Diagnostic approaches to renal genetic disorders using DNA analysis.

Recent developments in molecular genetic technology have made it possible to diagnose many genetic disorders affecting the kidney before they are clinically manifest. For a disorder to be diagnosed by DNA analysis, either the causative gene must be known and cloned, or a closely linked DNA segment must have been identified. If one of these criteria is met, the disorder may be diagnosed either by direct detection of a mutation, if it is known, or indirectly by linkage analysis of the region using closely linked genetic markers. The methodology currently employed for direct detection of mutation includes the Southern blot, which will detect large structural alterations of genes or mutations altering a restriction recognition site, or the use of allele-specific oligonucleotides, which will detect specific point mutations. Linkage analysis is performed on DNA from multiple family members of the person at risk. Polymorphic markers are "tracked" in the family to determine the allele segregating with the disease gene. These methods are now routinely applied to the diagnosis of mendelian disorders affecting the kidney. It is anticipated that progress over the next decade will extend these applications to detection of the genetic component(s) contributing to multifactorial conditions.