SAGE is a technique that allows for the digital analysis of overall gene expression patterns through the use of short sequence tags to uniquely identify transcripts without requiring preexisting clones. It works by linking these tags together into long serial molecules that can then be cloned and sequenced, with the number of times a particular tag is observed providing the expression level of the corresponding transcript. This allows for rapid sequencing analysis of multiple transcripts from a single sequencing event. SAGE is useful for comparative expression studies to identify differences in gene expression between tissues.

1. Serial analysis of gene expression:SAGE

2. SAGE SAGE is a powerful tool that allows the analysis of overall gene expression patterns with digital analysis. Because SAGE does not require a preexisting clone, it can be used to identify and quantitate new genes as well as known genes.

3. SAGE PRINCIPLE A short sequence tag (10-14bp) contains sufficient information to uniquely identify a transcript provided that that the tag is obtained from a unique position within each transcript; Sequence tags can be linked together to from long serial molecules that can be cloned and sequenced; and Quantitation of the number of times a particular tag is observed provides the expression level of the corresponding transcript.

4. SAGE ADVANTAGE Linking the tags together allows for rapid sequencing analysis of multiple transcripts. By linking the tags together, only one sequencing event is required to sequence every transcript within the cell. Makes the task of DNA expression profiling a much easier

5. SAGE METHODOLOGY Generate cDNA primed with biotin-oligo(dT) NlaIII Linker have restriction site for “tagging enzyme”(BsmFI)

7. Schematic of SAGE method:

8. What does the data look like?

9. SAGE APPLICATION SAGE is useful in comparative expression studies to identify differences in gene expression between two or more cellular sources of RNA. A big advantage of the method is its speed: all genes expressed at 0.5% of total mRNA in one tissue but not abundant in another could be found in a single day Approximately 1000 sequence tags from each tissue.

10. SAGEmap

11. http://www.sagenet.org/

12. Sage resources

13. Sage data