Demonstrated in Science , our exclusively licensed F.A.S.T.™ (Flexible Accelerated STOP TetO) technology is a versatile tool where a single targeting event yields a multi-purpose mouse line with the potential for five or more controllable functionalities from the same locus, just using mating. 
These functionalities can include:
Global gene knockout
Tissue/time-specific gene rescue
Ectopic gene expression
Inducible/reversible gene overexpression
Inducible/reversible gene knockdown
Depicted in the schematic below, Tanaka KF et al showed that the F.A.S.T.™ system achieves a spectrum of controllable expression levels from the Mlc1 gene, thereby streamlining the mouse model generation process.
Flexible Accelerated STOP Tetracycline Operator
As a knockout first, the Mlc1 gene function was rescued by mating the initial mouse line to a tissue specific Cre line of choice. Alternatively, gene expression can be induced through the F.A.S.T.™ cassette. A tetracycline transactivator (tTA) line was used to produce an ectopic gene expression model, and a tissue-specific over-expression model. A tetracycline trans-silencer line was used to generate a tissue-specific conditional knockdown/knockout.
These principals are possible for your gene of interest using the F.A.S.T.TM cassette, making your research more flexible.
1) Baudouin SJ et al. (2012) Shared synaptic pathophysiology in syndromic and nonsyndromic rodent models of autism. Science 338(6103): 128-132.
2) Tanaka KF et al. (2010) Flexible Accelerated STOP Tetracycline Operator-knockin (FAST): a versatile and efficient new gene modulating system Biol Psychiatry 67(8): 770-773.
Whitepaper – The F.A.S.T. (TM) Gene Modulating System
Tet Systems: principles and components
Tet Systems: homepage
Schönig K et al. (2010) The power of reversibility: regulating gene activities via tetracycline-controlled transcription. Methods Enzymol. 477: 429-453.
Stieger K et al. (2009) In vivo gene regulation using tetracycline-regulatable systems. Adv Drug Deliv Rev 61(7-8): 527-541. Review.