FISH for pre-implantation genetic diagnosis

Area of Science:

• Genetics
• Reproductive Medicine
• Molecular Biology

Background:

• Pre-implantation genetic diagnosis (PGD) is an alternative to prenatal diagnosis for selecting embryos.
• PGD is crucial for couples with familial monogenic diseases, chromosome rearrangements, recurrent miscarriages, or infertility.
• Assisted reproduction technology (ART) generates embryos for PGD, utilizing in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI).

Purpose of the Study:

• To detail the clinical application of fluorescence in situ hybridization (FISH) for single-cell pre-implantation genetic diagnosis (PGD).
• To describe probe selection, blastomere spreading techniques, and hybridization for PGD.
• To evaluate FISH for detecting chromosome imbalances and selecting embryos in specific genetic conditions.

Main Methods:

• Biopsy of cleavage-stage embryos (day 3 post-fertilization) for single-cell genetic testing.
• Application of fluorescence in situ hybridization (FISH) using target-specific DNA probes on biopsied cells.
• Detailed procedures for probe selection, blastomere nucleus spreading, in situ hybridization, and signal scoring.

Main Results:

• FISH is effective for detecting chromosome imbalance in rearrangements and selecting female embryos for X-linked disorders.
• FISH can identify chromosome aneuploidy (PGD-AS), but its predictive value for routine use is questionable.
• The described FISH techniques are optimized for clinical PGD settings.

Conclusions:

• Single-cell FISH is a valuable tool for PGD, particularly for monogenic diseases and chromosome rearrangements.
• The clinical utility of FISH for aneuploidy screening (PGD-AS) requires further validation and is not recommended routinely.
• Optimized FISH protocols enhance the accuracy and efficiency of embryo selection in PGD programs.