FlpO

FLPo is a codon-optimized variant of the Flp recombinase derived from Saccharomyces cerevisiae, engineered for efficient recombination at Flp recognition target (FRT) sites in mammalian cells and other higher organisms. It incorporates mammalian-optimized codons and often stabilizing changes to enhance catalytic activity at 37°C, enabling robust DNA manipulation in vivo where native Flp activity is limited.

The enzyme catalyzes site-specific recombination between two FRT sites. Depending on the orientation of the FRT sites, FLPo can excise a intervening DNA cassette, invert the sequence, or translocate genetic material. This makes FLPo useful for conditional gene disruption or activation, lineage tracing, and other genome engineering tasks that rely on precise rearrangements.

In practical use, FLPo is typically expressed under tissue-specific, inducible, or ubiquitous promoters in transgenic models. It is frequently employed in combination with Cre-loxP systems or within dual-recombinase strategies to enable intersectional genetics or sequential genetic modifications. Applications span mammalian model organisms, including mice, as well as other systems where robust Flp activity at mammalian body temperature is advantageous.

Advantages of FLPo include higher recombination efficiency in mammalian contexts compared with non-optimized Flp variants and compatibility with existing FRT-flanked constructs. Limitations can include dependency on adequate expression and access to chromatin regions containing FRT sites, potential off-target concerns being relatively low but not zero, and the need for careful experimental design when integrating Flp- and Cre-, or other recombinase-based, workflows.

See also: FRT, Flp recombinase, Cre-loxP, Dre-rox.