Menu

Asset Tag: Targeted sequencing,

July 7, 2019

Cloning of the ?-secalin gene family in a wheat 1BL/1RS translocation line using BAC clone sequencing

Wheat 1BL/1RS translocation lines are planted around the world for their disease resistance and high yield. Most of them are poor in bread making, which is partially caused by ?-secalins that are encoded by the ?-secalin gene family, which is located on the short arm of rye chromosome 1R (1RS). However, information on the structure and evolution of the ?-secalin gene family is still limited.

Read more
July 7, 2019

Genome editing in human pluripotent stem cells: approaches, pitfalls, and solutions.

Human pluripotent stem cells (hPSCs) with knockout or mutant alleles can be generated using custom-engineered nucleases. Transcription activator-like effector nucleases (TALENs) and clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 nucleases are the most commonly employed technologies for editing hPSC genomes. In this Protocol Review, we provide a brief overview of custom-engineered nucleases in the context of gene editing in hPSCs with a focus on the application of TALENs and CRISPR/Cas9. We will highlight the advantages and disadvantages of each method and discuss theoretical and technical considerations for experimental design. Copyright © 2016 Elsevier Inc. All rights reserved.

Read more
July 7, 2019

Gene duplication confers enhanced expression of 27-kDa ?-zein for endosperm modification in quality protein maize.

The maizeopaque2(o2) mutant has a high nutritional value but it develops a chalky endosperm that limits its practical use. Genetic selection foro2modifiers can convert the normally chalky endosperm of the mutant into a hard, vitreous phenotype, yielding what is known as quality protein maize (QPM). Previous studies have shown that enhanced expression of 27-kDa ?-zein in QPM is essential for endosperm modification. Taking advantage of genome-wide association study analysis of a natural population, linkage mapping analysis of a recombinant inbred line population, and map-based cloning, we identified a quantitative trait locus (q?27) affecting expression of 27-kDa ?-zein.q?27was mapped to the same region as the majoro2 modifier(o2 modifier1) on chromosome 7 near the 27-kDa ?-zein locus.q?27resulted from a 15.26-kb duplication at the 27-kDa ?-zein locus, which increases the level of gene expression. This duplication occurred before maize domestication; however, the gene structure ofq?27appears to be unstable and the DNA rearrangement frequently occurs at this locus. Because enhanced expression of 27-kDa ?-zein is critical for endosperm modification in QPM,q?27is expected to be under artificial selection. This discovery provides a useful molecular marker that can be used to accelerate QPM breeding.

Read more
July 7, 2019

A pigeonpea gene confers resistance to Asian soybean rust in soybean.

Asian soybean rust (ASR), caused by the fungus Phakopsora pachyrhizi, is one of the most economically important crop diseases, but is only treatable with fungicides, which are becoming less effective owing to the emergence of fungicide resistance. There are no commercial soybean cultivars with durable resistance to P. pachyrhizi, and although soybean resistance loci have been mapped, no resistance genes have been cloned. We report the cloning of a P. pachyrhizi resistance gene CcRpp1 (Cajanus cajan Resistance against Phakopsora pachyrhizi 1) from pigeonpea (Cajanus cajan) and show that CcRpp1 confers full resistance to P. pachyrhizi in soybean. Our findings show that legume species related to soybean such as pigeonpea, cowpea, common bean and others could provide a valuable and diverse pool of resistance traits for crop improvement.

Read more
July 7, 2019

Evolution of coreceptor utilization to escape CCR5 antagonist therapy.

The HIV-1 envelope interacts with coreceptors CCR5 and CXCR4 in a dynamic, multi-step process, its molecular details not clearly delineated. Use of CCR5 antagonists results in tropism shift and therapeutic failure. Here we describe a novel approach using full-length patient-derived gp160 quasispecies libraries cloned into HIV-1 molecular clones, their separation based on phenotypic tropism in vitro, and deep sequencing of the resultant variants for structure-function analyses. Analysis of functionally validated envelope sequences from patients who failed CCR5 antagonist therapy revealed determinants strongly associated with coreceptor specificity, especially at the gp120-gp41 and gp41-gp41 interaction surfaces that invite future research on the roles of subunit interaction and envelope trimer stability in coreceptor usage. This study identifies important structure-function relationships in HIV-1 envelope, and demonstrates proof of concept for a new integrated analysis method that facilitates laboratory discovery of resistant mutants to aid in development of other therapeutic agents. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Read more
July 7, 2019

Understanding the genetics of APOE and TOMM40 and role of mitochondrial structure and function in clinical pharmacology of Alzheimer’s disease.

The methodology of Genome-Wide Association Screening (GWAS) has been applied for more than a decade. Translation to clinical utility has been limited, especially in Alzheimer’s Disease (AD). It has become standard practice in the analyses of more than two dozen AD GWAS studies to exclude the apolipoprotein E (APOE) region because of its extraordinary statistical support, unique thus far in complex human diseases. New genes associated with AD are proposed frequently based on SNPs associated with odds ratio (OR) < 1.2. Most of these SNPs are not located within the associated gene exons or introns but are located variable distances away. Often pathologic hypotheses for these genes are presented, with little or no experimental support. By eliminating the analyses of the APOE-TOMM40 linkage disequilibrium region, the relationship and data of several genes that are co-located in that LD region have been largely ignored. Early negative interpretations limited the interest of understanding the genetic data derived from GWAS, particularly regarding the TOMM40 gene. This commentary describes the history and problem(s) in interpretation of the genetic interrogation of the "APOE" region and provides insight into a metabolic mitochondrial basis for the etiology of AD using both APOE and TOMM40 genetics. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Read more
July 7, 2019

Complete nucleotide sequence of pH11, an IncHI2 plasmid conferring multi-antibiotic resistance and multi-heavy metal resistance genes in a clinical Klebsiella pneumoniae isolate.

The complete 284,628bp sequence of pH11, an IncHI2 plasmid, was determined through single-molecule, real-time (SMRT) sequencing. Harbored by a clinical Klebsiella pneumoniae strain H11, and isolated in Beijing, this plasmid contains multiple antibiotic resistance genes, including catA2, aac(6′)-Ib, strB, strA, dfrA19, blaTEM-1, blaSHV-12, sul1, qacE delta 1, ereA, arr2, and aac3. The aac(6′)-Ib is carried by a class I integron. Plasmid pH11 also carries several genes associated with resistance to heavy metals, such as tellurium, mercury, cobalt, zinc, nickel, copper, lead and cadmium. This plasmid exhibits numerous characteristics, including HipBA and RelBE toxin-antitoxin systems, two major transfer (Tra) regions closely related to those of Salmonella enterica serovar plasmid pRH-R27, a type II restriction modification system (EcoRII R-M system), several methyltransferases and methylases and genes encoding Hha and StpA. These characteristics suggest that pH11 may adapt to various hosts and environments. Multiple insertion sequence elements, transposases, recombinases, resolvases and integrases are scattered throughout pH11. The presence of these genes may indicate that horizontal gene transfer occurs frequently in pH11 and thus may facilitate the dissemination of antimicrobial resistance determinants. Our data suggest that pH11 is a chimera gradually assembled through the integration of different horizontally acquired DNA segments via transposition or homologous recombination. Copyright © 2016 Elsevier Inc. All rights reserved.

Read more
July 7, 2019

Genomic organization of the zebrafish (Danio rerio) T cell receptor alpha/delta locus and analysis of expressed products.

In testing the hypothesis that all jawed vertebrate classes employ immunoglobulin heavy chain V (IgHV) gene segments in their T cell receptor (TCR)d encoding loci, we found that some basic characterization was required of zebrafish TCRd. We began by annotating and characterizing the TCRa/d locus of Danio rerio based on the most recent genome assembly, GRCz10. We identified a total of 141 theoretically functional V segments which we grouped into 41 families based upon 70 % nucleotide identity. This number represents the second greatest count of apparently functional V genes thus far described in an antigen receptor locus with the exception of cattle TCRa/d. Cloning, relative quantitative PCR, and deep sequencing results corroborate that zebrafish do express TCRd, but these data suggest only at extremely low levels and in limited diversity in the spleens of the adult fish. While we found no evidence for IgH-TCRd rearrangements in this fish, by determining the locus organization we were able to suggest how the evolution of the teleost a/d locus could have lost IgHVs that exist in sharks and frogs. We also found evidence of surprisingly low TCRd expression and repertoire diversity in this species.

Read more
July 7, 2019

ABO allele-level frequency estimation based on population-scale genotyping by next generation sequencing.

The characterization of the ABO blood group status is vital for blood transfusion and solid organ transplantation. Several methods for the molecular characterization of the ABO gene, which encodes the alleles that give rise to the different ABO blood groups, have been described. However, the application of those methods has so far been restricted to selected samples and not been applied to population-scale analysis.We describe a cost-effective method for high-throughput genotyping of the ABO system by next generation sequencing. Sample specific barcodes and sequencing adaptors are introduced during PCR, rendering the products suitable for direct sequencing on Illumina MiSeq or HiSeq instruments. Complete sequence coverage of exons 6 and 7 enables molecular discrimination of the ABO subgroups and many alleles. The workflow was applied to ABO genotype more than a million samples. We report the allele group frequencies calculated on a subset of more than 110,000 sampled individuals of German origin. Further we discuss the potential of the workflow for high resolution genotyping taking the observed allele group frequencies into account. Finally, sequence analysis revealed 287 distinct so far not described alleles of which the most abundant one was identified in 174 samples.The described workflow delivers high resolution ABO genotyping at low cost enabling population-scale molecular ABO characterization.

Read more
July 7, 2019

A hot L1 retrotransposon evades somatic repression and initiates human colorectal cancer.

Although human LINE-1 (L1) elements are actively mobilized in many cancers, a role for somatic L1 retrotransposition in tumor initiation has not been conclusively demonstrated. Here, we identify a novel somatic L1 insertion in the APC tumor suppressor gene that provided us with a unique opportunity to determine whether such insertions can actually initiate colorectal cancer (CRC), and if so, how this might occur. Our data support a model whereby a hot L1 source element on Chromosome 17 of the patient’s genome evaded somatic repression in normal colon tissues and thereby initiated CRC by mutating the APC gene. This insertion worked together with a point mutation in the second APC allele to initiate tumorigenesis through the classic two-hit CRC pathway. We also show that L1 source profiles vary considerably depending on the ancestry of an individual, and that population-specific hot L1 elements represent a novel form of cancer risk. © 2016 Scott et al.; Published by Cold Spring Harbor Laboratory Press.

Read more
July 7, 2019

Selfish drive can trump function when animal mitochondrial genomes compete.

Mitochondrial genomes compete for transmission from mother to progeny. We explored this competition by introducing a second genome into Drosophila melanogaster to follow transmission. Competitions between closely related genomes favored those functional in electron transport, resulting in a host-beneficial purifying selection. In contrast, matchups between distantly related genomes often favored those with negligible, negative or lethal consequences, indicating selfish selection. Exhibiting powerful selfish selection, a genome carrying a detrimental mutation displaced a complementing genome, leading to population death after several generations. In a different pairing, opposing selfish and purifying selection counterbalanced to give stable transmission of two genomes. Sequencing of recombinant mitochondrial genomes showed that the noncoding region, containing origins of replication, governs selfish transmission. Uniparental inheritance prevents encounters between distantly related genomes. Nonetheless, in each maternal lineage, constant competition among sibling genomes selects for super-replicators. We suggest that this relentless competition drives positive selection, promoting change in the sequences influencing transmission.

Read more
July 7, 2019

Resistance from relatives.

Crops are made resistant to pathogens such as wheat stem rust, Asian soybean rust and potato late blight by methods to access the pool of resistance genes present in related plants.

Read more
July 7, 2019

Multiplex enhancer-reporter assays uncover unsophisticated TP53 enhancer logic.

Transcription factors regulate their target genes by binding to regulatory regions in the genome. Although the binding preferences of TP53 are known, it remains unclear what distinguishes functional enhancers from nonfunctional binding. In addition, the genome is scattered with recognition sequences that remain unoccupied. Using two complementary techniques of multiplex enhancer-reporter assays, we discovered that functional enhancers could be discriminated from nonfunctional binding events by the occurrence of a single TP53 canonical motif. By combining machine learning with a meta-analysis of TP53 ChIP-seq data sets, we identified a core set of more than 1000 responsive enhancers in the human genome. This TP53 cistrome is invariably used between cell types and experimental conditions, whereas differences among experiments can be attributed to indirect nonfunctional binding events. Our data suggest that TP53 enhancers represent a class of unsophisticated cell-autonomous enhancers containing a single TP53 binding site, distinct from complex developmental enhancers that integrate signals from multiple transcription factors. © 2016 Verfaillie et al.; Published by Cold Spring Harbor Laboratory Press.

Read more
July 7, 2019

TERRA promotes telomerase-mediated telomere elongation in Schizosaccharomyces pombe.

Telomerase-mediated telomere elongation provides cell populations with the ability to proliferate indefinitely. Telomerase is capable of recognizing and extending the shortest telomeres in cells; nevertheless, how this mechanism is executed remains unclear. Here, we show that, in the fission yeast Schizosaccharomyces pombe, shortened telomeres are highly transcribed into the evolutionarily conserved long noncoding RNA TERRA A fraction of TERRA produced upon telomere shortening is polyadenylated and largely devoid of telomeric repeats, and furthermore, telomerase physically interacts with this polyadenylated TERRA in vivo We also show that experimentally enhanced transcription of a manipulated telomere promotes its association with telomerase and concomitant elongation. Our data represent the first direct evidence that TERRA stimulates telomerase recruitment and activity at chromosome ends in an organism with human-like telomeres. © 2016 The Authors.

Read more
July 7, 2019

Suppressed recombination and unique candidate genes in the divergent haplotype encoding Fhb1, a major Fusarium head blight resistance locus in wheat.

Fine mapping and sequencing revealed 28 genes in the non-recombining haplotype containing Fhb1 . Of these, only a GDSL lipase gene shows a pathogen-dependent expression pattern. Fhb1 is a prominent Fusarium head blight resistance locus of wheat, which has been successfully introgressed in adapted breeding material, where it confers a significant increase in overall resistance to the causal pathogen Fusarium graminearum and the fungal virulence factor and mycotoxin deoxynivalenol. The Fhb1 region has been resolved for the susceptible wheat reference genotype Chinese Spring, yet the causal gene itself has not been identified in resistant cultivars. Here, we report the establishment of a 1 Mb contig embracing Fhb1 in the donor line CM-82036. Sequencing revealed that the region of Fhb1 deviates from the Chinese Spring reference in DNA size and gene content, which explains the repressed recombination at the locus in the performed fine mapping. Differences in genes expression between near-isogenic lines segregating for Fhb1 challenged with F. graminearum or treated with mock were investigated in a time-course experiment by RNA sequencing. Several candidate genes were identified, including a pathogen-responsive GDSL lipase absent in susceptible lines. The sequence of the Fhb1 region, the resulting list of candidate genes, and near-diagnostic KASP markers for Fhb1 constitute a valuable resource for breeding and further studies aiming to identify the gene(s) responsible for F. graminearum and deoxynivalenol resistance.

Read more

Subscribe for blog updates:

Talk with an expert

If you have a question, need to check the status of an order, or are interested in purchasing an instrument, we're here to help.