Unknown,Transcriptomics,Genomics,Proteomics

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LongSAGE analysis significantly improves genome annotation

ABSTRACT: Owing to its increased tag length, LongSAGE tags are expected to be more reliable in direct assignment to genome sequences. Therefore, we evaluated the use of LongSAGE data in genome annotation by using our LongSAGE dataset of 202 015 tags (consisting of 41 718 unique tags), experimentally generated from mouse embryonic tail libraries. RESULTS: A fraction of LongSAGE tags could not be unambiguously assigned to its gene, due to the presence of widely conserved sequences downstream of particular CATG anchor sites. The presence of alternative forms of transcripts was confirmed in 45% of all detected genes. Surprisingly, a large fraction of LongSAGE tags with hits to the genome (66%) could not be assigned to any gene annotated in EnsEMBL. Among such cases, 2098 LongSAGE tags fell into a region containing a putative gene predicted by GenScan, providing experimental evidence for the presence of real genes, while 9112 genes were found out to be left out or wrongly annotated by the EnsEMBL pipeline. CONCLUSIONS: LongSAGE transcriptome data can significantly improve the genome annotation by identifying novel genes and alternative transcripts, even in the case of thus far best-characterized organisms like the mouse. Keywords: other Owing to its increased tag length, LongSAGE tags are expected to be more reliable in direct assignment to genome sequences. Therefore, we evaluated the use of LongSAGE data in genome annotation by using our LongSAGE dataset of 202 015 tags (consisting of 41 718 unique tags), experimentally generated from mouse embryonic tail libraries.

ORGANISM(S): Mus musculus

SUBMITTER: Matthias Wahl

PROVIDER: E-GEOD-2967 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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LongSAGE analysis significantly improves genome annotation: identifications of novel genes and alternative transcripts in the mouse.

Wahl Matthias B MB Heinzmann Ulrich U Imai Kenji K

Bioinformatics (Oxford, England) 20041210 8

<h4>Motivation</h4>Owing to its increased tag length, LongSAGE tags are expected to be more reliable in direct assignment to genome sequences. Therefore, we evaluated the use of LongSAGE data in genome annotation by using our LongSAGE dataset of 202 015 tags (consisting of 41 718 unique tags), experimentally generated from mouse embryonic tail libraries.<h4>Results</h4>A fraction of LongSAGE tags could not be unambiguously assigned to its gene, due to the presence of widely conserved sequences d ...[more]

PMID: 15591356

Publication: 1/2

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Project description:This study describes the application of the LongSAGE methodology to study the gene expression profile in Leishmania infantum chagasi. A tag library was created using the LongSAGE method and consisted of 14,208 tags of 17 bases. Of these, 8,427 (59.3%) were distinct. BLAST research of the 1,645 most abundant tags showed that 12.8% of them identified the coding sequences of genes, while 82% (1,349/1,645) identified one or more genomic sequences that did not correspond with open reading frames. Only 5.2% (84/1,645) of the tags were not aligned to any position in the L. infantum genome. The UTR size of Leishmania and the lack of CATG sites in some transcripts were decisive for the generation of tags in these regions. LongSAGE revealed the gene expression profile in promastigotes of L. i. chagasi. Additional analysis will allow a better understanding of the expression profile and discovering the key genes in this life cycle. The I-SAGETM Long kit (Invitrogen) was used to construct the L. i. chagasi library according to the manufacturer's recommendations. The following were included among the main steps: polyadenylates mRNAs were captured by oligo (dT) linked to magnetic beads and used for cDNA synthesis. The cDNA was digested with 60 U of NlaIII (anchoring enzyme) and the 3' ends of the cDNAs were isolated using the beads. The resulting cDNA 3' was divided into two equal portions and connected to two LongSAGE adapters, A and B. The long tags were released by the enzyme MmeI and linked to form ~130 bp ditags. Dilutions of 1:40 of the product were amplified in 27 PCR cycles (300 reactions in total). The precipitated PCR products were separated on 12% polyacrylamide gel and the 130 bp bands were cut out and the precipitated DNA was digested with NlaIII. The digestion products were separated on 12% polyacrylamide gel and ~34 bp ditags were cut out and linked to form concatemers. The concatemers were separated on 6% polyacrylamide gel and the fractions of 250-500 and 500-800pb were isolated and cloned into pZErO-1 vector digested with SphI. Vectors with concatemers were cloned in E. coli DH10b by electroporation and the isolated recombinant vectors were used as template for sequencing in the ABI Prism 3100 (Applied Biosystems).

Dataset Information

LongSAGE analysis significantly improves genome annotation

Publications

LongSAGE analysis significantly improves genome annotation: identifications of novel genes and alternative transcripts in the mouse.

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