serial analysis of gene expression

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The serial analysis of gene expression ( SAGE , of Engl. S erial A nalysis of G ene E xpression ) is an effective method to identify cDNAs by sequencing of so-called tags , which by means of the enzyme reverse transcriptase from mRNA were recovered molecules. The method was developed in 1995 by Victor Velculescu in the laboratories of Keneth W. Kinzler and Bert Vogelstein at Johns Hopkins University .

SAGE was developed because the methods predominant at the time for studying gene expression , such as Northern blot , RT-PCR and EST sequencing, only allowed the investigation of a few genes. SAGE is based on the fact that a nucleotide sequence of 10 bp at a defined position in the mRNA theoretically distinguishes over 1,000,000 (4 10 ) transcripts. While the original SAGE method only produced tags with 10–14 bp, the current variant SuperSAGE produced tags with a length of 26 to 28 bp. This enables a much better assignment to known gene sequences, allows the design of specific primers z. B. for RACE-PCR and opens up new analysis possibilities, e.g. B. the simultaneous analysis of several organisms. Due to the longer tags, SuperSAGE is also recommended for the analysis of organisms with unknown genomes and for the discovery of new genes and transcript variants.

With SAGE and its variants, the transcriptome of a cell , tissue or organ can be comprehensively analyzed at any stage of development or disease.

SAGE and its variants make it possible to analyze a very large number of genes . Furthermore, the number of gene-specific mRNA molecules can be determined relatively well; So SAGE is a quantifying method. Compared to the microarray method, which as a closed system can only detect known and spotted genes, SAGE as an open system offers the advantage that even unknown genes, or genes that were not expected to be found, can be detected and evaluated.

A disadvantage of the method is the high cost compared to microarrays. However, this disadvantage melts due to the falling costs of next generation sequencing . In addition, the detection is limited to poly-A transcripts and to cDNAs which are cut by the selected, frequently cutting restriction enzymes .

Individual evidence

  1. ↑ Velculescu, VE et al. (1995): Serial Analysis of Gene Expression. In: Science . Vol. 270, pp. 484-487. PMID 7570003
  2. ↑ Anisimov, SV (2008): Serial Analysis of Gene Expression (SAGE): 13 years of application in research. In: Curr Pharm Biotechnol . 9 (5): 338-350. doi: 10.2174 / 138920108785915148 , PMID 18855686 .