GIFtS: annotation landscape analysis with GeneCards

<p>Abstract</p> <p>Background</p> <p>Gene annotation is a pivotal component in computational genomics, encompassing prediction of gene function, expression analysis, and sequence scrutiny. Hence, quantitative measures of the annotation landscape constitute a pertinent bioinformatics tool. GeneCards^®is a gene-centric compendium of rich annotative information for over 50,000 human gene entries, building upon 68 data sources, including Gene Ontology (GO), pathways, interactions, phenotypes, publications and many more.</p> <p>Results</p> <p>We present the GeneCards Inferred Functionality Score (GIFtS) which allows a quantitative assessment of a gene's annotation status, by exploiting the unique wealth and diversity of GeneCards information. The GIFtS tool, linked from the GeneCards home page, facilitates browsing the human genome by searching for the annotation level of a specified gene, retrieving a list of genes within a specified range of GIFtS value, obtaining random genes with a specific GIFtS value, and experimenting with the GIFtS weighting algorithm for a variety of annotation categories. The bimodal shape of the GIFtS distribution suggests a division of the human gene repertoire into two main groups: the high-GIFtS peak consists almost entirely of protein-coding genes; the low-GIFtS peak consists of genes from all of the categories. Cluster analysis of GIFtS annotation vectors provides the classification of gene groups by detailed positioning in the annotation arena. GIFtS also provide measures which enable the evaluation of the databases that serve as GeneCards sources. An inverse correlation is found (for GIFtS>25) between the number of genes annotated by each source, and the average GIFtS value of genes associated with that source. Three typical source prototypes are revealed by their GIFtS distribution: genome-wide sources, sources comprising mainly highly annotated genes, and sources comprising mainly poorly annotated genes. The degree of accumulated knowledge for a given gene measured by GIFtS was correlated (for GIFtS>30) with the number of publications for a gene, and with the seniority of this entry in the HGNC database.</p> <p>Conclusion</p> <p>GIFtS can be a valuable tool for computational procedures which analyze lists of large set of genes resulting from wet-lab or computational research. GIFtS may also assist the scientific community with identification of groups of uncharacterized genes for diverse applications, such as delineation of novel functions and charting unexplored areas of the human genome.</p

Autonomous Bioluminescent Expression of the Bacterial Luciferase Gene Cassette (lux) in a Mammalian Cell Line

The bacterial luciferase (lux) gene cassette consists of five genes (luxCDABE) whose protein products synergistically generate bioluminescent light signals exclusive of supplementary substrate additions or exogenous manipulations. Historically expressible only in prokaryotes, the lux operon was re-synthesized through a process of multi-bicistronic, codon-optimization to demonstrate for the first time self-directed bioluminescence emission in a mammalian HEK293 cell line in vitro and in vivo.Autonomous in vitro light production was shown to be 12-fold greater than the observable background associated with untransfected control cells. The availability of reduced riboflavin phosphate (FMNH(2)) was identified as the limiting bioluminescence substrate in the mammalian cell environment even after the addition of a constitutively expressed flavin reductase gene (frp) from Vibrio harveyi. FMNH(2) supplementation led to a 151-fold increase in bioluminescence in cells expressing mammalian codon-optimized luxCDE and frp genes. When injected subcutaneously into nude mice, in vivo optical imaging permitted near instantaneous light detection that persisted independently for the 60 min length of the assay with negligible background.The speed, longevity, and self-sufficiency of lux expression in the mammalian cellular environment provides a viable and powerful alternative for real-time target visualization not currently offered by existing bioluminescent and fluorescent imaging technologies

Gradual transition from mosaic to global DNA methylation patterns during deuterostome evolution

<p>Abstract</p> <p>Background</p> <p>DNA methylation by the Dnmt family occurs in vertebrates and invertebrates, including ascidians, and is thought to play important roles in gene regulation and genome stability, especially in vertebrates. However, the global methylation patterns of vertebrates and invertebrates are distinctive. Whereas almost all CpG sites are methylated in vertebrates, with the exception of those in CpG islands, the ascidian genome contains approximately equal amounts of methylated and unmethylated regions. Curiously, methylation status can be reliably estimated from the local frequency of CpG dinucleotides in the ascidian genome. Methylated and unmethylated regions tend to have few and many CpG sites, respectively, consistent with our knowledge of the methylation status of CpG islands and other regions in mammals. However, DNA methylation patterns and levels in vertebrates and invertebrates have not been analyzed in the same way.</p> <p>Results</p> <p>Using a new computational methodology based on the decomposition of the bimodal distributions of methylated and unmethylated regions, we estimated the extent of the global methylation patterns in a wide range of animals. We then examined the epigenetic changes <it>in silico </it>along the phylogenetic tree. We observed a gradual transition from fractional to global patterns of methylation in deuterostomes, rather than a clear demarcation between vertebrates and invertebrates. When we applied this methodology to six piscine genomes, some of which showed features similar to those of invertebrates.</p> <p>Conclusions</p> <p>The mammalian global DNA methylation pattern was probably not acquired at an early stage of vertebrate evolution, but gradually expanded from that of a more ancient organism.</p

Monoallelic Expression of Multiple Genes in the CNS

The inheritance pattern of a number of major genetic disorders suggests the possible involvement of genes that are expressed from one allele and silent on the other, but such genes are difficult to detect. Since DNA methylation in regulatory regions is often a mark of gene silencing, we modified existing microarray-based assays to detect both methylated and unmethylated DNA sequences in the same sample, a variation we term the MAUD assay. We probed a 65 Mb region of mouse Chr 7 for gene-associated sequences that show two distinct DNA methylation patterns in the mouse CNS. Selected genes were then tested for allele-specific expression in clonal neural stem cell lines derived from reciprocal F1 (C57BL/6×JF1) hybrid mice. In addition, using a separate approach, we directly analyzed allele-specific expression of a group of genes interspersed within clusters of OlfR genes, since the latter are subject to allelic exclusion. Altogether, of the 500 known genes in the chromosomal region surveyed, five show monoallelic expression, four identified by the MAUD assay (Agc1, p (pink-eyed dilution), P4ha3 and Thrsp), and one by its proximity to OlfR genes (Trim12). Thrsp (thyroid hormone responsive SPOT14 homolog) is expressed in hippocampus, but the human protein homolog, S14, has also been implicated in aggressive breast cancer. Monoallelic expression of the five genes is not coordinated at a chromosome-wide level, but rather regulated at individual loci. Taken together, our results suggest that at least 1% of previously untested genes are subject to allelic exclusion, and demonstrate a dual approach to expedite their identification

Characterization of Two Mutations Associated with Epimerase-Deficiency Galactosemia, by Use of a Yeast Expression System for Human UDP-Galactose-4-Epimerase

SummaryUDP-galactose-4-epimerase (GALE) is a highly conserved enzyme that catalyzes the interconversion of UDP-galac-tose and UDP-glucose. Impairment of this enzyme in humans results in one of two clinically distinct forms of epi-merase-deficiency galactosemia—one benign, the other severe. The molecular and biochemical distinction between these disorders remains unknown. To enable structural and functional studies of both wild-type and patient-derived alleles of human GALE (hGALE), we have developed and applied a null-background yeast expression system for the human enzyme. We have demonstrated that wild-type hGALE sequences phenotypically complement a yeast gal10 deletion, and we have biochemically characterized the wild-type human enzyme isolated from these cells. Furthermore, we have expressed and characterized two mutant alleles, L183P-hGALE and N34S-h GALE, both derived from a patient with no detectable GALE activity in red blood cells but with −14% activity in cultured lymphoblasts. Analyses of crude extracts of yeast expressing L183P-hGALE demonstrated 4% wild-type activity and 6% wild-type abundance. Extracts of yeast expressing N34S-hGALE demonstrated −70% wild-type activity and normal abundance. However, yeast coexpressing both L183P-hGALE and N34S-hGALE exhibited only −7% wild-type levels of activity, thereby confirming the functional impact of both substitutions and raising the intriguing possibility that some form of dominant-negative interaction may exist between the mutant alleles found in this patient. The results reported here establish the utility of the yeast-based hGALE-expression system and set the stage for more-detailed studies of this important enzyme and its role in epimerase-deficiency galactosemia

Loss of Imprinting in Disease Progression in Chronic Myelogenous Leukemia

The pathophysiologic role of the Philadelphia chromosome translocation in chronic myelogenous leukemia (CML) has been known for nearly 20 years. However, the most significant morbidity and mortality in CML are caused by progression to blast crisis, about which comparatively little is known at the molecular level. Genomic imprinting is a chromosomal modification leading to parental-origin–specific gene expression in somatic cells. Recently, we and others have described loss of imprinting (LOI) of the insulin-like growth factor-II gene (IGF2), leading to biallelic rather than monoallelic expression in a wide variety of solid tumors. We have now examined the imprinting status of IGF2 in samples from CML patients in stable phase, accelerated phase, and blast crisis. Five of six stable-phase patients showed normal imprinting, but LOI was found in all six cases of advanced disease (three accelerated phase, three blast crisis), which was statistically highly significant (P &lt; .01). Thus, LOI represents a novel type of genetic alteration in CML that appears to be specifically associated with disease progression.</jats:p