In situ hybridization (ISH)

The Pathology Dictionary Team
April 5, 2023

What is in situ hybridization?

In situ hybridization (ISH) is a laboratory test used to see genetic material, such as DNA or RNA, within cells or tissues. It is commonly used in medicine to identify and visualize specific genes or gene products and to detect infectious agents such as viruses.

How does in situ hybridization work?

ISH involves using a small labeled piece of genetic material (a nucleic acid probe) that is complementary (opposite) to the target genetic material. The probe can be combined with various types of labels, such as fluorescent dyes, radioactive isotopes, or enzymes, which allow the probe to be seen inside cells.

In order to perform ISH, a tissue sample is first fixed and processed to preserve its structure and prepare it for hybridization. The tissue is then incubated with the labeled probe, which attaches (hybridizes) to the target genetic material if it is present. The leftover probe is then washed away, and the remaining probe-target combinations are detected using one of several methods.

in situ hybridization
In situ hybridization. This picture shows in situ hybridization used to detect genetic material from Epstein-Barr virus inside cancer cells.

What are the different types of in situ hybridization?

There are several different types of ISH techniques, including fluorescent in situ hybridization (FISH), chromogenic in situ hybridization (CISH), and RNA in situ hybridization (ISH-RNA). FISH and CISH use fluorescent or chromogenic labels, respectively, to visualize the location of the target genetic material, while ISH-RNA specifically detects RNA molecules within cells or tissues.

A+ A A-