Site-specific recombinase technology: Difference between revisions

Revision as of 18:30, 20 January 2011

Revision as of 18:33, 20 January 2011

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==Regulating Cre expression==

SSR technology involving the Cre-''loxP'' system incorporates methods which allow for both the spatial and temporal control of SSR activity. A common method facilitating the spatial control of genetic alteration involves the selection of a tissue-specific [[promotor (biology)|promoter]] that drives Cre activity. Cre expression is placed under the control of a specific promoter sequence, which in turn allows for the localized expression of Cre in certain tissues. For example, Leone et al. have placed the Cre under the control of the regulatory sequences of the [[myelin]] proteolipid protein (PLP) gene, leading to induced removal of targeted gene sequences in [[oligodendrocytes]] and [[Schwann cells]]. {Leone et al. 2003}. The specific DNA fragment targeted by Cre will remain intact in cells which do not express the PLP gene; this in turn facilitates empirical observation of the localized effects of genome alterations in the myelin sheath surrounding the [[central nervous system]] (CNS) and the [[peripheral nervous system]] (PNS). Selective Cre expression has been achieved in many other cells and tissue regions as well.{{Citation needed|date=April 2008}}

In order to control temporal activity of the Cre excision reaction, forms of Cre which take advantage of various [[ligand]] binding domains have been developed. One successful strategy for inducing temporally specific Cre activity involves fusing the enzyme with a mutated ligand-binding ___domain of the human [[estrogen receptor]] (ERt). Upon the introduction of the drug [[tamoxifen]] (an estrogen [[receptor antagonist]]), the Cre-ERt construct is able to penetrate the nucleus and induce targeted mutation. ERt binds tamoxifen with greater affinity than [[endogenous]] [[estrogens]], which allows Cre-ERt to remain [[cytoplasmic]] in animals untreated with tamoxifen. The temporal control of SSR activity by tamoxifen permits genetic changes to be induced later in [[embryogenesis]] and/or in adult tissues. This allows researchers to bypass embryonic lethality while still investigating the function of targeted genes.