiologic studies.

The neonatal mouse spinal cord is a model for studying the development of neural circuitries and locomotor movement. We demonstrate the spinal cord ...

Using the Gene Pulser MXcell Electroporation System to Transfect Primary Cells with High Efficiency

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser MXcell electroporation system and Gene Pulser electroporation buffer (Bio-Rad) were specifically developed to easily transfect nucleic acids into mammalian cells and difficult-to-transfect cells, such as primary and stem cells. We will demonstrate how to perform a simple experiment to quickly identify the best electroporation conditions. We will demonstrate how to run several samples through a range of electroporation conditions so that an experiment can be conducted at the same time as optimization is performed. We will also show how optimal conditions identified using 96-well electroporation plates can be used with standard electroporation cuvettes, facilitating the switch from electroporation plates to electroporation cuvettes while maintaining the same electroporation efficiency. In the video, we will also discuss some of the key factors that can lead to the success or failure of electroporation experiments.

This procedure shows how to use the Gene Pulser MXcell electroporation system to rapidly and easily identify the best electroporation conditions for mouse embryonic fibroblasts (MEFs) or other primary cells. Considerations for troubleshooting are also discussed in the associated video.

Using an Automated Cell Counter to Simplify Gene Expression Studies: siRNA Knockdown of IL-4 Dependent Gene Expression in Namalwa Cells

The use of siRNA mediated gene knockdown is continuing to be an important tool in studies of gene expression.  siRNA studies are being conducted not only to study the effects of downregulating single genes, but also to interrogate signaling pathways and other complex interaction networks.  These pathway analyses require both the use of relevant cellular models and methods that cause less perturbation to the cellular physiology.  Electroporation is increasingly being used as an effective way to introduce siRNA and other nucleic acids into difficult to transfect cell lines and primary cells without altering the signaling pathway under investigation. There are multiple critical steps to a successful siRNA experiment, and there are ways to simplify the work while improving the data quality at several experimental stages.  To help you get started with your siRNA mediated gene knockdown project, we will demonstrate how to perform a pathway study complete from collecting and counting the cells prior to electroporation through post transfection real-time PCR gene expression analysis.  The following study investigates the role of the transcriptional activator STAT6 in IL-4 dependent gene expression of CCL17 in a Burkitt lymphoma cell line (Namalwa).  The techniques demonstrated are useful for a wide range of siRNA-based experiments on both adherent and suspension cells.  We will also show how to streamline cell counting with the TC10 automated cell counter, how to electroporate multiple samples simultaneously using the MXcell electroporation system, and how to simultaneously assess RNA quality and quantity with the Experion automated electrophoresis system.

This procedure describes a quick and easy workflow to introduce siRNA into difficult to transfect cell lines and follow gene expression by real-time PCR. Use of an automated cell counter, multi-well electroporation plate, and automated electrophoresis station provide quick and reliable results without the need for expensive robotic handling.

The use of siRNA mediated gene knockdown is continuing to be an important tool in studies of gene expression.  siRNA studies are being conducted not only ...

A Reverse Genetic Approach to Test Functional Redundancy During Embryogenesis

Gene function during embryogenesis is typically defined by loss-of-function experiments, for example by targeted mutagenesis (knockout) in the mouse. In the zebrafish model, effective reverse genetic techniques have been developed using microinjection of gene-specific antisense morpholinos. Morpholinos target an mRNA through specific base-pairing and block gene function transiently by inhibiting translation or splicing for several days during embryogenesis (knockdown). However, in vertebrates such as mouse or zebrafish, some gene functions can be obscured by these approaches due to the presence of another gene that compensates for the loss. This is especially true for gene families containing sister genes that are co-expressed in the same developing tissues. In zebrafish, functional compensation can be tested in a relatively high-throughput manner, by co-injection of morpholinos that target knockdown of both genes simultaneously. Likewise, using morpholinos, a genetic interaction between any two genes can be demonstrated by knockdown of both genes together at sub-threshold levels. For example, morpholinos can be titrated such that neither individual knockdown generates a phenotype. If, under these conditions, co-injection of both morpholinos causes a phenotype, a genetic interaction is shown. Here we demonstrate how to show functional redundancy in the context of two related GATA transcription factors. GATA factors are essential for specification of cardiac progenitors, but this is revealed only by the loss of both Gata5 and Gata6. We show how to carry out microinjection experiments, validate the morpholinos, and evaluate the compensated phenotype for cardiogenesis.

Gene function can be obscured in loss-of-function experiments if there is compensation by another gene. The zebrafish model provides a relatively high-throughput means to reveal such functional redundancy in living embryos.

Gene function during embryogenesis is typically defined by loss-of-function experiments, for example by targeted mutagenesis (knockout) in the mouse. In ...

Paraffin-Embedded and Frozen Sections of Drosophila Adult Muscles

The molecular characterization of muscular dystrophies and myopathies in humans has revealed the complexity of muscle disease and genetic analysis of muscle specification, formation and function in model systems has provided valuable insight into muscle physiology. Therefore, identifying and characterizing molecular mechanisms that underlie muscle damage is critical. The structure of adult Drosophila multi-fiber muscles resemble vertebrate striated muscles 1 and the genetic tractability of Drosophila has made it a great system to analyze dystrophic muscle morphology and characterize the processes affecting muscular function in ageing adult flies 2. Here we present the histological technique for preparing paraffin-embedded and frozen sections of Drosophila thoracic muscles. These preparations allow for the tissue to be stained with classical histological stains and labeled with protein detecting dyes, and specifically cryosections are ideal for immunohistochemical detection of proteins in intact muscles. This allows for analysis of muscle tissue structure, identification of morphological defects, and detection of the expression pattern for muscle/neuron-specific proteins in Drosophila adult muscles. These techniques can also be slightly modified for sectioning of other body parts.

Paraffin-Embedded and Frozen Sections of Drosophila Adult Muscles

Identification of mechanisms underlying muscle damage is crucial. Here we present the histological technique for preparing paraffin-embedded and frozen sections of Drosophila thoracic muscles. This allows analysis of muscle morphology and localization of protein and other muscle cell components.

The molecular characterization of muscular dystrophies and myopathies in humans has revealed the complexity of muscle disease and genetic analysis of ...

In vitro Reconstitution of the Active T. castaneum Telomerase

Efforts to isolate the catalytic subunit of telomerase, TERT, in sufficient quantities for structural studies, have been met with limited success for more than a decade. Here, we present methods for the isolation of the recombinant Tribolium castaneum TERT (TcTERT) and the reconstitution of the active T. castaneum telomerase ribonucleoprotein (RNP) complex in vitro.
Telomerase is a specialized reverse transcriptase1 that adds short DNA repeats, called telomeres, to the 3' end of linear chromosomes2 that serve to protect them from end-to-end fusion and degradation. Following DNA replication, a short segment is lost at the end of the chromosome3 and without telomerase, cells continue dividing until eventually reaching their Hayflick Limit4. Additionally, telomerase is dormant in most somatic cells5 in adults, but is active in cancer cells6 where it promotes cell immortality7.
The minimal telomerase enzyme consists of two core components: the protein subunit (TERT), which comprises the catalytic subunit of the enzyme and an integral RNA component (TER), which contains the template TERT uses to synthesize telomeres8,9. Prior to 2008, only structures for individual telomerase domains had been solved10,11. A major breakthrough in this field came from the determination of the crystal structure of the active12, catalytic subunit of T. castaneum telomerase, TcTERT1.
Here, we present methods for producing large quantities of the active, soluble TcTERT for structural and biochemical studies, and the reconstitution of the telomerase RNP complex in vitro for telomerase activity assays. An overview of the experimental methods used is shown in Figure 1.

In vitro Reconstitution of the Active T. castaneum Telomerase

Efforts to isolate the catalytic subunit of telomerase, TERT, in sufficient quantities for structural studies, have been met with limited success for more than a decade. Here, we present methods for the isolation of the recombinant Tribolium castaneum TERT (TcTERT) and the reconstitution of the active T. castaneum telomerase ribonucleoprotein (RNP) complex in vitro.

Efforts to isolate the catalytic subunit of telomerase, TERT, in sufficient quantities for structural studies, have been met with limited success for more ...

Pharmacological and Functional Genetic Assays to Manipulate Regeneration of the Planarian Dugesia japonica

Free-living planarian flatworms have a long history of experimental usage owing to their remarkable regenerative abilities1. Small fragments excised from these animals reform the original body plan following regeneration of missing body structures. For example if a 'trunk' fragment is cut from an intact worm, a new 'head' will regenerate anteriorly and a 'tail' will regenerate posteriorly restoring the original 'head-to-tail' polarity of body structures prior to amputation (Figure 1A).
Regeneration is driven by planarian stem cells, known as 'neoblasts' which differentiate into ~30 different cell types during normal body homeostasis and enforced tissue regeneration. This regenerative process is robust and easy to demonstrate. Owing to the dedication of several pioneering labs, many tools and functional genetic methods have now been optimized for this model system. Consequently, considerable recent progress has been made in understanding and manipulating the molecular events underpinning planarian developmental plasticity2-9.
The planarian model system will be of interest to a broad range of scientists. For neuroscientists, the model affords the opportunity to study the regeneration of an entire nervous system, rather than simply the regrowth/repair of single nerve cell process that typically are the focus of study in many established models. Planarians express a plethora of neurotransmitters10, represent an important system for studying evolution of the central nervous system11, 12 and have behavioral screening potential13, 14. 
Regenerative outcomes are amenable to manipulation by pharmacological and genetic apparoaches. For example, drugs can be screened for effects on regeneration simply by placing body fragments in drug-containing solutions at different time points after amputation. The role of individual genes can be studied using knockdown methods (in vivo RNAi), which can be achieved either through cycles of microinjection or by feeding bacterially-expressed dsRNA constructs8, 9, 15. Both approaches can produce visually striking phenotypes at high penetrance- for example, regeneration of bipolar animals16-21. To facilitate adoption of this model and implementation of such methods, we showcase in this video article protocols for pharmacological and genetic assays (in vivo RNAi by feeding) using the planarian Dugesia japonica.

Pharmacological and Functional Genetic Assays to Manipulate Regeneration of the Planarian Dugesia japonica

An attractive model for studying stem cell differentiation within a live animal is the planarian flatworm. Regeneration is studied by simple amputation experiments that are easily performed in a basic laboratory and are amenable to pharmacological and genetic (in vivo RNAi) manipulation as detailed by protocols in this article.

Free-living planarian flatworms have a long history of experimental usage owing to their remarkable regenerative abilities1. Small fragments excised from ...

Small-scale Nuclear Extracts for Functional Assays of Gene-expression Machineries

A great deal of progress in understanding gene expression has been made using in vitro systems. For most studies, functional assays are carried out using extracts that are prepared in bulk from 10-50 or more liters of cells grown in suspension. However, these large-scale preparations are not amenable to rapidly testing in vitro effects that result from a variety of in vivo cellular treatments or conditions. This journal video article shows a method for preparing functional small-scale nuclear extracts, using HeLa cells as an example. This method is carried out using as few as three 150 mm plates of cells grown as adherent monolayers. To illustrate the efficiency of the small-scale extracts, we show that they are as active as bulk nuclear extracts for coupled RNA Polymerase II transcription/splicing reactions. To demonstrate the utility of the extract protocol, we show that splicing is abolished in extracts prepared from HeLa cells treated with the splicing inhibitor drug E7107. The small-scale protocol should be generally applicable to any process or cell type that can be investigated in vitro using cellular extracts. These include patient cells that are only available in limited quantities or cells exposed to numerous agents such as drugs, DNA damaging agents, RNAi, or transfection, which require the use of small cell populations. In addition, small amounts of freshly grown cells are convenient and/or required for some applications.

A protocol for preparation of robust, small-scale HeLa nuclear extracts is described. This protocol is valuable for assays that require use of small populations of cells, such as cells treated with drugs or RNAi. The method should be applicable to a wide variety of gene expression assays and other cell types, including patient cells.

A great deal of progress in understanding gene expression has been made using in vitro systems.  For most studies, functional assays are carried out using ...