| 1. |
- 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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| 2. |
- Hooper, Sean D., et al.
(författare)
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Genome-wide sequencing for the identification of rearrangements associated with Tourette syndrome and obsessive-compulsive disorder
- 2012
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Ingår i: BMC Medical Genetics. - : Springer Science and Business Media LLC. - 1471-2350. ; 13, s. 123-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Tourette Syndrome (TS) is a neuropsychiatric disorder in children characterized by motor and verbal tics. Although several genes have been suggested in the etiology of TS, the genetic mechanisms remain poorly understood. Methods: Using cytogenetics and FISH analysis, we identified an apparently balanced t(6,22)(q16.2;p13) in a male patient with TS and obsessive-compulsive disorder (OCD). In order to map the breakpoints and to identify additional submicroscopic rearrangements, we performed whole genome mate-pair sequencing and CGH-array analysis on DNA from the proband. Results: Sequence and CGH array analysis revealed a 400 kb deletion located 1.3 Mb telomeric of the chromosome 6q breakpoint, which has not been reported in controls. The deletion affects three genes (GPR63, NDUFA4 and KLHL32) and overlaps a region previously found deleted in a girl with autistic features and speech delay. The proband's mother, also a carrier of the translocation, was diagnosed with OCD and shares the deletion. We also describe a further potentially related rearrangement which, while unmapped in Homo sapiens, was consistent with the chimpanzee genome. Conclusions: We conclude that genome-wide sequencing at relatively low resolution can be used for the identification of submicroscopic rearrangements. We also show that large rearrangements may escape detection using standard analysis of whole genome sequencing data. Our findings further provide a candidate region for TS and OCD on chromosome 6q16.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- Wetterbom, Anna, et al.
(författare)
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Identification of novel exons and transcribed regions by chimpanzee transcriptome sequencing
- 2010
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Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1474-760X .- 1465-6906. ; 11:7, s. R78-
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Tidskriftsartikel (refereegranskat)abstract
- Background: We profile the chimpanzee transcriptome by using deep sequencing of cDNA from brain and liver, aiming to quantify expression of known genes and to identify novel transcribed regions. Results: Using stringent criteria for transcription, we identify 12,843 expressed genes, with a majority being found in both tissues. We further identify 9,826 novel transcribed regions that are not overlapping with annotated exons, mRNAs or ESTs. Over 80% of the novel transcribed regions map within or in the vicinity of known genes, and by combining sequencing data with de novo splice predictions we predict several of the novel transcribed regions to be new exons or 3' UTRs. For approximately 350 novel transcribed regions, the corresponding DNA sequence is absent in the human reference genome. The presence of novel transcribed regions in five genes and in one intergenic region is further validated with RT-PCR. Finally, we describe and experimentally validate a putative novel multi-exon gene that belongs to the ATP-cassette transporter gene family. This gene does not appear to be functional in human since one exon is absent from the human genome. In addition to novel exons and UTRs, novel transcribed regions may also stem from different types of noncoding transcripts. We note that expressed repeats and introns from unspliced mRNAs are especially common in our data. Conclusions: Our results extend the chimpanzee gene catalogue with a large number of novel exons and 3' UTRs and thus support the view that mammalian gene annotations are not yet complete.
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| 6. |
- Zaghlool, Ammar, 1980-, et al.
(författare)
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Efficient cellular fractionation improves RNA sequencing analysis of mature and nascent transcripts from human tissues
- 2013
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Ingår i: BMC Biotechnology. - : Springer Science and Business Media LLC. - 1472-6750. ; 13, s. 99-
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Tidskriftsartikel (refereegranskat)abstract
- Background: The starting material for RNA sequencing (RNA-seq) studies is usually total RNA or polyA+ RNA. Both forms of RNA represent heterogeneous pools of RNA molecules at different levels of maturation and processing. Such heterogeneity, in addition to the biases associated with polyA+ purification steps, may influence the analysis, sensitivity and the interpretation of RNA-seq data. We hypothesize that subcellular fractions of RNA may provide a more accurate picture of gene expression. Results: We present results for sequencing of cytoplasmic and nuclear RNA after cellular fractionation of tissue samples. In comparison with conventional polyA+ RNA, the cytoplasmic RNA contains a significantly higher fraction of exonic sequence, providing increased sensitivity in expression analysis and splice junction detection, and in improved de novo assembly of RNA-seq data. Conversely, the nuclear fraction shows an enrichment of unprocessed RNA compared with total RNA-seq, making it suitable for analysis of nascent transcripts and RNA processing dynamics. Conclusion: Our results show that cellular fractionation is a more rapid and cost effective approach than conventional polyA+ enrichment when studying mature RNAs. Thus, RNA-seq of separated cytosolic and nuclear RNA can significantly improve the analysis of complex transcriptomes from mammalian tissues.
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| 7. |
- Zaghlool, Ammar, et al.
(författare)
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Splicing in the Human Brain
- 2014
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Ingår i: Brain Transcriptome. - : Elsevier. - 9780128011058 ; , s. 95-125
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Bokkapitel (refereegranskat)abstract
- It has become increasingly clear over the past decade that RNA has important functions in human cells beyond its role as an intermediate translator of DNA to protein. It is now known that RNA plays highly specific roles in pathways involved in regulatory, structural, and catalytic functions. The complexity of RNA production and regulation has become evident with the advent of high-throughput methods to study the transcriptome. Deep sequencing has revealed an enormous diversity of RNA types and transcript isoforms in human cells. The transcriptome of the human brain is particularly interesting as it contains more expressed genes than other tissues and also displays an extreme diversity of transcript isoforms, indicating that highly complex regulatory pathways are present in the brain. Several of these regulatory proteins are now identified, including RNA-binding proteins that are neuron specific. RNA-binding proteins also play important roles in regulating the splicing process and the temporal and spatial isoform production. While significant progress has been made in understanding the human transcriptome, many questions still remain regarding the basic mechanisms of splicing and subcellular localization of RNA. A long-standing question is to what extent the splicing of pre-mRNA is cotranscriptional and posttranscriptional, respectively. Recent data, including studies of the human brain, indicate that splicing is primarily cotranscriptional in human cells. This chapter describes the current understanding of splicing and splicing regulation in the human brain and discusses the recent global sequence-based analyses of transcription and splicing.
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