Cre-Lox recombination is a site-specific recombinase technology, used to carry out deletions, insertions, translocations and inversions at specific sites in the DNA of cells. It allows the DNA modification to be targeted to a specific cell type or be triggered by a specific external stimulus.

Cre (Cre recombinase) is one of the tyrosine site-specific recombinases (T-SSRs) including flipase (Flp) and D6 specific recombinase (Dre) [1,2]. it was discovered as a 38-kDa DNA recombinase produced from cre (cyclization recombinase) gene of bacteriophage P1 [3,4,5,6].

Therefore, the Cre/loxP system allows for making a series of DNA sequence rearrangements, which helps to build one of the most versatile genetic tools in mice (2,3). The major application of Cre/loxP system is generation of cell- or tissue-specific conditional knockout alleles in mice (4).

Cre-dependent gene expression A 'lox-stop-lox' cassette can be placed upstream of a gene. Without Cre, the stop cassette prevents the translational expression of the gene. In the presence of Cre, the stop cassette is deleted and gene expression proceeds.