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  • 1. Berger, Juerg
    et al.
    Senti, Kirsten-Andre
    Senti, Gabriele
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institute.
    Newsome, Timothy P.
    Åsling, Bengt
    Dickson, Barry J.
    Suzuki, Takashi
    Systematic identification of genes that regulate neuronal wiring in the Drosophila visual system2008Inngår i: PLOS Genetics, ISSN 1553-7390, E-ISSN 1553-7404, Vol. 4, nr 5, s. Online-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Forward genetic screens in model organisms are an attractive means to identify those genes involved in any complex biological process, including neural circuit assembly. Although mutagenesis screens are readily performed to saturation, gene identification rarely is, being limited by the considerable effort generally required for positional cloning. Here, we apply a systematic positional cloning strategy to identify many of the genes required for neuronal wiring in the Drosophila visual system. From a large-scale forward genetic screen selecting for visual system wiring defects with a normal retinal pattern, we recovered 122 mutations in 42 genetic loci. For 6 of these loci, the underlying genetic lesions were previously identified using traditional methods. Using SNP-based mapping approaches, we have now identified 30 additional genes. Neuronal phenotypes have not previously been reported for 20 of these genes, and no mutant phenotype has been previously described for 5 genes. The genes encode a variety of proteins implicated in cellular processes such as gene regulation, cytoskeletal dynamics, axonal transport, and cell signalling. We conducted a comprehensive phenotypic analysis of 35 genes, scoring wiring defects according to 33 criteria. This work demonstrates the feasibility of combining large-scale gene identification with large-scale mutagenesis in Drosophila, and provides a comprehensive overview of the molecular mechanisms that regulate visual system wiring.

  • 2.
    Borg, Malin
    Södertörns högskola, Institutionen för livsvetenskaper.
    Does eutrophication cause directional genetic selection in three-spined stickleback (Gasterosteus aculeatus)?: A study of multiple Baltic Sea populations.2011Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Human-induced eutrophication is indirectly affecting aquatic organisms by altering their environment. This brings on altered selective pressures and could thereby cause changes in the genetic composition of exposed populations. Since anthropogenic environmental changes are usually occurring at a much higher rate than naturally occurring changes, they force populations to adapt to the new conditions faster than normal. Here, I have studied populations of three-spined sticklebacks (Gasterosteus aculeatus) from four eutrophicated and four adjacent reference sites, along the coast of Finland, to investigate if this species has responded genetically to the human-induced eutrophication of the Baltic Sea. For this purpose I used amplified fragment length polymorphism (AFLP) and found distinctions in genetic composition between the two habitats, as well as similarities between populations from eutrophicated sites. This suggests a similar genetic response to eutrophicated conditions by stickleback populations from different geographical areas. Moreover I found a distinct geographic structure among three-spined sticklebacks in the Baltic Sea.

    Fulltekst (pdf)
    Does_eutrophication_cause_directional_genetic_selection_in_three-spined_stickleback
  • 3.
    Borg, Malin
    Södertörns högskola, Institutionen för livsvetenskaper.
    Does eutrophication cause directional genetic selection in three-spined sticklebacks (Gasterosteus aculeatus)?: A study of multiple Baltic Sea populations2011Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Human-induced eutrophication is indirectly affecting aquatic organisms by altering their environment. This brings on altered selective pressures and could thereby cause changes in the genetic composition of exposed populations. Since anthropogenic environmental changes are usually occurring at a much higher rate than naturally occurring changes, they force populations to adapt to the new conditions faster than normal. Here, I have studied populations of three-spined sticklebacks (Gasterosteus aculeatus) from four eutrophicated and four adjacent reference sites, along the coast of Finland, to investigate if this species has responded genetically to the human-induced eutrophication of the Baltic Sea. For this purpose I used amplified fragment length polymorphism (AFLP) and found distinctions in genetic composition between the two habitats, as well as similarities between populations from eutrophicated sites. This suggests a similar genetic response to eutrophicated conditions by stickleback populations from different geographical areas. Moreover I found a distinct geographic structure among three-spined sticklebacks in the Baltic Sea.

    Fulltekst (pdf)
    Does eutrophication cause directional genetic selection in three-spined sticklebacks
  • 4.
    Bürglin, Thomas R.
    Södertörns högskola, Institutionen för livsvetenskaper.
    Evolution of hedgehog and hedgehog-related genes, their origin from Hog proteins in ancestral eukaryotes and discovery of a novel Hint motif2008Inngår i: BMC Genomics, E-ISSN 1471-2164, Vol. 9, s. 127-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: The Hedgehog (Hh) signaling pathway plays important roles in human and animal development as well as in carcinogenesis. Hh molecules have been found in both protostomes and deuterostomes, but curiously the nematode Caenorhabditis elegans lacks a bona-fide Hh. Instead a series of Hh-related proteins are found, which share the Hint/Hog domain with Hh, but have distinct N-termini. Results: We performed extensive genome searches such as the cnidarian Nematostella vectensis and several nematodes to gain further insights into Hh evolution. We found six genes in N. vectensis with a relationship to Hh: two Hh genes, one gene with a Hh N-terminal domain fused to a Willebrand factor type A domain (VWA), and three genes containing Hint/Hog domains with distinct novel N-termini. In the nematode Brugia malayi we find the same types of hh-related genes as in C. elegans. In the more distantly related Enoplea nematodes Xiphinema and Trichinella spiralis we find a bona-fide Hh. In addition, T. spiralis also has a quahog gene like C. elegans, and there are several additional hh-related genes, some of which have secreted N-terminal domains of only 15 to 25 residues. Examination of other Hh pathway components revealed that T. spiralis - like C. elegans - lacks some of these components. Extending our search to all eukaryotes, we recovered genes containing a Hog domain similar to Hh from many different groups of protists. In addition, we identified a novel Hint gene family present in many eukaryote groups that encodes a VWA domain fused to a distinct Hint domain we call Vint. Further members of a poorly characterized Hint family were also retrieved from bacteria. Conclusion: In Cnidaria and nematodes the evolution of hh genes occurred in parallel to the evolution of other genes that contain a Hog domain but have different N-termini. The fact that Hog genes comprising a secreted N-terminus and a Hog domain are found in many protists indicates that this gene family must have arisen in very early eukaryotic evolution, and gave rise eventually to hh and hh-related genes in animals. The results indicate a hitherto unsuspected ability of Hog domain encoding genes to evolve new N-termini. In one instance in Cnidaria, the Hh N-terminal signaling domain is associated with a VWA domain and lacks a Hog domain, suggesting a modular mode of evolution also for the N-terminal domain. The Hog domain proteins, the inteins and VWA-Vint proteins are three families of Hint domain proteins that evolved in parallel in eukaryotes.

  • 5. Chen, Nansheng
    et al.
    Mah, Allan
    Blacque, Oliver E.
    Chu, Jeffrey
    Phgora, Kiran
    Bakhoum, Mathieu W.
    Newbury, C. Rebecca Hunt
    Khattra, Jaswinder
    Chan, Susanna
    Go, Anne
    Efimenko, Evgeni
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institute.
    Johnsen, Robert
    Phirke, Prasad
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institute.
    Swoboda, Peter
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institute.
    Marra, Marco
    Moerman, Donald G.
    Leroux, Michel R.
    Baillie, David L.
    Stein, Lincoln D.
    Identification of ciliary and ciliopathy genes in Caenorhabditis elegans through comparative genomics2006Inngår i: Genome Biology, ISSN 1465-6906, E-ISSN 1474-760X, Vol. 7, nr 12, s. R126-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: The recent availability of genome sequences of multiple related Caenorhabditis species has made it possible to identify, using comparative genomics, similarly transcribed genes in Caenorhabditis elegans and its sister species. Taking this approach, we have identified numerous novel ciliary genes in C. elegans, some of which may be orthologs of unidentified human ciliopathy genes. Results: By screening for genes possessing canonical X-box sequences in promoters of three Caenorhabditis species, namely C. elegans, C. briggsae and C. remanei, we identified 93 genes ( including known X-box regulated genes) that encode putative components of ciliated neurons in C. elegans and are subject to the same regulatory control. For many of these genes, restricted anatomical expression in ciliated cells was confirmed, and control of transcription by the ciliogenic DAF-19 RFX transcription factor was demonstrated by comparative transcriptional profiling of different tissue types and of daf-19(+) and daf-19(-) animals. Finally, we demonstrate that the dye-filling defect of dyf-5( mn400) animals, which is indicative of compromised exposure of cilia to the environment, is caused by a nonsense mutation in the serine/threonine protein kinase gene M04C9.5. Conclusion: Our comparative genomics-based predictions may be useful for identifying genes involved in human ciliopathies, including Bardet-Biedl Syndrome ( BBS), since the C. elegans orthologs of known human BBS genes contain X-box motifs and are required for normal dye filling in C. elegans ciliated neurons.

  • 6.
    Cortobius Fredriksson, Moa
    Södertörns högskola, Institutionen för livsvetenskaper.
    ProBenefit: Implementing the Convention on Biological Diversity in the Ecuadorian Amazon2009Independent thesis Basic level (degree of Bachelor), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    Legislation on benefit sharing dates back to 1992 and the commandment of the UNConvention on Biological Diversity, hence implementation still has few cases to fall back on(CBD, 1992). The case study of the project ProBenefit presented by the thesis highlights howlack of deliberation can undermine a democratic process. The objective of the thesis is thatProBenefit’s attempt to implement the standards of the CBD on access and benefit sharingwill highlight not only problems met by this specific project, but difficulties that generallymeet democratic processes in contexts of high inequality. To define if the project ProBenefitsucceeded in carrying out a deliberative process the project will be analyzed by the criteria:access to information, representation, legitimacy and involvement.The population in the project area of ProBenefit had a long history of social marginalization,which made it hard for foreign projects to gain legitimacy. The lack of independentorganizations and the late establishment of the project, which resulted in time shortage, madeit impossible to prevent the distrust of the local population. The failure of the projectcoordinators to ensure active participation of all stakeholders resulted in a late and lowinvolvement of the local participants. The absence of independent organization also madedemocratic legitimacy of the process questionable. Even if ProBenefit had a vision ofdemocratic deliberation the project was unable to break down the prevailing unequal powerdistribution which resulted in an unsustainable process and failure. The conclusion of thethesis is that the attainment of deliberation foremost depends on how a project deals with theexisting distribution of power and how it succeeds in involving all stakeholders.

    Fulltekst (pdf)
    FULLTEXT01
  • 7.
    Ekwall, Karl
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institute.
    Epigenetic control of centromere behavior2007Inngår i: Annual review of genetics / [ed] Allan Campbell, Wyatt W Anderson, Elizabeth W Jones, Palo Atlo: Annual Reviews , 2007, s. 63-81Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The centromere is the DNA region that ensures genetic stability and is therefore of vital importance. Paradoxically, centromere proteins and centromeric structural domains are conserved despite that fact that centromere DNA sequences are highly variable and are not conserved. Remarkably, heritable states at the centromere can be propagated independent of the underlying centromeric DNA sequences. This review describes the epigenetic mechanisms governing centromere behavior, i.e., the mechanisms that control centromere assembly and propagation. A centromeric histone variant, CenH3, and histone modifications play key roles at centromeric chromatin. Histone modifications and RNA interference are important in assembly of pericentric heterochromatin structures. The molecular machinery that is directly involved in epigenetic control of centromeres is shared with regulation of gene expression. Nucleosome remodeling factors, histone chaperones, histone-modifying enzymes, transcription factors, and even RNA polymerase II itself control epigenetic states at centromeres.

  • 8.
    Ekwall, Karl
    Södertörns högskola, Institutionen för livsvetenskaper.
    Genome-wide analysis of HDAC function2005Inngår i: Trends in Genetics, ISSN 0168-9525, E-ISSN 1362-4555, Vol. 21, nr 11, s. 608-615Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article focuses on new developments in the genome-wide analysis of histone deacetylase (HDAC) function in yeast. HDACs are highly conserved in many organisms; therefore, their basic functions can be investigated using experimentally tractable model organisms, such as the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe. New microarray techniques have enabled the systematic study of HDACs by identifying their direct and indirect gene targets in addition to their physiological functions and enzymatic specificity. These new approaches have already provided new surprising insights into the basic function of HDACs.

  • 9.
    Ellencrona, Ellen
    et al.
    Södertörns högskola, Institutionen för livsvetenskaper.
    Melik, Wessam
    Södertörns högskola, Institutionen för livsvetenskaper.
    Johansson, Magnus
    Södertörns högskola, Institutionen för livsvetenskaper.
    Novel PDZ dependent cell associations of the NS5 proteins of Tick-borne encephalitis virus and West-Nile virusManuskript (preprint) (Annet vitenskapelig)
  • 10.
    Ellencrona, Karin
    Södertörns högskola, Institutionen för livsvetenskaper.
    Functional characterization of interactions between the flavivirus NS5 protein and PDZ proteins of the mammalian host2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Flaviviruses are found all over the world and affect and infect millions of people every year. Flavivirus infection can lead to severe clinical outcomes resulting in neuronal damages e.g. Tick-borne encephalitis virus (TBEV), or severe hemorrhagic fevers e.g. Dengue virus (DENV). In order to effectively treat infected patients and to prevent these diseases we must understand how these viruses work and how they interfere with the mammalian host. This thesis is focusing on interactions between the virus protein NS5 and human host cell proteins. The interactions presented here might be key factors for out-come of viral disease. NS5 is the largest of the non-structural proteins and is essential for the replication and the capping as it contains both RNA dependent RNA polymerase and Methyltransferase domains. We found that TBEV NS5 interacts with human PDZ domain protein Scribble, a polarization protein important e.g. in regulating membrane trafficking. We determined that the interaction depend on a novel internal motif in TBEVNS5. This interaction could be correlated to NS5s ability to interfere with the immune system as absence of Scribble prevented NS5 from blocking phosphorylation of STAT upon Interferon induction. The role of NS5 in human PDZ domain targeting was addressed further by using a PDZ array system. Both TBEVNS5 and DENVNS5 bind additional PDZ domains using the internal motif. The tight junction protein ZO-1 binds both DENVNS5 and TBEVNS5. DENVNS5 is mainly present in the nucleus and co-localize with ZO-1 in un-polarized cells. In polarized cells TBEVNS5 and ZO-1 co-localize at the plasmamembrane. Putative C-terminal PDZ binding motifs of TBEVNS5 and WNVNS5 were characterized using the PDZ array system. This detected four novel binding partners of TBEVNS5 but numerous of potential WNVNS5 binding partners. We found that TBEVNS5 co-localizes with ZO-2 in the cellular membrane. Further, we found that TBEVNS5 induce the AP-1 by a 2 fold over the control.

    Download (jpg)
    presentationsbild
  • 11.
    Grube, Martin
    et al.
    Graz university, Austria.
    Gutmann, B.
    Graz university, Austria.
    Arup, Ulf
    Graz university, Austria.
    Rios, A. de los
    Graz university, Austria.
    Mattsson, Jan-Eric
    Uppsala university.
    Wedin, Mats
    Natural History Museum, London.
    An exceptional group I intron-like insertion in SSU rDNA of lichen mycobionts1999Inngår i: Current Genetics, ISSN 0172-8083, E-ISSN 1432-0983, Vol. 35, s. 536-541Artikkel i tidsskrift (Fagfellevurdert)
  • 12. Hao, Limin
    et al.
    Johnsen, Robert
    Lauter, Gilbert
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institute.
    Baillie, David
    Bürglin, Thomas R.
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institute.
    Comprehensive analysis of gene expression patterns of hedgehog-related genes2006Inngår i: BMC Genomics, E-ISSN 1471-2164, Vol. 7, s. 280-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: The Caenorhabditis elegans genome encodes ten proteins that share sequence similarity with the Hedgehog signaling molecule through their C-terminal autoprocessing Hint/Hog domain. These proteins contain novel N-terminal domains, and C. elegans encodes dozens of additional proteins containing only these N-terminal domains. These gene families are called warthog, groundhog, ground-like and quahog, collectively called hedgehog (hh)-related genes. Previously, the expression pattern of seventeen genes was examined, which showed that they are primarily expressed in the ectoderm. Results: With the completion of the C. elegans genome sequence in November 2002, we reexamined and identified 61 hh-related ORFs. Further, we identified 49 hh-related ORFs in C. briggsae. ORF analysis revealed that 30% of the genes still had errors in their predictions and we improved these predictions here. We performed a comprehensive expression analysis using GFP fusions of the putative intergenic regulatory sequence with one or two transgenic lines for most genes. The hh-related genes are expressed in one or a few of the following tissues: hypodermis, seam cells, excretory duct and pore cells, vulval epithelial cells, rectal epithelial cells, pharyngeal muscle or marginal cells, arcade cells, support cells of sensory organs, and neuronal cells. Using time-lapse recordings, we discovered that some hh-related genes are expressed in a cyclical fashion in phase with molting during larval development. We also generated several translational GFP fusions, but they did not show any subcellular localization. In addition, we also studied the expression patterns of two genes with similarity to Drosophila frizzled, T23D8.1 and F27E11.3A, and the ortholog of the Drosophila gene dally-like, gpn-1, which is a heparan sulfate proteoglycan. The two frizzled homologs are expressed in a few neurons in the head, and gpn-1 is expressed in the pharynx. Finally, we compare the efficacy of our GFP expression effort with EST, OST and SAGE data. Conclusion: No bona-fide Hh signaling pathway is present in C. elegans. Given that the hh-related gene products have a predicted signal peptide for secretion, it is possible that they constitute components of the extracellular matrix (ECM). They might be associated with the cuticle or be present in soluble form in the body cavity. They might interact with the Patched or the Patched-related proteins in a manner similar to the interaction of Hedgehog with its receptor Patched.

  • 13. Isaac, Sara
    et al.
    Walfridsson, Julian
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institute.
    Zohar, Tal
    Lazar, David
    Kahan, Tamar
    Ekwall, Karl
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institute.
    Cohen, Amikam
    Interaction of Epe1 with the heterochromatin assembly pathway in Schizosaccharomyces pombe2007Inngår i: Genetics, ISSN 0016-6731, E-ISSN 1943-2631, Vol. 175, nr 4, s. 1549-1560Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Epe1 is a JmjC domain protein that antagonizes heterochromatization in Schizosaccharomyces pombe. Related JmjC domain proteins catalyze a histone demethylation reaction that depends on Fe(II) and alpha-ketoglutarate. However, no detectable demethylase activity is associated with Epe1, and its JmjC domain lacks conservation of Fe(II)-binding residues. We report that Swi6 recruits Epe1 to heterochromatin and that overexpression of epe1(+), like mutations in silencing genes or overexpression of swi6(+), upregulates expression of certain genes. A significant overlap was observed between the lists of genes that are upregulated by overexpression of epe1(+) and those that are upregulated by mutations in histone deacetylase genes. However, most of the common genes are not regulated by Clr4 histone methyltransferase. This suggests that Epe1 interacts with the heterochromatin assembly pathway at the stage of histone deacetylation. Mutational inactivation of Epe1 downregulates similar to 12% of S. pombe genes, and the list of these genes overlaps significantly with the lists of genes that are upregulated by mutations in silencing genes and genes that are hyperacetylated at their promoter regions in clr6-1 mutants. We propose that an interplay between the repressive HDACs activity and Epe1 helps to regulate gene expression in S. pombe.

  • 14.
    Jonsson, Magnus
    et al.
    Södertörns högskola, Institutionen för livsvetenskaper.
    Bertilsson, Maria
    Ehrlén, Johan
    Lönn, Mikael
    Södertörns högskola, Institutionen för livsvetenskaper.
    Genetic divergence of climatically marginal populations of Vicia pisiformis on the Scandinavian Peninsula2008Inngår i: Hereditas, ISSN 0018-0661, E-ISSN 1601-5223, Vol. 145, nr 1, s. 1-8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Vicia pisiformis L. is a perennial leguminous plant with a main distribution in broadleaved forest-steppes of eastern Europe. The species is classified as endangered (EN) according to the IUCN red-lists in both Norway and Sweden, due to severe fragmentation, small population sizes and continuing population decline. The populations on the Scandinavian Peninsula constitute the northern limit of the species distribution and are mostly restricted to warm stony slopes with predominantly southern aspects. In this study we used the AFLP method, which is a high-resolution genetic fingerprint method. Samples were collected from 22 Scandinavian populations. The overall genetic structure was analysed in an AMOVA, in a Mantel test and through constrained correspondence analysis (CCA). The ordination scores representing non-geographic genetic divergence were extracted from the CCA and analysed in a linear model using habitat variables and population size as explanatory variables. We found (i) a strong geographic structure, (ii) significant genetic divergence between populations, (iii) that this genetic divergence remained significant even after removing the effect of geography in a partial CCA and (iv) that the remaining non-geographic part of genetic divergence (distance from the ordination centre) was associated with aspect, populations with a northern aspect were more genetically divergent. Aspect explains more variation than population size and is the only variable retained in the minimal adequate model. We suggest that local adaptation has caused this divergence from an expected geographical pattern of genetic variation. This explanation is further supported by the association between aspect and specific AFLP fragments. Many plant populations are relics of a different climate (Aguirre-Planter et al. 2000; Despres et al. 2002; Pico and Riba 2002). In response to long-term climate change, populations can either migrate towards a more favourable climate or adapt to the new conditions (delaVega 1996; Jump et al. 2006). Species with limited dispersal ability are at risk of reaching isolated dead-ends of decreasingly suitable habitat, without any suitable habitat within dispersal distance (Colas et al. 1997). Isolated populations have to use their inherent evolutionary potential and adapt to changes in environmental conditions, or they will go extinct. As population fragments go extinct, those that remain will become increasingly isolated from each other both spatially and also genetically as the level of gene flow declines with increasing distance. Such correlation between genetic dissimilarities and geographic distances, known as isolation by distance (Slatkin 1993; Wright 1943), when found, suggests a history of geographically limited gene flow (Kimura and Weiss 1964). On top of an isolation by distance pattern there might be other genetic structures to be found. Occasional long-distance dispersal events for example may disturb geographic patterns with puzzling allele distributions as a result (Nichols and Hewitt 1994). Genetic drift is a process that will affect any pattern of genetic variation in a random fashion. Local adaptation through natural selection is a process that, if sufficiently strong in comparison with gene flow and genetic drift, will create patterns where genetic differentiation is associated with certain environmental conditions (Wright 1951). Several studies have shown the importance of local adaptation of populations (reviewed by Kawecki and Ebert 2004) (see also Bonin et al. 2006; Knight and Miller 2004; Kolseth and Lönn 2005; Lönn et al. 1998). Local adaptation can be strong also at small spatial scales (Snaydon and Davies 1976; Lönn 1993) even though it is sometimes very limited in terms of the number of genes involved (Kärkkainen et al. 2004) Environmental variability provides a base for biological variation by imposing differentiated selection pressures resulting in local adaptation. Topography provides large environmental variation within a relatively small area and thereby provides a basis for small-scale local adaptations. Depending on the local topographic possibilities populations can either migrate up and down slopes or along the same altitude to a different aspect to find a suitable microclimate. The dispersal distance will be much shorter per degree of temperature change during altitudinal migration (Hewitt 1996), than during simple latitudinal migration across a flat landscape. Slope and aspect are two important topographic parameters that determine the influx level of solar radiation, especially towards the poles where the total global radiation decreases (Larcher 2003). Vicia pisiformis is an endangered poorly-dispersed long-lived forest herb with its main distribution across the semi-open broadleaved forest steppes of eastern Europe. The Scandinavian populations are believed to be climate relict populations from warmer times. Earlier genetic studies of V. pisiformis using allozymes, RAPD:s and morhology, have found low to very low levels of genetic variation (Gustafsson and Gustafsson 1994; Black-Samuelsson et al. 1997; Black-Samuelsson and Lascoux 1999). Therefore we used AFLP (amplified fragment length polymorphism) markers, which detect even very small genetic differences between individuals. AFLP mainly analyse neutral variation, as the major fraction of most genomes is assumed to be neutral. However, since the AFLP-fragments are distributed randomly throughout the whole genome some fragments may be situated so close to regions under selection that they become more or less linked to them. This linkage disequilibrium between molecular markers and regions under selection, often referred to as quantitative trait loci (QTL), forms the basis for both QTL-mapping and marker assisted selection (MAS), reviewed by Dekkers and Hospital (2002). Gardner and Latta (2006) for example, found QTL under selection in both natural environments and in the greenhouse. Markers have been found to be connected to biomass production (Cavagnaro et al. 2006) and environmental variation (Bonin et al. 2006; Jump et al. 2006; Porcher et al. 2006). In this study we examine 22 Swedish and Norwegian populations of Vicia pisiformis and ask (i) if there is genetic differentiation between these populations, (ii) if there is can it be explained in its entirety by geographic location or (iii) can it partly be explained by habitat characteristics, suggesting local adaptation, or population size, suggesting genetic drift. We show that populations are differentiated geographically and that genetic variation in addition to the geographical pattern is associated with habitat.

  • 15.
    Kitambi, Satish Srinivas
    et al.
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institutet.
    Hauptmann, Giselbert
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institutet.
    The zebrafish orphan nuclear receptor genes nr2e1 and nr2e3 are expressed in developing eye and forebrain2007Inngår i: Gene Expression Patterns, ISSN 1567-133X, E-ISSN 1872-7298, Vol. 7, nr 4, s. 521-528Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mammalian Nr2e1 (Tailless, Mtll or Tlx) and Nr2e3 (photoreceptor-specific nuclear receptor, Pnr) are highly related orphan nuclear receptors, that are expressed in eye and forebrain-derived structures. In this study, we analyzed the developmental expression patterns of zebrafish nr2e1 and nr2e3. RT-PCR analysis showed that nr2e1 and nr2e3 are both expressed during embryonic and post-embryonic development. To examine the spatial distribution of nr2e1 and nr2e3 during development whole-mount in situ hybridization was performed. At tailbud stage, initial nr2e1 expression was localized to the rostral brain rudiment anterior to pax2.1 and eng2 expression at the prospective midbrain-hindbrain boundary. During Subsequent stages, nr2e1 became widely expressed in fore- and midbrain primordia, eye and olfactory placodes. At 24 hpf, strong nr2e1 expression was detected in telencephalon, hypothalamus, dorsal thalamus, pretectum, midbrain tectum, and retina. At 2 dpf, the initially widespread nr2e1 expression became more restricted to distinct regions within the fore- and midbrain and to the retinal ciliary margin, the germinal zone which gives rise to retina and presumptive iris. Express on of nr2e3 was exclusively found in the developing retina and epiphysis. In both structures, nr2e3 expression was found in photoreceptor cells. The developmental expression profile of zebrafish nr2e1 and nr2e3 is consistent with evolutionary conserved functions in eye and rostral brain structures.

  • 16.
    Larsson, Josefine
    et al.
    Södertörns högskola, Institutionen för livsvetenskaper, Biologi. Södertörns högskola, Institutionen för livsvetenskaper, Miljövetenskap.
    Henriksson, Oskar
    Södertörns högskola, Institutionen för livsvetenskaper, Biologi. Södertörns högskola, Institutionen för livsvetenskaper, Miljövetenskap.
    Grahn, Mats
    Södertörns högskola, Institutionen för livsvetenskaper, Biologi. Södertörns högskola, Institutionen för livsvetenskaper, Miljövetenskap.
    Population Genetic Structure and Connectivity of the Abundant Sea Urchin, Diadema setosum around Unguja Island (Zanzibar)2010Inngår i: Western Indian Ocean Journal of Marine Science, ISSN 0856-860X, E-ISSN 2683-6416, Vol. 9, nr 2, s. 165-174Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract—Uncontrolled growth of sea urchin populations may have a negative effect on coral reefs, making them barren. To avoid this, different methods of sea urchin reduction have been developed but, without knowledge of their genetic structure and connectivity, these methods may be ineffective. The aim of this study was to examine the fine-scale genetic structure and connectivity in the sea urchin, Diadema setosum, population around Unguja, Zanzibar, using AFLP. We found evidence of different genetic clusters, high migration between the sites and high genetic diversity within the sites. These findings indicate that a manual reduction of sea urchins with similar genetic connectivity, implemented on the same geographic scale as our study, would be ineffective since sites are probably repopulated from many sources.

  • 17.
    Larsson, Josefine
    et al.
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Biologi.
    Lind, Emma
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Biologi. Stockholms universitet.
    Hallgren, Stefan
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Biologi.
    From AFLP to sequence specific markers: Identifying genomic regions under selection in the three-spined stickleback caused by pulp mill effluentsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The processes underlying divergent selection and genetic adaptation have been on the evolutionary biologists agenda for a long time. In this study we used the three-spined stickleback (Gasterosteus aculeatus) study system, a perfect system to study the evolution of similar traits in different lineages exposed to similar environmental conditions. Lind and Grahn (2011) have found directional selection caused by pulp mill effluent on populations of three-spined stickleback along the Swedish coast. In their study, they identified 21 AFLP- outlier loci indicated to be under selection. Here we converted some of these anonymous AFLP loci into sequenced markers and aligned them to the stickleback genome. Four out of five loci, aligned within or close to coding regions, on chromosome I, chromosome VIII, chromosome XIX and chromosome XX. One of the locus, located on chromosome VIII, have been identified to be under selection for fresh water adaption in other studies, including Baltic Sea stickleback populations (Mäkinen et al. 2008a,b). We believe that this is feasibly method that can be used as a starting point for identification of genes and genomic regions possible involved in adaptation, both for model and non-model organisms. 

  • 18.
    Laurencon, Anne
    et al.
    Université de Lyon, France.
    Dubruille, Raphaelle
    Université de Lyon, France / University of Massachusetts Medical School, USA.
    Efimenko, Evgeni
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institute.
    Grenier, Guillaume
    Université de Lyon, France.
    Bissett, Ryan
    Université de Lyon, France / University of Glasgow, UK.
    Cortier, Elisabeth
    Université de Lyon, France.
    Rolland, Vivien
    Université de Lyon, France.
    Swoboda, Peter
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institute.
    Durand, Benedicte
    Université de Lyon, France.
    Identification of novel regulatory factor X (RFX) target genes by comparative genomics in Drosophila species2007Inngår i: Genome Biology, ISSN 1465-6906, E-ISSN 1474-760X, Vol. 8, nr 9, s. R195-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Regulatory factor X (RFX) transcription factors play a key role in ciliary assembly in nematode, Drosophila and mouse. Using the tremendous advantages of comparative genomics in closely related species, we identified novel genes regulated by dRFX in Drosophila. Results: We first demonstrate that a subset of known ciliary genes in Caenorhabditis elegans and Drosophila are regulated by dRFX and have a conserved RFX binding site (X-box) in their promoters in two highly divergent Drosophila species. We then designed an X-box consensus sequence and carried out a genome wide computer screen to identify novel genes under RFX control. We found 412 genes that share a conserved X-box upstream of the ATG in both species, with 83 genes presenting a more restricted consensus. We analyzed 25 of these 83 genes, 16 of which are indeed RFX target genes. Two of them have never been described as involved in ciliogenesis. In addition, reporter construct expression analysis revealed that three of the identified genes encode proteins specifically localized in ciliated endings of Drosophila sensory neurons. Conclusion: Our X-box search strategy led to the identification of novel RFX target genes in Drosophila that are involved in sensory ciliogenesis. We also established a highly valuable Drosophila cilia and basal body dataset. These results demonstrate the accuracy of the X-box screen and will be useful for the identification of candidate genes for human ciliopathies, as several human homologs of RFX target genes are known to be involved in diseases, such as Bardet-BiedI syndrome.

  • 19. Li, Chunmei
    et al.
    Inglis, Peter N.
    Leitch, Carmen C.
    Efimenko, Evgeni
    Södertörns högskola, Institutionen för livsvetenskaper.
    Zaghloul, Norann A.
    Mok, Calvin A.
    Davis, Erica E.
    Bialas, Nathan J.
    Healey, Michael P.
    Heon, Elise
    Zhen, Mei
    Swoboda, Peter
    Södertörns högskola, Institutionen för livsvetenskaper.
    Katsanis, Nicholas
    Leroux, Michel R.
    An essential role for DYF-11/MIP-T3 in assembling functional intraflagellar transport complexes2008Inngår i: PLOS Genetics, ISSN 1553-7390, E-ISSN 1553-7404, Vol. 4, nr 3, s. e1000044-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    MIP-T3 is a human protein found previously to associate with microtubules and the kinesin-interacting neuronal protein DISC1 ( Disrupted-in-Schizophrenia 1), but whose cellular function(s) remains unknown. Here we demonstrate that the C. elegans MIP-T3 ortholog DYF-11 is an intraflagellar transport (IFT) protein that plays a critical role in assembling functional kinesin motor-IFT particle complexes. We have cloned a loss of function dyf-11 mutant in which several key components of the IFT machinery, including Kinesin-II, as well as IFT subcomplex A and B proteins, fail to enter ciliary axonemes and/or mislocalize, resulting in compromised ciliary structures and sensory functions, and abnormal lipid accumulation. Analyses in different mutant backgrounds further suggest that DYF-11 functions as a novel component of IFT subcomplex B. Consistent with an evolutionarily conserved cilia-associated role, mammalian MIP-T3 localizes to basal bodies and cilia, and zebrafish mipt3 functions synergistically with the Bardet-Biedl syndrome protein Bbs4 to ensure proper gastrulation, a key cilium- and basal body-dependent developmental process. Our findings therefore implicate MIP-T3 in a previously unknown but critical role in cilium biogenesis and further highlight the emerging role of this organelle in vertebrate development.

  • 20.
    Lind, Emma
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Biologi. Stockholms universitet.
    Genetic response to pollution in sticklebacks; natural selection in the wild2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The last century, humans have been altering almost all natural environments at an accelerating rate, including the Baltic Sea that has highly eutrophicated areas and many coastal industries such as Pulp-mills. For animals living in a habitat that changes there are basically two alternatives, either to cope with the change or become locally extinct. This thesis aims to investigate if recent anthropogenic disturbance in the Baltic Sea can affect natural populations on a genetic level through natural selection.

    First, we found a fine-scale genetic structure in three-spine sticklebacks (Gasterosteus aculeatus) populations along the Swedish coast (paper I), indicating limited gene-flow between populations in geographic proximity. Different genetic markers, specifically Amplified Fragment Lenght Polymorpism (AFLP, and microsatellites,  gave different results, highlighting the heterogeneous character of genomes which demonstrates that it is important to choose a genetic marker that is relevant for the question at hand. With a population genomic approach, and a multilocus genetic marker (AFLP), we detected convergent evolution in genotype composition in stickleback populations living in environments affected by pulp-mill effluent (paper II) and in highly eutrophicated environments (paper III), compared to adjacent reference populations. We found loci, in both studies (paper II, III), that were different from a neutral distribution and thus probably under divergent selection for the habitat differences investigated. The selective effect from pulp-mill effluents were more pronounced, but the two different habitats had mutual characters (AFLP loci). In paper IV, we converted five anonymous AFLP loci to sequenced markers and aligned them to the stickleback genome. Four out of five loci aligned within, or close to, coding regions on chromosome I, chromosome VIII, chromosome XIX and chromosome XX. One of the loci, located on chromosome VIII and identified as under divergent selection in both paper II and III, has been identified in other studies as to be under selection for fresh water adaptation, including Baltic Sea stickleback populations.

    In conclusion, anthropogenic alterations of natural environments can have evolutionary consequences, probably adaptive, for the animals living there and the evolutionary response exhibited by natural populations can be very fast.

  • 21.
    Lind, Emma E
    et al.
    Södertörns högskola, Institutionen för livsvetenskaper, Biologi. Södertörns högskola, Institutionen för livsvetenskaper, Molekylärbiologi.
    Grahn, Mats
    Södertörns högskola, Institutionen för livsvetenskaper, Miljövetenskap. Södertörns högskola, Institutionen för livsvetenskaper, Biologi.
    Directional genetic selection by pulp mill effluent on multiple natural populations of three-spined stickleback (Gasterosteus aculeatus)2011Inngår i: Ecotoxicology, ISSN 0963-9292, E-ISSN 1573-3017, Vol. 20, s. 503-512Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Contamination can cause a rapid environmental change which may require populations to respond with evolutionary changes. To evaluate the effects of pulp mill effluents on population genetics, we sampled three-spined sticklebacks (Gasterosteus aculeatus) near four pulp mills and four adjacent reference sites and analyzed Amplified Fragment Length Polymorphism (AFLP) to compare genetic variability. A fine scale genetic structure was detected and samples from polluted sites separated from reference sites in multidimensional scaling plots (P < 0.005, 1000 permutations) and locus-by-locus Analysis of Molecular Variance (AMOVA) further confirmed that habitats are significantly separated (F(ST) = 0.021, P < 0.01, 1023 permutations). The amount of genetic variation between populations did not differ between habitats, and populations from both habitats had similar levels of heterozygosity (polluted sites Nei's Hs = 0.11, reference sites Nei's Hs = 0.11). Still, pairwise F(ST): s between three, out of four, pairs of polluted-reference sites were significant. A F(ST)-outlier analysis showed that 21 (8.4%) loci were statistically different from a neutral distribution at the P < 0.05 level and therefore indicated to be under divergent selection. When removing 13 F(ST)-outlier loci, significant at the P < 0.01 level, differentiation between habitats disappeared in a multidimensional scaling plot. In conclusion, pulp mill effluence has acted as a selective agent on natural populations of G. aculeatus, causing a convergence in genotype composition change at multiple sites in an open environment.

  • 22.
    Lind, Emma
    et al.
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Biologi. Stockholms universitet.
    Larsson, Josefine
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Biologi.
    Tuomainen, Ulla
    University of Helsinki.
    Borg, Malin
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik.
    Candolin, Ulrika
    University of Helsinki.
    Grahn, Mats
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Biologi.
    Genetic response to eutrophication in three-spined sticklebacks (Gasterosteus aculeatus): A study of multiple Baltic Sea populationsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Anthropogenic activities are causing change in natural habitats at an accelerating rate and affecting populations by altered selection pressures. One example is human-induced eutrophication in the Baltic Sea, were behaviour alterations are well documented in three-spined sticklebacks (Gasterosteus aculeatus). Here we have used 204 variable Amplified Fragment Length Polymorphism (AFLP) markers to investigate genetic differences between a set of ten hierarchal sampled populations of sticklebacks, five populations inhabiting eutrophicated habitats and five from control populations, in total 292 individuals. We found significant genetic variation that could be attributed to habitat (4.3% AMOVA). A combination of FST outlier analysis and classification analysis revealed seven AFLP-loci likely to be affected by divergent selection by eutrophication. Four of these seven loci have earlier been identified as under selection in stickleback populations living in pulp-mill effluents suggesting some similar selective factors between eutrophication and pulp-mill effluent effected habitats. 

  • 23.
    Lind, Emma
    et al.
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Biologi. Stockholms universitet.
    Ohlin, Helena
    Mälardalens högskola.
    Grahn, Mats
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, Biologi.
    Fine scale genetic structure in Thresspine sticklback (Gasterosteus aculeatus) along Sweden's coastManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    There are three basic types of population structures in marine environments; populations that are distinct, with a continuous change and without any differentiation. In each type the population units are characterized by groups of individuals with panmixia within groups and site fidelity to a limited geographic area. Earlier studies of the population genetic structure on sticklebacks in the Baltic Sea have shown none or only little structure. We have sampled 8 sites (253 individuals) along Sweden’s coast to estimate the genetic structure, using five microsatellites and 173 Amplified Fragment Length Polymorphism (AFLP) markers and detected a fine scale genetic structure (AFLP FST= 25%, microsatellites FST = 2.7%). With AFLPs the observed variation followed isolation by distance model (but not with microsatellites). Even sites separated by only 2 km of water are significantly separated. Both Bayesian clustering analysis and Capscale separated populations and identified populations from Gulf of Bothnia (4 psu) and from the west coast (20 psu) as genetically distinctly different from Baltic populations (about 7-8 psu).  In conclusion, gene flow is limited between sampled sites, and since no geographic barriers can be distinguished the population structure is likely caused by the sticklebacks’ behavior. Hence, we have probably sampled either stationary populations of marine sticklebacks, or homing sticklebacks. In this study AFLP and microsatellites did not give congruent results; with AFLPs we got high separation, and genetic variation followed isolation by distance model and supported the continuous change type of population structure.

  • 24.
    Lönn, Mikael
    et al.
    Södertörns högskola, Institutionen för livsvetenskaper.
    Alexandersson, Ronny
    Gustafsson, Susanne
    Hybrids and fruit set in a mixed flowering-time population of Gymnadenia conopsea (Orchidaceae).2006Inngår i: Hereditas, ISSN 0018-0661, E-ISSN 1601-5223, Vol. 143, s. 222-228Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have recently found that the morphologically determined subspecies Gymnadenia conopsea ssp conopsea in Sweden includes early and late flowering individuals. We were interested in the interactions between the flowering time groups; if there were gene flow between them and if so this was detrimental or advantageous. A spatially mixed population of early and late flowering individuals was studied using three microsatellite loci. We measured patterns in genetic differentiation and inferred occurrence of hybridisation and introgression. Variation in flowering time, fertility and relative and absolute fruit set was measured. The pattern of introgression between flowering-time groups differed between loci. In two of the three investigated loci, allele separation was distinct between early and late flowering plants and one genetically obvious hybrid was infertile. In the third locus, several alleles were shared between the two flowering time variants. The degree of introgression was associated to fruit set failure, which was higher in the late flowering plants and lower in early flowering plants. A small group of early flowering individuals with somewhat delayed flowering compared to the main group was genetically distinct and had lower relative and absolute fruit set. This group was not genetically intermediate, but rather constituting an independent group, with lower fruit set possibly caused by absence of pollinators. There seem to be a strong barrier against introgression into the late flowering group which is kept genetically distinct and less diverse. The early flowering group is diverse, includes two subgroups and seems to benefit from gene flow

  • 25.
    Moradi, Hossein
    et al.
    Södertörns högskola, Institutionen för livsvetenskaper. Stockholm University.
    Simoff, Ivailo
    Södertörns högskola, Institutionen för livsvetenskaper. Stockholm University.
    Bartish, Galyna
    Södertörns högskola, Institutionen för livsvetenskaper. Stockholm University.
    Nygård, Odd
    Södertörns högskola, Institutionen för livsvetenskaper.
    Functional features of the C-terminal region of yeast ribosomal protein L52008Inngår i: Molecular Genetics and Genomics, ISSN 1617-4615, E-ISSN 1617-4623, Vol. 280, nr 4, s. 337-350Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study was to analyze the functional importance of the C-terminus of the essential yeast ribosomal protein L5 (YrpL5). Previous studies have indicated that the C-terminal region of YrpL5 forms an alpha-helix with a positively charged surface that is involved in protein-5S rRNA interaction. Formation of an YrpL5 center dot 5S rRNA complex is a prerequisite for nuclear import of YrpL5. Here we have tested the importance of the alpha-helix and the positively charged surface for YrpL5 function in Saccharomyces cerevisiae using site directed mutagenesis in combination with functional complementation. Alterations in the sequence forming the putative alpha-helix affected the functional capacity of YrpL5. However, the effect did not correlate with a decreased ability of the protein to bind to 5S rRNA as all rpL5 mutants tested were imported to the nucleus whether or not the alpha-helix or the positively charged surface were intact. The alterations introduced in the C-terminal sequence affected the growth rate of cells expressing mutant but functional forms of YrpL5. The reduced growth rate was correlated with a reduced ribosomal content per cell indicating that the alterations introduced in the C-terminus interfered with ribosome assembly.

  • 26.
    Senti, Gabriele
    et al.
    Södertörns högskola, Institutionen för livsvetenskaper.
    Ezcurra, Marina
    Löbner, Jana
    Södertörns högskola, Institutionen för livsvetenskaper.
    Schafer, William R.
    Swoboda, Peter
    Södertörns högskola, Institutionen för livsvetenskaper, Molekylärbiologi.
    Worms With a Single Functional Sensory Cilium Generate Proper Neuron-Specific Behavioral Output2009Inngår i: Genetics, ISSN 0016-6731, E-ISSN 1943-2631, Vol. 183, nr 2, s. 595-605Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studying the development and mechanisms of sensory perception is challenging in organisms with complex neuronal networks. The worm Caenorhabditis elegans possesses a simple neuronal network of 302 neurons that includes 60 ciliated sensory neurons (CSNs) for detecting external sensory input. C. elegans is thus an excellent model in which to study sensory neuron development., function, and behavior. We have generated a genetic rescue system that allows in vivo analyses of isolated CSNs at both cellular and systemic levels. We used the RFX transcription factor DAF-19, a key regulator of ciliogenesis. Mutations in daf-19 result in the complete absence of all sensory cilia and thus of external sensory input. In daf-19 mutants, we used cell-specific rescue of DAF-19 function in selected neurons, thereby generating animals with single, fully functional CSNs. Otherwise and elsewhere these animals are completely devoid of any environmental input through cilia. We demonstrated the rescue of fully functional, single cilia using fluorescent markers, sensory behavioral assays, and calcium imaging. Our technique, functional rescue in single sensory cilia (FRISSC), can thus cell-autonomously and cell-specifically restore the function of single sensory neurons and their ability to respond to sensory input. FRISSC can be adapted to many different CSNs and thus constitutes an excellent tool for studying sensory behaviors, both in single animals and in populations of worms. FRISSC will be Very useful for the molecular dissection of sensory perception in CSNs and for the analysis of the developmental aspects of ciliogenesis.

  • 27.
    Silverstein, Rebecca A
    et al.
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institutet.
    Ekwall, Karl
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institutet.
    Sin3: a flexible regulator of global gene expression and genome stability2005Inngår i: Current Genetics, ISSN 0172-8083, E-ISSN 1432-0983, Vol. 47, nr 1, s. 1-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    SIN3 was first identified genetically as a global regulator of transcription. Sin3 is a large protein composed mainly of protein-interaction domains, whose function is to provide structural support for a heterogeneous Sin3/histone deacetylase (HDAC) complex. The core Sin3/HDAC complex is conserved from yeast to man and consists of eight proteins. In addition to HDACs, Sin3 can sequester other enzymatic functions, including nucleosome remodeling, DNA methylation, N-acetylglucoseamine transferase activity, and histone methylation. Since the Sin3/HDAC complex lacks any DNA-binding activity, it must be targeted to gene promoters by interacting with DNA-binding proteins. Although most research on Sin3 has focused on its role as a corepressor, mounting evidence suggests that Sin3 can also positively regulate transcription. Furthermore, Sin3 is key to the propagation of epigenetically silenced domains and is required for centromere function. Thus, Sin3 provides a platform to deliver multiple combinations modifications to the chromatin, using both sequence-specific and sequence-independent mechanisms.

  • 28.
    Simoff, Ivailo
    et al.
    Södertörns högskola, Institutionen för livsvetenskaper.
    Moradi, Hossein
    Södertörns högskola, Institutionen för livsvetenskaper.
    Nygård, Odd
    Södertörns högskola, Institutionen för livsvetenskaper, Biologi. Södertörns högskola, Institutionen för livsvetenskaper, Miljövetenskap.
    Functional characterization of ribosomal protein L15 from Saccharomyces cerevisiae2009Inngår i: Current Genetics, ISSN 0172-8083, E-ISSN 1432-0983, Vol. 55, nr 2, s. 111-125Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study we provide general information on the little studied eukaryotic ribosomal protein rpL15. Saccharomyces cerevisiae has two genes, YRPL15A and YRPL15B that could potentially code for yeast rpL15 (YrpL15). YRPL15A is essential while YRPL15B is dispensable. However, a plasmid-borne copy of the YRPL15B gene, controlled by the GAL1 promoter or by the promoter controlling expression of the YRPL15A gene, can functionally complement YrpL15A in yeast cells, while the same gene controlled by the authentic promoter is inactive. Analysis of the levels of YrpL15B-mRNA in yeast cells shows that the YRPL15B gene is inactive in transcription. The function of YrpL15A is highly resilient to single and multiple amino acid substitutions. In addition, minor deletions from both the N- and C-terminal ends of YrpL15A has no effect on protein function, while addition of a C-terminal tag that could be used for detection of plasmid-encoded YrpL15A is detrimental to protein function. YrpL15A could also be replaced by the homologous protein from Arabidopsis thaliana despite almost 30% differences in the amino acid sequence, while the more closely related protein from Schizosaccharomyces pombe was inactive. The lack of function was not caused by a failure of the protein to enter the yeast nucleus.

  • 29.
    Sinha, Indranil
    et al.
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institutet.
    Wirén, Marianna
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institutet.
    Ekwall, Karl
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institutet.
    Genome-wide patterns of histone modifications in fission yeast2006Inngår i: Chromosome Research, ISSN 0967-3849, E-ISSN 1573-6849, Vol. 14, nr 1, s. 95-105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have used oligonucleotide tiling arrays to construct genome-wide high-resolution histone acetylation maps for fission yeast. The maps are corrected for nucleosome density and reveal surprisingly uniform patterns of modifications for five different histone acetylation sites. We found that histone acetylation and methylation patterns are generally polar, i.e. they change as a function of distance from the ATG codon. A typical fission yeast gene shows a distinct peak of histone acetylation around the ATG and gradually decreased acetylation levels in the coding region. The patterns are independent of gene length but dependent on the gene expression levels. H3K9Ac shows a stronger peak near the ATG and is more reduced in the coding regions of genes with high expression compared with genes with low expression levels. H4K16Ac is strongly reduced in coding regions of highly expressed genes. A second microarray platform was used to confirm the 5' to 3' polarity effects observed with tiling microarrays. By comparing coding region histone acetylation data in HDAC mutants and wild type, we found that hos2 affects primarily the 5' regions, sir2 and clr6 affect middle regions, and clr6 affects 3' regions. Thus, mechanisms involving different HDACs modulate histone acetylation levels to maintain a 5' to 3' polarity within the coding regions.

  • 30. Strålfors, Annelie
    et al.
    Walfridsson, Julian
    Södertörns högskola, Institutionen för livsvetenskaper, Molekylärbiologi.
    Bhuiyan, Hasanuzzaman
    Södertörns högskola, Institutionen för livsvetenskaper, Molekylärbiologi.
    Ekwall, Karl
    Södertörns högskola, Institutionen för livsvetenskaper, Molekylärbiologi.
    The FUN30 Chromatin Remodeler, Fft3, Protects Centromeric and Subtelomeric Domains from Euchromatin Formation2011Inngår i: PLOS Genetics, ISSN 1553-7390, E-ISSN 1553-7404, Vol. 7, nr 3, artikkel-id e1001334Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The chromosomes of eukaryotes are organized into structurally and functionally discrete domains. This implies the presence of insulator elements that separate adjacent domains, allowing them to maintain different chromatin structures. We show that the Fun30 chromatin remodeler, Fft3, is essential for maintaining a proper chromatin structure at centromeres and subtelomeres. Fft3 is localized to insulator elements and inhibits euchromatin assembly in silent chromatin domains. In its absence, euchromatic histone modifications and histone variants invade centromeres and subtelomeres, causing a mis-regulation of gene expression and severe chromosome segregation defects. Our data strongly suggest that Fft3 controls the identity of chromatin domains by protecting these regions from euchromatin assembly.

  • 31. Thon, G
    et al.
    Bjerling, Pernilla
    Södertörns högskola, Avdelning Naturvetenskap.
    Bunner, C M
    Verhein-Hansen, J
    Expression-state boundaries in the mating-type region of fission yeast2002Inngår i: Genetics, ISSN 0016-6731, E-ISSN 1943-2631, Vol. 161, nr 2, s. 611-622Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A transcriptionally silent chromosomal domain is found in the mating-type region of fission yeast. Here we show that this domain is delimited by 2-kb inverted repeats, IR-I, and IR-R, IR-I, and IR-R prevent the expansion of transcription-permissive chromatin into the silenced region and that of silenced chromatin into the expressed region. Their insulator activity is partially orientation dependent. The silencing defects that follow deletion or inversion of IR-R are suppressed by high dosage of the chromodomain protein Swi6. Combining chromosomal deletions and Swi6 overexpression shows that IR-I, and IR-R provide firm borders in a region where competition between silencing and transcriptional competence occurs. IR-R possesses autonomously replicating sequence (ARS) activity, leading to a model where replication factors, or replication itself, participate in boundary formation.

  • 32.
    Xue-Franzen, Yongtao
    et al.
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institutet.
    Kjaerulff, Soren
    University of Copenhagen, Copenhagen, Denmark.
    Holmberg, Christian
    University of Copenhagen, Copenhagen, Denmark.
    Wright, Anthony
    Södertörns högskola, Institutionen för livsvetenskaper. Karolinska Institutet.
    Nielsen, Olaf
    University of Copenhagen, Copenhagen, Denmark.
    Genomewide identification of pheromone-targeted transcription in fission yeast2006Inngår i: BMC Genomics, E-ISSN 1471-2164, Vol. 7, s. 303-, artikkel-id 303Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Fission yeast cells undergo sexual differentiation in response to nitrogen starvation. In this process haploid M and P cells first mate to form diploid zygotes, which then enter meiosis and sporulate. Prior to mating, M and P cells communicate with diffusible mating pheromones that activate a signal transduction pathway in the opposite cell type. The pheromone signalling orchestrates mating and is also required for entry into meiosis. Results: Here we use DNA microarrays to identify genes that are induced by M-factor in P cells and by P-factor in M-cells. The use of a cyr1 genetic background allowed us to study pheromone signalling independently of nitrogen starvation. We identified a total of 163 genes that were consistently induced more than two-fold by pheromone stimulation. Gene disruption experiments demonstrated the involvement of newly discovered pheromone-induced genes in the differentiation process. We have mapped Gene Ontology ( GO) categories specifically associated with pheromone induction. A direct comparison of the M- and P-factor induced expression pattern allowed us to identify cell-type specific transcripts, including three new M- specific genes and one new P-specific gene. Conclusion: We found that the pheromone response was very similar in M and P cells. Surprisingly, pheromone control extended to genes fulfilling their function well beyond the point of entry into meiosis, including numerous genes required for meiotic recombination. Our results suggest that the SteII transcription factor is responsible for the majority of pheromone-induced transcription. Finally, most cell-type specific genes now appear to be identified in fission yeast.

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