ABSTRACT
OBJECTIVE: To develop and validate a new strategy to distinguish between balanced/euploid carrier and noncarrier embryos in preimplantation genetic diagnosis (PGD) cycles for reciprocal translocations and to successfully achieve a live birth after selective transfer of a noncarrier embryo. DESIGN: Retrospective and prospective study. SETTING: In vitro fertilization (IVF) units. PATIENT(S): Eleven patients undergoing mate pair sequencing for identification of translocation breakpoints, followed by clinical PGD cycles. INTERVENTION(S): Embryo biopsy with 24-chromosome testing to determine carrier status of balanced/euploid embryos. MAIN OUTCOME MEASURE(S): Definition of translocation breakpoints and polymerase chain reaction (PCR) diagnostic primers, correct diagnosis of euploid embryos for carrier status, and a live birth with a normal karyotype after transfer of a noncarrier embryo. RESULT(S): In 9 of 11 patients (82%), translocation breakpoints were successfully identified. In four patients with a term PGD pregnancy established with a balanced/euploid embryo of unknown carrier status, the correct carrier status was retrospectively determined, matching with the cytogenetic karyotype of the resulting newborns. In a prospective PGD cycle undertaken by a patient with a 46,XY,t(7;14)(q22;q24.3) translocation, the four balanced/euploid embryos identified comprised three carriers and one noncarrier. Transfer of the noncarrier embryo resulted in birth of a healthy girl who was subsequently confirmed with a normal 46,XX karyotype. CONCLUSION(S): The combination of mate pair sequencing and PCR breakpoint analysis of balanced reciprocal translocation derivatives is a novel, reliable, and accurate strategy for distinguishing between carrier and noncarrier balanced/euploid embryos. The method has potential application in clinical PGD cycles for patients with reciprocal translocations or other structural rearrangements.
Subject(s)
Embryo Transfer/methods , Fertilization in Vitro , Genetic Carrier Screening/methods , Preimplantation Diagnosis/methods , Translocation, Genetic , Adult , Female , Fertilization in Vitro/methods , Humans , Infant, Newborn , Karyotyping , Male , Ploidies , Polymerase Chain Reaction/methods , Pregnancy , Prenatal Diagnosis/methods , Retrospective StudiesSubject(s)
Preimplantation Diagnosis , Translocation, Genetic , Chromosomes, Human, Pair 12 , Chromosomes, Human, Pair 22 , Chromosomes, Human, Pair 4 , Female , Fertilization in Vitro , Heart Defects, Congenital/diagnosis , Heart Defects, Congenital/genetics , Humans , In Situ Hybridization, FluorescenceABSTRACT
Blastocysts more commonly have a normal karyotype than cleavage-stage embryos do. Moreover, blastocysts have also made a metabolic transition from catabolism and recycling of the oocyte's reserves and resources, processes that fuel the first 3 days of cleavage. Although not all blastocysts are karyotypically equal, it is still to be determined to what extent a mosaic karyotype might be a normal feature among embryos, both at the cleavage stage and the blastocyst stage--and when looking for karyotypic abnormalities by embryo biopsy might help the chance of implantation rather than harm it. It is also still impractical to look at all the chromosomes that can, through their aneuploidy, stand in the way of successful embryonic and fetal development. We report a randomized clinical trial of blastocyst biopsy followed by preimplantation genetic screening (PGS) for aneuploidy using 5-colour FISH. The trial was suspended and then terminated early when we were unable to show an advantage for PGS. If we are correct in assuming that mitotic non-disjunction is common by the stage of the blastocyst (and that it is much less ominous than meiotic non-disjunction), then further studies of effective PGS of blastocysts for aneuploidy require methods of analysis that cover all the chromosomes and can differentiate the triallelic and monoallelic states of meiotically derived aneuploidies from the biallelic state of mitotic aneuploidies.
