Publications by authors named "Mark S Chee"

The SARS-CoV-2 proteome shares regions of conservation with endemic human coronaviruses (CoVs), but it remains unknown to what extent these may be cross-recognized by the antibody response. Here, we study cross-reactivity using a highly multiplexed peptide assay (PepSeq) to generate an epitope-resolved view of IgG reactivity across all human CoVs in both COVID-19 convalescent and negative donors. PepSeq resolves epitopes across the SARS-CoV-2 Spike and Nucleocapsid proteins that are commonly targeted in convalescent donors, including several sites also recognized in some uninfected controls.

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A high-resolution understanding of the antibody response to SARS-CoV-2 is important for the design of effective diagnostics, vaccines and therapeutics. However, SARS-CoV-2 antibody epitopes remain largely uncharacterized, and it is unknown whether and how the response may cross-react with related viruses. Here, we use a multiplexed peptide assay ('PepSeq') to generate an epitope-resolved view of reactivity across all human coronaviruses.

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Article Synopsis
  • - The National Cancer Institute held a think-tank meeting to gather expert insights on using multiomic single-cell analyses, particularly single-cell proteomics, to create advanced cancer biomarkers for risk assessment, early detection, diagnosis, and treatment targets.
  • - The discussion covered challenges in single-cell analysis, including methods for analyzing cells from different tissue states, detecting secreted molecules, identifying new cell types, and integrating multiple types of data effectively.
  • - Experts also explored technical improvements needed for single-cell proteomics, including enhancing measurement sensitivity, achieving adequate data coverage, and effectively visualizing complex data sets to better understand intercellular communication in cancerous tissues.
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Background: There is a growing appreciation of the role of proteolytic processes in human health and disease, but tools for analysis of such processes on a proteome-wide scale are limited. Furin is a ubiquitous proprotein convertase that cleaves after basic residues and transforms secretory proproteins into biologically active proteins. Despite this important role, many furin substrates remain unknown in the human proteome.

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We report a scalable and cost-effective technology for generating and screening high-complexity customizable peptide sets. The peptides are made as peptide-cDNA fusions by in vitro transcription/translation from pools of DNA templates generated by microarray-based synthesis. This approach enables large custom sets of peptides to be designed in silico, manufactured cost-effectively in parallel, and assayed efficiently in a multiplexed fashion.

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Background: The hepatitis C virus (HCV) genome encodes a long polyprotein, which is processed by host cell and viral proteases to the individual structural and non-structural (NS) proteins. HCV NS3/4A serine proteinase (NS3/4A) is a non-covalent heterodimer of the N-terminal, ∼180-residue portion of the 631-residue NS3 protein with the NS4A co-factor. NS3/4A cleaves the polyprotein sequence at four specific regions.

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Ultra-deep targeted sequencing (UDT-Seq) can identify subclonal somatic mutations in tumor samples. Early assays' limited breadth and depth restrict their clinical utility. Here, we target 71 kb of mutational hotspots in 42 cancer genes.

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Half of prostate cancers harbor gene fusions between TMPRSS2 and members of the ETS transcription factor family. To date, little is known about the presence of non-ETS fusion events in prostate cancer. We used next-generation transcriptome sequencing (RNA-seq) in order to explore the whole transcriptome of 25 human prostate cancer samples for the presence of chimeric fusion transcripts.

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We have developed FusionSeq to identify fusion transcripts from paired-end RNA-sequencing. FusionSeq includes filters to remove spurious candidate fusions with artifacts, such as misalignment or random pairing of transcript fragments, and it ranks candidates according to several statistics. It also has a module to identify exact sequences at breakpoint junctions.

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A step toward the molecular classification of prostate cancer was the discovery of recurrent erythroblast transformation-specific rearrangements, most commonly fusing the androgen-regulated TMPRSS2 promoter to ERG. The TMPRSS2-ERG fusion is observed in around 90% of tumors that overexpress the oncogene ERG. The goal of the current study was to complete the characterization of these ERG-overexpressing prostate cancers.

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The lack of efficient high-throughput methods for enrichment of specific sequences from genomic DNA represents a key bottleneck in exploiting the enormous potential of next-generation sequencers. Such methods would allow for a systematic and targeted analysis of relevant genomic regions. Recent studies reported sequence enrichment using a hybridization step to specific DNA capture probes as a possible solution to the problem.

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Article Synopsis
  • The study analyzes over 3 million genetic variations from the International HapMap Project to identify regions of the human genome that have undergone positive natural selection.
  • Using advanced methods, researchers pinpointed over 300 candidate regions, specifically narrowing down to 22 strong areas for further scrutiny.
  • The analysis highlights 26 specific gene variations under positive selection, demonstrating similar evolutionary pressures in related genes across different populations, including regions tied to virus infection and traits like skin pigmentation and hair follicle development.
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We describe the Phase II HapMap, which characterizes over 3.1 million human single nucleotide polymorphisms (SNPs) genotyped in 270 individuals from four geographically diverse populations and includes 25-35% of common SNP variation in the populations surveyed. The map is estimated to capture untyped common variation with an average maximum r2 of between 0.

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Recent developments in highly parallel genome-wide assays are transforming the study of human health and disease. High-resolution whole-genome association studies of complex diseases are finally being undertaken after much hypothesizing about their merit for finding disease loci. The availability of inexpensive high-density SNP-genotyping arrays has made this feasible.

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We have developed a high-throughput method for analyzing the methylation status of hundreds of preselected genes simultaneously and have applied it to the discovery of methylation signatures that distinguish normal from cancer tissue samples. Through an adaptation of the GoldenGate genotyping assay implemented on a BeadArray platform, the methylation state of 1536 specific CpG sites in 371 genes (one to nine CpG sites per gene) was measured in a single reaction by multiplexed genotyping of 200 ng of bisulfite-treated genomic DNA. The assay was used to obtain a quantitative measure of the methylation level at each CpG site.

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Oligonucleotide probe arrays have enabled massively parallel analysis of gene expression levels from a single cDNA sample. Application of microarray technology to analyzing genomic DNA has been stymied by the sequence complexity of the entire human genome. A robust, single base-resolution direct genomic assay would extend the reach of microarray technology.

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We have developed a highly informative set of single-nucleotide polymorphism (SNP) assays designed for linkage mapping of the human genome. These assays were developed on a robust multiplexed assay system to provide a combination of very high accuracy and data completeness with high throughput for linkage studies. The linkage panel is comprised of approximately 4,700 SNPs with 0.

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We have developed a new microarray technology for quantitative gene-expression profiling on the basis of randomly assembled arrays of beads. Each bead carries a gene-specific probe sequence. There are multiple copies of each sequence-specific bead in an array, which contributes to measurement precision and reliability.

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We report a flexible, sensitive, and quantitative gene-expression profiling system for assaying more than 400 genes, with three probes per gene, for 96 samples in parallel. The cDNA-mediated annealing, selection, extension and ligation (DASL) assay targets specific transcripts, using oligonucleotides containing unique address sequences that can hybridize to universal arrays. Cell-specific gene expression profiles were obtained using this assay for hormone-treated cell lines and laser-capture microdissected cancer tissues.

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We have developed a simple and efficient algorithm to identify each member of a large collection of DNA-linked objects through the use of hybridization, and have applied it to the manufacture of randomly assembled arrays of beads in wells. Once the algorithm has been used to determine the identity of each bead, the microarray can be used in a wide variety of applications, including single nucleotide polymorphism genotyping and gene expression profiling. The algorithm requires only a few labels and several sequential hybridizations to identify thousands of different DNA sequences with great accuracy.

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Three methods for the conjugation of oligonucleotides to antibodies and the subsequent application of these conjugates to protein detection at attomole levels in immunoassays are described. The methods are based on chemical modification of both antibody and oligonucleotide. Aldehydes were introduced onto antibodies by modification of primary amines or oxidation of carbohydrate residues.

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The Human Genome Project has opened the door to personalized medicine, provided that human genetic diversity can be analyzed in a high-throughput and cost-effective way Illumina has developed a genotyping system that combines very high throughput and accuracy with low cost per SNP analysis. The system uses our BeadArray platform, a high level of multiplexing, and modular, scalable automation to meet the requirements for cost-effective, genome-wide linkage disequilibrium studies. As implemented in a high-throughput genotyping service facility at Illumina, the system has a current capacity of one million SNP assays per day and is easily expandable.

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The human transcriptome is marked by extensive alternative mRNA splicing and the expression of many closely related genes, which may be difficult to distinguish using standard microarray techniques. Here we describe a sensitive and specific assay for parallel analysis of mRNA isoforms on a fiber-optic microarray platform. The method permits analysis of mRNA transcripts without prior RNA purification or cDNA synthesis.

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