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1.  Transmissive Nanohole Arrays for Massively-Parallel Optical Biosensing 
ACS Photonics  2014;1(3):241-245.
A high-throughput optical biosensing technique is proposed and demonstrated. This hybrid technique combines optical transmission of nanoholes with colorimetric silver staining. The size and spacing of the nanoholes are chosen so that individual nanoholes can be independently resolved in massive parallel using an ordinary transmission optical microscope, and, in place of determining a spectral shift, the brightness of each nanohole is recorded to greatly simplify the readout. Each nanohole then acts as an independent sensor, and the blocking of nanohole optical transmission by enzymatic silver staining defines the specific detection of a biological agent. Nearly 10000 nanoholes can be simultaneously monitored under the field of view of a typical microscope. As an initial proof of concept, biotinylated lysozyme (biotin-HEL) was used as a model analyte, giving a detection limit as low as 0.1 ng/mL.
doi:10.1021/ph400111u
PMCID: PMC4266487  PMID: 25530982
nanohole array; transmission optical microscope; immunoassay; biosensing; enzymatic silver staining; colorimetric detection
2.  Genetic association study of QT interval highlights role for calcium signaling pathways in myocardial repolarization 
Arking, Dan E. | Pulit, Sara L. | Crotti, Lia | van der Harst, Pim | Munroe, Patricia B. | Koopmann, Tamara T. | Sotoodehnia, Nona | Rossin, Elizabeth J. | Morley, Michael | Wang, Xinchen | Johnson, Andrew D. | Lundby, Alicia | Gudbjartsson, Daníel F. | Noseworthy, Peter A. | Eijgelsheim, Mark | Bradford, Yuki | Tarasov, Kirill V. | Dörr, Marcus | Müller-Nurasyid, Martina | Lahtinen, Annukka M. | Nolte, Ilja M. | Smith, Albert Vernon | Bis, Joshua C. | Isaacs, Aaron | Newhouse, Stephen J. | Evans, Daniel S. | Post, Wendy S. | Waggott, Daryl | Lyytikäinen, Leo-Pekka | Hicks, Andrew A. | Eisele, Lewin | Ellinghaus, David | Hayward, Caroline | Navarro, Pau | Ulivi, Sheila | Tanaka, Toshiko | Tester, David J. | Chatel, Stéphanie | Gustafsson, Stefan | Kumari, Meena | Morris, Richard W. | Naluai, Åsa T. | Padmanabhan, Sandosh | Kluttig, Alexander | Strohmer, Bernhard | Panayiotou, Andrie G. | Torres, Maria | Knoflach, Michael | Hubacek, Jaroslav A. | Slowikowski, Kamil | Raychaudhuri, Soumya | Kumar, Runjun D. | Harris, Tamara B. | Launer, Lenore J. | Shuldiner, Alan R. | Alonso, Alvaro | Bader, Joel S. | Ehret, Georg | Huang, Hailiang | Kao, W.H. Linda | Strait, James B. | Macfarlane, Peter W. | Brown, Morris | Caulfield, Mark J. | Samani, Nilesh J. | Kronenberg, Florian | Willeit, Johann | Smith, J. Gustav | Greiser, Karin H. | zu Schwabedissen, Henriette Meyer | Werdan, Karl | Carella, Massimo | Zelante, Leopoldo | Heckbert, Susan R. | Psaty, Bruce M. | Rotter, Jerome I. | Kolcic, Ivana | Polašek, Ozren | Wright, Alan F. | Griffin, Maura | Daly, Mark J. | Arnar, David O. | Hólm, Hilma | Thorsteinsdottir, Unnur | Denny, Joshua C. | Roden, Dan M. | Zuvich, Rebecca L. | Emilsson, Valur | Plump, Andrew S. | Larson, Martin G. | O'Donnell, Christopher J. | Yin, Xiaoyan | Bobbo, Marco | D'Adamo, Adamo P. | Iorio, Annamaria | Sinagra, Gianfranco | Carracedo, Angel | Cummings, Steven R. | Nalls, Michael A. | Jula, Antti | Kontula, Kimmo K. | Marjamaa, Annukka | Oikarinen, Lasse | Perola, Markus | Porthan, Kimmo | Erbel, Raimund | Hoffmann, Per | Jöckel, Karl-Heinz | Kälsch, Hagen | Nöthen, Markus M. | consortium, HRGEN | den Hoed, Marcel | Loos, Ruth J.F. | Thelle, Dag S. | Gieger, Christian | Meitinger, Thomas | Perz, Siegfried | Peters, Annette | Prucha, Hanna | Sinner, Moritz F. | Waldenberger, Melanie | de Boer, Rudolf A. | Franke, Lude | van der Vleuten, Pieter A. | Beckmann, Britt Maria | Martens, Eimo | Bardai, Abdennasser | Hofman, Nynke | Wilde, Arthur A.M. | Behr, Elijah R. | Dalageorgou, Chrysoula | Giudicessi, John R. | Medeiros-Domingo, Argelia | Barc, Julien | Kyndt, Florence | Probst, Vincent | Ghidoni, Alice | Insolia, Roberto | Hamilton, Robert M. | Scherer, Stephen W. | Brandimarto, Jeffrey | Margulies, Kenneth | Moravec, Christine E. | Fabiola Del, Greco M. | Fuchsberger, Christian | O'Connell, Jeffrey R. | Lee, Wai K. | Watt, Graham C.M. | Campbell, Harry | Wild, Sarah H. | El Mokhtari, Nour E. | Frey, Norbert | Asselbergs, Folkert W. | Leach, Irene Mateo | Navis, Gerjan | van den Berg, Maarten P. | van Veldhuisen, Dirk J. | Kellis, Manolis | Krijthe, Bouwe P. | Franco, Oscar H. | Hofman, Albert | Kors, Jan A. | Uitterlinden, André G. | Witteman, Jacqueline C.M. | Kedenko, Lyudmyla | Lamina, Claudia | Oostra, Ben A. | Abecasis, Gonçalo R. | Lakatta, Edward G. | Mulas, Antonella | Orrú, Marco | Schlessinger, David | Uda, Manuela | Markus, Marcello R.P. | Völker, Uwe | Snieder, Harold | Spector, Timothy D. | Ärnlöv, Johan | Lind, Lars | Sundström, Johan | Syvänen, Ann-Christine | Kivimaki, Mika | Kähönen, Mika | Mononen, Nina | Raitakari, Olli T. | Viikari, Jorma S. | Adamkova, Vera | Kiechl, Stefan | Brion, Maria | Nicolaides, Andrew N. | Paulweber, Bernhard | Haerting, Johannes | Dominiczak, Anna F. | Nyberg, Fredrik | Whincup, Peter H. | Hingorani, Aroon | Schott, Jean-Jacques | Bezzina, Connie R. | Ingelsson, Erik | Ferrucci, Luigi | Gasparini, Paolo | Wilson, James F. | Rudan, Igor | Franke, Andre | Mühleisen, Thomas W. | Pramstaller, Peter P. | Lehtimäki, Terho J. | Paterson, Andrew D. | Parsa, Afshin | Liu, Yongmei | van Duijn, Cornelia | Siscovick, David S. | Gudnason, Vilmundur | Jamshidi, Yalda | Salomaa, Veikko | Felix, Stephan B. | Sanna, Serena | Ritchie, Marylyn D. | Stricker, Bruno H. | Stefansson, Kari | Boyer, Laurie A. | Cappola, Thomas P. | Olsen, Jesper V. | Lage, Kasper | Schwartz, Peter J. | Kääb, Stefan | Chakravarti, Aravinda | Ackerman, Michael J. | Pfeufer, Arne | de Bakker, Paul I.W. | Newton-Cheh, Christopher
Nature genetics  2014;46(8):826-836.
The QT interval, an electrocardiographic measure reflecting myocardial repolarization, is a heritable trait. QT prolongation is a risk factor for ventricular arrhythmias and sudden cardiac death (SCD) and could indicate the presence of the potentially lethal Mendelian Long QT Syndrome (LQTS). Using a genome-wide association and replication study in up to 100,000 individuals we identified 35 common variant QT interval loci, that collectively explain ∼8-10% of QT variation and highlight the importance of calcium regulation in myocardial repolarization. Rare variant analysis of 6 novel QT loci in 298 unrelated LQTS probands identified coding variants not found in controls but of uncertain causality and therefore requiring validation. Several newly identified loci encode for proteins that physically interact with other recognized repolarization proteins. Our integration of common variant association, expression and orthogonal protein-protein interaction screens provides new insights into cardiac electrophysiology and identifies novel candidate genes for ventricular arrhythmias, LQTS,and SCD.
doi:10.1038/ng.3014
PMCID: PMC4124521  PMID: 24952745
genome-wide association study; QT interval; Long QT Syndrome; sudden cardiac death; myocardial repolarization; arrhythmias
3.  Genome-Wide Meta-Analysis of Myopia and Hyperopia Provides Evidence for Replication of 11 Loci 
PLoS ONE  2014;9(9):e107110.
Refractive error (RE) is a complex, multifactorial disorder characterized by a mismatch between the optical power of the eye and its axial length that causes object images to be focused off the retina. The two major subtypes of RE are myopia (nearsightedness) and hyperopia (farsightedness), which represent opposite ends of the distribution of the quantitative measure of spherical refraction. We performed a fixed effects meta-analysis of genome-wide association results of myopia and hyperopia from 9 studies of European-derived populations: AREDS, KORA, FES, OGP-Talana, MESA, RSI, RSII, RSIII and ERF. One genome-wide significant region was observed for myopia, corresponding to a previously identified myopia locus on 8q12 (p = 1.25×10−8), which has been reported by Kiefer et al. as significantly associated with myopia age at onset and Verhoeven et al. as significantly associated to mean spherical-equivalent (MSE) refractive error. We observed two genome-wide significant associations with hyperopia. These regions overlapped with loci on 15q14 (minimum p value = 9.11×10−11) and 8q12 (minimum p value 1.82×10−11) previously reported for MSE and myopia age at onset. We also used an intermarker linkage- disequilibrium-based method for calculating the effective number of tests in targeted regional replication analyses. We analyzed myopia (which represents the closest phenotype in our data to the one used by Kiefer et al.) and showed replication of 10 additional loci associated with myopia previously reported by Kiefer et al. This is the first replication of these loci using myopia as the trait under analysis. “Replication-level” association was also seen between hyperopia and 12 of Kiefer et al.'s published loci. For the loci that show evidence of association to both myopia and hyperopia, the estimated effect of the risk alleles were in opposite directions for the two traits. This suggests that these loci are important contributors to variation of refractive error across the distribution.
doi:10.1371/journal.pone.0107110
PMCID: PMC4169415  PMID: 25233373
4.  Comparative and Evolutionary Analysis of Major Peanut Allergen Gene Families 
Genome Biology and Evolution  2014;6(9):2468-2488.
Peanut (Arachis hypogaea L.) causes one of the most serious food allergies. Peanut seed proteins, Arah1, Arah2, and Arah3, are considered to be among the most important peanut allergens. To gain insights into genome organization and evolution of allergen-encoding genes, approximately 617 kb from the genome of cultivated peanut and 215 kb from a wild relative were sequenced including three Arah1, one Arah2, eight Arah3, and two Arah6 gene family members. To assign polarity to differences between homoeologous regions in peanut, we used as outgroups the single orthologous regions in Medicago, Lotus, common bean, chickpea, and pigeonpea, which diverged from peanut about 50 Ma and have not undergone subsequent polyploidy. These regions were also compared with orthologs in many additional dicot plant species to help clarify the timing of evolutionary events. The lack of conservation of allergenic epitopes between species, and the fact that many different proteins can be allergenic, makes the identification of allergens across species by comparative studies difficult. The peanut allergen genes are interspersed with low-copy genes and transposable elements. Phylogenetic analyses revealed lineage-specific expansion and loss of low-copy genes between species and homoeologs. Arah1 syntenic regions are conserved in soybean, pigeonpea, tomato, grape, Lotus, and Arabidopsis, whereas Arah3 syntenic regions show genome rearrangements. We infer that tandem and segmental duplications led to the establishment of the Arah3 gene family. Our analysis indicates differences in conserved motifs in allergen proteins and in the promoter regions of the allergen-encoding genes. Phylogenetic analysis and genomic organization studies provide new insights into the evolution of the major peanut allergen-encoding genes.
doi:10.1093/gbe/evu189
PMCID: PMC4202325  PMID: 25193311
Arachis hypogaea L.; allergens; gene synteny; genome organization; homologs; evolution
5.  Haptoglobin Genotype and the Rate of Renal Function Decline in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study 
Diabetes  2013;62(9):3218-3223.
Many patients with type 1 diabetes develop renal disease despite moderately good metabolic control, suggesting other risk factors may play a role. Recent evidence suggests that the haptoglobin (HP) 2-2 genotype, which codes for a protein with reduced antioxidant activity, may predict renal function decline in type 1 diabetes. We examined this hypothesis in 1,303 Caucasian participants in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study. HP genotype was determined by polyacrylamide gel electrophoresis. Glomerular filtration rate was estimated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and albumin excretion based on timed urine samples. Participants were followed up for a mean of 22 years. HP genotype was significantly associated with the development of sustained estimated glomerular filtration rate (GFR) <60 mL/min/1.73 m2 and with end-stage renal disease (ESRD), with HP 2-2 having greater risk than HP 2-1 and 1-1. No association was seen with albuminuria. Although there was no treatment group interaction, the associations were only significant in the conventional treatment group, where events rates were much higher. We conclude that the HP genotype is significantly associated with the development of reduced GFR and ESRD in the DCCT/EDIC study.
doi:10.2337/db13-0256
PMCID: PMC3749329  PMID: 23761102
6.  Germline Mutation of RPS20, Encoding a Ribosomal Protein, Causes Predisposition to Hereditary Nonpolyposis Colorectal Carcinoma Without DNA Mismatch Repair Deficiency 
Gastroenterology  2014;147(3):595-598.e5.
Little is known about the genetic factors that contribute to familial colorectal cancer type X (FCCX), characterized by hereditary nonpolyposis colorectal carcinoma with no mismatch repair defects. Genetic linkage analysis, exome sequencing, tumor studies, and functional investigations of 4 generations of a FCCX family led to the identification of a truncating germline mutation in RPS20, which encodes a component (S20) of the small ribosomal subunit and is a new colon cancer predisposition gene. The mutation was associated with a defect in pre–ribosomal RNA maturation. Our findings show that mutations in a gene encoding a ribosomal protein can predispose individuals to microsatellite-stable colon cancer. Evaluation of additional FCCX families for mutations in RPS20 and other ribosome-associated genes is warranted.
doi:10.1053/j.gastro.2014.06.009
PMCID: PMC4155505  PMID: 24941021
Colon Cancer; Hereditary Nonpolyposis Colorectal Cancer; Ribosome; Exome Sequencing; FCCX, hereditary nonpolyposis colorectal cancer type X; rRNA, ribosomal RNA
7.  The repetitive component of the A genome of peanut (Arachis hypogaea) and its role in remodelling intergenic sequence space since its evolutionary divergence from the B genome 
Annals of Botany  2013;112(3):545-559.
Background and Aims
Peanut (Arachis hypogaea) is an allotetraploid (AABB-type genome) of recent origin, with a genome of about 2·8 Gb and a high repetitive content. This study reports an analysis of the repetitive component of the peanut A genome using bacterial artificial chromosome (BAC) clones from A. duranensis, the most probable A genome donor, and the probable consequences of the activity of these elements since the divergence of the peanut A and B genomes.
Methods
The repetitive content of the A genome was analysed by using A. duranensis BAC clones as probes for fluorescence in situ hybridization (BAC-FISH), and by sequencing and characterization of 12 genomic regions. For the analysis of the evolutionary dynamics, two A genome regions are compared with their B genome homeologues.
Key Results
BAC-FISH using 27 A. duranensis BAC clones as probes gave dispersed and repetitive DNA characteristic signals, predominantly in interstitial regions of the peanut A chromosomes. The sequences of 14 BAC clones showed complete and truncated copies of ten abundant long terminal repeat (LTR) retrotransposons, characterized here. Almost all dateable transposition events occurred <3·5 million years ago, the estimated date of the divergence of A and B genomes. The most abundant retrotransposon is Feral, apparently parasitic on the retrotransposon FIDEL, followed by Pipa, also non-autonomous and probably parasitic on a retrotransposon we named Pipoka. The comparison of the A and B genome homeologous regions showed conserved segments of high sequence identity, punctuated by predominantly indel regions without significant similarity.
Conclusions
A substantial proportion of the highly repetitive component of the peanut A genome appears to be accounted for by relatively few LTR retrotransposons and their truncated copies or solo LTRs. The most abundant of the retrotransposons are non-autonomous. The activity of these retrotransposons has been a very significant driver of genome evolution since the evolutionary divergence of the A and B genomes.
doi:10.1093/aob/mct128
PMCID: PMC3718217  PMID: 23828319
Arachis hypogaea; A. duranensis; peanut; groundnut; BAC-FISH; BAC sequencing; retrotransposons; genome evolution; phylogeny; homeology
8.  Meta-analysis of genome-wide association studies in five cohorts reveals common variants in RBFOX1, a regulator of tissue-specific splicing, associated with refractive error 
Human Molecular Genetics  2013;22(13):2754-2764.
Visual refractive errors (REs) are complex genetic traits with a largely unknown etiology. To date, genome-wide association studies (GWASs) of moderate size have identified several novel risk markers for RE, measured here as mean spherical equivalent (MSE). We performed a GWAS using a total of 7280 samples from five cohorts: the Age-Related Eye Disease Study (AREDS); the KORA study (‘Cooperative Health Research in the Region of Augsburg’); the Framingham Eye Study (FES); the Ogliastra Genetic Park-Talana (OGP-Talana) Study and the Multiethnic Study of Atherosclerosis (MESA). Genotyping was performed on Illumina and Affymetrix platforms with additional markers imputed to the HapMap II reference panel. We identified a new genome-wide significant locus on chromosome 16 (rs10500355, P = 3.9 × 10−9) in a combined discovery and replication set (26 953 samples). This single nucleotide polymorphism (SNP) is located within the RBFOX1 gene which is a neuron-specific splicing factor regulating a wide range of alternative splicing events implicated in neuronal development and maturation, including transcription factors, other splicing factors and synaptic proteins.
doi:10.1093/hmg/ddt116
PMCID: PMC3674806  PMID: 23474815
9.  Building the sugarcane genome for biotechnology and identifying evolutionary trends 
BMC Genomics  2014;15(1):540.
Background
Sugarcane is the source of sugar in all tropical and subtropical countries and is becoming increasingly important for bio-based fuels. However, its large (10 Gb), polyploid, complex genome has hindered genome based breeding efforts. Here we release the largest and most diverse set of sugarcane genome sequences to date, as part of an on-going initiative to provide a sugarcane genomic information resource, with the ultimate goal of producing a gold standard genome.
Results
Three hundred and seventeen chiefly euchromatic BACs were sequenced. A reference set of one thousand four hundred manually-annotated protein-coding genes was generated. A small RNA collection and a RNA-seq library were used to explore expression patterns and the sRNA landscape. In the sucrose and starch metabolism pathway, 16 non-redundant enzyme-encoding genes were identified. One of the sucrose pathway genes, sucrose-6-phosphate phosphohydrolase, is duplicated in sugarcane and sorghum, but not in rice and maize. A diversity analysis of the s6pp duplication region revealed haplotype-structured sequence composition. Examination of hom(e)ologous loci indicate both sequence structural and sRNA landscape variation. A synteny analysis shows that the sugarcane genome has expanded relative to the sorghum genome, largely due to the presence of transposable elements and uncharacterized intergenic and intronic sequences.
Conclusion
This release of sugarcane genomic sequences will advance our understanding of sugarcane genetics and contribute to the development of molecular tools for breeding purposes and gene discovery.
Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-540) contains supplementary material, which is available to authorized users.
doi:10.1186/1471-2164-15-540
PMCID: PMC4122759  PMID: 24984568
Saccharum; Bacterial artificial chromosome sequencing; Polyploidy; Genome; Genetics; Grasses
10.  Biofuel and energy crops: high-yield Saccharinae take center stage in the post-genomics era 
Genome Biology  2013;14(6):210.
The Saccharinae, especially sugarcane, Miscanthus and sorghum, present remarkable characteristics for bioenergy production. Biotechnology of these plants will be important for a sustainable feedstock supply. Herein, we review knowledge useful for their improvement and synergies gained by their parallel study.
doi:10.1186/gb-2013-14-6-210
PMCID: PMC3707038  PMID: 23805917
11.  GWAS identifies an NAT2 acetylator status tag single nucleotide polymorphism to be a major locus for skin fluorescence 
Diabetologia  2014;57(8):1623-1634.
Aims/hypothesis
Skin fluorescence (SF) is a non-invasive marker of AGEs and is associated with the long-term complications of diabetes. SF increases with age and is also greater among individuals with diabetes. A familial correlation of SF suggests that genetics may play a role. We therefore performed parallel genome-wide association studies of SF in two cohorts.
Methods
Cohort 1 included 1,082 participants, 35–67 years of age with type 1 diabetes. Cohort 2 included 8,721 participants without diabetes, aged 18–90 years.
Results
rs1495741 was significantly associated with SF in Cohort 1 (p < 6 × 10−10), which is known to tag the NAT2 acetylator phenotype. The fast acetylator genotype was associated with lower SF, explaining up to 15% of the variance. In Cohort 2, the top signal associated with SF (p = 8.3 × 10−42) was rs4921914, also in NAT2, 440 bases upstream of rs1495741 (linkage disequilibrium r2 = 1.0 for rs4921914 with rs1495741). We replicated these results in two additional cohorts, one with and one without type 1 diabetes. Finally, to understand which compounds are contributing to the NAT2–SF signal, we examined 11 compounds assayed from skin biopsies (n = 198): the fast acetylator genotype was associated with lower levels of the AGEs hydroimidazolones of glyoxal (p = 0.017).
Conclusions/interpretation
We identified a robust association between NAT2 and SF in people with and without diabetes. Our findings provide proof of principle that genetic variation contributes to interindividual SF and that NAT2 acetylation status plays a major role.
Electronic supplementary material
The online version of this article (doi:10.1007/s00125-014-3286-9) contains peer-reviewed but unedited supplementary material, which is available to authorised users.
doi:10.1007/s00125-014-3286-9
PMCID: PMC4079945  PMID: 24934506
Acetylation; Genome-wide association study; NAT2; Skin autofluorescence; Skin fluorescence; Skin intrinsic fluorescence
12.  Using a Bayesian latent variable approach to detect pleiotropy in the Genetic Analysis Workshop 18 data 
BMC Proceedings  2014;8(Suppl 1):S77.
Pleiotropy, which occurs when a single genetic factor influences multiple phenotypes, is present in many genetic studies of complex human traits. Longitudinal family data, such as the Genetic Analysis Workshop 18 data, combine the features of longitudinal studies in individuals and cross-sectional studies in families, thus providing richer information about the genetic and environmental factors associated with the trait of interest. We recently proposed a Bayesian latent variable methodology for the study of pleiotropy, in the presence of longitudinal and family correlation. The purpose of this work is to evaluate the Bayesian latent variable method in a real data setting using the Genetic Analysis Workshop 18 blood pressure phenotypes and sequenced genotype data. To detect single-nucleotide polymorphisms with pleiotropic effect on both diastolic and systolic blood pressure, we focused on a set of 6 single-nucleotide polymorphisms from chromosome 3 that was reported in the literature to be significantly associated with either diastolic blood pressure or the binary hypertension trait. Our analysis suggests that both diastolic blood pressure and systolic blood pressure are associated with the latent hypertension severity variable, but the analysis did not find any of the 6 single-nucleotide polymorphisms to have statistically significant pleiotropic effect on both diastolic blood pressure and systolic blood pressure.
doi:10.1186/1753-6561-8-S1-S77
PMCID: PMC4143687  PMID: 25519405
13.  Evaluation of gene-based association tests for analyzing rare variants using Genetic Analysis Workshop 18 data 
BMC Proceedings  2014;8(Suppl 1):S9.
The focus of our work is to evaluate several recently developed pooled association tests for rare variants and assess the impact of different gene annotation methods and binning strategies on the analyses of rare variants under Genetic Analysis Workshop 18 real and simulated data settings. We considered the sample of 103 unrelated individuals with sequence data, genotypes of rare variants from chromosome 3, real phenotype of hypertension status and simulated phenotypes of systolic blood pressure (SBP) and diastolic blood pressure (DBP), and covariates of age, sex, and the interaction between age and sex. In the analysis of real phenotype data, we did not obtain significant results for any binning strategy; however, we observed a slight deviation of the p-values from the uniform distribution based on the protein-damaging variant grouping strategy. Evaluation of methods using simulated data showed lack of power even at the conservative level of 0.05 for most of the causal genes on chromosome 3. Nevertheless, analysis of MAP4 produced good power for all tests at various levels of the tests for both DBP and SBP. Our results also confirmed that Fisher's method is not only robust but can also improve power over individual pooled linear and quadratic tests and is often better than other robust tests such as SKAT-O.
doi:10.1186/1753-6561-8-S1-S9
PMCID: PMC4143759  PMID: 25519417
14.  Dynamic pathway analysis of genes associated with blood pressure using whole genome sequence data 
BMC Proceedings  2014;8(Suppl 1):S106.
Groups of genes assigned to a pathway, also called a module, have similar functions. Finding such modules, and the topology of the changes of the modules over time, is a fundamental problem in understanding the mechanisms of complex diseases. Here we investigated an approach that categorized variants into rare or common and used a hierarchical model to jointly estimate the group effects of the variants in a pathway for identifying enriched pathways over time using whole genome sequencing data and blood pressure data. Our results suggest that the method can identify potentially biologically meaningful genes in modules associated with blood pressure over time.
doi:10.1186/1753-6561-8-S1-S106
PMCID: PMC4143637  PMID: 25519360
15.  Genetic Analysis Workshop 18 single-nucleotide variant prioritization based on protein impact, sequence conservation, and gene annotation 
BMC Proceedings  2014;8(Suppl 1):S11.
Grouping variants based on gene mapping can augment the power of rare variant association tests. Weighting or sorting variants based on their expected functional impact can provide additional benefit. We defined groups of prioritized variants based on systematic annotation of Genetic Analysis Workshop 18 (GAW18) single-nucleotide variants; we focused on variants detected by whole genome sequencing, specifically on the high-quality subset presented in the genotype files. First, we divided variants between coding and noncoding. Coding variants are fewer than 1% of the total and are more likely to have a biological effect than noncoding variants. Coding variants were further stratified into protein changing and protein damaging groups based on the effect on protein amino acid sequence. In particular, missense variants predicted to be damaging, splice-site alterations, and stop gains were assigned to the protein damaging category. Impact of noncoding variants is more difficult to predict. We decided to rely uniquely on conservation: we combined (a) the mammalian phastCons Conserved Element and (b) the PhyloP score, which identify conserved intervals and the single-nucleotide position, respectively. This reduced the noncoding variants to a number comparable to coding variants. Finally, using gene structure definition from the widely used RefSeq database, we mapped variants to genes to support association tests that require collapsing rare variants to genes. Companion GAW18 papers used these variant priority groups and gene mapping; one of these paper specifically found evidence of stronger association signal for protein damaging variants.
doi:10.1186/1753-6561-8-S1-S11
PMCID: PMC4143669  PMID: 25519362
16.  Transcriptome and methylome profiling reveals relics of genome dominance in the mesopolyploid Brassica oleracea 
Genome Biology  2014;15(6):R77.
Background
Brassica oleracea is a valuable vegetable species that has contributed to human health and nutrition for hundreds of years and comprises multiple distinct cultivar groups with diverse morphological and phytochemical attributes. In addition to this phenotypic wealth, B. oleracea offers unique insights into polyploid evolution, as it results from multiple ancestral polyploidy events and a final Brassiceae-specific triplication event. Further, B. oleracea represents one of the diploid genomes that formed the economically important allopolyploid oilseed, Brassica napus. A deeper understanding of B. oleracea genome architecture provides a foundation for crop improvement strategies throughout the Brassica genus.
Results
We generate an assembly representing 75% of the predicted B. oleracea genome using a hybrid Illumina/Roche 454 approach. Two dense genetic maps are generated to anchor almost 92% of the assembled scaffolds to nine pseudo-chromosomes. Over 50,000 genes are annotated and 40% of the genome predicted to be repetitive, thus contributing to the increased genome size of B. oleracea compared to its close relative B. rapa. A snapshot of both the leaf transcriptome and methylome allows comparisons to be made across the triplicated sub-genomes, which resulted from the most recent Brassiceae-specific polyploidy event.
Conclusions
Differential expression of the triplicated syntelogs and cytosine methylation levels across the sub-genomes suggest residual marks of the genome dominance that led to the current genome architecture. Although cytosine methylation does not correlate with individual gene dominance, the independent methylation patterns of triplicated copies suggest epigenetic mechanisms play a role in the functional diversification of duplicate genes.
doi:10.1186/gb-2014-15-6-r77
PMCID: PMC4097860  PMID: 24916971
17.  Sequencing of transcriptomes from two Miscanthus species reveals functional specificity in rhizomes, and clarifies evolutionary relationships 
BMC Plant Biology  2014;14:134.
Background
Miscanthus is a promising biomass crop for temperate regions. Despite the increasing interest in this plant, limited sequence information has constrained research into its biology, physiology, and breeding. The whole genome transcriptomes of M. sinensis and M. sacchariflorus presented in this study may provide good resources to understand functional compositions of two important Miscanthus genomes and their evolutionary relationships.
Results
For M. sinensis, a total of 457,891 and 512,950 expressed sequence tags (ESTs) were produced from leaf and rhizome tissues, respectively, which were assembled into 12,166 contigs and 89,648 singletons for leaf, and 13,170 contigs and 112,138 singletons for rhizome. For M. sacchariflorus, a total of 288,806 and 267,952 ESTs from leaf and rhizome tissues, respectively, were assembled into 8,732 contigs and 66,881 singletons for leaf, and 8,104 contigs and 63,212 singletons for rhizome. Based on the distributions of synonymous nucleotide substitution (Ks), sorghum and Miscanthus diverged about 6.2 million years ago (MYA), Saccharum and Miscanthus diverged 4.6 MYA, and M. sinensis and M. sacchariflorus diverged 1.5 MYA. The pairwise alignment of predicted protein sequences from sorghum-Miscanthus and two Miscanthus species found a total of 43,770 and 35,818 nsSNPs, respectively. The impacts of striking mutations found by nsSNPs were much lower between sorghum and Miscanthus than those between the two Miscanthus species, perhaps as a consequence of the much higher level of gene duplication in Miscanthus and resulting ability to buffer essential functions against disturbance.
Conclusions
The ESTs generated in the present study represent a significant addition to Miscanthus functional genomics resources, permitting us to discover some candidate genes associated with enhanced biomass production. Ks distributions based on orthologous ESTs may serve as a guideline for future research into the evolution of Miscanthus species as well as its close relatives sorghum and Saccharum.
doi:10.1186/1471-2229-14-134
PMCID: PMC4046999  PMID: 24884969
Miscanthus sinensis; Miscanthus sacchariflorus; Expressed sequence tags; Synonymous substitution; Orthologous sequences; Nonsynonymous SNPs
18.  A Novel Susceptibility Locus on Rat Chromosome 8 Affects Spontaneous but Not Experimentally Induced Type 1 Diabetes 
Diabetes  2007;56(6):1731-1736.
OBJECTIVE
The biobreeding diabetes-prone (BBDP) rat spontaneously develops type 1 diabetes. Two of the genetic factors contributing to this syndrome are the major histocompatibility complex (Iddm1) and a Gimap5 mutation (Iddm2) responsible for a T-lymphopenia. Susceptibility to experimentally induced type 1 diabetes is widespread among nonlymphopenic (wild-type Iddm2) rat strains provided they share the BBDP Iddm1 allele. The question follows as to whether spontaneous and experimentally induced type 1 diabetes share susceptibility loci besides Iddm1. Our objectives were to map a novel, serendipitously discovered Iddm locus, confirm its effects by developing congenic sublines, and assess its differential contribution to spontaneous and experimentally induced type 1 diabetes.
RESEARCH DESIGN AND METHODS
An unexpected reduction in spontaneous type 1 diabetes incidence (86 to 31%, P < 0.0001) was observed in a BBDP line congenic for a Wistar Furth–derived allotypic marker, RT7 (chromosome 13). Genome-wide analysis revealed that, besides the RT7 locus, a Wistar Furth chromosome 8 fragment had also been introduced. The contribution of these intervals to diabetes resistance was assessed through linkage analysis using 134 F2 (BBDP × double congenic line) animals and a panel of congenic sublines. One of these sublines, resistant to spontaneous type 1 diabetes, was tested for susceptibility to experimentally induced type 1 diabetes.
RESULTS
Both linkage analysis and congenic sublines mapped a novel locus (Iddm24) to the telomeric 10.34 Mb of chromosome 8, influencing cumulative incidence and age of onset of spontaneous type 1 diabetes but not insulitis nor experimentally induced type 1 diabetes.
CONCLUSIONS
This study has identified a type 1 diabetes susceptibility locus that appears to act after the development of insulitis and that regulates spontaneous type 1 diabetes exclusively.
doi:10.2337/db06-1790
PMCID: PMC3987115  PMID: 17389329
19.  SNPhylo: a pipeline to construct a phylogenetic tree from huge SNP data 
BMC Genomics  2014;15:162.
Background
Phylogenetic trees are widely used for genetic and evolutionary studies in various organisms. Advanced sequencing technology has dramatically enriched data available for constructing phylogenetic trees based on single nucleotide polymorphisms (SNPs). However, massive SNP data makes it difficult to perform reliable analysis, and there has been no ready-to-use pipeline to generate phylogenetic trees from these data.
Results
We developed a new pipeline, SNPhylo, to construct phylogenetic trees based on large SNP datasets. The pipeline may enable users to construct a phylogenetic tree from three representative SNP data file formats. In addition, in order to increase reliability of a tree, the pipeline has steps such as removing low quality data and considering linkage disequilibrium. A maximum likelihood method for the inference of phylogeny is also adopted in generation of a tree in our pipeline.
Conclusions
Using SNPhylo, users can easily produce a reliable phylogenetic tree from a large SNP data file. Thus, this pipeline can help a researcher focus more on interpretation of the results of analysis of voluminous data sets, rather than manipulations necessary to accomplish the analysis.
doi:10.1186/1471-2164-15-162
PMCID: PMC3945939  PMID: 24571581
Polymorphisms; Linkage disequilibrium; Maximum likelihood
20.  Ancient Gene Duplicates in Gossypium (Cotton) Exhibit Near-Complete Expression Divergence 
Genome Biology and Evolution  2014;6(3):559-571.
Whole genome duplication (WGD) is widespread in flowering plants and is a driving force in angiosperm diversification. The redundancy introduced by WGD allows the evolution of novel gene interactions and functions, although the patterns and processes of diversification are poorly understood. We identified ∼2,000 pairs of paralogous genes in Gossypium raimondii (cotton) resulting from an approximately 60 My old 5- to 6-fold ploidy increase. Gene expression analyses revealed that, in G. raimondii, 99.4% of the gene pairs exhibit differential expression in at least one of the three tissues (petal, leaf, and seed), with 93% to 94% exhibiting differential expression on a per-tissue basis. For 1,666 (85%) pairs, differential expression was observed in all tissues. These observations were mirrored in a time series of G. raimondii seed, and separately in leaf, petal, and seed of G. arboreum, indicating expression level diversification before species divergence. A generalized linear model revealed 92.4% of the paralog pairs exhibited expression divergence, with most exhibiting significant gene and tissue interactions indicating complementary expression patterns in different tissues. These data indicate massive, near-complete expression level neo- and/or subfunctionalization among ancient gene duplicates, suggesting these processes are essential in their maintenance over ∼60 Ma.
doi:10.1093/gbe/evu037
PMCID: PMC3971588  PMID: 24558256
21.  ADCK4 mutations promote steroid-resistant nephrotic syndrome through CoQ10 biosynthesis disruption  
The Journal of Clinical Investigation  2013;123(12):5179-5189.
Identification of single-gene causes of steroid-resistant nephrotic syndrome (SRNS) has furthered the understanding of the pathogenesis of this disease. Here, using a combination of homozygosity mapping and whole human exome resequencing, we identified mutations in the aarF domain containing kinase 4 (ADCK4) gene in 15 individuals with SRNS from 8 unrelated families. ADCK4 was highly similar to ADCK3, which has been shown to participate in coenzyme Q10 (CoQ10) biosynthesis. Mutations in ADCK4 resulted in reduced CoQ10 levels and reduced mitochondrial respiratory enzyme activity in cells isolated from individuals with SRNS and transformed lymphoblasts. Knockdown of adck4 in zebrafish and Drosophila recapitulated nephrotic syndrome-associated phenotypes. Furthermore, ADCK4 was expressed in glomerular podocytes and partially localized to podocyte mitochondria and foot processes in rat kidneys and cultured human podocytes. In human podocytes, ADCK4 interacted with members of the CoQ10 biosynthesis pathway, including COQ6, which has been linked with SRNS and COQ7. Knockdown of ADCK4 in podocytes resulted in decreased migration, which was reversed by CoQ10 addition. Interestingly, a patient with SRNS with a homozygous ADCK4 frameshift mutation had partial remission following CoQ10 treatment. These data indicate that individuals with SRNS with mutations in ADCK4 or other genes that participate in CoQ10 biosynthesis may be treatable with CoQ10.
doi:10.1172/JCI69000
PMCID: PMC3859425  PMID: 24270420
22.  NADPH oxidase complex and IBD candidate gene studies: identification of a rare variant in NCF2 that results in reduced binding to RAC2 
Gut  2011;61(7):1028-1035.
Objective
The NOX2 NADPH oxidase complex produces reactive oxygen species and plays a critical role in the killing of microbes by phagocytes. Genetic mutations in genes encoding components of the complex result in both X-linked and autosomal recessive forms of chronic granulomatous disease (CGD). Patients with CGD often develop intestinal inflammation that is histologically similar to Crohn's colitis, suggesting a common aetiology for both diseases. The aim of this study is to determine if polymorphisms in NOX2 NADPH oxidase complex genes that do not cause CGD are associated with the development of inflammatory bowel disease (IBD).
Methods
Direct sequencing and candidate gene approaches were used to identify susceptibility loci in NADPH oxidase complex genes. Functional studies were carried out on identified variants. Novel findings were replicated in independent cohorts.
Results
Sequence analysis identified a novel missense variant in the neutrophil cytosolic factor 2 (NCF2) gene that is associated with very early onset IBD (VEO-IBD) and subsequently found in 4% of patients with VEO-IBD compared with 0.2% of controls (p=1.3×10−5, OR 23.8 (95% CI 3.9 to 142.5); Fisher exact test). This variant reduced binding of the NCF2 gene product p67phox to RAC2. This study found a novel genetic association of RAC2 with Crohn's disease (CD) and replicated the previously reported association of NCF4 with ileal CD.
Conclusion
These studies suggest that the rare novel p67phox variant results in partial inhibition of oxidase function and are associated with CD in a subgroup of patients with VEO-IBD; and suggest that components of the NADPH oxidase complex are associated with CD.
doi:10.1136/gutjnl-2011-300078
PMCID: PMC3806486  PMID: 21900546
23.  A Whole-Genome DNA Marker Map for Cotton Based on the D-Genome Sequence of Gossypium raimondii L. 
G3: Genes|Genomes|Genetics  2013;3(10):1759-1767.
We constructed a very-high-density, whole-genome marker map (WGMM) for cotton by using 18,597 DNA markers corresponding to 48,958 loci that were aligned to both a consensus genetic map and a reference genome sequence. The WGMM has a density of one locus per 15.6 kb, or an average of 1.3 loci per gene. The WGMM was anchored by the use of colinear markers to a detailed genetic map, providing recombinational information. Mapped markers occurred at relatively greater physical densities in distal chromosomal regions and lower physical densities in the central regions, with all 1 Mb bins having at least nine markers. Hotspots for quantitative trait loci and resistance gene analog clusters were aligned to the map and DNA markers identified for targeting of these regions of high practical importance. Based on the cotton D genome reference sequence, the locations of chromosome structural rearrangements plotted on the map facilitate its translation to other Gossypium genome types. The WGMM is a versatile genetic map for marker assisted breeding, fine mapping and cloning of genes and quantitative trait loci, developing new genetic markers and maps, genome-wide association mapping, and genome evolution studies.
doi:10.1534/g3.113.006890
PMCID: PMC3789800  PMID: 23979945
quantitative trait loci; resistance gene analog; simple sequence repeat; restriction fragment length polymorphism; inversions
24.  Different patterns of gene structure divergence following gene duplication in Arabidopsis 
BMC Genomics  2013;14:652.
Background
Divergence in gene structure following gene duplication is not well understood. Gene duplication can occur via whole-genome duplication (WGD) and single-gene duplications including tandem, proximal and transposed duplications. Different modes of gene duplication may be associated with different types, levels, and patterns of structural divergence.
Results
In Arabidopsis thaliana, we denote levels of structural divergence between duplicated genes by differences in coding-region lengths and average exon lengths, and the number of insertions/deletions (indels) and maximum indel length in their protein sequence alignment. Among recent duplicates of different modes, transposed duplicates diverge most dramatically in gene structure. In transposed duplications, parental loci tend to have longer coding-regions and exons, and smaller numbers of indels and maximum indel lengths than transposed loci, reflecting biased structural changes in transposed duplications. Structural divergence increases with evolutionary time for WGDs, but not transposed duplications, possibly because of biased gene losses following transposed duplications. Structural divergence has heterogeneous relationships with nucleotide substitution rates, but is consistently positively correlated with gene expression divergence. The NBS-LRR gene family shows higher-than-average levels of structural divergence.
Conclusions
Our study suggests that structural divergence between duplicated genes is greatly affected by the mechanisms of gene duplication and may be not proportional to evolutionary time, and that certain gene families are under selection on rapid evolution of gene structure.
doi:10.1186/1471-2164-14-652
PMCID: PMC3848917  PMID: 24063813
Gene structure; Divergence; Transposed duplication; Whole-genome duplication; Selection; Arabidopsis
25.  Pilot Genome Wide Association Search Identifies Potential loci for Risk of Erectile Dysfunction in Type 1 Diabetes Using the DCCT/EDIC Study Cohort 
The Journal of urology  2012;188(2):514-520.
Purpose
To identify genetic predictors of diabetes-associated ED using genome wide and candidate gene approaches in a cohort of men with type I diabetes.
Methods
We examined 528 white men with T1D (125 with ED) from the DCCT and its observational follow up EDIC Study. ED was defined from a single item of the IIEF. An Illumina Human1M BeadChip was used for genotyping. 867,125 single nucleotide polymorphisms (SNPs) were subjected to analysis. Whole genome and candidate gene approaches tested the hypothesis that genetic polymorphisms may predispose men with T1D to ED. Univariate and multivariate models were used controlling for age, HbA1c, diabetes duration, and prior randomization to intensive or conventional insulin therapy during DCCT. A stratified false discovery rate was used to perform the candidate gene approach.
Results
Two SNPs located on chromosome 3 in one genomic loci were associated with ED with p < 1×10−6. rs9810233 had a p-value of 7 × 10−7 and rs1920201 had a p-value of 9×10−7 The nearest gene to these two SNPs is ALCAM. The genetic association results at these loci were similar in univariate and multivariate analysis. No candidate genes met criteria for statistical significance.
Conclusions
Two SNPs, rs9810233 and rs1920101, which are 25 kb apart, are both associated with ED, albeit not meeting the standard GWAS significance criteria of p < 5 × 10−8. Other studies with larger sample sizes will be required to determine whether ALCAM represents a novel gene in the pathogenesis of diabetes associated ED.
doi:10.1016/j.juro.2012.04.001
PMCID: PMC3764461  PMID: 22704111
Erectile Dysfunction; Diabetes; Genetics

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