Preimplantation Genetic Diagnosis for Single Gene Disorders

Preimplantation genetic diagnosis (PGD) has become an assisted reproductive technique for couples who are at risk that enables them to have unaffected baby without facing the risk of pregnancy termination after invasive prenatal diagnosis. The molecular biology and technology for single-cell genetics has reached an extremely high level of accuracy, and has enabled the possibility of performing multiple diagnoses on one cell using whole genome amplification. These technological advances have contributed to the avoidance of misdiagnosis in PGD for single gene disorders. Polymerase chain reaction (PCR)-based PGD will lead to a significant increase in the number of disorders diagnosed and will find more widespread use, benefiting many more couples who are at risk of transmitting an inherited disease to their baby. In this review, we will focus on the molecular biological techniques that are currently in use in the most advanced centers for PGD for single gene disorders, including biopsy procedure, multiplex PCR and post-PCR diagnostic methods, and multiple displacement amplification (MDA) and the problems in the single cell genetic analysis.

Successful Preimplantation Genetic Diagnosis for Ornithine Transcarbamylase Deficiency, Junctional Epidermolysis Bullosa and Lactic Acidosis Using Duplex Nested PCR: Delivery of Healthy Baby by Specific Preimplantation Genetic Diagnosis for Ornithine Tran / 대한산부인과학회잡지

OBJECTIVE: Preimplantation genetic diagnosis (PGD) is reserved for couples with a risk of transmitting a serious and incurable disease, and hence avoids the undesirable therapeutic abortion. Herein, we report the result of PGD to carriers at risk of transmitting ornithine transcarbamylase (OTC) deficiency, junctional epidermolysis bullosa (EB) and lactic acidosis (LA) due to defect of pyruvate dehydrogenase alpha1 gene, respectively. METHODS: The ovarian stimulation, oocyte retrieval and ICSI procedure were undergone by conventional protocols. PGD for single gene disorders was carried out after biopsy of one or two blastomeres from the embryos on the third day. We performed the duplex nested PCR of the simultaneous amplification for the causative mutation loci as well as the SRY gene on Y chromosome in case of OTC deficiency and LA. Two different mutation loci of ITGB4 gene in EB case were amplified by the same protocol. The PCR products were analyzed by agarose gel electrophoresis, restriction fragment length polymorphism analysis or direct DNA sequencing. RESULTS: A total of 26 embryos were analyzed by duplex nested PCR. One or two blastomeres were biopsied, and successful diagnosis rate of PGD with PCR was 92.3% (24/26). There was no contamination in all PCR samples of negative controls (n=67). Five embryos (19.2%) were diagnosed as normal embryos, which were transferred to the mothers' uterus in each cases. In OTC deficiency case, singleton pregnancy was established. At 17 weeks of gestation, genetic normality of OTC gene in fetus was confirmed by amniocentesis. A healthy baby was successfully delivered at 36 weeks of gestation in OTC deficiency case. Unfortunately, pregnancies were not achievement in cases of EB and LA. CONCLUSION: This is the first report in Korea that healthy baby was born after specific PGD for OTC deficiency. Our results demonstrate that duplex nested PCR for single cell is an efficient method in identifying the gender and single gene mutation or two different mutation loci, simultaneously. This PGD procedure could provide normal healthy baby to the couple with a high risk of transmitting genetic diseases.