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Biomedical subjects

Jiannis Ragoussis

Publications and source records attributed to Jiannis Ragoussis.

At least 19 recordsLinked to original sources

Toward a unified approach: Considerations for bioinformatic and sequencing activities & data in wastewater surveillance of biologic public health threats.

Genomic technologies such as PCR and next-generation sequencing (NGS) have greatly advanced public health surveillance, especially during COVID-19, by enabling detailed tracking of pathogen spread, origins, and variants. While PCR is vital for targeted detection, falling NGS costs have made large-scale, high-throughput sequencing more feasible, supporting broader pathogen monitoring-including the detection of vaccine escape variants and new strains. Applying NGS to wastewater offers valuable population-level insights but faces challenges such as variable sample complexity, the need for skilled staff, suitable platforms, and robust IT infrastructure. Although there are currently a lot of efforts towards defining guidelines for sampling, analysis, and integrating wastewater data into public health policy, such as the recently published International Cookbook for Wastewater Practitioners, they often lack universal applicability, emphasizing the analytical approaches in favour of the NGS-based approaches. However, standardising protocols for sampling, sequencing, and analysis is crucial to ensure reliable, comparable data across surveillance systems worldwide. Pilot studies and continuous refinement are recommended to overcome implementation hurdles and fully realise the benefits of NGS in wastewater surveillance. This work attempts to outline these challenges and opportunities across the entire wastewater surveillance workflow, from data generation to reporting, and provide some concrete suggestions and considerations across the spectrum of activities. We further highlight that the infrastructure, funding and government-policy context in which surveillance operates acts as an enabling condition for these activities, and that technical standardisation alone is unlikely to deliver durable, comparable surveillance in its absence.

considerations↗

TUCAN (CARD8) genetic variants and inflammatory bowel disease.

BACKGROUND & AIMS: The identification of the association between Crohn's disease (CD) and NOD2 (CARD15) confirmed both the heritability of CD and highlighted the role of the nuclear factor kappaB (NFkappaB) pathway in disease pathogenesis. Other susceptibility loci exist. TUCAN (CARD8) is located beneath a CD peak of linkage on chromosome 19q. TUCAN is expressed in the gut and is a negative regulator of NFkappaB, making it an excellent candidate gene for gastrointestinal inflammation. METHODS: Ten single nucleotide polymorphisms (SNP) across TUCAN were genotyped in 365 controls, 372 patients with CD, and 373 patients with ulcerative colitis. A diagnostic panel for CD was constructed using smoking status and TUCAN, NOD2, IBD5, NOD1, and TNFSF15 data. RESULTS: We demonstrate significant association between a TUCAN SNP and CD (OR 1.35, P = .0083). The association was more pronounced with disease affecting sites other than the colon (odds ratio, 1.52) and NOD2-negative CD (odds ratio, 1.50). Combination of these data with smoking and NOD2, IBD5, NOD1, and TNFSF15 status demonstrated very strong associations with CD and high sensitivities (96.3%), specificities (99.4%), and likelihood ratios (12.8) for CD, although further work will be needed before this model can be translated into direct clinical utility. CONCLUSIONS: We have shown an association between a likely functional polymorphism in TUCAN and CD. The combination of these data in a genetic panel suggests that clinicians may soon be able to translate genetic advances into direct benefits for patients.

CARD Signaling Adaptor Proteins↗

The leukocyte receptor complex in chicken is characterized by massive expansion and diversification of immunoglobulin-like Loci.

The innate and adaptive immune systems of vertebrates possess complementary, but intertwined functions within immune responses. Receptors of the mammalian innate immune system play an essential role in the detection of infected or transformed cells and are vital for the initiation and regulation of a full adaptive immune response. The genes for several of these receptors are clustered within the leukocyte receptor complex (LRC). The purpose of this study was to carry out a detailed analysis of the chicken (Gallus gallus domesticus) LRC. Bacterial artificial chromosomes containing genes related to mammalian leukocyte immunoglobulin-like receptors were identified in a chicken genomic library and shown to map to a single microchromosome. Sequencing revealed 103 chicken immunoglobulin-like receptor (CHIR) loci (22 inhibitory, 25 activating, 15 bifunctional, and 41 pseudogenes). A very complex splicing pattern was found using transcript analyses and seven hypervariable regions were detected in the external CHIR domains. Phylogenetic and genomic analysis showed that CHIR genes evolved mainly by block duplications from an ancestral inhibitory receptor locus, with transformation into activating receptors occurring more than once. Evolutionary selection pressure has led not only to an exceptional expansion of the CHIR cluster but also to a dramatic diversification of CHIR loci and haplotypes. This indicates that CHIRs have the potential to complement the adaptive immune system in fighting pathogens.

Alternative Splicing↗

Concordant regulation of gene expression by hypoxia and 2-oxoglutarate-dependent dioxygenase inhibition: the role of HIF-1alpha, HIF-2alpha, and other pathways.

Studies of gene regulation by oxygen have revealed novel signal pathways that regulate the hypoxia-inducible factor (HIF) transcriptional system through post-translational hydroxylation of specific prolyl and asparaginyl residues in HIF-alpha subunits. These oxygen-sensitive modifications are catalyzed by members of the 2-oxoglutarate (2-OG) dioxygenase family (PHD1, PHD2, PHD3, and FIH-1), raising an important question regarding the extent of involvement of these and other enzymes of the same family in directing the global changes in gene expression that are induced by hypoxia. To address this, we compared patterns of gene expression induced by hypoxia and by a nonspecific 2-OG-dependent dioxygenase inhibitor, dimethyloxalylglycine (DMOG), among a set of 22,000 transcripts, by microarray analysis of MCF7 cells. By using short interfering RNA-based suppression of HIF-alpha subunits, we also compared responses that were dependent on, or independent of, the HIF system. Results revealed striking concordance between patterns of gene expression induced by hypoxia and by DMOG, indicating the central involvement of 2-OG-dependent dioxygenases in oxygen-regulated gene expression. Many of these responses were suppressed by short interfering RNAs directed against HIF-1alpha and HIF-2alpha, with HIF-1alpha suppression manifesting substantially greater effects than HIF-2alpha suppression, supporting the importance of HIF pathways. Nevertheless, the definition of genes regulated by both hypoxia and DMOG, but not HIF, distinguished other pathways most likely involving the action of 2-OG-dependent dioxygenases on non-HIF substrates.

Amino Acids, Dicarboxylic↗

Determination of the mutation spectrum of the EXT1/EXT2 genes in British Caucasian patients with multiple osteochondromas, and exclusion of six candidate genes in EXT negative cases.

We describe here the spectrum and distribution of mutations in the EXT1 and EXT2 genes in the largest reported British Caucasian multiple osteochondromas (MO) population. Furthermore, we report for the first time the screening of the EXT1 and EXT2 promoters, 5'UTRs, and 3'UTRs, and exclude six potential MO candidate genes in individuals without a detectable mutation within the coding region of EXT1 and EXT2. The coding exons of EXT1 and EXT2 were screened in 72 unrelated probands affected with MO. Forty-six different mutations were identified in 56 probands, of which 29 were novel. Mutation in the EXT1 and EXT2 genes each accounted for 50% of the mutations identified. Of the 72 probands, 42 were of British Caucasian descent, which when added to the 41 British Caucasian families previously reported from our total cohort, gave a total of 83 families. This cohort's proportional frequency for EXT1/EXT2 mutation was 53%/47%. We also validated the technique of high-resolution melting analysis in a blind study using 27 unique EXT1 or EXT2 mutations. This technique was found to be sensitive with a detection rate of 100% regarding heterozygote detection for EXT mutation scanning. Furthermore, this technique has a very high throughput and is very cost-effective.

Chromatography, High Pressure Liquid↗

Alpha-haemoglobin stabilising protein is a quantitative trait gene that modifies the phenotype of beta-thalassaemia.

It has been suggested that altered levels or function of alpha-haemoglobin stabilising protein (AHSP), an erythroid-specific protein that binds specifically to free alpha-(haemo)globin, might account for some of the clinical variability in beta-thalassaemia. To assess the variation of AHSP expression, mRNA levels in circulating reticulocytes of 103 healthy individuals were measured by quantitative reverse transcription-polymerase chain reaction. AHSP expression varied up to threefold, and did not correlate with age or sex. A systematic survey of the AHSP locus identified eight sequence variants, of which six were common. Four common variants, including the longer homopolymer (T18) in the putative promoter, are strongly associated with AHSP expression. Reporter assays in K562 cells showed that the activity of the shorter (T15) reporter was relatively lower than that of the T18 reporter. In a study of nine anaemic patients who were heterozygous for beta-thalassaemia and also heterozygous for the triplicated alpha-globin gene (alpha alpha alpha/alpha alpha), frequency of the shorter homopolymer was higher than expected. AHSP expression is variable, with cis control accounting for some of its variance. In some families, the subtle altered levels in AHSP related to the AHSP genotype appears to be a relevant contributory factor in the haematological phenotype.

Adult↗

Matrix-assisted laser desorption/ionisation, time-of-flight mass spectrometry in genomics research.

The beginning of this millennium has seen dramatic advances in genomic research. Milestones such as the complete sequencing of the human genome and of many other species were achieved and complemented by the systematic discovery of variation at the single nucleotide (SNP) and whole segment (copy number polymorphism) level. Currently most genomics research efforts are concentrated on the production of whole genome functional annotations, as well as on mapping the epigenome by identifying the methylation status of CpGs, mainly in CpG islands, in different tissues. These recent advances have a major impact on the way genetic research is conducted and have accelerated the discovery of genetic factors contributing to disease. Technology was the critical driving force behind genomics projects: both the combination of Sanger sequencing with high-throughput capillary electrophoresis and the rapid advances in microarray technologies were keys to success. MALDI-TOF MS-based genome analysis represents a relative newcomer in this field. Can it establish itself as a long-term contributor to genetics research, or is it only suitable for niche areas and for laboratories with a passion for mass spectrometry? In this review, we will highlight the potential of MALDI-TOF MS-based tools for resequencing and for epigenetics research applications, as well as for classical complex genetic studies, allele quantification, and quantitative gene expression analysis. We will also identify the current limitations of this approach and attempt to place it in the context of other genome analysis technologies.

Animals↗

Quantitative profiling of protein-DNA binding on microarrays.

Recent studies on genome-wide localization of transcription factor (TF) binding to DNA have shown that a large proportion of identified sequences do not contain consensus motifs predicted by databases of transcription factor binding sites, such as TRANSFAC. The main limitation of these databases is that they are based on a literature search of published examples of binding; consequently the data are not from a systematic survey and may be subject to sampling biases if investigators focused on particular motifs. Thus, there is an urgent need for systematic profiling of vertebrate transcription factor binding to DNA. We have developed a high-throughput platform for the quantitative analysis of protein-DNA interactions based on microarray technology.

Base Sequence↗

Genomic reconstruction by serial mitotic recombination of yeast artificial chromosomes.

DNA cloned in yeast artificial chromosomes (YACs) is a valuable resource for functional experiments in cell culture as well as whole animal systems. Where the size or chimerism of a YAC clone are limiting factors it may be desirable to generate recombinant YAC clones. One such approach is based on mitotic recombination, and we describe the development of a methodology that allows multiple recombination cycles for serial reconstruction of overlapping YACs. This approach employs retrofitting with standard plasmid vectors, transfer of YACs to a common haploid host by Kar1 mating, and selection for recombination with 5-fluoro-orotic acid.

Chromosomes, Artificial, Yeast↗

Affymetrix GeneChip system: moving from research to the clinic.

Affymetrix Inc.'s GeneChip technology has become the industry standard in microarray-based research. Due to the high density of content per array that can be achieved today (an industry leading 6.5 million features) the GeneChips can be used for high-throughput mutation detection, single nucleotide polymorphism genotyping, expression profiling and detection of chromosomal aberrations. This in turn opens the way for clinical applications in genetics, cytogenetics, pharmacogenetics, oncology and pathogen recognition. Establishing standards is a central issue in improving data quality and, in combination with automatic, easy-to-interpret reports, will form the basis of the clinical applicability. Future pricing policies and the resolving of ethical considerations will also dictate the technology's full translation from research into clinical laboratories.

Animals↗

Single nucleotide polymorphisms in TNFSF15 confer susceptibility to Crohn's disease.

The inflammatory bowel diseases (IBDs), Crohn's disease (CD) and ulcerative colitis, are chronic inflammatory disorders of the digestive tract. The pathogenesis of IBD is complicated, and it is widely accepted that immunologic, environmental and genetic components contribute to its etiology. To identify genetic susceptibility factors in CD, we performed a genome-wide association study in Japanese patients and controls using nearly 80,000 gene-based single nucleotide polymorphism (SNP) markers and investigated the haplotype structure of the candidate locus in Japanese and European patients. We identified highly significant associations (P = 1.71 x 10(-14) with odds ratio of 2.17) of SNPs and haplotypes within the TNFSF15 (the gene encoding tumor necrosis factor superfamily, member 15) genes in Japanese CD patients. The association was confirmed in the study of two European IBD cohorts. Interestingly, a core TNFSF15 haplotype showing association with increased risk to the disease was common in the two ethnic groups. Our results suggest that the genetic variations in the TNFSF15 gene contribute to the susceptibility to IBD in the Japanese and European populations.

Adult↗

Dissecting the genetic complexity of human 6p deletion syndromes by using a region-specific, phenotype-driven mouse screen.

Monosomy of the human chromosome 6p terminal region results in a variety of congenital malformations that include brain, craniofacial, and organogenesis abnormalities. To examine the genetic basis of these phenotypes, we have carried out an unbiased functional analysis of the syntenic region of the mouse genome (proximal Mmu13). A genetic screen for recessive mutations in this region recovered thirteen lines with phenotypes relevant to a variety of clinical conditions. These include two loci that cause holoprosencephaly, two that underlie anophthalmia, one of which also contributes to other craniofacial abnormalities such as microcephaly, agnathia, and palatogenesis defects, and one locus responsible for developmental heart and kidney defects. Analysis of heterozygous carriers of these mutations shows that a high proportion of these loci manifest with behavioral activity and sensorimotor deficits in the heterozygous state. This finding argues for the systematic, reciprocal phenotypic assessment of dominant and recessive mouse mutants. In addition to providing a resource of single gene mutants that model 6p-associated disorders, the work reveals unsuspected genetic complexity at this region. In particular, many of the phenotypes associated with 6p deletions can be elicited by mutation in one of a number of genes. This finding implies that phenotypes associated with contiguous gene deletion syndromes can result not only from dosage sensitivity of one gene in the region but also from the combined effect of monosomy for multiple genes that function within the same biological process.

Animals↗

SW-ARRAY: a dynamic programming solution for the identification of copy-number changes in genomic DNA using array comparative genome hybridization data.

Comparative genome hybridization (CGH) to DNA microarrays (array CGH) is a technique capable of detecting deletions and duplications in genomes at high resolution. However, array CGH studies of the human genome noting false negative and false positive results using large insert clones as probes have raised important concerns regarding the suitability of this approach for clinical diagnostic applications. Here, we adapt the Smith-Waterman dynamic-programming algorithm to provide a sensitive and robust analytic approach (SW-ARRAY) for detecting copy-number changes in array CGH data. In a blind series of hybridizations to arrays consisting of the entire tiling path for the terminal 2 Mb of human chromosome 16p, the method identified all monosomies between 267 and 1567 kb with a high degree of statistical significance and accurately located the boundaries of deletions in the range 267-1052 kb. The approach is unique in offering both a nonparametric segmentation procedure and a nonparametric test of significance. It is scalable and well-suited to high resolution whole genome array CGH studies that use array probes derived from large insert clones as well as PCR products and oligonucleotides.

Algorithms↗

Development and evaluation of real competitive PCR for high-throughput quantitative applications.

Real competitive PCR (rcPCR) has been shown to have high sensitivity, reproducibility, and high-throughput potential. We describe further development and evaluation of this methodology as a tool for measuring nucleic acid abundance within a cell. Modifications to the original protocol allow analysis of gene expression levels using standard conditions regardless of mRNA abundance and assay type, thereby increasing throughput and ease of reaction setup while decreasing optimization time. In addition, we have developed a software package, TITAN, to automatically analyze the results. The details are relevant to researchers performing competitive PCR using any detection technique. The effectiveness of the described developments is demonstrated using 12 genes known to have differential expression in cell lines grown under normal and hypoxic conditions. Quantitative and qualitative comparisons to real-time PCR are presented. It is also demonstrated that the technique is capable of detecting submicroscopic chromosomal DNA deletions.

Breast Neoplasms↗

Genetically indistinguishable SNPs and their influence on inferring the location of disease-associated variants.

As part of a recent high-density linkage disequilibrium (LD) study of chromosome 20, we obtained genotypes for approximately 30,000 SNPs at a density of 1 SNP/2 kb on four different population samples (47 CEPH founders; 91 UK unrelateds [unrelated white individuals of western European ancestry]; 97 African Americans; 42 East Asians). We observed that approximately 50% of SNPs had at least one genetically indistinguishable partner; i.e., for every individual considered, their genotype at the first locus was identical to their genotype at the second locus, or in LD terms, the SNPs were in "perfect" LD (r2 = 1.0). These "genetically indistinguishable SNPs" (giSNPs) formed into clusters of varying size. The larger the cluster, the greater the tendency to be located within genes and to overlap with giSNP clusters in other population samples. As might be expected for this map density, many giSNPs were located close to one another, thus reflecting local regions of undetected recombination or haplotype blocks. However, approximately 1/3 of giSNP clusters had intermingled, non-indistinguishable SNPs with incomplete LD (D' and r2 <1), sometimes spanning hundreds of kilobases, comprising up to 70 indistinguishable markers and overlapping multiple haplotype blocks. These long-range, nonconsecutive giSNPs have implications for disease gene localization by allelic association as evidence for association at one locus will be indistinguishable from that at another locus, even though both loci may be situated far apart. We describe the distribution of giSNPs on this map of chromosome 20 and illustrate the potential impact they can have on association mapping.

Black or African American↗

Quantitative high-throughput analysis of transcription factor binding specificities.

We present a general high-throughput approach to accurately quantify DNA-protein interactions, which can facilitate the identification of functional genetic polymorphisms. The method tested here on two structurally distinct transcription factors (TFs), NF-kappaB and OCT-1, comprises three steps: (i) optimized selection of DNA variants to be tested experimentally, which we show is superior to selecting variants at random; (ii) a quantitative protein-DNA binding assay using microarray and surface plasmon resonance technologies; (iii) prediction of binding affinity for all DNA variants in the consensus space using a statistical model based on principal coordinates analysis. For the protein-DNA binding assay, we identified a polyacrylamide/ester glass activation chemistry which formed exclusive covalent bonds with 5'-amino-modified DNA duplexes and hindered non-specific electrostatic attachment of DNA. Full accessibility of the DNA duplexes attached to polyacrylamide-modified slides was confirmed by the high degree of data correlation with the electromobility shift assay (correlation coefficient 93%). This approach offers the potential for high-throughput determination of TF binding profiles and predicting the effects of single nucleotide polymorphisms on TF binding affinity. New DNA binding data for OCT-1 are presented.

Acrylic Resins↗

Refined genotype-phenotype correlations in cases of chromosome 6p deletion syndromes.

Clinical reports of cases with deletions in chromosome 6p are relatively rare. We present a detailed study by fluorescent in situ hybridisation (FISH) of six new cases with distinct but overlapping 6p deletions involving the 6p24-pter chromosomal segment. Chromosomal breakpoints in individual cases were investigated using a large panel of probes previously mapped and characterised in our laboratory to cover the distal region of 6p. These cases have allowed refinement of genotype-phenotype correlations and strongly suggest a gene involved in regulating the development of hearing is localised within 6p25. There is also evidence for one or more loci involved in heart, skeletal and craniofacial development in the 6p24-p25 region. Furthermore, the Dandy-Walker malformation is associated with deletion of 6p24-pter.

Abnormalities, Multiple↗