Conditional gene targeting in the kidney.

Complete mapping of the genome in a number of organisms provides a challenge for experimental nephrologists to identify potential functions of a vast number of new genes in the kidney. Since knockout technologies have evolved in the early eighties the mouse has become a valuable model organism. Researchers can now artificially eliminate the expression of specific genes in a mammalian organism and examine the phenotype. New developments have emerged that allow investigators to knock out a gene specifically in the kidney. Several kidney-specific promoters provide valuable tools and bacterial artificial chromosome (BAC) based techniques like recombineering will enhance both number and accuracy of new mouse lines with spatially controlled gene expression. In addition to spatial control, tetracycline- or tamoxifen-inducible systems, provide the possibility of influencing the temporal expression pattern of a gene enabling researchers to dissect its functions in adult organisms. Knocking out a gene will continue to be the gold standard for defining the role of a specific gene whereas tissue-specific gene knockdown using RNA interference represents an alternative approach for generating lower-priced and fast loss of function models. In addition to reverse genetic approaches, forward genetic techniques like random mutagenesis in mice continue to evolve and will enhance our understanding of disease mechanisms in the kidney.