Name: candidate gene testing in clinical cohort studies with multiplexed genotyping and mass spectrometry
Uploaded: 2018-06-21T12:30:00
Description: Watch this Scientific Journal Video about Candidate Gene Testing in Clinical Cohort Studies with Multiplexed Genotyping and Mass Spectrometry at JoVE.com

The authors have no acknowledgements.

The genetic material used herein was ethically approved for use by the Office for Children HREC (Human Research Ethics Committee) (CDF/07/492), the Department of Human Services HREC (10/07) and the Royal Children&#8217;s Hospital (RCH) HREC (27047).
1. Designing the Multiplexed Assay
<ol>
	<li>Prepare a SNP list for assay design.
	<ol>
		<li>Input the target region into the tagger function of Haploview (https://www.broadinstitute.org/haploview/downloads). Use the LD (correlation, r2</su...

<ol>
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Y., 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=Pretreatment+epidermal+growth+factor+receptor+(EGFR)+T790M+mutation+predicts+shorter+EGFR+tyrosine+kinase+inhibitor+response+duration+in+patients+with+non-small-cell+lung+cancer.">Pretreatment epidermal growth factor receptor (EGFR) T790M mutation predicts shorter EGFR tyrosine kinase inhibitor response duration in patients with non-small-cell lung cancer.</a> Journal of clinical oncology. 30 (4), 433-440 (2012).</li><li>Singhal, N., Kumar, M., Kanaujia, P. K., Virdi, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MALDI-TOF+mass+spectrometry:+an+emerging+technology+for+microbial+identification+and+diagnosis.">MALDI-TOF mass spectrometry: an emerging technology for microbial identification and diagnosis.</a> Frontiers in microbiology. 6, 791 (2015).</li><li>Cricca, 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=High-throughput+genotyping+of+high-risk+Human+Papillomavirus+by+MALDI-TOF+Mass+Spectrometry-based+method.">High-throughput genotyping of high-risk Human Papillomavirus by MALDI-TOF Mass Spectrometry-based method.</a> New Microbiologica. 38 (2), 211-223 (2015).</li><li>Ashley, 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=Genetic+Variation+at+the+Th2+Immune+Gene+IL13+is+Associated+with+IgE-mediated+Paediatric+Food+Allergy.">Genetic Variation at the Th2 Immune Gene IL13 is Associated with IgE-mediated Paediatric Food Allergy.</a> Clinical &amp; Experimental Allergy. 47 (8), 1032-1037 (2017).</li><li>Bousman, C. 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=Effects+of+NRG1+and+DAOA+genetic+variation+on+transition+to+psychosis+in+individuals+at+ultra-high+risk+for+psychosis.">Effects of NRG1 and DAOA genetic variation on transition to psychosis in individuals at ultra-high risk for psychosis.</a> Translational psychiatry. 3 (4), e251 (2013).</li><li>Moffatt, M. 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Here, we demonstrate the method of multiplexed genotyping using mass spectrometry. The representative results were generated using PCR paired with MALDI-TOF mass spectrometry4 with assay chemistry listed in the Table of Materials13. With this platform, we generated a total of 11,295 genotypes on 1,255 individuals for 9 SNPs within 40 h in the lab.
We illustrate the usefulness of the technique in answering genetic hypotheses by ge...

In human complex disease, genetic variants contribute to disease susceptibility and quantifying these variants may be useful for understanding pathogenesis, identifying high risk patient groups, and treatment responders. Indeed, the promise of precision medicine is dependent upon utilizing genomic information to identify patient subgroups1. Unfortunately, within the complex disease biology space, where disease phenotypes are underpinned by substantial genetic heterogeneity, low penetrance, and variable expressivity, cohort size requirements for genome-wide approaches to identify novel candidates are often prohibitively large2. Alternatively, a targeted candidate gene approach begins with an a priori hypothesis about specific genes/pathways in disease etiology3. Pathway analysis tools are commonly used to investigate the pathophysiology of an identified target loci, generating numerous candidate pathways to be explored. We demonstrate here a multiplexed genotyping approach allowing for the investigation of tens to hundreds of SNPs with one assay, suited to human cohort studies4. This approach is relatively high through-put, permitting hundreds to thousands of DNA samples to be genotyped for novel discovery studies and investigation of specific pathways. The methods outlined here are useful for identifying risk alleles and their associations with clinical traits in a relatively rapid and inexpensive manner. This platform has been highly advantageous for screening and diagnostic purposes5,6, and more recently, for microbial infection7 and human papillomavirus8.
This protocol begins with selection of a set of genes for investigation, i.e., the target regions, typically determined through literature searching, or a priori hypotheses for involvement in the disease process; or perhaps selected for replication as the leading associations of a discovery genome-wide association (GWA) study. From the gene set, the researcher will select a refined list of tag SNPs. That is, the linkage disequilibrium (LD), or correlation, amongst variants in the region is used to identify a representative &#39;tag SNP&#39; for a group of SNPs in high LD, known as a haplotype. The high LD of the region means that the SNPs are often inherited together such that genotyping one SNP is sufficient to represent the variation at all SNPs in the haplotype. Alternatively, if following up on a definitive list of SNPs from many regions, e.g., replication for a GWA study, this process may be unnecessary. For multiplexed genotyping, an assay must then be designed around these targets such that the amplification primers are of differing mass to those of the extension primers and products to produce interpretable mass spectra. These parameters are easily implemented by a multiplexed genotyping assay design tool. The forward and reverse primers from this design will be used to target the markers of interest and amplify the sequence containing the SNP. The extension primers attach directly proximal to the SNPs and a single, mass-modified, &#39;terminator&#39; base that is complementary to the SNP is added. The terminator base prevents further extension of the DNA. The mass-modification of the base enables fragments differing by a single base to be detected by mass spectrometry. The plate containing the genotyping chemistry is then applied to a chip for measurement on a mass spectrometry platform. After applying appropriate quality controls to the raw genotyping calls detected by the system, the data can be exported and used for statistical analysis to test for association with disease phenotypes.

<table border="0" cellpadding="0" cellspacing="0" width="695">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Genomic DNA&#160;</td>
			<td style="width:127px;">-</td>
			<td style="width:119px;">-</td>
			<td style="width:235px;">1 &#956;L at a concentration of 5-10 ng/&#956;L</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Primers: forward and reverse amplification and extension</td>
			<td style="width:127px;">IDT</td>
			<td style="width:119px;">-</td>
			<td style="width:235px;">see manuscript section 1.2.1 on design of primers</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Deionized water&#160;</td>
			<td style="width:127px;">E.g. Milli-Q water&#160;</td>
			<td style="width:119px;">-</td>
			<td>deionized with 18.2 M&#937;.cm resistivity</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Genotyping reagent kit. iPLEX Gold Chemistry reagent set&#160;</td>
			<td>Agena Bioscience</td>
			<td style="width:119px;">#10148-2</td>
			<td style="width:235px;">includes all reagents for reactions in 2.2.1, 2.3.1 and 2.4.2 , chip and resin</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">PCR plates (384-well)</td>
			<td style="width:127px;">Abgene</td>
			<td style="width:119px;">#ABGAB-1384</td>
			<td style="width:235px;">For the MassARRAY system plates by Abgene are compatible</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Micropipettes</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td>single and 8-channel</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Centrifuge&#160;</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td>compatible with 384-well plates</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Thermocycler</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td style="width:235px;">compatible with PCR programs as detailed in 2.2.4, 2.3.2 and 2.4.3</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dimple resin plate&#160;</td>
			<td>Agena Bioscience</td>
			<td style="width:119px;"></td>
			<td>6mg, 384-well</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plate rotator&#160;</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">MassARRAY Analyzer 4 System</td>
			<td style="width:127px;">Agena Biosciences</td>
			<td style="width:119px;"></td>
			<td style="width:235px;">MALDI-TOF (matrix-assisted laser desorption/ionization &#8211; time of flight) Mass Spectrometer.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">RS1000 Nanodispenser</td>
			<td style="width:127px;">Agena Biosciences</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Assay Design Suite</td>
			<td style="width:127px;">Agena Biosciences</td>
			<td style="width:119px;"></td>
			<td>Tool used to design the multiplex genotyping assays</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hot Start Taq</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td>DNA polymerase enzyme&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Resin&#160;</td>
			<td style="width:127px;">Agena Biosciences</td>
			<td style="width:119px;"></td>
			<td>Supplied with iPLEX kit</td>
		</tr>
	</tbody>
</table>

candidate gene testing in clinical cohort studies with multiplexed genotyping and mass spectrometry

Complex diseases are often underpinned by multiple common genetic variants that contribute to disease susceptibility. Here, we describe a cost-effective tag single nucleotide polymorphism (SNP) approach using a multiplexed genotyping assay with mass spectrometry, to investigate gene pathway associations in clinical cohorts. We investigate the food allergy candidate locus Interleukin13 (IL13) as an example. This method efficiently maximizes the coverage by taking advantage of shared linkage disequilibrium (LD) within a region. Selected LD SNPs are then designed into a multiplexed assay, enabling up to 40 different SNPs to be analyzed simultaneously, boosting cost-effectiveness. Polymerase chain reaction (PCR) is used to amplify the target loci, followed by single nucleotide extension, and the amplicons are then measured using matrix-assisted laser desorption/ionization-time of flight(MALDI-TOF) mass spectrometry. The raw output is analyzed with the genotype calling software, using stringent quality control definitions and cut-offs, and high probability genotypes are determined and output for data analysis.

With the protocol described above, we genotyped tag SNPs across the Th2 immune gene IL13 in a cohort of food allergy cases and controls9. We applied logistic regression analysis, adjusted for ancestry and other potential covariates, to test whether the genetic variants within the region of interest increased food allergy risk. Table 109 shows that one variant rs1295686 is associated with challenge-proven food allerg...

Watch this Scientific Journal Video about Candidate Gene Testing in Clinical Cohort Studies with Multiplexed Genotyping and Mass Spectrometry at JoVE.com

Candidate Gene Testing in Clinical Cohort Studies with Multiplexed Genotyping and Mass Spectrometry

Identification of genetic variants contributing to complex human disease allows us to identify novel mechanisms. Here, we demonstrate a multiplex genotyping approach to candidate genes or gene pathway analysis that maximizes the coverage at low cost and is amenable to cohort-based studies.

Complex diseases are often underpinned by multiple common genetic variants that contribute to disease susceptibility. Here, we describe a cost-effective ...

This method can help answer key questions in the clinical diagnostics and genetics fields, such as detecting genetic markers associated with disease outcomes, included the human papilloma virus. The main advantage to this technique is that it's a cost effective targeted and time efficient diagnostic method. To begin this procedure, reconstitute any ordered lyophilized primers with molecular-grade water.Pull the forward and reverse primers for each multiplexed assay into a stock primer mix, such that it contains each primer at a concentration of zero-point-five millimolar. After this, prepare a master mix for the PCR as outlined in the text protocol. Add four microliters of this mix to each well of a 384-well PCR plate, along with one microliter of genomic DNA at a concentration between five and 10 nanograms per microliter.Cover the plate with a plate cover, and centrifuge for 200 times G for one minute at room temperature. Then run the PCR as outlined in the text protocol. Load one microliter of PCR product with three microliters of loading buffer on a 2%agarose gel.Run at 100 volts for 45 minutes to ensure that the DNA amplification was successful. Next, prepare an SAP master mix as outlined in the text protocol. Add two microliters of the freshly made SAP master mix to each well of the previously run PCR plate.Centrifuge briefly at 1, 000 times G for one minute. And then return the plate to the thermocycler. Run the thermocycler at 37-degrees Celsius for 40 minutes.And then at 85-degrees Celsius for five minutes to inactivate the enzyme. After calculating the dilution factor for each primer, combine the determined volumes of each to make up a primer pool. Add water as necessary to dilute this pool.Assemble the extension master mix for either the high plex assay or the low plex assay, as outlined in the text protocol. Add two microliters of the extension master mix to each well of the plate, bringing the total volume in each well up to nine microliters. Centrifuge briefly at 1, 000 times G for one minute, and then return the plate to the thermocycler.After this, add 16 microliters of deionized water to each well, bringing the total volume up to 25 microliters per well. Apply six milligrams of resin evenly across an entire dimple resin plate. Let the resin dry for 20 minutes at room temperature.Then, apply the resin to the reaction plate. Using a suspension mixer, rotate the plate at a slow speed for five minutes at room temperature. Next, centrifuge the plate at 3, 200 times G for five minutes to avoid applying the resin to the mass spectra chip.Upload the plate's sample layout to the system's software interface. Using a dispensing system, apply the genotyping analyte mixture from the plate to the genotyping chip. Load the chip into the MALDI-TOF system to generate the mass spectra from the analyte mixture, and interpret it using the platform's software interface.In this study, multiplex genotyping is accomplished using mass spectrometry. Representative SNP data is generated and analyzed for the candidate gene IL13 in a discovery clinical cohort phenotyped for food allergy. One variant, rs1295686, is associated with challenge-proven food allergy.This is association is confirmed in a replication cohort using the multiplex genotyping approach demonstrated in this protocol. A meta-analysis of the results from the two cohorts provides strong evidence of the association between IL13 with FA.While attempting this procedure, it's important not to contaminate any samples or reagents. It's also important to prepare an extra 10%master mix for each PCR in order to account for any pipetting error.Following this procedure, other methods like real-time PCR can be performed in order to answer additional questions such as whether gene expression correlates with the identified disease-associated genetic markers. After it's development, this technique paved the way for researchers in the fields of clinical diagnostics and genetics to explore disease associations in patient cohorts. Don't forget that when working with genotyping reagents and the MALDI-TOF system can be hazardous, and precautions such as wearing gloves and a lab coat should always be taken when performing this procedure.

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Research

JoVE Journal

Genetics

Subtyping of Campylobacter jejuni ssp. doylei Isolates Using Mass Spectrometry-based PhyloProteomics (MSPP)

MALDI-TOF MS offers the possibility to differentiate some bacteria not only at the species and subspecies level but even below, at the strain level. Allelic isoforms of the detectable biomarker ions result in isolate-specific mass shifts. Mass spectrometry-based phyloproteomics (MSPP) is a novel technique that combines the mass spectrometric detectable biomarker masses in a scheme that allows deduction of phyloproteomic relations from isolate specific mass shifts compared to a genome sequenced reference strain. The deduced amino acid sequences are then used to calculate MSPP-based dendrograms.
Here we describe the workflow of MSPP by typing a Campylobacter jejuni ssp. doylei isolate collection of seven strains. All seven strains were of human origin and multilocus sequence typing (MLST) demonstrated their genetic diversity. MSPP-typing resulted in seven different MSPP sequence types, sufficiently reflecting their phylogenetic relations.
The C. jejuni ssp. doylei MSPP scheme includes 14 different biomarker ions, mostly ribosomal proteins in the mass range of 2 to 11 kDa. MSPP can in principle, be adapted to other mass spectrometric platforms with an extended mass range. Therefore, this technique has the potential to become a useful tool for strain level microbial typing.

Subtyping of Campylobacter jejuni ssp. doylei Isolates Using Mass Spectrometry-based PhyloProteomics MSPP

Mass spectrometry-based phyloproteomics (MSPP) was used to type a collection of Campylobacter jejuni ssp. doylei isolates at the strain level in comparison to multilocus sequence typing (MLST).

MALDI-TOF MS offers the possibility to differentiate some bacteria not only at the species and subspecies level but even below, at the strain level. ...

Improved Polymerase Chain Reaction-restriction Fragment Length Polymorphism Genotyping of Toxic Pufferfish by Liquid Chromatography/Mass Spectrometry

An improved version of a polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method for genotyping toxic pufferfish species by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) is described. DNA extraction is carried out using a silica membrane-based DNA extraction kit. After the PCR amplification using a detergent-free PCR buffer, restriction enzymes are added to the solution without purifying the reaction solution. A reverse-phase silica monolith column and a Fourier transform high resolution mass spectrometer having a modified Kingdon trap analyzer are employed for separation and detection, respectively. The mobile phase, consisting of 400 mM 1,1,1,3,3,3-hexafluoro-2-propanol, 15 mM triethylamine (pH 7.9) and methanol, is delivered at a flow rate of 0.4 ml/min. The cycle time for LC/ESI-MS analysis is 8 min including equilibration of the column. Deconvolution software having an isotope distribution model of the oligonucleotide is used to calculate the corresponding monoisotopic mass from the mass spectrum. For analysis of oligonucleotides (range 26-79 nucleotides), mass accuracy was 0.62 &#177; 0.74 ppm (n = 280) and excellent accuracy and precision were sustained for 180 hr without use of a lock mass standard.

An improved polymerase chain reaction-restriction fragment length polymorphism method for genotyping pufferfish species by liquid chromatography/mass spectrometry is described. A reverse-phase silica monolith column is employed for separating digested amplicons. This method can elucidate the monoisotopic masses of oligonucleotides, which is useful for identifying base composition.

An improved version of a polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method for genotyping toxic pufferfish species by ...

Perturbations of Circulating miRNAs in Irritable Bowel Syndrome Detected Using a Multiplexed High-throughput Gene Expression Platform

The gene expression platform assay allows for robust and highly reproducible quantification of the expression of up to 800 transcripts (mRNA or miRNAs) in a single reaction. The miRNA assay counts transcripts by directly imaging and digitally counting miRNA molecules that are labeled with color-coded fluorescent barcoded probe sets (a reporter probe and a capture probe). Barcodes are hybridized directly to mature miRNAs that have been elongated by ligating a unique oligonucleotide tag (miRtag) to the 3&#39; end. Reverse transcription and amplification of the transcripts are not required. Reporter probes contain a sequence of six color positions populated using a combination of four fluorescent colors. The four colors over six positions are used to construct a gene-specific color barcode sequence. Post-hybridization processing is automated on a robotic prep station. After hybridization, the excess probes are washed away, and the tripartite structures (capture probe-miRNA-reporter probe) are fixed to a streptavidin-coated slide via the biotin-labeled capture probe. Imaging and barcode counting is done using a digital analyzer. The immobilized barcoded miRNAs are visualized and imaged using a microscope and camera, and the unique barcodes are decoded and counted. Data quality control (QC), normalization, and analysis are facilitated by a custom-designed data processing and analysis software that accompanies the assay software. The assay demonstrates high linearity over a broad range of expression, as well as high sensitivity. Sample and assay preparation does not involve enzymatic reactions, reverse transcription, or amplification; has few steps; and is largely automated, reducing investigator effects and resulting in high consistency and technical reproducibility. Here, we describe the application of this technology to identifying circulating miRNA perturbations in irritable bowel syndrome.

We describe the use of a multiplexed high-throughput gene expression platform that quantitates gene expression by barcoding and counting molecules in biological substrates without the need for amplification. We used the platform to quantitate microRNA (miRNA) expression in whole blood in subjects with and without irritable bowel syndrome.

The gene expression platform assay allows for robust and highly reproducible quantification of the expression of up to 800 transcripts (mRNA or miRNAs) in ...

Rearing and Double-stranded RNA-mediated Gene Knockdown in the Hide Beetle, Dermestes maculatus

Advances in genomics have raised the possibility of probing biodiversity at an unprecedented scale. However, sequence alone will not be informative without tools to study gene function. The development and sharing of detailed protocols for the establishment of new model systems in laboratories, and for tools to carry out functional studies, is thus crucial for leveraging the power of genomics. Coleoptera (beetles) are the largest clade of insects and occupy virtually all types of habitats on the planet. In addition to providing ideal models for fundamental research, studies of beetles can have impacts on pest control as they are often pests of households, agriculture, and food industries. Detailed protocols for rearing and maintenance of D. maculatus laboratory colonies and for carrying out dsRNA-mediated interference in D. maculatus are presented. Both embryonic and parental RNAi procedures-including apparatus set up, preparation, injection, and post-injection recovery-are described. Methods are also presented for analyzing embryonic phenotypes, including viability, patterning defects in hatched larvae, and cuticle preparations for unhatched larvae. These assays, together with in situ hybridization and immunostaining for molecular markers, make D. maculatus an accessible model system for basic and applied research. They further provide useful information for establishing procedures in other emerging insect model systems.

Rearing and Double-stranded RNA-mediated Gene Knockdown in the Hide Beetle, Dermestes maculatus

Here, we present protocols for rearing an intermediate-germ beetle, Dermestes maculatus (D. maculatus) in the lab. We also share protocols for embryonic and parental RNAi and methods for analyzing embryonic phenotypes to study gene function in this species.

Advances in genomics have raised the possibility of probing biodiversity at an unprecedented scale. However, sequence alone will not be informative ...

Single-cell Gene Expression Profiling Using FACS and qPCR with Internal Standards

Gene expression measurements from bulk populations of cells can obscure the considerable transcriptomic variation of individual cells within those populations. Single-cell gene expression measurements can help assess the role of noise in gene expression, identify correlations in the expression of pairs of genes, and reveal subpopulations of cells that respond differently to a stimulus. Here, we describe a procedure to measure the expression of up to 96 genes in single mammalian cells isolated from a population growing in tissue culture. Cells are sorted into lysis buffer by fluorescence-activated cell sorting (FACS), and the mRNA species of interest are reverse-transcribed and amplified. Gene expression is then measured using a microfluidic real-time PCR machine, which performs up to 96 qPCR assays on up to 96 samples at a time. We also describe the generation and use of PCR amplicon standards to enable the estimation of the absolute number of each transcript. Compared with other methods of measuring gene expression in single cells, this approach allows for the quantification of more distinct transcripts than RNA FISH at a lower cost than RNA-Seq.

We describe a method to sort single mammalian cells and to quantify the expression of up to 96 target genes of interest in each cell. This method includes the use of internal qPCR standards to enable the estimation of absolute transcript counts.

Gene expression measurements from bulk populations of cells can obscure the considerable transcriptomic variation of individual cells within those ...

High-resolution Melting PCR for Complement Receptor 1 Length Polymorphism Genotyping: An Innovative Tool for Alzheimer's Disease Gene Susceptibility Assessment

Complement receptor 1 (CR1), a transmembrane glycoprotein that plays a key role in the innate immune system, is expressed on many cell types, but especially on red blood cells (RBCs). As a receptor for the complement components C3b and C4b, CR1 regulates the activation of the complement cascade and promotes the phagocytosis of immune complexes and cellular debris, as well as the amyloid-beta (A&#946;) peptide in Alzheimer's disease (AD). Several studies have confirmed AD-associated single nucleotide polymorphisms (SNPs), as well as a copy-number variation (CNV) in the CR1 gene. Here, we describe an innovative method for determining the length polymorphism of the CR1 receptor. The receptor includes three domains, called long homologous repeats (LHR)-LHR-A, LHR-C, and LHR-D-and an n domain, LHR-B, where n is an integer between 0 and 3. Using a single pair of specific primers, the genetic material is used to amplify a first fragment of the LHR-B domain (the variant amplicon B) and a second fragment of the LHR-C domain (the invariant amplicon). The variant amplicon B and the invariant amplicon display differences at five nucleotides outside of the hybridization areas of said primers. The numbers of variant amplicons B and of invariant amplicons is deduced using a quantitative tool (high-resolution melting (HRM) curves), and the ratio of the variant amplicon B to the invariant amplicon differs according to the CR1 length polymorphism. This method provides several advantages over the canonical phenotype method, as it does not require fresh material and is cheaper, faster, and therefore applicable to larger populations. Thus, the use of this method should be helpful to better understand the role of CR1 isoforms in the pathogenesis of diseases such as AD.

High-resolution Melting PCR for Complement Receptor 1 Length Polymorphism Genotyping: An Innovative Tool for Alzheimer&#039;s Disease Gene Susceptibility Assessment

Here, we describe an innovative method to determine complement receptor 1 (CR1) length polymorphisms for use in several applications, particularly the assessment of susceptibility to diseases such as Alzheimer&#39;s disease (AD). This method could be useful to better understand the role of CR1 isoforms in the pathogenesis of AD.

Complement receptor 1 (CR1), a transmembrane glycoprotein that plays a key role in the innate immune system, is expressed on many cell types, but ...

Generation of a Gene-disrupted Streptococcus mutans Strain Without Gene Cloning

Typical methods for the elucidation of the function of a particular gene involve comparative phenotypic analyses of the wild-type strain and a strain in which the gene of interest has been disrupted. A gene-disruption DNA construct containing a suitable antibiotic resistance marker gene is useful for the generation of gene-disrupted strains in bacteria. However, conventional construction methods, which require gene cloning steps, involve complex and time-consuming protocols. Here, a relatively facile, rapid, and cost-effective method for targeted gene disruption in Streptococcus mutans is described. The method utilizes a 2-step fusion polymerase chain reaction (PCR) to generate the disruption construct and electroporation for genetic transformation. This method does not require an enzymatic reaction, other than PCR, and additionally offers greater flexibility in terms of the design of the disruption construct. Employment of electroporation facilitates the preparation of competent cells and improves the transformation efficiency. The present method may be adapted for the generation of gene-disrupted strains of various species.

Generation of a Gene-disrupted Streptococcus mutans Strain Without Gene Cloning

We describe a facile, rapid, and relatively inexpensive method for the generation of gene-disrupted Streptococcus mutans strains; this technique may be adapted for the generation of gene-disrupted strains of various species.

Typical methods for the elucidation of the function of a particular gene involve comparative phenotypic analyses of the wild-type strain and a strain in ...

Measuring Gene Expression in Bombarded Barley Aleurone Layers with Increased Throughput

The aleurone layer of barley grains is an important model system for hormone-regulated gene expression in plants. In aleurone cells, genes required for germination or early seedling development are activated by gibberellin (GA), while genes associated with stress responses are activated by abscisic acid (ABA). The mechanisms of GA and ABA signaling can be interrogated by introducing reporter gene constructs into aleurone cells via particle bombardment, with the resulting transient expression measured using enzyme assays. An improved protocol is reported that partially automates and streamlines the grain homogenization step and the enzyme assays, allowing significantly more throughput than existing methods. Homogenization of the grain samples is carried out using an automated tissue homogenizer, and GUS (&#946;-glucuronidase) assays are carried out using a 96-well plate system. Representative results using the protocol suggest that phospholipase D activity may play an important role in the activation of HVA1 gene expression by ABA, through the transcription factor TaABF1.

An improved protocol is presented for the measurement of transient gene expression from reporter constructs in barley aleurone cells after particle bombardment. The combination of automated grain grinding with 96-well plate enzyme assays provides high throughput for the procedure.

The aleurone layer of barley grains is an important model system for hormone-regulated gene expression in plants. In aleurone cells, genes required for ...

A Method to Study the C924T Polymorphism of the Thromboxane A2 Receptor Gene

The thromboxane A2 receptor (TBXA2R) gene is a member of the G-protein coupled superfamily with seven-transmembrane regions. It is involved in atherogenesis progression, ischemia, and myocardial infarction. Here we present a methodology of patient genotyping to investigate the post-transcriptional role of the C924T polymorphism (rs4523) situated at the 3&#39; region of the TBXA2 receptor gene. This method relies on DNA extraction from whole blood, polymerase chain reaction (PCR) amplification of the TBXA2 gene portion containing the C924T mutation, and identification of wild type and/or mutant genotypes using a restriction digest analysis, specifically a restriction fragment length polymorphism (RFLP) on agarose gel. In addition, the results were confirmed by sequencing the TBXA2R gene. This method features several potential advantages, such as high efficiency and the rapid identification of the C924T polymorphism by PCR and restriction enzyme analysis. This approach allows a predictive study for plaque formation and atherosclerosis progression by analyzing patient genotypes for the TBXA2R C924T polymorphism. Application of this method has the potential to identify subjects who are more susceptible to atherothrombotic processes, in particular subjects in a high-risk, aspirin-treated group.

In the present study, we describe a methodology to analyze the C924T genotype. The protocol consists of three phases: DNA extraction, amplification by polymerase chain reaction (PCR), and analysis of the restriction fragment length polymorphism (RFLP) on agarose gel.

The thromboxane A2 receptor (TBXA2R) gene is a member of the G-protein coupled superfamily with seven-transmembrane regions. It is involved in ...

A Fast and Quantitative Method for Post-translational Modification and Variant Enabled Mapping of Peptides to Genomes

Cross-talk between genes, transcripts, and proteins is the key to cellular responses; hence, analysis of molecular levels as distinct entities is slowly being extended to integrative studies to enhance the understanding of molecular dynamics within cells. Current tools for the visualization and integration of proteomics with other omics datasets are inadequate for large-scale studies. Furthermore, they only capture basic sequence identify, discarding post-translational modifications and quantitation. To address these issues, we developed PoGo to map peptides with associated post-translational modifications and quantification to reference genome annotation. In addition, the tool was developed to enable the mapping of peptides identified from customized sequence databases incorporating single amino acid variants. While PoGo is a command line tool, the graphical interface PoGoGUI enables non-bioinformatics researchers to easily map peptides to 25 species supported by Ensembl genome annotation. The generated output borrows file formats from the genomics field and, therefore, visualization is supported in most genome browsers. For large-scale studies, PoGo is supported by TrackHubGenerator to create web-accessible repositories of data mapped to genomes that also enable an easy sharing of proteogenomics data. With little effort, this tool can map millions of peptides to reference genomes within only a few minutes, outperforming other available sequence-identity based tools. This protocol demonstrates the best approaches for proteogenomics mapping through PoGo with publicly available datasets of quantitative and phosphoproteomics, as well as large-scale studies.

Here we present the proteogenomic tool PoGo and protocols for fast, quantitative, post-translational modification and variant enabled mapping of peptides identified through mass spectrometry onto reference genomes. This tool is of use to integrate and visualize proteogenomic and personal proteomic studies interfacing with orthogonal genomics data.

Cross-talk between genes, transcripts, and proteins is the key to cellular responses; hence, analysis of molecular levels as distinct entities is slowly ...