Single-nucleotide polymorphisms (SNPs) are the most frequent type of variation in the human genome, and they provide powerful tools for a variety of medical genetic studies. In a large-scale survey for SNPs, 2.3 megabases of human genomic DNA was examined by a combination of gel-based sequencing and high-density variation-detection DNA chips. A total of 3241 candidate SNPs were identified. A genetic map was constructed showing the location of 2227 of these SNPs. Prototype genotyping chips were developed that allow simultaneous genotyping of 500 SNPs. The results provide a characterization of human diversity at the nucleotide level and demonstrate the feasibility of large-scale identification of human SNPs.

https://science.sciencemag.org/content/sci/280/5366/1077.full.pdf

Large-Scale Identification, Mapping, and Genotyping of Single-Nucleotide Polymorphisms in the Human Genome

An Architectural role for a nuclear noncoding RNA : NEAT1 RNA is essential for the structure of paraspeckles

Here we present the successful application of the microarray technology platform to the analysis of DNA polymorphisms. Using the rice genome as a model, we demonstrate the potential of a highthroughput genome analysis method called Diversity Array Technology, DArT. In the format presented here the technology is assaying for the presence (or amount) of a specific DNA fragment in a representation derived from the total genomic DNA of an organism or a population of organisms. Two different approaches are presented: the first involves contrasting two representations on a single array while the second involves contrasting a representation with a reference DNA fragment common to all elements of the array. The Diversity Panels created using this method allow genetic fingerprinting of any organism or group of organisms belonging to the gene pool from which the panel was developed. Diversity Arrays enable rapid and economical application of a highly parallel, solid-state genotyping technology to any genome or complex genomic mixtures.

Diversity Arrays: a solid state technology for sequence information independent genotyping

Disclosed are compositions and a method for of amplifying nucleic acid sequences useful for detecting the presence of molecules of interest. The method is useful for detecting specific nucleic acids in a sample with high specificity and sensitivity. The method also has an inherently low level of background signal. A preferred form of the method consists of a DNA ligation operation, an amplification operation, and a detection operation. The DNA ligation operation circularizes a specially designed nucleic acid probe molecule. This operation is dependent on hybridization of the probe to a target sequence and forms circular probe molecules in proportion to the amount of target sequence present in a sample. The amplification operation is rolling circle replication of the circularized probe. A single round of amplification using rolling circle replication results in a large amplification of the circularized probe sequences. Following rolling circle replication, the amplified probe sequences are detected and quantified using any of the conventional detection systems for nucleic acids such as detection of fluorescent labels, enzyme-linked detection systems, antibody-mediated label detection, and detection of radioactive labels. Because, the amplified product is directly proportional to the amount of target sequence present in a sample, quantitative measurements reliably represent the amount of a target sequence in a sample. Major advantages of this method are that the ligation step can be manipulated to obtain allelic discrimination, the DNA replication step is isothermal, and signals are strictly quantitative because the amplification reaction is linear and is catalyzed by a highly processive enzyme. In multiplex assays, the primer oligonucleotide used for the DNA polymerase reaction can be the same for all probes. Also described are modes of the method in which additional amplification is obtained using a cascade of strand displacement reactions.

Rolling circle replication reporter systems

Denaturing high-performance liquid chromatography (DHPLC) compares two or more chromosomes as a mixture of denatured and reannealed PCR amplicons, revealing the presence of a mutation by the differential retention of homo- and heteroduplex DNA on reversed-phase chromatography supports under partial denaturation Temperature determines sensitivity, and its optimum can be predicted by computation Single-nucleotide substitutions, deletions, and insertions have been detected successfully by on-line UV or fluorescence monitoring within 2-3 minutes in unpurified amplicons as large as 15 Kb Sensitivity and specificity of DHPLC consistently exceed 96% These features and its low cost make DHPLC one of the most powerful tools for the re-sequencing of the human and other genomes Aside from its application to the mutational analysis of candidate genes, DHPLC has proven instrumental in elucidating human evolution and in the mapping of genes Employing completely denaturing conditions, the utility of DHPLC has been extended to the genotyping of known polymorphisms by utilizing the ability of poly(styrene-divinylbenzene) to resolve single-stranded DNA molecules of identical size that differ in a single base Under completely denaturing conditions, it is thus possible to resolve all possible base substitutions with the single exception of C-->G transversions Improvements in throughput became feasible with the recent introduction of monolithic poly(styrene-divinylbenzene) capillaries that lend themselves to the fabrication of arrays connected to a multi-color laser induced fluorescence scanner or a mass spectrometer

https://onlinelibrary.wiley.com/doi/pdf/10.1002/humu.1130

Denaturing high-performance liquid chromatography: A review.

We report a simple method, the PinPoint assay, for detecting and identifying single-base variations (polymorphisms) at specific locations within DNA sequences. An oligonucleotide primer is annealed to the target DNA immediately upstream of the polymorphic site and is extended by a single base in the presence of all four dideoxynucleotide triphosphates and a thermostable DNA polymerase. The extension products are desalted, concentrated, and subjected to delayed-extraction MALDI-TOF mass spectrometry. The base at the polymorphic site is identified by the mass added onto the primer. Heterozygous targets produce two mass-resolved species that represent the addition of both bases complementary to those at the polymorphic site. The assay is suitable for double-stranded PCR products without purification or strand separation. More than one primer can be simultaneously extended and then mass-analyzed. The mass spectrometric method thus shows promise for high-volume diagnostic or genotyping applications.

/pdf/single-nucleotide-polymorphism-identification-assays-using-a-50i8f4sli4.pdf

Single-Nucleotide Polymorphism Identification Assays Using a Thermostable DNA Polymerase and Delayed Extraction MALDI-TOF Mass Spectrometry

The invention relates to method for determining sequence information in polynucleotides by combining the recent disparate technologies of mass spectrometry and polynucleotide hybridization, amplification, extension and/or ligation techniques. Broadly, in a first step, the method for determining sequence information in a sample polynucleotide includes hybridizing with a sample nucleotide one or a mixture of oligonucleotide probes having a nucleotide sequence complementary to a portion of the sample polynucleotide, thereby forming a complex. Then, in a second step, the complex is contacted with at least a member selected from the group consisting of nucleosides, dideoxynucleosides, polymerases, nucleases, transcriptases, ligases and restriction enzymes to alter at least a subset of said oligonucleotide probes. In a third step, the method provides for determining the molecular weight of at least the subset of altered probes by mass spectrometry and infering the sequence information of the sample polynucleotide therefrom.

Methods for determining sequence information in polynucleotides using mass spectrometry

A delayed ion extraction technique is shown to dramatically improve mass resolution and the overall quality of matrix-assisted laser desorption ionization (MALDI) mass spectra of oligonucleotides. Isotope limited mass resolution was obtained on samples up to 10-kDa molecular mass in linear mode, and as high as 7500 mass resolution (defined at half peak height) was observed in reflector mode. This performance is as good as that achieved to date for peptides and proteins. Applications included the detection of oxidized byproducts of phosphorothioate DNA and separation of components differing only by 15 Da at 9.5-kDa molecular mass. In addition to single components, complex mixtures could also be analyzed at greatly improved performance over conventional MALDI. An example is shown for sequence verification of an oligonucleotide of 31 bases in length by analyzing the failure products. Mass accuracy was adequate to verify sequences of oligodeoxyribonucleotides up to 9500-Da molecular mass. Fast fragmentation t...

Applications of delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry to oligonucleotide analysis.

A simple mass spectrometric based assay, the PinPoint assay, has previously been described for typing single nucleotide polymorphisms. The identity of a polymorphism is determined by mass differences of single base extended genotyping primers as determined by MALDI-TOF mass spectrometry. A simple method for multiplexing the assay is described, employing multiple primers with 5'oligo(dT) sequences (MassTags) which serve to mass discriminate the peaks of multiple extended and non-extended primers. The assay is extremely rapid and requires no labeling reagents.

/pdf/multiplex-genotyping-of-pcr-products-with-masstag-labeled-30chgow7so.pdf

Multiplex genotyping of PCR products with MassTag-labeled primers

Matrix-assisted laser desorption/ionization (MALDI) time of flight mass spectrometry was used to detect and order DNA fragments generated by Sanger dideoxy cycle sequencing. This was accomplished by improving the sensitivity and resolution of the MALDI method using a delayed ion extraction technique (DE-MALDI). The cycle sequencing chemistry was optimized to produce as much as 100 fmol of each specific dideoxy terminated fragment, generated from extension of a 13-base primer annealed on 40- and 50-base templates. Analysis of the resultant sequencing mixture by DE-MALDI identified the appropriate termination products. The technique provides a new non-gel-based method to sequence DNA which may ultimately have considerable speed advantages over traditional methodologies.

https://www.pnas.org/content/pnas/93/10/4724.full.pdf

Lawrence A. Haff

Papers

Single-Nucleotide Polymorphism Identification Assays Using a Thermostable DNA Polymerase and Delayed Extraction MALDI-TOF Mass Spectrometry

Methods for determining sequence information in polynucleotides using mass spectrometry

Applications of delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry to oligonucleotide analysis.

Multiplex genotyping of PCR products with MassTag-labeled primers

Dna sequencing by delayed extraction-matrix-assisted laser desorption/ionization time of flight mass spectrometry