Transgenic animal models as a tool in the diagnosis of kidney diseases.

Transgenic expression of proteins represents a valid tool for the study of their function in vivo. Genomic regulatory elements attached to a reporter gene can be used as the transgenic DNA to study regulation of gene expression, whereas the coding region of a gene placed between a strong promoter and a poly A sequence is used to study gene function. In addition to transgenic animals overexpressing proteins, gene targeting by homologous recombination to inactivate genes in embryonic stem cells for the generation of chimeric "knockout" mice as well as tissue-specific disruption of genes are discussed. Examples are provided by which transgenic animals overexpressing proteins or knockout mice that are deficient in proteins may lead to important insights into the pathogenesis of renal disease.