Choose a FISH probe by matching the biological question, target locus, specimen type, expected signal pattern, fluorophore/filter compatibility and validated workflow. Break-apart probes answer a different question from dual-fusion, enumeration or locus-specific probes. Rapid hybridisation is a property of the validated probe/workflow, not a universal setting.
Fluorescence in situ hybridisation (FISH) is only as informative as the probe design and scoring strategy behind it. Selecting a probe because it targets the right gene name is not enough: researchers also need to know what genomic event they are trying to detect, what signal pattern the assay is expected to generate, whether the specimen is compatible with the probe workflow and whether the fluorophores can be resolved by the microscope.
1. Start with the biological question
The first decision is the event you need to observe. Common research questions include gene amplification or deletion, chromosome copy number, chromosomal rearrangement, a defined gene fusion, localisation of a genomic locus, or localisation of an RNA transcript.
2. Match the probe design to the event
| Probe design | Best suited to | Typical signal logic |
|---|---|---|
| Locus-specific / gene probe | Defined genomic region, copy-number change, locus localisation | Count or localise target-associated signals; usually interpreted with an internal/reference control when copy number is the question. |
| Centromeric enumeration probe (CEP) | Chromosome enumeration and ploidy context | Signal number approximates copy number of the targeted chromosome/centromeric region. |
| Break-apart probe | Rearrangement of a locus when the fusion partner may vary | Signals flanking the breakpoint separate when the locus is rearranged. Probe-specific scoring criteria define a positive pattern. |
| Dual-fusion / dual-colour fusion | A known fusion between two defined loci | Co-localisation/fusion of differently coloured signals supports proximity of the two targeted loci. |
| RNA-FISH probe set | Transcript localisation or expression at cellular/subcellular level | Discrete or distributed RNA-associated fluorescence depending on probe design and transcript abundance. |
3. Match the probe to the specimen
FFPE tissue
FFPE provides archival morphology but introduces cross-linking, paraffin removal and variable target accessibility. Confirm that the probe workflow is validated for FFPE and that the pretreatment kit or protease conditions match the specimen.
Blood, bone marrow and cytology preparations
Interphase nuclei and metaphase preparations are common FISH substrates. Specimen preparation, cell density, fixation and slide ageing can materially affect signal quality.
Cultured cells
Cells are useful for research validation because specimen handling can be standardised, but fixation and permeabilisation still need to preserve both target accessibility and nuclear morphology.
4. Define the expected signal pattern before ordering
Write down the expected normal and abnormal patterns before the assay begins. For break-apart or fusion probes, obtain the manufacturer's interpretation diagram and scoring guidance. For copy-number work, decide whether a reference/centromeric control is needed and how section truncation or aneuploidy will be handled.
5. Check fluorophore and microscope compatibility
- Confirm that the excitation/emission spectra of every probe fluorophore match the installed filter sets or spectral detector.
- Plan DAPI or another nuclear counterstain without obscuring probe channels.
- For multiplex experiments, avoid excessive spectral overlap and validate exposure settings using single-colour controls where necessary.
6. Decide whether you need Fast FISH or a conventional workflow
Turnaround time matters, but it should come after target/specimen compatibility. OGT/CytoCell publishes validated 2-hour FAST FISH products, while other conventional systems use overnight hybridisation. A Wuhan HealthCare Biotechnology Fast Probe brochure describes approximately 2-hour tissue and 1-hour cell hybridisation for its rapid probe chemistry. Use the FAST FISH vs conventional FISH guide to compare the two approaches.
7. Check validation and controls
- Use a known positive specimen where practical.
- Include a normal/negative control appropriate to the assay.
- Document expected signal number, spacing and localisation.
- Validate scoring reproducibility between observers when interpretation is partly visual.
- For new specimen types or modified hybridisation times, perform analytical verification before relying on the assay.
Questions to ask before buying a FISH probe
- What exact gene, locus, chromosome or transcript am I targeting?
- Am I detecting rearrangement, fusion, amplification, deletion, enumeration or RNA localisation?
- What specimen type will I use?
- What does a normal and abnormal signal pattern look like?
- Is the probe validated for this specimen/workflow?
- Do the fluorophores match my microscope filters?
- Do I need an internal/reference probe?
- Do I need same-day results, and is a validated rapid protocol available?
Frequently asked questions
What is the best FISH probe for a translocation?
If one locus can rearrange with multiple partners, a break-apart design is often appropriate. If the biological question is a specific fusion between two known partners, a dual-fusion design may provide more direct evidence. The correct choice depends on the target and scoring criteria.
Can a centromeric probe diagnose gene amplification?
A centromeric probe can provide chromosome-copy context, but amplification of a specific gene requires a locus-specific strategy and appropriate ratio/scoring rules. Do not equate chromosome polysomy with focal gene amplification.
Can one probe work on both FFPE and cells?
Sometimes, but specimen preparation and pretreatment differ substantially. Confirm the manufacturer's validated specimen types rather than assuming transferability.
Related resources
- Fluorescence in situ hybridisation (FISH) protocol
- FAST FISH vs conventional FISH
- FISH troubleshooting guide
References and technical sources
- Fluorescence In situ Hybridization: Cell-Based Genetic Diagnostic and Research Applications.
- Fluorescence In Situ Hybridization of Cells, Chromosomes, and FFPE Tissues.
- OGT/CytoCell FAST FISH example and 2-hour hybridisation protocol.
Explore FISH probes at ABMIUM
ABMIUM provides access to 444 Fast FISH probes for research applications. Browse the FISH probe range or contact us with the target, specimen type and preferred fluorophores if you need help narrowing the options.