Targeted gene regulation and gene ablation

Investigations of the mechanisms involved in appropriate, developmentally r egulated tissue-specific gene transcription have laid the foundations for t ransgenic and gene-therapy technologies directing specific induction or abl ation of genes of interest in a tissue-restricted manner. This technology h as further evolved to allow for temporal control of gene expression and abl ation. Genes can now be switched on and off or be ablated by administering exogenous compounds. These technologies are based on the development of lig and-inducible transcription factors or recombinases that regulate gene expr ession or ablation by the administration of specific ligands and should lea d to animal models that are better suited for investigating the molecular b asis of human disease. This review describes the evolution, components and applications of systems that are currently being employed in transgenic and mutant-mouse technology for the conditional regulation of gene expression and ablation.