Visualization of Gene Expression Patterns by In Situ Hybridization

Abstract

The identification of the expression pattern of genes in embryonic and adult tissues provides critical information about the temporal and spatial action of genes and thus constitutes a first important step in understanding their function. The most straightforward method to visualize gene expression patterns in space and time is in situ hybridization on tissue sections or on whole mount specimens. in situ hybridization is very sensitive, particularly when antisense ribonucleic acid (RNA) probes are used. The procedure consists of four steps: the preparation of tissue -fixation, dehydration, embedding, and sectioning; the preparation of the probe; the application and annealing of the probe and subsequent removal of the nonhybridized probe by RNase digestion and washing; and the visualization of the expression pattern. Mounting the tissue onto a wooden block is easily performed if there is sufficient wax around all sides of the embedded tissue.