Fluorescence in situ hybridization (FISH) is a genetic screening method for the detection of DNA (deoxyribonucleic acid) in nuclei of individual cells.
This method involves the use of specific DNA probes that can only provide information about genomic regions for which the probe used is specific.
Indications (areas of application)
- Suspicion of numerical chromosomal aberration:
- Detection of numerical chromosomal abnormalities (e.g., trisomy 21).
- For quantification of mosaics for chromosomal aberrations (e.g., in Ullrich-Turner syndrome).
- Detection for microdeletions (e.g., monosomy 22q11.2).
- Detection of chromosomal aberrations (e.g., chronic lymphocytic leukemia (CLL), non-Hodgkin lymphoma).
The above indications are analyzed by interphase FISH (see “The Laboratory Procedure” for details).
The procedure
Material required
- Heparin blood (minimum 1-2 ml)
Preparation of the patient
- Not necessary
Disruptive factors
- None known
The laboratory method
Fluorescence in situ hybridization (FISH) involves the use of fluorescently labeled DNA probes (FISH probes). These can bind to a specific DNA site on a chromosome, which is called hybridization. Upon or after binding of the fluorescently labeled probe, evaluation can be performed using a microscope. In this process, the number of fluorescence signals within interphase nuclei is determined. Furthermore, an assessment of the location (e.g. translocation/shift of location/to another chromosome) at metaphase chromosomes is possible.
When different fluorescent dyes are used for different target DNAs in the FISH procedure, it is referred to as multicolor FISH. This allows complete visualization of the genome.
In some cases, the DNA probe is not directly labeled with a fluorescent dye, which is called an indirect procedure. Instead, it is labeled with substances such as biotin or digoxigenin. This method is considered more complicated but is more sensitive.
