| 1. |
- Andersen, Oivind, et al.
(författare)
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Polymorphism, selection and tandem duplication of transferrin genes in Atlantic cod (Gadus morhua) - Conserved synteny between fish monolobal and tetrapod bilobal transferrin loci.
- 2011
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Ingår i: BMC genetics. - : Springer Science and Business Media LLC. - 1471-2156. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: BACKGROUND: The two homologous iron-binding lobes of transferrins are thought to have evolved by gene duplication of an ancestral monolobal form, but any conserved synteny between bilobal and monolobal transferrin loci remains unexplored. The important role played by transferrin in the resistance to invading pathogens makes this polymorphic gene a highly valuable candidate for studying adaptive divergence among local populations. RESULTS: The Atlantic cod genome was shown to harbour two tandem duplicated serum transferrin genes (Tf1, Tf2), a melanotransferrin gene (MTf), and a monolobal transferrin gene (Omp) expressed in the otoliths. Fish, chicken and mammals showed highly conserved syntenic regions in which monolobal and bilobal transferrins reside, but contrasting with tetrapods, the fish transferrin genes are positioned on three different linkage groups. Sequence alignment of cod Tf1 cDNAs from Northeast (NE) and Northwest (NW) Atlantic populations revealed 22 single nucleotide polymorphisms (SNP) causing the replacement of 16 amino acids, including eight surface residues revealed by the modelled 3D-structures, which might influence the binding of pathogens for removal of iron. SNP analysis of a total of 375 individuals from 14 trans-Atlantic populations showed that the Tf1-NE variant was almost fixed in the Baltic cod and predominated in the other NE Atlantic populations, whereas the NW Atlantic populations were more heterozygous and showed high frequencies of the Tf-NW SNP alleles. CONCLUSIONS: The highly conserved synteny between fish and tetrapod transferrin loci infers that the fusion of tandem duplicated Omp-like genes gave rise to the modern transferrins. The multiple nonsynonymous substitutions in cod Tf1 with putative structural effects, together with highly divergent allele frequencies among different cod populations, strongly suggest evidence for positive selection and local adaptation in trans-Atlantic cod populations.
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| 2. |
- Dussex, Nicolas, et al.
(författare)
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Adaptation to the High-Arctic island environment despite long-term reduced genetic variation in Svalbard reindeer
- 2023
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Ingår i: iScience. - 2589-0042. ; 26:10
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Tidskriftsartikel (refereegranskat)abstract
- Typically much smaller in number than their mainland counterparts, island populations are ideal systems to investigate genetic threats to small populations. The Svalbard reindeer (Rangifer tarandus platyrhynchus) is an endemic subspecies that colonized the Svalbard archipelago ca. 6,000–8,000 years ago and now shows numerous physiological and morphological adaptations to its arctic habitat. Here, we report a de-novo chromosome-level assembly for Svalbard reindeer and analyze 133 reindeer genomes spanning Svalbard and most of the species’ Holarctic range, to examine the genomic consequences of long-term isolation and small population size in this insular subspecies. Empirical data, demographic reconstructions, and forward simulations show that long-term isolation and high inbreeding levels may have facilitated the reduction of highly deleterious—and to a lesser extent, moderately deleterious—variation. Our study indicates that long-term reduced genetic diversity did not preclude local adaptation to the High Arctic, suggesting that even severely bottlenecked populations can retain evolutionary potential.
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| 3. |
- Lien, Sigbjorn, et al.
(författare)
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The Atlantic salmon genome provides insights into rediploidization
- 2016
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 533:7602, s. 200-205
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Tidskriftsartikel (refereegranskat)abstract
- The whole-genome duplication 80 million years ago of the common ancestor of salmonids (salmonid-specific fourth vertebrate whole-genome duplication, Ss4R) provides unique opportunities to learn about the evolutionary fate of a duplicated vertebrate genome in 70 extant lineages. Here we present a high-quality genome assembly for Atlantic salmon (Salmo salar), and show that large genomic reorganizations, coinciding with bursts of transposon-mediated repeat expansions, were crucial for the post-Ss4R rediploidization process. Comparisons of duplicate gene expression patterns across a wide range of tissues with orthologous genes from a pre-Ss4R outgroup unexpectedly demonstrate far more instances of neofunctionalization than subfunctionalization. Surprisingly, we find that genes that were retained as duplicates after the teleost-specific whole-genome duplication 320 million years ago were not more likely to be retained after the Ss4R, and that the duplicate retention was not influenced to a great extent by the nature of the predicted protein interactions of the gene products. Finally, we demonstrate that the Atlantic salmon assembly can serve as a reference sequence for the study of other salmonids for a range of purposes.
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| 4. |
- Stenmark, Bianca, 1987-, et al.
(författare)
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Complete genome and methylome analysis of Neisseria meningitidis associated with increased serogroup Y disease
- 2020
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Invasive meningococcal disease (IMD) due to serogroup Y Neisseria meningitidis emerged in Europe during the 2000s. Draft genomes of serogroup Y isolates in Sweden revealed that although the population structure of these isolates was similar to other serogroup Y isolates internationally, a distinct strain (YI) and more specifically a sublineage (1) of this strain was responsible for the increase of serogroup Y IMD in Sweden. We performed single molecule real-time (SMRT) sequencing on eight serogroup Y isolates from different sublineages to unravel the genetic and epigenetic factors delineating them, in order to understand the serogroup Y emergence. Extensive comparisons between the serogroup Y sublineages of all coding sequences, complex genomic regions, intergenic regions, and methylation motifs revealed small point mutations in genes mainly encoding hypothetical and metabolic proteins, and non-synonymous variants in genes involved in adhesion, iron acquisition, and endotoxin production. The methylation motif CACNNNNNTAC was only found in isolates of sublineage 2. Only seven genes were putatively differentially expressed, and another two genes encoding hypothetical proteins were only present in sublineage 2. These data suggest that the serogroup Y IMD increase in Sweden was most probably due to small changes in genes important for colonization and transmission.
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| 5. |
- Stenmark, Bianca, 1987-, et al.
(författare)
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Methylome comparison of two meningococcal sub-lineages of serogroup Y cc23
- 2018
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Konferensbidrag (refereegranskat)abstract
- Introduction: A significant increase in invasive meningococcal disease (IMD) due to serogroup Y Neisseria meningitidis (MenY) ST-23 clonal complex (cc23) emerged in the United States during the 1990s, spreading to Europe shortly thereafter. The largest increase was observed in Sweden with incidence proportions up to 53%. Genome analysis of all MenY isolates causing IMD between 1995 to 2012 in Sweden revealed that a distinct strain (YI) and more specifically a subtype (1) of this strain was found to be responsible for the increase of MenY IMD in Sweden [1]. In this study, we compared the methylomes of subtype 1 to the less successful subtype 2, using Single Molecule Real-Time (SMRT) sequencing technology.Methods: Ten genomes belonging to subtype 1 (n=7) and 2 (n=3) and one MenY genome without connection to a specific lineage were sequenced using SMRT sequencing on a PacBio®RS II. The analysis platform SMRT Portal v2 was used to identify modified positions and for the genome-wide analysis of modified motifs. DNA methyltransferase genes associated with the different methyltransferase recognition motifs identified were searched using SEQWARE. The modification-dependent restriction endonucleases MspJI and FspEI were used to determine the m5C recognition sites of the active m5C methylases in the strains.Results: The genome-wide analysis of the methylomes identified two m6A modified motifs: GATC and CACNNNNNTAC, but the latter was only found in isolates belonging to subtype 2 due to a transposase inserted in the candidate gene in subtype 1 strains: a Type I restriction system specificity protein (NEIS2535). The motif CACNNNNNTAC was only found in one other meningococcal isolate in REBASE, belonging to cc23, suggesting that this is a cc23 specific motif. Eleven putative restriction modification (RM) systems were found when comparing the sequences of all 11 genomes to DNA methyltransferase genes in REBASE. Five m5C genes were predicted, however, only three of these corresponding to the motifs: GCRYGC, GGNNCC and CCAGR were confirmed as active using MspJI and FspEI cleavage. The apparent CCAGR motif may be the result of two methylases, one recognizing CCWGG and the other CCAGA, but this will have to be verified.Conclusion: These results are consistent with previous studies [2] that have shown that the composition of different RM systems are clade specific suggesting that the unique RM system of cc23 isolates will most likely result in a specific DNA methylation pattern unique to this particular cc. However, although the majority of methyltransferases were shared between the two subtypes, there was one difference in a m6A modified motif between these two highly similar cc23 subtypes, which may lead to an altered gene expression pattern.
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