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Site Specific Recombination

FLP FRT System

Since 1998, ingenious targeting laboratory has utilized the FLP FRT recombination system in hundreds of gene targeting projects, providing researchers with versatile tools for conditional gene expression and sophisticated allele conversion strategies.

The FLP FRT system offers an orthogonal recombination platform that complements Cre lox technology, enabling complex genetic manipulations including dual recombinase strategies and sequential allele conversion.

2,500+
Projects Completed
800+
Publications
26+
Years Experience
100%
Success Rate

Applications of the FLP FRT System

Dual Recombinase Strategies

  • Sequential FLP then Cre recombination
  • Intersectional approaches for precise targeting
  • Conditional rescue in Cre defined populations

Gene Expression Control

  • FRT Stop FRT cassettes block downstream expression
  • Tissue specific activation via FLP driver lines
  • FLP dependent reporter activation for lineage tracing

FLP FRT vs Cre Lox

FeatureFLP FRTCre Lox
OriginYeast 2 micron plasmidBacteriophage P1
Recognition site34 bp FRT34 bp LoxP
Temperature optimum30°C (wild type)37°C
Driver availabilityLimitedExtensive catalog
Primary useCassette removalConditional deletion
ToxicityMinimalPossible at high levels

FLP Variants and Driver Lines

FLPe (Enhanced)

Four point mutations improve stability at 37°C, approximately 4 fold higher efficiency

FLPo (Optimized)

Codon optimized for mammalian expression, highest recombination efficiency

FlpERT2 (Inducible)

Tamoxifen inducible FLP for temporal control of recombination

Driver LineExpressionPrimary Use
ActFLPeUbiquitous from beta actin promoterGermline cassette removal
Rosa26 FLPeUbiquitous from Rosa26 locusGermline cassette removal
Nestin FLPNeural progenitorsBrain specific recombination
Syn FLPMature neuronsNeuronal specific recombination

What Researchers Say

The Hephaestin flox model ingenious has made for us has been great. It has helped generate eight research publications.

Joshua Dunaief, PhD, MD

University of Pennsylvania

Start Your FLP FRT Project

Our scientific consultants can help you determine whether FLP FRT, Cre lox, or a combination approach best meets your experimental requirements.

Frequently asked questions

FLP recombinase activity is generally efficient but may vary by target locus and driver strength, similar to Cre. Enhanced FLP variants (FLPe, FLPo) work well at 37°C in mammalian cells. For cassette removal applications, germline FLP expression provides efficient removal in offspring.

Yes. Dual recombinase designs use both FRT (for FLP) and LoxP (for Cre) sites, enabling independent control. For example, FLP removes FRT flanked cassettes to generate clean conditional alleles, then Cre controls gene deletion. This sequential use enables flexible allele architecture from knockout first designs.

Germline FLP expression lines include ActFLPe (ubiquitous from beta actin promoter) and Rosa26 FLPe (ubiquitous from Rosa26 locus). Tissue specific FLP drivers are more limited than Cre drivers. Nestin FLP and Syn FLP provide neural specific recombination, but fewer options exist for other tissues.