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The DNA sequence quality machine at IFOM: a simple Web-based tool for quantitative assessment of sequencing reactions.

DNA sequence quality is a factor of paramount importance in the world of modern genetic and genomics. Both the sequencing of Human Genome in the "post-draft" era [NHGRI Standard for quality of Human Genomic Sequences, Rev. 7 July (2002) where http://www.nhgri.nih.gov/Grant_info/Funding/ Statements/RFA/quality_standard.html is the HTTP address] and recent "high-throughput" approaches to genetic investigation such as SAGE [Velculescu, V.E., Zhang, L., Vogelstein, B. et al. (1995) "Serial analysis of gene expression", Science 270, 484-487] need a reliable, standardized measure of the quality of a sequencing reaction. The increasing importance of SNP studies also requires a stronger quality control on sequencing reactions by the final user. We propose here a simple, web-based tool for integrated sequence quality evaluation, high quality region quantitative value calculation and chromatogram display. This software is aimed at the small to medium DNA sequence laboratory or to the single researcher, interested in getting a quantitative measure of the sequence quality, browsing the chromatogram and checking the quality values base by base. The program is freely available from the IFOM bioinformatics web Server at http://bio.ifom-firc.it/Phred20/index.html.

Algorithms↗

[Genomic medicine].

The International Human Genome Sequencing Consortium announced they have got a draft sequence of the human genome that covers about 94% of the human genome in February, 2001. This statement implies that we will soon have the complete human genome sequence and that we will be able to use genomic information in every field including medicine, drug production as well as prophylaxis of many diseases. Two major advances in technology have made it possible to apply genomic information for medicine: microarray technology and high-throughput sequencing technology. Microarray provides us a new method to classify various diseases on the basis of gene expression and high-throughput sequencing enables us to draw high-resolution SNPs map.

Chromosome Mapping↗

HTS in the new millennium: the role of pharmacology and flexibility.

Over the past decade, high throughput screening (HTS) has become the focal point for discovery programs within the pharmaceutical industry. The role of this discipline has been and remains the rapid and efficient identification of lead chemical matter within chemical libraries for therapeutics development. Recent advances in molecular and computational biology, i.e., genomic sequencing and bioinformatics, have resulted in the announcement of publication of the first draft of the human genome. While much work remains before a complete and accurate genomic map will be available, there can be no doubt that the number of potential therapeutic intervention points will increase dramatically, thereby increasing the workload of early discovery groups. One current drug discovery paradigm integrates genomics, protein biosciences and HTS in establishing what the authors refer to as the "gene-to-screen" process. Adoption of the "gene-to-screen" paradigm results in a dramatic increase in the efficiency of the process of converting a novel gene coding for a putative enzymatic or receptor function into a robust and pharmacologically relevant high throughput screen. This article details aspects of the identification of lead chemical matter from HTS. Topics discussed include portfolio composition (molecular targets amenable to small molecule drug discovery), screening file content, assay formats and plating densities, and the impact of instrumentation on the ability of HTS to identify lead chemical matter.

Animals↗

Primer on medical genomics. Part VI: Genomics and molecular genetics in clinical practice.

An important milestone in medical science is the recent completion of a "working draft" of the human genome sequence. The identification of all human genes and their regulatory regions provides the framework to expedite our understanding of the molecular basis of disease. This advance has also formed the foundation for a broad range of genomic tools that can be applied to medical science. These developments in global gene and gene product analysis as well as targeted molecular genetic testing are destined to change the practice of modern medicine. Despite these exciting advances, many practicing clinicians perceive that the role of molecular genetics, especially that of genomics, is confined primarily to the research arena with little current clinical applicability. The aim of this article is to highlight advances in DNA/RNA-based methods of susceptibility screening, disease diagnosis and prognostication, and prediction of treatment outcome in regard to both drug toxicity and response as they apply to various areas of clinical medicine.

Cardiovascular Diseases↗

Quantitative DNA fiber mapping in genome research and construction of physical maps.

Efforts to prepare a first draft of the human DNA genomic sequence forced multidisciplinary teams of researchers to face unique challenges. At the same time, these unprecedented obstacles stimulated the development of many highly innovative approaches to biomedical problem solving, robotics, and bioinformatics. High-resolution physical maps are required for ordering individual segments of information for the construction of a comprehensive map of the entire genome. This chapter describes a novel way to identify, delineate, and characterize selected, often small DNA sequences along a larger piece of the human genome. The technology is based on immobilization of high molecular weight DNA molecules on a solid substrate (such as a glass slide) followed by uniform stretching of the DNA molecule by the force of a receding meniscus. The hydrodynamic force stretches the DNA molecules homogeneously to approximately 2.3 kb/microm, so that distances measured after probe binding in microm can be converted directly into kb distances. Out of a large number of applications, this article focuses on mapping of genomic sequences relative to one another, the assembly of physical maps with near kb resolution, and, finally, quality control during physical map assembly and sequencing.

Chromosomes, Artificial↗

ECR Browser: a tool for visualizing and accessing data from comparisons of multiple vertebrate genomes.

With an increasing number of vertebrate genomes being sequenced in draft or finished form, unique opportunities for decoding the language of DNA sequence through comparative genome alignments have arisen. However, novel tools and strategies are required to accommodate this large volume of genomic information and to facilitate the transfer of predictions generated by comparative sequence alignment to researchers focused on experimental annotation of genome function. Here, we present the ECR Browser, a tool that provides easy and dynamic access to whole genome alignments of human, mouse, rat and fish sequences. This web-based tool (http://ecrbrowser.dcode.org) provides the starting point for discovery of novel genes, identification of distant gene regulatory elements and prediction of transcription factor binding sites. The genome alignment portal of the ECR Browser also permits fast and automated alignments of any user-submitted sequence to the genome of choice. The interconnection of the ECR Browser with other DNA sequence analysis tools creates a unique portal for studying and exploring vertebrate genomes.

Animals↗

A case for evolutionary genomics and the comprehensive examination of sequence biodiversity.

Comparative analysis is one of the most powerful methods available for understanding the diverse and complex systems found in biology, but it is often limited by a lack of comprehensive taxonomic sampling. Despite the recent development of powerful genome technologies capable of producing sequence data in large quantities (witness the recently completed first draft of the human genome), there has been relatively little change in how evolutionary studies are conducted. The application of genomic methods to evolutionary biology is a challenge, in part because gene segments from different organisms are manipulated separately, requiring individual purification, cloning, and sequencing. We suggest that a feasible approach to collecting genome-scale data sets for evolutionary biology (i.e., evolutionary genomics) may consist of combination of DNA samples prior to cloning and sequencing, followed by computational reconstruction of the original sequences. This approach will allow the full benefit of automated protocols developed by genome projects to be realized; taxon sampling levels can easily increase to thousands for targeted genomes and genomic regions. Sequence diversity at this level will dramatically improve the quality and accuracy of phylogenetic inference, as well as the accuracy and resolution of comparative evolutionary studies. In particular, it will be possible to make accurate estimates of normal evolution in the context of constant structural and functional constraints (i.e., site-specific substitution probabilities), along with accurate estimates of changes in evolutionary patterns, including pairwise coevolution between sites, adaptive bursts, and changes in selective constraints. These estimates can then be used to understand and predict the effects of protein structure and function on sequence evolution and to predict unknown details of protein structure, function, and functional divergence. In order to demonstrate the practicality of these ideas and the potential benefit for functional genomic analysis, we describe a pilot project we are conducting to simultaneously sequence large numbers of vertebrate mitochondrial genomes.

Animals↗

Leveraging the mouse genome for gene prediction in human: from whole-genome shotgun reads to a global synteny map.

The availability of draft sequences for both the mouse and human genomes makes it possible, for the first time, to annotate whole mammalian genomes using comparative methods. TWINSCAN is a gene-prediction system that combines the methods of single-genome predictors like GENSCAN with information derived from genome comparison, thereby improving accuracy. Because TWINSCAN uses genomic sequence only, it is less biased toward highly and/or ubiquitously expressed genes than GENEWISE, GENOMESCAN, and other methods based on evidence derived from transcripts. We show that TWINSCAN improves gene prediction in human using intermediate products from various stages of the sequencing and analysis of the mouse genome, from low-redundancy, whole-genome shotgun reads to the draft assembly and the synteny map. TWINSCAN improves on the prior state of the art even when alignments from only 1X coverage of the mouse genome are available. Gene prediction accuracy improves steadily from 1X through 3X, more slowly from 3X to 4X, and relatively little thereafter. The assembly and the synteny map greatly speed the computations, however. Our human annotation using the mouse assembly is conservative, predicting only 25,622 genes, and appears to be one of the best de novo annotations of the human genome to date.

Animals↗

Challenges to environmental toxicology and epidemiology: where do we stand and which way do we go?

Modern toxicology investigates a wide array of both old and new health hazards. Priority setting is needed to select agents for research from the plethora of exposure circumstances. The changing societies and a growing fraction of the aged have to be taken into consideration. A precise exposure assessment is of importance for risk estimation and regulation. Toxicology contributes to the exploration of pathomechanisms to specify the exposure metrics for risk estimation. Combined effects of co-existing agents are not yet sufficiently understood. Animal experiments allow a separate administration of agents which can not be disentangled by epidemiological means, but their value is limited for low exposure levels in many of today's settings. As an experimental science, toxicology has to keep pace with the rapidly growing knowledge about the language of the genome and the changing paradigms in cancer development. During the pioneer era of assembling a working draft of the human genome, toxicogenomics has been developed. Gene and pathway complexity have to be considered when investigating gene-environment interactions. For a best conduct of studies, modern toxicology needs a close liaison with many other disciplines like epidemiology and bioinformatics.

Animals↗

Functional genomics: lessons from yeast.

Functional genomics represents a systematic approach to elucidating the function of the novel genes revealed by complete genome sequences. Such an approach should adopt a hierarchical strategy since this will both limit the number of experiments to be performed and permit a closer and closer approximation to the function of any individual gene to be achieved. Moreover, hierarchical analyses have, in their early stages, tremendous integrative power and functional genomics aims at a comprehensive and integrative view of the workings of living cells. The first draft of the human genome sequence has just been produced, and the complete genome sequences of a number of eukaryotic human pathogens (including the parasitic protozoa Plasmodium, Leishmania, and Trypanosoma) will soon be available. However, the most rapid progress in the elucidation of gene function will initially be made using model organisms. Yeast is an excellent eukaryotic model and at least 40% of single-gene determinants of human heritable diseases find homologues in yeast. We have adopted a systematic approach to the functional analysis of the Saccharomyces cerevisiae genome. A number of the approaches for the functional analysis of novel yeast genes are discussed. The different approaches are grouped into four domains: genome, transcriptome, proteome, and metabolome. The utility of genetic, biochemical, and physico-chemical methods for the analysis of these domains is discussed, and the importance of framing precise biological questions, when using these comprehensive analytical methods, is emphasized. Finally, the prospects for elucidating the function of protozoan genes by using the methods pioneered with yeast, and even exploiting Saccharomyces itself, as a surrogate, are explored.

Fungal Proteins↗

Genome-wide analysis of the human Alu Yb-lineage.

The Alu Yb-lineage is a 'young' primarily human-specific group of short interspersed element (SINE) subfamilies that have integrated throughout the human genome. In this study, we have computationally screened the draft sequence of the human genome for Alu Yb-lineage subfamily members present on autosomal chromosomes. A total of 1,733 Yb Alu subfamily members have integrated into human autosomes. The average ages of Yb-lineage subfamilies, Yb7, Yb8 and Yb9, are estimated as 4.81, 2.39 and 2.32 million years, respectively. In order to determine the contribution of the Alu Yb-lineage to human genomic diversity, 1,202 loci were analysed using polymerase chain reaction (PCR)-based assays, which amplify the genomic regions containing individual Yb-lineage subfamily members. Approximately 20 percent of the Yb-lineage Alu elements are polymorphic for insertion presence/absence in the human genome. Fewer than 0.5 percent of the Yb loci also demonstrate insertions at orthologous positions in non-human primate genomes. Genomic sequencing of these unusual loci demonstrates that each of the orthologous loci from non-human primate genomes contains older Y, Sg and Sx Alu family members that have been altered, through various mechanisms, into Yb8 sequences. These data suggest that Alu Yb-lineage subfamily members are largely restricted to the human genome. The high copy number, level of insertion polymorphism and estimated age indicate that members of the Alu Yb elements will be useful in a wide range of genetic analyses.

Alu Elements↗

The Anopheles gambiae genome: an update.

As a result of an international collaborative effort, the first draft of the Anopheles gambiae genome sequence and its preliminary annotation were published in October 2002. Since then, the assembly, annotation and means of accession of the An. gambiae genome have been under continuous development. This article reviews progress and considers limitations in the current sequence assembly and gene annotation, as well as approaches to address these problems and outstanding issues that users of the data must bear in mind.

Animals↗

The Atlas genome assembly system.

Atlas is a suite of programs developed for assembly of genomes by a "combined approach" that uses DNA sequence reads from both BACs and whole-genome shotgun (WGS) libraries. The BAC clones afford advantages of localized assembly with reduced computational load, and provide a robust method for dealing with repeated sequences. Inclusion of WGS sequences facilitates use of different clone insert sizes and reduces data production costs. A core function of Atlas software is recruitment of WGS sequences into appropriate BACs based on sequence overlaps. Because construction of consensus sequences is from local assembly of these reads, only small (<0.1%) units of the genome are assembled at a time. Once assembled, each BAC is used to derive a genomic layout. This "sequence-based" growth of the genome map has greater precision than with non-sequence-based methods. Use of BACs allows correction of artifacts due to repeats at each stage of the process. This is aided by ancillary data such as BAC fingerprint, other genomic maps, and syntenic relations with other genomes. Atlas was used to assemble a draft DNA sequence of the rat genome; its major components including overlapper and split-scaffold are also being used in pure WGS projects.

Animals↗

Chicken genome: new tools and concepts.

Last spring, the Second International Chicken Genome Workshop was held at the Stowers Institute for Medical Research, less than 2 months after the first draft of the chicken genome was publicly released in March, 2004. This major event was highly anticipated by the chicken community, because of the invaluable resources that would be newly provided. In addition, from an evolutionary standpoint, birds are the species most closely related to mammals, whose genome has been sequenced. The meeting gathered both agricultural and academic chicken communities and provided the opportunity to discuss the status of the chicken genome sequencing, the preliminary analysis of the chicken genome sequences freshly available, and the impact on avian genetic tools.

Animals↗

Progress in bioinformatics and the importance of being earnest.

In silico biology has gathered momentum as, worldwide, scientists have united in a common quest to sequence, store and analyse complete genomes. This year, a pivotal achievement of this cooperative endeavour was realised in the release of a public draft of the human genome, and with it the promises to improve our understanding of diverse aspects of biology and to yield a healthier future with safe personalized medicines. Key to these goals will be the need to elucidate and characterise the genes and gene products encoded not just in the human genome, but in many genomes. These tasks are underpinned by the concepts and processes of genome and gene/protein evolution, regulation of gene expression, mechanisms of protein folding, the manifestation of protein function, and so on, all of which must be understood in the context of complex, dynamic biological systems. Our use of computers to model such concepts and systems must be placed in the context of the current limits of our understanding of them:- it is important to recognise, for example, that we don't have a common understanding either of what constitutes a gene or a protein function; we can't invariably say that a particular sequence or fold has arisen via divergent or convergent evolution; and we don't fully understand the rules of protein folding. Accepting what we can't do in silico is essential in appreciating what we can do. Without this understanding, it is easy to be misled, as notions of what particular computational approaches can achieve are sometimes rather optimistic. There are valuable lessons to be learned here from the field of Artificial Intelligence, principal among which is the realisation that capturing and representing complex knowledge is time consuming, expensive and hard. Thus, we argue here that if bioinformatics is to tackle biological complexity in earnest, it would be wise to absorb the experience distilled from decades of artificial intelligence research, and to approach the road ahead with caution, rigour and pragmatism.

Artificial Intelligence↗

Strategies for the systematic sequencing of complex genomes.

Recent spectacular advances in the technologies and strategies for DNA sequencing have profoundly accelerated the detailed analysis of genomes from myriad organisms. The past few years alone have seen the publication of near-complete or draft versions of the genome sequence of several well-studied, multicellular organisms - most notably, the human. As well as providing data of fundamental biological significance, these landmark accomplishments have yielded important strategic insights that are guiding current and future genome-sequencing projects.

Animals↗