Publications by authors named "Cedric Howald"

22 Publications

  • Page 1 of 1

Genetic variant effects on gene expression in human pancreatic islets and their implications for T2D.

Nat Commun 2020 09 30;11(1):4912. Epub 2020 Sep 30.

Department of Genetics, University of North Carolina, Chapel Hill, NC, 27599, USA.

Most signals detected by genome-wide association studies map to non-coding sequence and their tissue-specific effects influence transcriptional regulation. However, key tissues and cell-types required for functional inference are absent from large-scale resources. Here we explore the relationship between genetic variants influencing predisposition to type 2 diabetes (T2D) and related glycemic traits, and human pancreatic islet transcription using data from 420 donors. We find: (a) 7741 cis-eQTLs in islets with a replication rate across 44 GTEx tissues between 40% and 73%; (b) marked overlap between islet cis-eQTL signals and active regulatory sequences in islets, with reduced eQTL effect size observed in the stretch enhancers most strongly implicated in GWAS signal location; (c) enrichment of islet cis-eQTL signals with T2D risk variants identified in genome-wide association studies; and (d) colocalization between 47 islet cis-eQTLs and variants influencing T2D or glycemic traits, including DGKB and TCF7L2. Our findings illustrate the advantages of performing functional and regulatory studies in disease relevant tissues.
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http://dx.doi.org/10.1038/s41467-020-18581-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7528108PMC
September 2020

Combined genetic and transcriptome analysis of patients with SLE: distinct, targetable signatures for susceptibility and severity.

Ann Rheum Dis 2019 08 5;78(8):1079-1089. Epub 2019 Jun 5.

Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas (FORTH), Heraklion, Greece

Objectives: Systemic lupus erythematosus (SLE) diagnosis and treatment remain empirical and the molecular basis for its heterogeneity elusive. We explored the genomic basis for disease susceptibility and severity.

Methods: mRNA sequencing and genotyping in blood from 142 patients with SLE and 58 healthy volunteers. Abundances of cell types were assessed by CIBERSORT and cell-specific effects by interaction terms in linear models. Differentially expressed genes (DEGs) were used to train classifiers (linear discriminant analysis) of SLE versus healthy individuals in 80% of the dataset and were validated in the remaining 20% running 1000 iterations. Transcriptome/genotypes were integrated by expression-quantitative trail loci (eQTL) analysis; tissue-specific genetic causality was assessed by regulatory trait concordance (RTC).

Results: SLE has a 'susceptibility signature' present in patients in clinical remission, an 'activity signature' linked to genes that regulate immune cell metabolism, protein synthesis and proliferation, and a 'severity signature' best illustrated in active nephritis, enriched in druggable granulocyte and plasmablast/plasma-cell pathways. Patients with SLE have also perturbed mRNA splicing enriched in immune system and interferon signalling genes. A novel transcriptome index distinguished active versus inactive disease-but not low disease activity-and correlated with disease severity. DEGs discriminate SLE versus healthy individuals with median sensitivity 86% and specificity 92% suggesting a potential use in diagnostics. Combined eQTL analysis from the Genotype Tissue Expression (GTEx) project and SLE-associated genetic polymorphisms demonstrates that susceptibility variants may regulate gene expression in the blood but also in other tissues.

Conclusion: Specific gene networks confer susceptibility to SLE, activity and severity, and may facilitate personalised care.
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http://dx.doi.org/10.1136/annrheumdis-2018-214379DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6691930PMC
August 2019

Cellular circadian period length inversely correlates with HbA levels in individuals with type 2 diabetes.

Diabetologia 2019 08 27;62(8):1453-1462. Epub 2019 May 27.

Department of Medicine, Division of Endocrinology, Diabetes, Hypertension and Nutrition, Faculty of Medicine, University of Geneva, Rue Michel-Servet, 1, CH-1211, 14, Geneva, Switzerland.

Aims/hypothesis: The circadian system plays an essential role in regulating the timing of human metabolism. Indeed, circadian misalignment is strongly associated with high rates of metabolic disorders. The properties of the circadian oscillator can be measured in cells cultured in vitro and these cellular rhythms are highly informative of the physiological circadian rhythm in vivo. We aimed to discover whether molecular properties of the circadian oscillator are altered as a result of type 2 diabetes.

Methods: We assessed molecular clock properties in dermal fibroblasts established from skin biopsies taken from nine obese and eight non-obese individuals with type 2 diabetes and 11 non-diabetic control individuals. Following in vitro synchronisation, primary fibroblast cultures were subjected to continuous assessment of circadian bioluminescence profiles based on lentiviral luciferase reporters.

Results: We observed a significant inverse correlation (ρ = -0.592; p < 0.05) between HbA values and circadian period length within cells from the type 2 diabetes group. RNA sequencing analysis conducted on samples from this group revealed that ICAM1, encoding the endothelial adhesion protein, was differentially expressed in fibroblasts from individuals with poorly controlled vs well-controlled type 2 diabetes and its levels correlated with cellular period length. Consistent with this circadian link, the ICAM1 gene also displayed rhythmic binding of the circadian locomotor output cycles kaput (CLOCK) protein that correlated with gene expression.

Conclusions/interpretation: We provide for the first time a potential molecular link between glycaemic control in individuals with type 2 diabetes and circadian clock machinery. This paves the way for further mechanistic understanding of circadian oscillator changes upon type 2 diabetes development in humans.

Data Availability: RNA sequencing data and clinical phenotypic data have been deposited at the European Genome-phenome Archive (EGA), which is hosted by the European Bioinformatics Institute (EBI) and the Centre for Genomic Regulation (CRG), ega-box-1210, under accession no. EGAS00001003622.
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http://dx.doi.org/10.1007/s00125-019-4907-0DOI Listing
August 2019

High-fat diet impacts more changes in beta-cell compared to alpha-cell transcriptome.

PLoS One 2019 8;14(3):e0213299. Epub 2019 Mar 8.

Molecular Diabetes Laboratory, Division of Endocrinology, Diabetes, Hypertension and Nutrition, University Hospital/Diabetes Center/University of Geneva Medical School, Geneva, Switzerland.

Characterization of endocrine-cell functions and associated molecular signatures in diabetes is crucial to better understand why and by which mechanisms alpha and beta cells cause and perpetuate metabolic abnormalities. The now recognized role of glucagon in diabetes control is a major incentive to have a better understanding of dysfunctional alpha cells. To characterize molecular alterations of alpha cells in diabetes, we analyzed alpha-cell transcriptome from control and diabetic mice using diet-induced obesity model. To this aim, we quantified the expression levels of total mRNAs from sorted alpha and beta cells of low-fat and high-fat diet-treated mice through RNAseq experiments, using a transgenic mouse strain allowing collections of pancreatic alpha- and beta-cells after 16 weeks of diet. We now report that pancreatic alpha cells from obese hyperglycemic mice displayed minor variations of their transcriptome compared to controls. Depending on analyses, we identified 11 to 39 differentially expressed genes including non-alpha cell markers mainly due to minor cell contamination during purification process. From these analyses, we identified three new target genes altered in diabetic alpha cells and potently involved in cellular stress and exocytosis (Upk3a, Adcy1 and Dpp6). By contrast, analysis of the beta-cell transcriptome from control and diabetic mice revealed major alterations of specific genes coding for proteins involved in proliferation and secretion. We conclude that alpha cell transcriptome is less reactive to HFD diet compared to beta cells and display adaptations to cellular stress and exocytosis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0213299PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6407777PMC
December 2019

Angiogenin and Osteoprotegerin are type II muscle specific myokines protecting pancreatic beta-cells against proinflammatory cytokines.

Sci Rep 2018 07 3;8(1):10072. Epub 2018 Jul 3.

UMR DIATHEC, EA 7294, Centre Européen d'Etude du Diabète, Université de Strasbourg, Fédération de Médecine Translationnelle de Strasbourg (FMTS), Bld René Leriche, 67200, Strasbourg, France.

Tissue cross-talk is emerging as a determinant way to coordinate the different organs implicated in glucose homeostasis. Among the inter-organ communication factors, muscle-secreted myokines can modulate the function and survival of pancreatic beta-cells. Using primary human myotubes from soleus, vastus lateralis and triceps brachii muscles, we report here that the impact of myokines on beta-cells depends on fiber types and their metabolic status. We show that Type I and type II primary myotubes present specific mRNA and myokine signatures as well as a different sensitivity to TNF-alpha induced insulin resistance. Finally, we show that angiogenin and osteoprotegerin are triceps specific myokines with beta-cell protective actions against proinflammatory cytokines. These results suggest that type I and type II muscles could impact insulin secretion and beta-cell mass differentially in type 2 diabetes through specific myokines secretion.
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http://dx.doi.org/10.1038/s41598-018-28117-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6030123PMC
July 2018

Transcriptomic analyses reveal rhythmic and CLOCK-driven pathways in human skeletal muscle.

Elife 2018 04 16;7. Epub 2018 Apr 16.

Division of Endocrinology, Diabetes, Hypertension and Nutrition, Department of Internal Medicine Specialties, University Hospital of Geneva, Geneva, Switzerland.

Circadian regulation of transcriptional processes has a broad impact on cell metabolism. Here, we compared the diurnal transcriptome of human skeletal muscle conducted on serial muscle biopsies in vivo with profiles of human skeletal myotubes synchronized in vitro. More extensive rhythmic transcription was observed in human skeletal muscle compared to in vitro cell culture as a large part of the in vivo mRNA rhythmicity was lost in vitro. siRNA-mediated clock disruption in primary myotubes significantly affected the expression of ~8% of all genes, with impact on glucose homeostasis and lipid metabolism. Genes involved in GLUT4 expression, translocation and recycling were negatively affected, whereas lipid metabolic genes were altered to promote activation of lipid utilization. Moreover, basal and insulin-stimulated glucose uptake were significantly reduced upon depletion. Our findings suggest an essential role for the circadian coordination of skeletal muscle glucose homeostasis and lipid metabolism in humans.
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http://dx.doi.org/10.7554/eLife.34114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5902165PMC
April 2018

The genomic landscape of human cellular circadian variation points to a novel role for the signalosome.

Elife 2017 09 4;6. Epub 2017 Sep 4.

Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.

The importance of natural gene expression variation for human behavior is undisputed, but its impact on circadian physiology remains mostly unexplored. Using umbilical cord fibroblasts, we have determined by genome-wide association how common genetic variation impacts upon cellular circadian function. Gene set enrichment points to differences in protein catabolism as one major source of clock variation in humans. The two most significant alleles regulated expression of COPS7B, a subunit of the COP9 signalosome. We further show that the signalosome complex is imported into the nucleus in timed fashion to stabilize the essential circadian protein BMAL1, a novel mechanism to oppose its proteasome-mediated degradation. Thus, circadian clock properties depend in part upon a genetically-encoded competition between stabilizing and destabilizing forces, and genetic alterations in these mechanisms provide one explanation for human chronotype.
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http://dx.doi.org/10.7554/eLife.24994DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5601996PMC
September 2017

Extension of human lncRNA transcripts by RACE coupled with long-read high-throughput sequencing (RACE-Seq).

Nat Commun 2016 08 17;7:12339. Epub 2016 Aug 17.

Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire CB10 1HH, UK.

Long non-coding RNAs (lncRNAs) constitute a large, yet mostly uncharacterized fraction of the mammalian transcriptome. Such characterization requires a comprehensive, high-quality annotation of their gene structure and boundaries, which is currently lacking. Here we describe RACE-Seq, an experimental workflow designed to address this based on RACE (rapid amplification of cDNA ends) and long-read RNA sequencing. We apply RACE-Seq to 398 human lncRNA genes in seven tissues, leading to the discovery of 2,556 on-target, novel transcripts. About 60% of the targeted loci are extended in either 5' or 3', often reaching genomic hallmarks of gene boundaries. Analysis of the novel transcripts suggests that lncRNAs are as long, have as many exons and undergo as much alternative splicing as protein-coding genes, contrary to current assumptions. Overall, we show that RACE-Seq is an effective tool to annotate an organism's deep transcriptome, and compares favourably to other targeted sequencing techniques.
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http://dx.doi.org/10.1038/ncomms12339DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4992054PMC
August 2016

IL-13 improves beta-cell survival and protects against IL-1beta-induced beta-cell death.

Mol Metab 2016 Feb 17;5(2):122-131. Epub 2015 Nov 17.

Department of Genetic Medicine and Development, University of Geneva Medical Center, Geneva, Switzerland.

Objectives: IL-13 is a cytokine classically produced by anti-inflammatory T-helper-2 lymphocytes; it is decreased in the circulation of type 2 diabetic patients and impacts positively on liver and skeletal muscle. Although IL-13 can exert positive effects on beta-cell lines, its impact and mode of action on primary beta-cell function and survival remain largely unexplored.

Methods: Beta-cells were cultured for 48 h in the presence of IL-13 alone or in combination with IL-1β or cytokine cocktail (IL-1β, IFNγ, TNFα).

Results: IL-13 protected human and rat beta-cells against cytokine induced death. However, IL-13 was unable to protect from IL-1β impaired glucose stimulated insulin secretion and did not influence NFκB nuclear relocalization induced by IL-1β. IL-13 induced phosphorylation of Akt, increased IRS2 protein expression and counteracted the IL-1β induced regulation of several beta-cell stress response genes.

Conclusions: The prosurvival effects of IL-13 thus appear to be mediated through IRS2/Akt signaling with NFκB independent regulation of gene expression. In addition to previously documented beneficial effects on insulin target tissues, these data suggest that IL-13 may be useful for treatment of type 2 diabetes by preserving beta-cell mass or slowing its rate of decline.
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http://dx.doi.org/10.1016/j.molmet.2015.11.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4735661PMC
February 2016

Genome-wide association study identifies shared risk loci common to two malignancies in golden retrievers.

PLoS Genet 2015 Feb 2;11(2):e1004922. Epub 2015 Feb 2.

Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America; Science for Life Laboratory, Dept. of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.

Dogs, with their breed-determined limited genetic background, are great models of human disease including cancer. Canine B-cell lymphoma and hemangiosarcoma are both malignancies of the hematologic system that are clinically and histologically similar to human B-cell non-Hodgkin lymphoma and angiosarcoma, respectively. Golden retrievers in the US show significantly elevated lifetime risk for both B-cell lymphoma (6%) and hemangiosarcoma (20%). We conducted genome-wide association studies for hemangiosarcoma and B-cell lymphoma, identifying two shared predisposing loci. The two associated loci are located on chromosome 5, and together contribute ~20% of the risk of developing these cancers. Genome-wide p-values for the top SNP of each locus are 4.6×10-7 and 2.7×10-6, respectively. Whole genome resequencing of nine cases and controls followed by genotyping and detailed analysis identified three shared and one B-cell lymphoma specific risk haplotypes within the two loci, but no coding changes were associated with the risk haplotypes. Gene expression analysis of B-cell lymphoma tumors revealed that carrying the risk haplotypes at the first locus is associated with down-regulation of several nearby genes including the proximal gene TRPC6, a transient receptor Ca2+-channel involved in T-cell activation, among other functions. The shared risk haplotype in the second locus overlaps the vesicle transport and release gene STX8. Carrying the shared risk haplotype is associated with gene expression changes of 100 genes enriched for pathways involved in immune cell activation. Thus, the predisposing germ-line mutations in B-cell lymphoma and hemangiosarcoma appear to be regulatory, and affect pathways involved in T-cell mediated immune response in the tumor. This suggests that the interaction between the immune system and malignant cells plays a common role in the tumorigenesis of these relatively different cancers.
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http://dx.doi.org/10.1371/journal.pgen.1004922DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4333733PMC
February 2015

Comparative analysis of the transcriptome across distant species.

Nature 2014 Aug;512(7515):445-8

Functional Genomics, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.

The transcriptome is the readout of the genome. Identifying common features in it across distant species can reveal fundamental principles. To this end, the ENCODE and modENCODE consortia have generated large amounts of matched RNA-sequencing data for human, worm and fly. Uniform processing and comprehensive annotation of these data allow comparison across metazoan phyla, extending beyond earlier within-phylum transcriptome comparisons and revealing ancient, conserved features. Specifically, we discover co-expression modules shared across animals, many of which are enriched in developmental genes. Moreover, we use expression patterns to align the stages in worm and fly development and find a novel pairing between worm embryo and fly pupae, in addition to the embryo-to-embryo and larvae-to-larvae pairings. Furthermore, we find that the extent of non-canonical, non-coding transcription is similar in each organism, per base pair. Finally, we find in all three organisms that the gene-expression levels, both coding and non-coding, can be quantitatively predicted from chromatin features at the promoter using a 'universal model' based on a single set of organism-independent parameters.
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http://dx.doi.org/10.1038/nature13424DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4155737PMC
August 2014

Genome-wide analyses implicate 33 loci in heritable dog osteosarcoma, including regulatory variants near CDKN2A/B.

Genome Biol 2013 Dec 12;14(12):R132. Epub 2013 Dec 12.

Background: Canine osteosarcoma is clinically nearly identical to the human disease, but is common and highly heritable, making genetic dissection feasible.

Results: Through genome-wide association analyses in three breeds (greyhounds, Rottweilers, and Irish wolfhounds), we identify 33 inherited risk loci explaining 55% to 85% of phenotype variance in each breed. The greyhound locus exhibiting the strongest association, located 150 kilobases upstream of the genes CDKN2A/B, is also the most rearranged locus in canine osteosarcoma tumors. The top germline candidate variant is found at a >90% frequency in Rottweilers and Irish wolfhounds, and alters an evolutionarily constrained element that we show has strong enhancer activity in human osteosarcoma cells. In all three breeds, osteosarcoma-associated loci and regions of reduced heterozygosity are enriched for genes in pathways connected to bone differentiation and growth. Several pathways, including one of genes regulated by miR124, are also enriched for somatic copy-number changes in tumors.

Conclusions: Mapping a complex cancer in multiple dog breeds reveals a polygenic spectrum of germline risk factors pointing to specific pathways as drivers of disease.
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http://dx.doi.org/10.1186/gb-2013-14-12-r132DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4053774PMC
December 2013

GENCODE: the reference human genome annotation for The ENCODE Project.

Genome Res 2012 Sep;22(9):1760-74

Wellcome Trust Sanger Institute, Wellcome Trust Campus, Hinxton, Cambridge CB10 1SA, United Kingdom.

The GENCODE Consortium aims to identify all gene features in the human genome using a combination of computational analysis, manual annotation, and experimental validation. Since the first public release of this annotation data set, few new protein-coding loci have been added, yet the number of alternative splicing transcripts annotated has steadily increased. The GENCODE 7 release contains 20,687 protein-coding and 9640 long noncoding RNA loci and has 33,977 coding transcripts not represented in UCSC genes and RefSeq. It also has the most comprehensive annotation of long noncoding RNA (lncRNA) loci publicly available with the predominant transcript form consisting of two exons. We have examined the completeness of the transcript annotation and found that 35% of transcriptional start sites are supported by CAGE clusters and 62% of protein-coding genes have annotated polyA sites. Over one-third of GENCODE protein-coding genes are supported by peptide hits derived from mass spectrometry spectra submitted to Peptide Atlas. New models derived from the Illumina Body Map 2.0 RNA-seq data identify 3689 new loci not currently in GENCODE, of which 3127 consist of two exon models indicating that they are possibly unannotated long noncoding loci. GENCODE 7 is publicly available from gencodegenes.org and via the Ensembl and UCSC Genome Browsers.
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http://dx.doi.org/10.1101/gr.135350.111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3431492PMC
September 2012

Combining RT-PCR-seq and RNA-seq to catalog all genic elements encoded in the human genome.

Genome Res 2012 Sep;22(9):1698-710

Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland.

Within the ENCODE Consortium, GENCODE aimed to accurately annotate all protein-coding genes, pseudogenes, and noncoding transcribed loci in the human genome through manual curation and computational methods. Annotated transcript structures were assessed, and less well-supported loci were systematically, experimentally validated. Predicted exon-exon junctions were evaluated by RT-PCR amplification followed by highly multiplexed sequencing readout, a method we called RT-PCR-seq. Seventy-nine percent of all assessed junctions are confirmed by this evaluation procedure, demonstrating the high quality of the GENCODE gene set. RT-PCR-seq was also efficient to screen gene models predicted using the Human Body Map (HBM) RNA-seq data. We validated 73% of these predictions, thus confirming 1168 novel genes, mostly noncoding, which will further complement the GENCODE annotation. Our novel experimental validation pipeline is extremely sensitive, far more than unbiased transcriptome profiling through RNA sequencing, which is becoming the norm. For example, exon-exon junctions unique to GENCODE annotated transcripts are five times more likely to be corroborated with our targeted approach than with extensive large human transcriptome profiling. Data sets such as the HBM and ENCODE RNA-seq data fail sampling of low-expressed transcripts. Our RT-PCR-seq targeted approach also has the advantage of identifying novel exons of known genes, as we discovered unannotated exons in ~11% of assessed introns. We thus estimate that at least 18% of known loci have yet-unannotated exons. Our work demonstrates that the cataloging of all of the genic elements encoded in the human genome will necessitate a coordinated effort between unbiased and targeted approaches, like RNA-seq and RT-PCR-seq.
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http://dx.doi.org/10.1101/gr.134478.111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3431487PMC
September 2012

Landscape of transcription in human cells.

Nature 2012 Sep;489(7414):101-8

Centre for Genomic Regulation and UPF, Doctor Aiguader 88, Barcelona 08003, Catalonia, Spain.

Eukaryotic cells make many types of primary and processed RNAs that are found either in specific subcellular compartments or throughout the cells. A complete catalogue of these RNAs is not yet available and their characteristic subcellular localizations are also poorly understood. Because RNA represents the direct output of the genetic information encoded by genomes and a significant proportion of a cell's regulatory capabilities are focused on its synthesis, processing, transport, modification and translation, the generation of such a catalogue is crucial for understanding genome function. Here we report evidence that three-quarters of the human genome is capable of being transcribed, as well as observations about the range and levels of expression, localization, processing fates, regulatory regions and modifications of almost all currently annotated and thousands of previously unannotated RNAs. These observations, taken together, prompt a redefinition of the concept of a gene.
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http://dx.doi.org/10.1038/nature11233DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3684276PMC
September 2012

The GENCODE pseudogene resource.

Genome Biol 2012 Sep 26;13(9):R51. Epub 2012 Sep 26.

Program in Computational Biology and Bioinformatics, Yale University, New Haven, CT 06520, USA.

Background: Pseudogenes have long been considered as nonfunctional genomic sequences. However, recent evidence suggests that many of them might have some form of biological activity, and the possibility of functionality has increased interest in their accurate annotation and integration with functional genomics data.

Results: As part of the GENCODE annotation of the human genome, we present the first genome-wide pseudogene assignment for protein-coding genes, based on both large-scale manual annotation and in silico pipelines. A key aspect of this coupled approach is that it allows us to identify pseudogenes in an unbiased fashion as well as untangle complex events through manual evaluation. We integrate the pseudogene annotations with the extensive ENCODE functional genomics information. In particular, we determine the expression level, transcription-factor and RNA polymerase II binding, and chromatin marks associated with each pseudogene. Based on their distribution, we develop simple statistical models for each type of activity, which we validate with large-scale RT-PCR-Seq experiments. Finally, we compare our pseudogenes with conservation and variation data from primate alignments and the 1000 Genomes project, producing lists of pseudogenes potentially under selection.

Conclusions: At one extreme, some pseudogenes possess conventional characteristics of functionality; these may represent genes that have recently died. On the other hand, we find interesting patterns of partial activity, which may suggest that dead genes are being resurrected as functioning non-coding RNAs. The activity data of each pseudogene are stored in an associated resource, psiDR, which will be useful for the initial identification of potentially functional pseudogenes.
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http://dx.doi.org/10.1186/gb-2012-13-9-r51DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491395PMC
September 2012

Evidence for transcript networks composed of chimeric RNAs in human cells.

PLoS One 2012 4;7(1):e28213. Epub 2012 Jan 4.

Bioinformatics and Genomics, Centre for Genomic Regulation and Universitat Pompeu Fabra, Barcelona, Catalonia, Spain.

The classic organization of a gene structure has followed the Jacob and Monod bacterial gene model proposed more than 50 years ago. Since then, empirical determinations of the complexity of the transcriptomes found in yeast to human has blurred the definition and physical boundaries of genes. Using multiple analysis approaches we have characterized individual gene boundaries mapping on human chromosomes 21 and 22. Analyses of the locations of the 5' and 3' transcriptional termini of 492 protein coding genes revealed that for 85% of these genes the boundaries extend beyond the current annotated termini, most often connecting with exons of transcripts from other well annotated genes. The biological and evolutionary importance of these chimeric transcripts is underscored by (1) the non-random interconnections of genes involved, (2) the greater phylogenetic depth of the genes involved in many chimeric interactions, (3) the coordination of the expression of connected genes and (4) the close in vivo and three dimensional proximity of the genomic regions being transcribed and contributing to parts of the chimeric RNAs. The non-random nature of the connection of the genes involved suggest that chimeric transcripts should not be studied in isolation, but together, as an RNA network.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0028213PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3251577PMC
May 2012

The origins, evolution, and functional potential of alternative splicing in vertebrates.

Mol Biol Evol 2011 Oct 6;28(10):2949-59. Epub 2011 May 6.

Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, UK.

Alternative splicing (AS) has the potential to greatly expand the functional repertoire of mammalian transcriptomes. However, few variant transcripts have been characterized functionally, making it difficult to assess the contribution of AS to the generation of phenotypic complexity and to study the evolution of splicing patterns. We have compared the AS of 309 protein-coding genes in the human ENCODE pilot regions against their mouse orthologs in unprecedented detail, utilizing traditional transcriptomic and RNAseq data. The conservation status of every transcript has been investigated, and each functionally categorized as coding (separated into coding sequence [CDS] or nonsense-mediated decay [NMD] linked) or noncoding. In total, 36.7% of human and 19.3% of mouse coding transcripts are species specific, and we observe a 3.6 times excess of human NMD transcripts compared with mouse; in contrast to previous studies, the majority of species-specific AS is unlinked to transposable elements. We observe one conserved CDS variant and one conserved NMD variant per 2.3 and 11.4 genes, respectively. Subsequently, we identify and characterize equivalent AS patterns for 22.9% of these CDS or NMD-linked events in nonmammalian vertebrate genomes, and our data indicate that functional NMD-linked AS is more widespread and ancient than previously thought. Furthermore, although we observe an association between conserved AS and elevated sequence conservation, as previously reported, we emphasize that 30% of conserved AS exons display sequence conservation below the average score for constitutive exons. In conclusion, we demonstrate the value of detailed comparative annotation in generating a comprehensive set of AS transcripts, increasing our understanding of AS evolution in vertebrates. Our data supports a model whereby the acquisition of functional AS has occurred throughout vertebrate evolution and is considered alongside amino acid change as a key mechanism in gene evolution.
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http://dx.doi.org/10.1093/molbev/msr127DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3176834PMC
October 2011

An atypical 7q11.23 deletion in a normal IQ Williams-Beuren syndrome patient.

Eur J Hum Genet 2010 Jan;18(1):33-8

Department of Pediatrics, University of Torino, Torino, Italy.

Williams-Beuren syndrome (WBS; OMIM no. 194050) is a multisystemic neurodevelopmental disorder caused by a hemizygous deletion of 1.55 Mb on chromosome 7q11.23 spanning 28 genes. Haploinsufficiency of the ELN gene was shown to be responsible for supravalvular aortic stenosis and generalized arteriopathy, whereas LIMK1, CLIP2, GTF2IRD1 and GTF2I genes were suggested to be linked to the specific cognitive profile and craniofacial features. These insights for genotype-phenotype correlations came from the molecular and clinical analysis of patients with atypical deletions and mice models. Here we report a patient showing mild WBS physical phenotype and normal IQ, who carries a shorter 1 Mb atypical deletion. This rearrangement does not include the GTF2IRD1 and GTF2I genes and only partially the BAZ1B gene. Our results are consistent with the hypothesis that hemizygosity of the GTF2IRD1 and GTF2I genes might be involved in the facial dysmorphisms and in the specific motor and cognitive deficits observed in WBS patients.
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http://dx.doi.org/10.1038/ejhg.2009.108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2987159PMC
January 2010

Infantile spasms is associated with deletion of the MAGI2 gene on chromosome 7q11.23-q21.11.

Am J Hum Genet 2008 Jul 19;83(1):106-11. Epub 2008 Jun 19.

Program in Genetics & Genomic Biology and The Centre for Applied Genomics, Hospital for Sick Children, Toronto, ON M5G 1L7, Canada.

Infantile spasms (IS) is the most severe and common form of epilepsy occurring in the first year of life. At least half of IS cases are idiopathic in origin, with others presumed to arise because of brain insult or malformation. Here, we identify a locus for IS by high-resolution mapping of 7q11.23-q21.1 interstitial deletions in patients. The breakpoints delineate a 500 kb interval within the MAGI2 gene (1.4 Mb in size) that is hemizygously disrupted in 15 of 16 participants with IS or childhood epilepsy, but remains intact in 11 of 12 participants with no seizure history. MAGI2 encodes the synaptic scaffolding protein membrane-associated guanylate kinase inverted-2 that interacts with Stargazin, a protein also associated with epilepsy in the stargazer mouse.
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http://dx.doi.org/10.1016/j.ajhg.2008.06.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2443840PMC
July 2008

Submicroscopic deletion in patients with Williams-Beuren syndrome influences expression levels of the nonhemizygous flanking genes.

Am J Hum Genet 2006 Aug 23;79(2):332-41. Epub 2006 Jun 23.

Center for Integrative Genomics, Genopode Building, University of Lausanne, Lausanne, Switzerland.

Genomic imbalance is a common cause of phenotypic abnormalities. We measured the relative expression level of genes that map within the microdeletion that causes Williams-Beuren syndrome and within its flanking regions. We found, unexpectedly, that not only hemizygous genes but also normal-copy neighboring genes show decreased relative levels of expression. Our results suggest that not only the aneuploid genes but also the flanking genes that map several megabases away from a genomic rearrangement should be considered possible contributors to the phenotypic variation in genomic disorders.
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http://dx.doi.org/10.1086/506371DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1559497PMC
August 2006

The subcellular localization of the ChoRE-binding protein, encoded by the Williams-Beuren syndrome critical region gene 14, is regulated by 14-3-3.

Hum Mol Genet 2004 Jul 26;13(14):1505-14. Epub 2004 May 26.

Department of Genetic Medicine and Development, University of Geneva Medical School, Switzerland.

The Williams-Beuren syndrome (WBS) is a contiguous gene syndrome caused by chromosomal rearrangements at chromosome band 7q11.23. Several endocrine phenotypes, in particular impaired glucose tolerance and silent diabetes, have been described for this clinically complex disorder. The WBSCR14 gene, one of the genes mapping to the WBS critical region, encodes a member of the basic-helix-loop-helix leucine zipper family of transcription factors, which dimerizes with the Max-like protein, Mlx. This heterodimeric complex binds and activates, in a glucose-dependent manner, carbohydrate response element (ChoRE) motifs in the promoter of lipogenic enzymes. We identified five novel WBSCR14-interacting proteins, four 14-3-3 isotypes and NIF3L1, which form a single polypeptide complex in mammalian cells. Phosphatase treatment abrogates the association between WBSCR14 and 14-3-3, as shown previously for multiple 14-3-3 interactors. WBSCR14 is exported actively from the nucleus through a CRM1-dependent mechanism. This translocation is contingent upon the ability to bind 14-3-3. Through this mechanism the 14-3-3 isotypes directly affect the WBSCR14:Mlx complexes, which activate the transcription of lipogenic genes.
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http://dx.doi.org/10.1093/hmg/ddh163DOI Listing
July 2004