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  • 1
    Publication Date: 2015-04-25
    Description: Balancing selection maintains advantageous genetic and phenotypic diversity in populations. When selection acts for long evolutionary periods selected polymorphisms may survive species splits and segregate in present-day populations of different species. Here, we investigate the role of long-term balancing selection in the evolution of protein-coding sequences in the Homo–Pan clade. We sequenced the exome of 20 humans, 20 chimpanzees, and 20 bonobos and detected eight coding trans-species polymorphisms (trSNPs) that are shared among the three species and have segregated for approximately 14 My of independent evolution. Although the majority of these trSNPs were found in three genes of the major histocompatibility locus cluster, we also uncovered one coding trSNP (rs12088790) in the gene LAD1 . All these trSNPs show clustering of sequences by allele rather than by species and also exhibit other signatures of long-term balancing selection, such as segregating at intermediate frequency and lying in a locus with high genetic diversity. Here, we focus on the trSNP in LAD1 , a gene that encodes for Ladinin-1, a collagenous anchoring filament protein of basement membrane that is responsible for maintaining cohesion at the dermal-epidermal junction; the gene is also an autoantigen responsible for linear IgA disease. This trSNP results in a missense change (Leucine257Proline) and, besides altering the protein sequence, is associated with changes in gene expression of LAD1 .
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
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  • 2
    Publication Date: 2015-06-27
    Description: : Oasis is a web application that allows for the fast and flexible online analysis of small-RNA-seq (sRNA-seq) data. It was designed for the end user in the lab, providing an easy-to-use web frontend including video tutorials, demo data and best practice step-by-step guidelines on how to analyze sRNA-seq data. Oasis’ exclusive selling points are a differential expression module that allows for the multivariate analysis of samples, a classification module for robust biomarker detection and an advanced programming interface that supports the batch submission of jobs. Both modules include the analysis of novel miRNAs, miRNA targets and functional analyses including GO and pathway enrichment. Oasis generates downloadable interactive web reports for easy visualization, exploration and analysis of data on a local system. Finally, Oasis’ modular workflow enables for the rapid (re-) analysis of data. Availability and implementation: Oasis is implemented in Python, R, Java, PHP, C++ and JavaScript. It is freely available at http://oasis.dzne.de . Contact: stefan.bonn@dzne.de Supplementary information: Supplementary data are available at Bioinformatics online.
    Print ISSN: 1367-4803
    Electronic ISSN: 1460-2059
    Topics: Biology , Computer Science , Medicine
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  • 3
    Publication Date: 2014-12-03
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 4
    Publication Date: 2012-04-24
    Description: The transcription factors Gli2 (glioma-associated factor 2), which is a transactivator of Sonic Hedgehog (Shh) signalling, and myocyte enhancer factor 2C (MEF2C) play important roles in the development of embryonic heart muscle and enhance cardiomyogenesis in stem cells. Although the physiological importance of Shh signalling and MEF2 factors in heart development is well known, the mechanistic understanding of their roles is unclear. Here, we demonstrate that Gli2 and MEF2C activated each other's expression while enhancing cardiomyogenesis in differentiating P19 EC cells. Furthermore, dominant-negative mutant proteins of either Gli2 or MEF2C repressed each other's expression, while impairing cardiomyogenesis in P19 EC cells. In addition, chromatin immunoprecipitation (ChIP) revealed association of Gli2 to the Mef2c gene, and of MEF2C to the Gli2 gene in differentiating P19 cells. Finally, co-immunoprecipitation studies showed that Gli2 and MEF2C proteins formed a complex, capable of synergizing on cardiomyogenesis-related promoters containing both Gli- and MEF2-binding elements. We propose a model whereby Gli2 and MEF2C bind each other's regulatory elements, activate each other's expression and form a protein complex that synergistically activates transcription, enhancing cardiac muscle development. This model links Shh signalling to MEF2C function during cardiomyogenesis and offers mechanistic insight into their in vivo functions.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 5
    Publication Date: 2014-04-03
    Description: The Puf family of RNA-binding proteins regulates gene expression primarily by interacting with the 3' untranslated region (3' UTR) of targeted mRNAs and inhibiting translation and/or stimulating decay. Physical association and computational analyses of yeast Puf3p identified 〉150 potential mRNA targets involved in mitochondrial function. However, only COX17 has been established as a target of Puf3p-mediated deadenylation and decapping. We have identified 10 new targets that are rapidly degraded in a Puf3p-dependent manner. We also observed changes in Puf3p activity in response to environmental conditions. Puf3p promotes rapid degradation of mRNA targets in the fermentable carbon source dextrose. However, Puf3p-mediated decay activity is inhibited in carbon sources that require mitochondrial function for efficient cell growth. In addition, the activity of Puf3p is rapidly altered by changing the carbon source. PUF3 expression is not decreased at the RNA or protein level by different carbon sources and localization is not significantly altered, suggesting that Puf3p activity is regulated posttranslationally. Finally, under conditions when Puf3p is unable to stimulate decay, Puf3p can still bind its target mRNAs. Together, these experiments provide insight into the carbon source-specific control of Puf3p activity and how such alterations allow Puf3p to dynamically regulate mitochondrial function.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 6
    Publication Date: 2014-10-18
    Description: Motivation: Oncogenes are known drivers of cancer phenotypes and targets of molecular therapies; however, the complex and diverse signaling mechanisms regulated by oncogenes and potential routes to targeted therapy resistance remain to be fully understood. To this end, we present an approach to infer regulatory mechanisms downstream of the HER2 driver oncogene in SUM-225 metastatic breast cancer cells from dynamic gene expression patterns using a succession of analytical techniques, including a novel MP grammars method to mathematically model putative regulatory interactions among sets of clustered genes. Results: Our method highlighted regulatory interactions previously identified in the cell line and a novel finding that the HER2 oncogene, as opposed to the proto-oncogene, upregulates expression of the E2F2 transcription factor. By targeted gene knockdown we show the significance of this, demonstrating that cancer cell-matrix adhesion and outgrowth were markedly inhibited when E2F2 levels were reduced. Thus, validating in this context that upregulation of E2F2 represents a key intermediate event in a HER2 oncogene-directed gene expression-based signaling circuit. This work demonstrates how predictive modeling of longitudinal gene expression data combined with multiple systems-level analyses can be used to accurately predict downstream signaling pathways. Here, our integrated method was applied to reveal insights as to how the HER2 oncogene drives a specific cancer cell phenotype, but it is adaptable to investigate other oncogenes and model systems. Availability and implementation: Accessibility of various tools is listed in methods; the Log-Gain Stoichiometric Stepwise algorithm is accessible at http://www.cbmc.it/software/Software.php . Contact: bollig@karmanos.org Supplementary information: Supplementary data are available at Bioinformatics online.
    Print ISSN: 1367-4803
    Electronic ISSN: 1460-2059
    Topics: Biology , Computer Science , Medicine
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  • 7
    Publication Date: 2014-06-03
    Description: Artificial transcription factors are powerful tools for regulating gene expression. Here we report results with engineered zinc-finger transcription factors (ZF-TFs) targeting four protein-coding genes, OCT4 , SOX2 , KLF4 and c-MYC , and one noncoding ribonucleic acid (RNA) gene, the microRNA (miRNA) miR302/367 cluster. We designed over 300 ZF-TFs whose targets lie within 1 kb of the transcriptional start sites (TSSs), screened them for increased messenger RNA or miRNA levels in transfected cells, and identified potent ZF-TF activators for each gene. Furthermore, we demonstrate that selected ZF-TFs function with alternative activation domains and in multiple cell lines. For OCT4 , we expanded the target range to –2.5 kb and +500 bp relative to the TSS and identified additional active ZF-TFs, including three highly active ZF-TFs targeting distal enhancer, proximal enhancer and downstream from the proximal promoter. Chromatin immunoprecipitation (FLAG-ChIP) results indicate that several inactive ZF-TFs targeting within the same regulatory region bind as well as the most active ZF-TFs, suggesting that efficient binding within one of these regulatory regions may be necessary but not sufficient for activation. These results further our understanding of ZF-TF design principles and corroborate the use of ZF-TFs targeting enhancers and downstream from the TSS for transcriptional activation.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 8
    Publication Date: 2013-07-26
    Description: Hoyeraal–Hreidarsson syndrome (HHS), a severe variant of dyskeratosis congenita (DC), is characterized by early onset bone marrow failure, immunodeficiency and developmental defects. Several factors involved in telomere length maintenance and/or protection are defective in HHS/DC, underlining the relationship between telomere dysfunction and these diseases. By combining whole-genome linkage analysis and exome sequencing, we identified compound heterozygous RTEL1 ( regulator of telomere elongation helicase 1 ) mutations in three patients with HHS from two unrelated families. RTEL1 is a DNA helicase that participates in DNA replication, DNA repair and telomere integrity. We show that, in addition to short telomeres, RTEL1-deficient cells from patients exhibit hallmarks of genome instability, including spontaneous DNA damage, anaphase bridges and telomeric aberrations. Collectively, these results identify RTEL1 as a novel HHS-causing gene and highlight its role as a genomic caretaker in humans.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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  • 9
    Publication Date: 2012-05-23
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 10
    Publication Date: 2013-03-21
    Description: The rapid molecular evolution of reproductive genes is nearly ubiquitous across animals, yet the selective forces and functional targets underlying this divergence remain poorly understood. Humans and closely related species of great apes show strongly divergent mating systems, providing a powerful system to investigate the influence of sperm competition on the evolution of reproductive genes. This is complemented by detailed information on male reproductive biology and unparalleled genomic resources in humans. Here, we have used custom microarrays to capture and sequence 285 genes encoding proteins present in the ejaculate as well as 101 randomly selected control genes in 21 gorillas, 20 chimpanzees, 20 bonobos, and 20 humans. In total, we have generated 〉25 x average genomic coverage per individual for over 1 million target base pairs. Our analyses indicate high levels of evolutionary constraint across much of the ejaculate combined with more rapid evolution of genes involved in immune defense and proteolysis. We do not find evidence for appreciably more positive selection along the lineage leading to bonobos and chimpanzees, although this would be predicted given more intense sperm competition in these species. Rather, the extent of positive and negative selection depended more on the effective population sizes of the species. Thus, general patterns of male reproductive protein evolution among apes and humans depend strongly on gene function but not on inferred differences in the intensity of sperm competition among extant species.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
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