In situ polymerase chain reaction: Overview of procedures and applications

The evaluation of gene expression in the context of cellular morphology is essential to the full understanding of cell biology. A variety of methods f or detection of nucleic acids are currently available. Solution polymerase chain reaction (PCR) requires disruption of the sample and detection of the amplified material by electrophoresis in agarose gels. In situ hybridizati on methods, on the other hand, permit morphologic correlation and provide a high sensitivity sufficient for many applications. In some instances, howe ver, the amount of target in the sample is below the limit of detection of this technique. In situ PCR allows the detection of minimal amounts of nucl eic acids with exquisite sensitivity and specificity, while the integrity o f the cells and the morphology of tissues remains preserved. This technique , although not exempt from difficulties, is undergoing methodologic simplif ications that will make it suitable for an increasing number of basic scien ce and clinical applications. The following is a review, of the principles, methods, and applications of in situ PCR.