| 1. |
- Ameur, Adam, et al.
(författare)
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Global and unbiased detection of splice junctions from RNA-seq data
- 2010
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Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1474-760X .- 1465-6906. ; 11:3, s. R34-
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a new strategy for de novo prediction of splice junctions in short-read RNA-seq data, suitable for detection of novel splicing events and chimeric transcripts. When tested on mouse RNA-seq data, > 31,000 splice events were predicted, of which 88% bridged between two regions separated by <= 100 kb, and 74% connected two exons of the same RefSeq gene. Our method also reports genomic rearrangements such as insertions and deletions.
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| 2. |
- Ameur, Adam, et al.
(författare)
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Total RNA sequencing reveals nascent transcription and widespread co-transcriptional splicing in the human brain
- 2011
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 18:12, s. 1435-1440
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Tidskriftsartikel (refereegranskat)abstract
- Transcriptome sequencing allows for analysis of mature RNAs at base pair resolution. Here we show that RNA-seq can also be used for studying nascent RNAs undergoing transcription. We sequenced total RNA from human brain and liver and found a large fraction of reads (up to 40%) within introns. Intronic RNAs were abundant in brain tissue, particularly for genes involved in axonal growth and synaptic transmission. Moreover, we detected significant differences in intronic RNA levels between fetal and adult brains. We show that the pattern of intronic sequence read coverage is explained by nascent transcription in combination with co-transcriptional splicing. Further analysis of co-transcriptional splicing indicates a correlation between slowly removed introns and alternative splicing. Our data show that sequencing of total RNA provides unique insight into the transcriptional processes in the cell, with particular importance for normal brain development.
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| 3. |
- Lamichhaney, Sangeet, et al.
(författare)
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Population-scale sequencing reveals genetic differentiation due to local adaptation in Atlantic herring
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:47, s. 19345-19350
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Tidskriftsartikel (refereegranskat)abstract
- The Atlantic herring (Clupea harengus), one of the most abundant marine fishes in the world, has historically been a critical food source in Northern Europe. It is one of the few marine species that can reproduce throughout the brackish salinity gradient of the Baltic Sea. Previous studies based on few genetic markers have revealed a conspicuous lack of genetic differentiation between geographic regions, consistent with huge population sizes and minute genetic drift. Here, we present a cost-effective genome-wide study in a species that lacks a genome sequence. We first assembled amuscle transcriptome and then aligned genomic reads to the transcripts, creating an "exome assembly," capturing both exons and flanking sequences. We then resequenced pools of fish from a wide geographic range, including the Northeast Atlantic, as well as different regions in the Baltic Sea, aligned the reads to the exome assembly, and identified 440,817 SNPs. The great majority of SNPs showed no appreciable differences in allele frequency among populations; however, several thousand SNPs showed striking differences, some approaching fixation for different alleles. The contrast between low genetic differentiation at most loci and striking differences at others implies that the latter category primarily reflects natural selection. A simulation study confirmed that the distribution of the fixation index F-ST deviated significantly from expectation for selectively neutral loci. This study provides insights concerning the population structure of an important marine fish and establishes the Atlantic herring as a model for population genetic studies of adaptation and natural selection.
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| 4. |
- Lysholm, Fredrik, et al.
(författare)
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Characterization of the viral microbiome in patients with severe lower respiratory tract infections, using metagenomic sequencing
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:2
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Tidskriftsartikel (refereegranskat)abstract
- The human respiratory tract is heavily exposed to microorganisms. Viral respiratory tract pathogens, like RSV, influenza and rhinoviruses cause major morbidity and mortality from respiratory tract disease. Furthermore, as viruses have limited means of transmission, viruses that cause pathogenicity in other tissues may be transmitted through the respiratory tract. It is therefore important to chart the human virome in this compartment. We have studied nasopharyngeal aspirate samples submitted to the Karolinska University Laboratory, Stockholm, Sweden from March 2004 to May 2005 for diagnosis of respiratory tract infections. We have used a metagenomic sequencing strategy to characterize viruses, as this provides the most unbiased view of the samples. Virus enrichment followed by 454 sequencing resulted in totally 703,790 reads and 110,931 of these were found to be of viral origin by using an automated classification pipeline. The snapshot of the respiratory tract virome of these 210 patients revealed 39 species and many more strains of viruses. Most of the viral sequences were classified into one of three major families; Paramyxoviridae, Picornaviridae or Orthomyxoviridae. The study also identified one novel type of Rhinovirus C, and identified a number of previously undescribed viral genetic fragments of unknown origin.
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| 5. |
- Nystedt, Björn, et al.
(författare)
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The Norway spruce genome sequence and conifer genome evolution
- 2013
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 497:7451, s. 579-584
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Tidskriftsartikel (refereegranskat)abstract
- Conifers have dominated forests for more than 200 million years and are of huge ecological and economic importance. Here we present the draft assembly of the 20-gigabase genome of Norway spruce (Picea abies), the first available for any gymnosperm. The number of well-supported genes (28,354) is similar to the >100 times smaller genome of Arabidopsis thaliana, and there is no evidence of a recent whole-genome duplication in the gymnosperm lineage. Instead, the large genome size seems to result from the slow and steady accumulation of a diverse set of long-terminal repeat transposable elements, possibly owing to the lack of an efficient elimination mechanism. Comparative sequencing of Pinus sylvestris, Abies sibirica, Juniperus communis, Taxus baccata and Gnetum gnemon reveals that the transposable element diversity is shared among extant conifers. Expression of 24-nucleotide small RNAs, previously implicated in transposable element silencing, is tissue-specific and much lower than in other plants. We further identify numerous long (>10,000 base pairs) introns, gene-like fragments, uncharacterized long non-coding RNAs and short RNAs. This opens up new genomic avenues for conifer forestry and breeding.
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| 6. |
- Wetterbom, Anna, et al.
(författare)
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Comparative genomic analysis of human and chimpanzee indicates a key role for indels in primate evolution
- 2006
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Ingår i: Journal of Molecular Evolution. - : Springer Science and Business Media LLC. - 0022-2844 .- 1432-1432. ; 63:5, s. 682-690
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Tidskriftsartikel (refereegranskat)abstract
- Sequence comparison of humans and chimpanzees is of interest to understand the mechanisms behind primate evolution. Here we present an independent analysis of human chromosome 21 and the high-quality BAC clone sequences of the homologous chimpanzee chromosome 22. In contrast to previous studies, we have used global alignment methods and Ensembl predictions of protein coding genes (n = 224) for the analysis. Divergence due to insertions and deletions (indels) along with substitutions was examined separately for different genomic features (coding, noncoding genic, and intergenic sequence). The major part of the genomic divergence could be attributed to indels (5.07%), while the nucleotide divergence was estimated as 1.52%. Thus the total divergence was estimated as 6.58%. When excluding repeats and low-complexity DNA the total divergence decreased to 2.37%. The chromosomal distribution of nucleotide substitutions and indel events was significantly correlated. To further examine the role of indels in primate evolution we focused on coding sequences. Indels were found within the coding sequence of 13% of the genes and approximately half of the indels have not been reported previously. In 5% of the chimpanzee genes, indels or substitutions caused premature stop codons that rendered the affected transcripts nonfunctional. Taken together, our findings demonstrate that indels comprise the majority of the genomic divergence. Furthermore, indels occur frequently in coding sequences. Our results thereby support the hypothesis that indels may have a key role in primate evolution.
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| 7. |
- Wetterbom, Anna, et al.
(författare)
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Deep sequencing of the chimpanzee transcriptome identifies numerous novel transcribed regions in frontal cortex and liver
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We have performed the first global profiling of the chimpanzee transcriptome by using deep sequencing of cDNA from brain and liver. This enabled us to quantify expression of RefSeq transcripts, identify novel transcribed regions with no previous annotations in databases and additionally search for transcribed regions with no support in the human genome. Using stringent criteria for transcription, we identified 9,061 expressed RefSeq transcripts and 5,532 novel transcribed regions., of which the vast majority were found intronically in RefSeq transcripts and ~ 15 % mapped intergenically. In addition, a little less than 150 novel transcribed regions in the chimpanzee appeared to be absent from the human reference sequence. Novel transcribed regions may represent new coding regions, untranslated regions unspliced mRNAs or diferent types of non-coding transcripts. The transcriptional profile of the brain stands out in several ways: a higher number of RefSeq transcripts were expressed in brain than in liver and novel transcribed regions were also more abundant in brain. Furthermore, we identified an interesting subset of RefSeq genes with a high density of novel transcribed regions scattered across the introns. These genes clustered in central pathways of the nervous system, with an overrepresentation of genes acting in the synapse and many of which have been associated to cognitive disorders in the human. Our results support the prevailing view of wide-spread transcription in mammalian genomes and further highlight the vast, mostly uncharacterized, transcript variability in the primate brain.
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| 8. |
- Wetterbom, Anna, 1977-
(författare)
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Genome and Transcriptome Comparisons between Human and Chimpanzee
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The chimpanzee is humankind’s closest living relative and the two species diverged ~6 million years ago. Comparative studies of the human and chimpanzee genomes and transcriptomes are of great interest to understand the molecular mechanisms of speciation and the development of species-specific traits. The aim of this thesis is to characterize differences between the two species with regard to their genome sequences and the resulting transcript profiles. The first two papers focus on indel divergence and in particular, indels causing premature termination codons (PTCs) in 8% of the chimpanzee genes. The density of PTC genes is correlated with both the distance to the telomere and the indel divergence. Many PTC genes have several associated transcripts and since not all are affected by the PTC we propose that PTCs may affect the pattern of expressed isoforms. In the third paper, we investigate the transcriptome divergence in cerebellum, heart and liver, using high-density exon arrays. The results show that gene expression differs more between tissues than between species. Approximately 15% of the genes are differentially expressed between species, and half of the genes show different splicing patterns. We identify 28 cassette exons which are only included in one of the species, often in a tissue-specific manner. In the fourth paper, we use massive parallel sequencing to study the chimpanzee transcriptome in frontal cortex and liver. We estimate gene expression and search for novel transcribed regions (TRs). The majority of TRs are located close to genes and possibly extend the annotations. A subset of TRs are not found in the human genome. The brain transcriptome differs substantially from that of the liver and we identify a subset of genes enriched with TRs in frontal cortex. In conclusion, this thesis provides evidence of extensive genomic and transcriptomic variability between human and chimpanzee. The findings provide a basis for further studies of the underlying differences affecting phenotypic divergence between human and chimpanzee.
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| 9. |
- Wetterbom, Anna, et al.
(författare)
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Genome-wide analysis of chimpanzee genes with premature termination codons
- 2009
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Ingår i: BMC Genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 10, s. 56-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Premature termination codons (PTCs) cause mRNA degradation or a truncated protein and thereby contribute to the transcriptome and proteome divergence between species. Here we present the first genome-wide study of PTCs in the chimpanzee. By comparing the human and chimpanzee genome sequences we identify and characterize genes with PTCs, in order to understand the contribution of these mutations to the transcriptome diversity between the species. RESULTS: We have studied a total of 13,487 human-chimpanzee gene pairs and found that ~8% were affected by PTCs in the chimpanzee. A majority (764/1,109) of PTCs were caused by insertions or deletions and the remaining part was caused by substitutions. The distribution of PTC genes varied between chromosomes, with Y having the highest proportion. Furthermore, the density of PTC genes varied on a megabasepair scale within chromosomes and we found the density to be correlated both with indel divergence and proximity to the telomere. Within genes, PTCs were more common close to the 5' and 3' ends of the amino acid sequence. Gene Ontology classification revealed that olfactory receptor genes were over represented among the PTC genes. CONCLUSION: Our results showed that the density of PTC genes fluctuated across the genome depending on the local genomic context. PTCs were preferentially located in the terminal parts of the transcript, which generally have a lower frequency of functional domains, indicating that selection was operating against PTCs at sites central to protein function. The enrichment of GO terms associated with olfaction suggests that PTCs may have influenced the difference in the repertoire of olfactory genes between humans and chimpanzees. In summary, 8% of the chimpanzee genes were affected by PTCs and this type of variation is likely to have an important effect on the transcript and proteomic divergence between humans and chimpanzees.
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| 10. |
- Wetterbom, Anna, 1977-, et al.
(författare)
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Global comparison of the human and chimpanzee transcriptomes using Affymetrix exon arrays
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We have used high-density exon arrays to study the human and chimpanzee transcriptome in cerebellum, heart and liver excluding probesets with mismatches to the chimpanzee. A total of 6281 RefSeq genes were expressed in our samples, the majority being expressed in two or more tissues, while ~ 6 % lacked expression in one of the species. A total of 923 RefSeq genes showed differences in expression between human and chimpanzes. More genes were differentially expressed in cerebellum (8.4 %) than in liver (6.9 %) and heart (4.5 %). Genes showing differential expression between species to a large extent also showed strong tissue-specific expression within species. Of the differentially expressed genes, more were upregulated in human versus chimpanzee, than the other way around. Liver had the highest proportion of genes with spliced genes (50 %), followed by cerebellum (40 %) and heart (30 %). Differentially expressed genes were often detected also as spliced (66-78 %). As one type of splice variation, we identified 26 genes with cassette exons, i.e. the exon is only included in one species. Cassette exon usage was tissue specific to a large extent and for the majority of cassette exons we observed expression in both human and chimpanzee in the other tissues. Taken together, our results indicate that splicing differences represents an extensive and important source of variation between species.
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