Transgenic Research

, Volume 16, Issue 4, pp 405–413 | Cite as

Adopting the good reFLEXes when generating conditional alterations in the mouse genome



Major advances have been made in the use of the Cre/loxP system for conditional gene targeting in the mouse. By combining the ability of Cre recombinase to invert or excise a DNA fragment, depending upon the orientation of the flanking loxP sites, and the use of wild-type loxP and variant lox511 sites, we devised an efficient and reliable Cre-mediated genetic switch, called FLEX, through which expression of a given gene can be turned off, while expression of another one can be simultaneously turned on. We discuss how this innovative, flexible and powerful approach, which virtually adapts to any kind of site-specific recombinase (e.g., Cre and Flp recombinases), can be used to easily generate, even at high throughput and genome wide scale, many genetic modifications in a conditional manner, including those which were considered as difficult or impossible to achieve.


FRT Heterotypic sites Conditional allele Recombinase-mediated cassette exchange (RMCE) Point mutation Gene trap 


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Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  1. 1.Department of Molecular HaematologyUniversity of Frankfurt Medical SchoolFrankfurt am MainGermany
  2. 2.IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Inserm U596, CNRS UMR7104IllkirchFrance
  3. 3.Université Louis PasteurStrasbourgFrance
  4. 4.IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire)Illkirch CedexFrance

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