Document Type: Review Paper
Deptartment of Medical Genetics, School of Medical Sciences, Tarbiat Modarres Univ., Tehran, I.R. Iran.
2Institute of Human Genetics, CNRS UPR ll42, Montpellier, France.
Preimplantation genetic diagnosis (PGD) is a novel approach for the prevention of genetic disorders in couples at risk of having offspring with genetic disease. Although the original idea dates back to early 1960s when sexing of rabbit blastocysts was attempted, the first clinical application of PGD was reported about three decades later, describing the use of PCR for sexing embryos from couples at risk of X-linked disease. The development of PCR-based tests led to PGD for screening well known monogenic diseases such as thalassaemia and cystic fibrosis. The introduction of fluorescence in situ hybridization (FISH) quickly replaced PCR-based methods which had led to misdiagnoses for sexing embryos. FISH can be used for aneuploidy screening of up to seven clinically significant chromosomes and translocation detection. The advent of molecular genetic techniques has brought forth new procedures for in situ chromosomal analysis. One of these techniques is the primed in situ labeling (PRINS) procedure which constitutes a fast and efficient alternative to conventional fluorescence in situ hybridization for nucleic acid detection. This technique has the potential to become a powerful tool for cytogenetic investigations. The recent achievements reported show that PRINS can constitute an efficient complement to PCR and FISH. Adaptation of this technique to preimplantation embryo screening both at chromosomal level and gene localization opens a promising perspective for being used in the field of PGD.