Technical innovations of signal amplification in fluorescence in situ hybridization

The in situ hybridization approach is used to detect nucleotide sequences in cells, tissue slices, as well as even three-dimensional organs and organisms. This approach is based on the complementary binding of nucleotide probes and unique DNA or RNA target sequences. These probes can be labeled with fluorescent, radioactive or antigen molecules. Depending on the type of probe labeling, fluorescence microscopy, autoradiography or immunohistochemistry is employed for imaging. In situ hybridization is frequently used not only for basic research, but also for diagnostic purposes. However, the low sensitivity of the conventional strategy of in situ hybridization has greatly hindered its application on low-abundance targets. In recent years, several new techniques such as RNA Scope, PLISH and SABER, have been developed, with great improvements in accuracy and sensitivity. Here we review the advances of signal amplification methods in fluorescence in situ hybridization and discuss the advantages and limitations of these new methods.